Image forming apparatus

Abstract

In a configuration that controls the fixing temperature according to the image to be printed, it is possible to determine the fixing temperature while reducing the processing load of image analysis. [Solution] The image forming apparatus 100 is configured to include an image forming unit 160, a fixing unit 30, a generation unit 352 that generates image data and attribute data indicating the attributes of the image data, including at least whether or not it is text, a compression unit 350 that compresses the image data to generate compressed image data and compresses the attribute data to generate compressed attribute data, a setting unit 325 that analyzes the compressed image data or compressed attribute data of a one-page image formed on a single recording material 11 in a compressed state and sets a target temperature for the fixing unit 30 when fixing the one-page image to the recording material based on the analysis results, and a control unit 391 that controls the fixing unit 30 based on the target temperature set by the setting unit 325.

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus provided with a fixing device that fixes a toner image onto a recording material. [Background Art]

[0002] In an image forming apparatus provided with a fixing device that fixes a toner image formed by an electrophotographic method onto a recording material, the temperature of the fixing device (fixing temperature) is often determined in advance in accordance with the amount of toner per unit area to be deposited on the recording material. Normally, the maximum value of the toner amount per unit area is determined in advance, and temperature adjustment is performed such that the fixing temperature is set to a level that can reliably fix an image having the toner amount at this maximum value onto the recording material.

[0003] On the other hand, depending on the image to be output, the toner amount may be significantly lower than the assumed maximum toner amount. When outputting such an image, excessive heating is performed, resulting in wasted power consumption.

[0004] To address this problem, Patent Document 1 discloses a technique for reducing power consumption by adjusting the fixing temperature in accordance with image data to be printed.

[0005] Generally, when toner is present at a high density, a large amount of heat is absorbed from the fixing member during fixing. Further, in the case of a text image, toner is deposited line by line, so heat from the fixing member is less likely to be absorbed during fixing. From these characteristics, the fixing temperature can be determined based on the toner density and the image type. In this case, it is necessary to analyze the density information and image type of the image data of the entire page to be printed. [Prior Art Documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2022-130158 [Summary of the Invention] [Problems that the invention aims to solve]

[0007] By the way, since the fixing temperature is controlled with a target fixing temperature several pages later, it is necessary to perform image analysis on the target page several pages before it is fixed and notify the fixing temperature control unit of the target temperature. This is because temperature control of the fixing device takes a certain amount of time.

[0008] Image forming machines store image data input from external devices such as client PCs, or image data scanned by a scanner, in memory for several pages until printing begins. Generally, the memory capacity used is reduced by compressing the image data stored in memory. Therefore, to analyze the image data several pages in advance for fixing temperature control, it is necessary to use spooled compressed image data. Conventionally, the analysis process was performed after decompressing the compressed image data.

[0009] When analyzing expanded image data, the processing load is high because the entire image data of the page is analyzed. Therefore, in image forming machines with high material transport speeds, for example, the image data analysis may not keep up, and it may become necessary to wait for image formation to finish in order to adjust the fixing temperature, which can lead to a decrease in print productivity.

[0010] Therefore, the objective of the present invention is to enable the determination of the fixing temperature while reducing the processing load of image analysis in a configuration that controls the fixing temperature according to the image to be printed. [Means for solving the problem]

[0011] The above objective is achieved by the image forming apparatus according to the present invention. In summary, the present invention provides an image forming apparatus comprising: an image forming unit that forms an image on a recording material with toner based on image data; a fixing unit that applies heat to the recording material on which the image has been formed by the image forming unit to fix the image to the recording material; a generation unit that generates the image data and also generates attribute data indicating the attributes of the image data, including at least whether or not it is text; a compression unit that compresses the image data to generate compressed image data and compresses the attribute data to generate compressed attribute data; a setting unit that analyzes the compressed image data or compressed attribute data of a one-page image formed on a single recording material in a compressed state and sets a target temperature for the fixing unit when fixing the one-page image to the recording material based on the analysis results; and a control unit that controls the fixing unit based on the target temperature set by the setting unit. [Effects of the Invention]

[0012] According to the present invention, in a configuration that controls the fixing temperature according to the image to be printed, it is possible to determine the fixing temperature while reducing the processing load of image analysis. [Brief explanation of the drawing]

[0013] [Figure 1] This is a block diagram showing the schematic configuration of an image forming apparatus. [Figure 2] This is a schematic cross-sectional view of the printer section. [Figure 3] This is a block diagram of the controller section. [Figure 4] This is a block diagram of the system control unit and the printer control unit. [Figure 5] This is a schematic diagram showing the structure of packet data. [Figure 6] This is a schematic diagram showing tile image data. [Figure 7] This is a block diagram of each image processing unit (print processing unit, loopback processing unit, scan processing unit). [Figure 8] This is an explanatory diagram illustrating an example of attribute data format. [Figure 9] FIG. 4 is an explanatory diagram of PackBits compression. [Figure 10] FIG. 5 is a flowchart of fixing temperature control. [Figure 11] FIG. 6 is a flowchart of fixing temperature determination processing. [Figure 12] FIG. 7 is a flowchart of attribute information analysis processing. DETAILED DESCRIPTION OF EMBODIMENTS

[0014] Hereinafter, the image forming apparatus according to the present invention will be described in further detail with reference to the drawings.

[0015] Example 1 Schematic Configuration of Image Forming Apparatus FIG. 1 is a block diagram showing a schematic configuration of an image forming apparatus 100 according to the present embodiment. Although a recording material is also referred to as paper herein, the recording material is not limited to being formed of paper, and includes materials other than paper such as plastic sheets and synthetic paper, or members formed of materials including materials other than paper. Further, the image forming apparatus 100 may be, for example, a copier, a printer, a facsimile apparatus, a multifunction peripheral having a plurality of these functions, a printing press, or the like.

[0016] A scanner unit 110 optically reads an image of a document and converts the image into image data. The scanner unit 110 includes a document reading unit 112 and a document feeding unit 111. The document reading unit 112 has a function of reading a document. The document feeding unit 111 has a function of conveying a document.

[0017] The printer unit 140 transports sheet-like recording material (transfer material, paper, sheet) such as paper, prints (prints, imprints) image data onto the recording material as a visible image, and discharges the printed material outside the image forming apparatus 100. The printer unit 140 is composed of a paper feed unit 142, a transfer and fixing unit 141, and a paper discharge unit 143. The paper feed unit 142 has multiple types of paper feed cassettes. The transfer and fixing unit 141 has the function of transferring image data onto the recording material as a visible image and fixing it onto the recording material. The paper discharge unit 143 has the function of outputting the printed recording material outside the machine. The paper discharge unit 143 may also have the function of performing post-processing such as sorting and stapling on the printed recording material before outputting it outside the machine.

[0018] The controller unit 120 is electrically connected to the scanner unit 110 and the printer unit 140, and is also connected to a network 150 such as a LAN, public telephone line, or internet / intranet. The controller unit 120 controls the scanner unit 110 to read image data from a document and controls the printer unit 140 to output the image data as a visible image onto recording material (copy function). The controller unit 120 also provides a function to convert the image data read from the scanner unit 110 into coded data and transmit it via the network 150 to an external device such as a host computer 500 (scanner function). The controller unit 120 also provides a function to convert the coded data received from the host computer 500 via the network 150 into image data and output it to the printer unit 140 (printer function). Furthermore, the controller unit 120 provides a function to receive data from a public telephone line and print it (FAX receiving function) and a function to send scanned data to a public telephone line (FAX transmission function). These processes such as scanning, printing, and FAX transmission / reception are called "jobs". The controller unit 120 controls and processes jobs according to instructions. Depending on the combination, jobs can be processed simultaneously.

[0019] The operation unit 130 is connected to the controller unit 120. In this embodiment, the operation unit 130 is composed of a liquid crystal touch panel having the functions of an input unit and a display unit. The operation unit 130 provides a user interface for operating the image forming apparatus 100.

[0020] <Printer unit configuration and image formation operation> Figure 2 is a schematic cross-sectional view of the printer unit 140 that constitutes the image forming apparatus 100 of this embodiment. In this embodiment, the printer unit 140 is capable of forming full-color images using an electrophotographic method and employs an intermediate transfer method and a tandem method.

[0021] The printer unit 140 has four image forming units (stations) 10Y, 10M, 10C, and 10K, which form images of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Elements with the same or corresponding functions or configurations provided for each color may be described collectively by omitting the Y, M, C, and K at the end of the symbols indicating that they are elements for any of the colors. In this embodiment, the image forming unit 10 is composed of a photoreceptor 22, a charger 23, an exposure device 24, a developer 26, and the like.

[0022] The photoreceptor (photosensitive drum) 22, which acts as an image carrier, rotates when a driving force is transmitted from a drive motor 25, which acts as a driving means. The drive motor 25 rotates the photoreceptor 22 in a counterclockwise direction in the figure according to the image forming operation. The surface of the rotating photoreceptor 22 is uniformly charged by a charger (injection charger) 23, which acts as a charging means. The charger 23 is provided with a charging sleeve 23S that carries magnetic particles that come into contact with the surface of the photoreceptor 22 and rotates. The charged surface of the photoreceptor 22 is selectively exposed by laser light irradiated by an exposure device (laser scanner) 24, which acts as an exposure means, according to image information, and an electrostatic latent image (electrostatic image) is formed on the photoreceptor 22. The electrostatic latent image formed on the photoreceptor 22 is developed (visualized) by the supply of toner by a developer 26, which acts as a developing means, and a toner image (toner image, developer image) is formed on the photoreceptor 22. The developing unit 26 is equipped with a developing sleeve 26S that rotates while carrying a two-component developing agent comprising toner (non-magnetic toner particles) and carrier (magnetic carrier particles) as the developing agent. In this embodiment, each developing unit 26 is detachable from the main body of the image forming apparatus 100.

[0023] An intermediate transfer belt 28, composed of an endless belt, is positioned opposite the four photoreceptors 22 as an intermediate transfer body. The intermediate transfer belt 28 is stretched over a plurality of tension rollers. The intermediate transfer belt 28 rotates (circumferentially moves) in a clockwise direction in the figure when a driving force is transmitted from a drive motor (not shown) as a driving means to a drive roller, which is one of the plurality of tension rollers. On the inner circumferential surface side of the intermediate transfer belt 28, primary transfer rollers 27Y, 27M, 27C, and 27K are positioned opposite each of the photoreceptors 22Y, 22M, 22C, and 22K, respectively, as primary transfer means. The primary transfer rollers 27 are pressed toward the photoreceptors 22, forming a primary transfer section where the photoreceptors 22 and the intermediate transfer belt 28 come into contact. The toner image formed on the photoreceptors 22 is transferred (primary transfer) onto the rotating intermediate transfer belt 28 in the primary transfer section. During the primary transfer, a predetermined primary transfer bias (primary transfer voltage) is applied to the primary transfer roller 27. By creating a difference between the rotation speed of the photoreceptor 22 and the rotation speed of the intermediate transfer belt 28, the toner image can be efficiently transferred onto the intermediate transfer belt 28. For example, when forming a full-color image, the toner images of yellow, magenta, cyan, and black formed on each photoreceptor 22 are sequentially transferred onto the intermediate transfer belt 28, overlapping them. Toner remaining on the photoreceptor 22 during the primary transfer (primary transfer residue toner) is collected by the developer 26. A cleaning device may be provided to remove and collect the primary transfer residue toner from the photoreceptor 22.

[0024] On the outer circumferential surface of the intermediate transfer belt 28, a secondary transfer roller 29 is positioned opposite a secondary transfer opposing roller, which is one of a plurality of tension rollers, serving as a secondary transfer means. The secondary transfer roller 29 is pressed toward the secondary transfer opposing roller, forming a secondary transfer section where the intermediate transfer belt 28 and the secondary transfer roller 29 come into contact. The toner image formed on the intermediate transfer belt 28 is transferred (secondary transfer) to the recording material 11, which is held and transported between the intermediate transfer belt 28 and the secondary transfer roller 29, in the secondary transfer section. During secondary transfer, a predetermined secondary transfer bias (secondary transfer voltage) is applied to the secondary transfer roller 29. Toner remaining on the intermediate transfer belt 28 during secondary transfer is removed and recovered from the intermediate transfer belt 28 by a belt cleaning device 21, which serves as an intermediate transfer body cleaning means.

[0025] The recording material 11 is housed in the paper feed tray 41. The recording material 11 housed in the paper feed tray 41 is fed out of the paper feed tray 41 by the paper feed roller 42 and transported to the secondary transfer section by the transport roller 43 or the like. Alternatively, the recording material 11 is loaded in the manual feed tray 44. The recording material 11 loaded in the manual feed tray 44 is fed out of the manual feed tray 44 by the manual feed paper feed roller 45 and transported to the secondary transfer section by the transport roller 43 or the like. In this embodiment, the paper feed section 143 (Figure 1) is composed of the paper feed tray 41, the paper feed roller 42, the manual feed tray 44, the manual feed paper feed roller 45, and the like. The secondary transfer roller 29 is positioned to contact the intermediate transfer belt 28 via the recording material 11, as shown by the solid line, while the toner image is being transferred onto the recording material 11, and after the print process, it is positioned away from the intermediate transfer belt 28, as shown by the dashed line.

[0026] The recording material 11 onto which the toner image has been transferred is transported to a fixing device 30, which serves as a fixing means (fixing unit). The fixing device 30 includes a fixing roller (heating roller) 32 as a heating rotating body that heats the recording material 11, and a pressure roller 33 as a pressing rotating body that presses against the fixing roller 32. The pressure roller 33 presses the recording material 11 against the fixing roller 32. The fixing roller 32 and the pressure roller 33 are each made of hollow rollers. Heaters 34 and 35 are arranged inside the hollow parts of the fixing roller 32 and the pressure roller 33, respectively. The fixing device 30 transports the recording material 11 holding the toner image by clamping it between the fixing roller 32 and the pressure roller 33. In this way, the fixing device 30 applies heat and pressure to the recording material 11 holding the toner image, fixing (melting, solidifying) the toner image onto the recording material 11. Furthermore, the fuser unit 30 is equipped with a temperature sensor 31 as a detection means for detecting the temperature of the fuser unit 30, for example, the temperature of the fuser roller 32. The temperature sensor 31 is composed of a thermistor or the like. The controller unit 120 controls the temperature of the fuser unit 30 (fixing temperature) by controlling the power supplied to the heaters 34 and 35 based on the temperature detection result from the temperature sensor 31. The fixing temperature is represented, for example, by the temperature of the fuser roller 32. Based on the detection result from the temperature sensor 31, the controller unit 120 controls the fuser unit 30 to perform the fixing operation only when a temperature sufficient for fixing has been confirmed. For example, the controller unit 120 (more specifically, the fixing temperature control unit 319 of the printer control unit 280, which will be described later) turns the power supplied to the heaters 34 and 35 on / off based on the temperature detection result from the temperature sensor 31. In this way, the controller unit 120 controls the fuser unit 30 so that the fixing temperature reaches (or exceeds) the target temperature. For example, the controller unit 120 outputs a control signal to turn on the heaters 34 and 35 if the detected temperature is lower than the target temperature. Also, the controller unit 120 outputs a control signal to turn off the heaters 34 and 35 if the detected temperature is higher than the set temperature.

[0027] The recording material 11 on which the toner image has been fixed is then discharged (output) to a paper output tray (not shown) by an output roller 46 or the like. In this embodiment, the paper output section 143 (Figure 1) is formed by the output roller 46 or the like. With this, the image forming operation is completed.

[0028] In this embodiment, the transfer and fixing unit 141 (Figure 1) is composed of each image forming unit 10, an intermediate transfer belt 28, each primary transfer roller 27, a secondary transfer roller 29, a fixing device 30, etc. In this embodiment, the image forming unit 160 is composed of each image forming unit 10, an intermediate transfer belt 28, each primary transfer roller 27, a secondary transfer roller 29, etc., which forms a toner image on the recording material 11.

[0029] <Controller section> Figure 3 is a block diagram of the controller unit 120 in this embodiment.

[0030] The controller unit 120 includes a system control unit 210, a printer control unit 280, an image ring bus 220, a print processing unit 230, a loopback processing unit 240, a scan processing unit 250, a RAM controller 260, and RAM 270.

[0031] The system control unit 210 has an internal CPU and controls scanning processing using the scanner unit 110 and printing processing using the printer unit 140 of the image forming apparatus 100. The system control unit 210 also transfers image data for these processes via the image ring bus 220. Furthermore, the system control unit 210 performs data transmission to the network 150, data reception from the network 150, and display processing to the operation unit 130. In this way, the system control unit 210 provides overall control of the entire system.

[0032] The printer control unit 280 has an internal CPU and works in conjunction with the system control unit 210 to control the printer unit 140. Specifically, the printer control unit 280 controls the temperature (fixing temperature) of the fixing device 30 that constitutes the transfer fixing unit 141.

[0033] The image ring bus 220 is a bus for transferring image data to various blocks within the controller unit 120, such as the system control unit 210, print processing unit 230, loopback processing unit 240, and scan processing unit 250. In this embodiment, data lines for transferring image data to each of these units are connected in a ring shape via the image ring bus 220. This allows the system control unit 210, the print processing unit 230, the loopback processing unit 240, and the scan processing unit 250 to exchange image data with each other.

[0034] The print processing unit 230 performs various image processing operations, such as color space conversion, intermediate length processing, and gamma correction, for printing image data on the printer unit 140. The print processing unit 230 receives image data from the image ring bus 220, applies these image processing operations to the image data, and then outputs the image data to the printer unit 140.

[0035] The loopback processing unit 240 is a block that performs image processing that may be used in either the print or scan process. The loopback processing unit 240 receives image data from the system control unit 210 via the image ring bus 220, performs image processing internally, and then returns the image data to the system control unit 210 via the image ring bus 220.

[0036] The scan processing unit 250 applies image processing such as shading correction, MTF correction, input gamma correction, and filtering to the image data read by the scanner unit 110. After applying these image processing steps to the image data transferred from the scanner unit 110, the scan processing unit 250 transfers the image data to the image ring bus 220. The image data transferred to the image ring bus 220 is then transferred to the system control unit 210 via the image ring bus 220.

[0037] The RAM controller 260 receives image data from the print processing unit 230, loopback processing unit 240, and scan processing unit 250, respectively, and controls the temporary writing of this data to the RAM 270. The RAM controller 260 also reads the image data written to the RAM 270 according to instructions from these units and transfers it to them. The print processing unit 230, loopback processing unit 240, and scan processing unit 250 each use the RAM 270 as a temporary image buffer to perform internal image processing or to change the order of image data. Furthermore, the image data from the print processing unit 230, loopback processing unit 240, and scan processing unit 250 are multiplexed and transmitted between the RAM controller 260 and the RAM 270.

[0038] <Systems Control Department> Figure 4 is a block diagram of the system control unit 210 and the printer control unit 280 in this embodiment. First, the internal blocks of the system control unit 210 will be described.

[0039] The system control unit 210 includes a CPU 310, a ROM controller 320, a ROM 321, a RAM controller 330, a RAM 331, an operation interface 340, an HDD controller 360, an HDD 361, a LAN controller 370, a PHY 371, a modem 372, an image compression unit 350, an image decompression unit 351, a rendering unit 352, a fixing temperature calculation unit 325, a printer communication I / F unit 313, and an image ring interface 301. Each block constituting the interior of the system control unit 210 is connected by a system bus 300.

[0040] The CPU310 is the processor that controls the entire system. The CPU310 comprehensively controls job-related processes such as printing and scanning, according to the OS (operating system) and control programs deployed in RAM331.

[0041] The ROM controller 320 is a control module for accessing the ROM 321, which stores the system's boot program. When the power to the image forming apparatus 100 is turned ON, the CPU 310 accesses the ROM 321 via the ROM controller 320 and boots the program.

[0042] The RAM controller 330 is a control module for accessing RAM 331, which stores the system's control programs and image data. The RAM controller 330 has registers for configuring and controlling RAM 331, and these registers are accessible from the CPU 310.

[0043] The control interface 340 controls the reception of operation instructions and the display of operation results when a user operates the control unit 130.

[0044] HDD361 is a hard disk drive that stores system software, application programs, image data, and page and job information corresponding to each image file. HDD361 is connected to the system bus 300 via HDD controller 360 and reads and writes data according to instructions from CPU 310.

[0045] The LAN controller 370 is connected to the network 150 via the PHY 371 and performs input and output of information such as image data with external devices such as the host computer 500.

[0046] The modem 372 is connected to a public telephone line (not shown) and communicates data with external fax equipment when performing fax transmission and fax reception jobs.

[0047] The image compression unit 350 compresses image data stored in the RAM 331 or HDD 361 into JPEG format. The image compression unit 350 also compresses attribute data, which is additional image information stored in the RAM 331 or HDD 361, using the packbits compression method. The image compression unit 350 is a compression unit that compresses image data to generate compressed image data and compresses attribute data to generate compressed attribute data. Compression refers to representing digital data with less information by utilizing the redundancy and regularity contained in the digital data. In this embodiment, attribute data compression is generally performed by recording the character and the number of repetitions when the same character appears consecutively, thereby reversibly representing the attribute data with less information. Attribute data and the packbits compression method will be described later with reference to Figures 8 and 9.

[0048] The image decompression unit 351 performs decompression processing on image data compressed in JPEG format (hereinafter also referred to as "compressed image data") and attribute data compressed using packbits (hereinafter also referred to as "compressed attribute data").

[0049] The rendering unit 352 receives image data (PDL code) from an external device such as a host computer 500 via the LAN controller 370 from the network 150 and expands it into bitmap data (bitmap image data) which is image data (i.e., generates image data). At the same time, the rendering unit 352 generates attribute data, which will be described later, based on the PDL code. The rendering unit 352 is a generation unit that generates image data and also generates attribute data that indicates the attributes of the image data, including at least whether or not it is text. This bitmap data (image data) and attribute data are converted to a packet data format, which will be described later, then compressed by the image compression unit 350 and stored in the RAM 331 or HDD 361. This bitmap data and attribute data are used in the print function. Furthermore, the image compression unit 350 compresses the bitmap data using JPEG compression and the attribute data using packbits compression, and these are used for analysis in their compressed state by the fixing temperature calculation unit 325, which will be described later.

[0050] The fixing temperature calculation unit 325 calculates the target fixing temperature (hereinafter also referred to as the "target fixing temperature") necessary to print the page to be printed. This is done by analyzing the attribute data mentioned above in a compressed state. As a result, the fixing temperature calculation unit 325 calculates an appropriate target fixing temperature according to the image data. The fixing temperature calculation unit 325 analyzes the compressed attribute data of the image of one page formed on a single recording material in a compressed state, and constitutes a setting unit that sets the target temperature of the fixing unit (fixing device) 30 when fixing the image of the one page to the recording material based on the analysis results. Details of the operation of the fixing temperature calculation unit 325 will be described later using the flowcharts in Figures 10 to 12.

[0051] The printer communication interface unit 313 is an interface unit for communication between the system control unit 210 and the printer control unit 280. Information communicated via the printer communication interface unit 313 includes control signals from the system control unit 210 and fixing target temperature information necessary for printing each page, calculated by the fixing temperature calculation unit 325.

[0052] The image ring interface 301 is an interface block that connects the system bus 300 inside the system control unit 210 to each image processing block outside the system control unit 210 (print processing unit 230, loopback processing unit 240, scan processing unit 250) via the image ring bus 220. The data flowing through the image ring bus 220 is called "packet data" or simply "packet". The image ring interface 301 transmits packet data stored in RAM 331 or HDD 361 to the image ring bus 220. The image ring interface 301 also stores packet data received from the image ring bus 220 in RAM 331 or HDD 361. Details of the packet data will be described later using Figures 5 and 6.

[0053] <Printer Control Unit> Next, we will describe the internal blocks of the printer control unit 280.

[0054] The printer control unit 280 includes a CPU 391, a ROM controller 392, a ROM 393, a RAM controller 394, a RAM 395, a fuser temperature control unit 319, and a system communication I / F unit 396. Each block constituting the inside of the printer control unit 280 is connected by a system bus 395.

[0055] The CPU 391, ROM controller 392, ROM 393, RAM controller 394, and RAM 395 have the same functions as those described with respect to the system control unit 210, and are used for controlling the printer unit 140.

[0056] The fixing temperature control unit 319 controls the temperature of the fixing device 30 based on the fixing target temperature determined by the fixing temperature calculation unit 325. The fixing temperature control unit 319 constitutes a control unit that controls the fixing unit (fixing device) 30 based on the target temperature set by the setting unit (fixing temperature calculation unit) 325.

[0057] The system communication interface unit 396 is an interface unit for communication between the system control unit 210 and the printer control unit 280. The system communication interface unit 396 is paired with the printer communication interface unit 313. Information communicated via the system communication interface unit 396 includes control signals from the system control unit 210 and fixing temperature information necessary for printing each page, calculated by the fixing temperature calculation unit 325.

[0058] <Packet Data Format> Next, the packet data handled by the image forming apparatus 100 of this embodiment will be described.

[0059] Figure 5 is a schematic diagram showing an example of packet data flowing through the image ring bus 220 in this embodiment. The packet data 600 is broadly divided into a header section 650, a data section 620, and an attribute data section 630. The header section 650 is further divided into the information shown in 601 to 612 in Figure 5.

[0060] Packet type 601 indicates whether the packet data is image data or a command. If packet type 601 indicates image data, the data section 620 stores the image data, and the attribute data section 630 stores attribute data. If packet type 601 indicates a command, the data section 620 stores a setting address and data indicating the setting value for setting coefficients, modes, etc., for each image processing unit (print processing unit 230, loopback processing unit 240, scan processing unit 250).

[0061] Chip ID 602 ​​indicates an ID (identifier) ​​for identifying the target processing unit to which the packet data will be transmitted. For example, if chip ID 602 ​​is 0, it indicates the print processing unit 230; if chip ID 602 ​​is 1, it indicates the loopback processing unit 240; and if chip ID 602 ​​is 2, it indicates the scan processing unit 250.

[0062] Page ID 603 indicates the page number to which the packet data belongs. Scanning and printing operations may involve multiple pages, and page ID 603 indicates which page the packet data belongs to.

[0063] Job ID 604 indicates the job number to which the packet data belongs. For example, if a scan job and a print job are executed simultaneously, the packet data for the scan job will be assigned job number 1, and the packet data for the print job will be assigned job number 2, making it possible to identify the jobs.

[0064] The packet Y coordinate 605 indicates the Y coordinate (coordinate in the sub-scanning direction) of the image data stored in the data section 620, if such image data is stored in the data section 620.

[0065] The packet X coordinate 606 indicates the location of the image data (coordinate in the main scanning direction) within the page, if the image data is stored in the data unit 620.

[0066] In this embodiment, the image data stored in the data unit 620 is obtained by dividing page-level image data into rectangles of a predetermined number of pixels (for example, 32 pixels × 32 pixels). Therefore, when regenerating page data from packet data, the above coordinate data is referenced. This image data is compressed by a compressor (described later) implemented inside the image compression unit 350 or each image processing unit, and is stored in the data unit 620 as compressed image data.

[0067] The packet byte length of 607 indicates the total number of bytes in the packet data.

[0068] The data byte length 608 indicates the total number of bytes in the data portion 620 of the packet data.

[0069] The attribute byte length 609 indicates the total number of bytes in the attribute data section 630 of the packet data.

[0070] For example, the data byte length is 4096 bytes (32 pixels x 32 pixels x 4 bytes) when each pixel is 4 bytes and the compression ratio is 1 / 1, and 512 bytes when the compression ratio is 1 / 8. Similarly, the attribute byte length is 1024 bytes (32 pixels x 32 pixels x 4 bytes) when each pixel is 1 byte and the compression ratio is 1 / 1, and 128 bytes when the compression ratio is 1 / 8.

[0071] The data compression flag 610 indicates whether or not the data section 620 is compressed. The data compression flag 610 may also indicate the compression method used if compression is performed. In this embodiment, JPEG compression is assumed.

[0072] The attribute compression flag 611 is a flag that indicates whether or not the attribute data section 630 is compressed. If it is compressed, the attribute compression flag 611 may also indicate what compression method is used. In this embodiment, it is assumed that it is compressed using packbits, which will be described later.

[0073] In other words, in this embodiment, an image of one page formed on a single recording material (more specifically, the entire image-forming area where a toner image can be formed) is divided into multiple regions, and image data and attribute data are generated for each region, thereby generating multiple packets containing the image data and attribute data for each divided region. In this embodiment, an image of one page is divided into multiple regions of a predetermined number of pixels, and image data and attribute data are generated for each region, thereby generating multiple packets containing the image data and attribute data for each divided region. Furthermore, in this embodiment, the image data and attribute data are compressed for each packet.

[0074] Thumbnail data612 stores thumbnail data. In this embodiment, Thumbnail data612 stores the average values ​​(comp1~4) of the color data, such as RGB and CMYK, for each 32x32 pixel image data of each packet, in 8 bits. By referring to the values ​​in Thumbnail data612, it is possible to determine the approximate density of the image on a packet-by-packet basis. For example, if the packet consists entirely of pixels of text and all colors in Thumbnail data612 are at their maximum density, it can be determined that the text color is black.

[0075] Next, we will explain the packet data format. Figure 6 is a schematic diagram of the tile image data in this embodiment.

[0076] In this embodiment, image data 701 for one page is divided and processed into image data 702 in 32-pixel x 32-pixel tile units. For example, consider the case where an A4-sized document is scanned by the scanner unit 110 at a resolution of 600 x 600 dpi and divided into 32 x 32 pixel tiles. In this case, 34,320 tile image data are generated from the A4-sized document. When generating tile images, the tile images can be made into a shape and pixel count that is easy to handle by setting the scanning resolution and image processing requirements.

[0077] The tile unit does not have to be 32x32 pixels; for example, it may be 64x64 pixels. Also, the tile does not have to be square; for example, it may be a rectangle or other rectangular shape. When compressing image data, instead of compressing the data for an entire page at once, only the image data is compressed for each tile (packet). Regarding the compression unit, compression may be performed for each block 703, which is obtained by further dividing the tile (packet) into 8x8 pixel units, which are the unit units of JPEG. On the other hand, in this embodiment, attribute data will be compressed using packbits compression, which will be described later using Figures 8 to 9.

[0078] In this embodiment, packet data as described above flows through the image ring bus 220. Each image processing unit receives and interprets the packet data. If the packet indicates a command, it sets the processing mode and coefficients, and if the packet indicates image data, it performs image processing on the image data.

[0079] In this embodiment, for convenience, the exchange of packet data, which consists of image data obtained by dividing a page image into predetermined pixel units and attribute data that is additional information to this image data, may be described as the exchange of image data.

[0080] Next, we will explain each image processing unit (print processing unit 230, loopback processing unit 240, scan processing unit 250) using Figure 7.

[0081] <Print Processing Unit> Figure 7(a) is a block diagram showing the internal structure of the print processing unit 230.

[0082] When the packet input / output interface (PIP) I / F 400 receives packet data, it refers to the chip ID 603 in the header section 610 and checks whether it is the same as the chip ID assigned to it. If the ID indicated by chip ID 603 is different from the chip ID assigned to it, the packet input / output interface (PIP) I / F 400 determines that the packet data should not be processed by its image processing unit and forwards the packet data to the next image processing unit. On the other hand, if the ID indicated by chip ID 603 is the same as the chip ID assigned to it, and the packet is image data, it passes it through the internal image processing path (from the decompressor 401 to the printer image processing unit 403) and performs image processing. Also, if the packet is a command, the packet input / output interface (PIP) I / F 400 refers to the setting address and setting value stored in the data section 620 and sets the coefficients and modes of the specified image processing unit.

[0083] The decompressor 401 decompresses the compressed image data received from the packet input / output interface 400 and restores it to a pixel state that can be processed by subsequent image processing.

[0084] The packet raster conversion unit 402 receives the expanded pixel data from the decompressor 401 and converts it into raster image data. As mentioned above, in this embodiment, the image data in the packet is a 32x32 pixel rectangle. In the electrophotographic image forming apparatus 100, the printing process in the printer unit 140 is performed in raster order (line order), so the packet raster conversion unit 402 converts the arrangement of pixels in the image data into raster order. In this embodiment, RAM 270 is used as a temporary buffer for converting the image data from a 32x32 pixel rectangle to raster order, and the packet raster conversion unit 402 accesses RAM 270 via RAM controller 260.

[0085] The printer image processing unit 403 receives image data converted in raster order from the packet raster conversion unit 402 and performs image processing as pre-processing for printing the image data in the printer unit 140. Specifically, this includes color space conversion processing from RGB to CMYK, intermediate length processing using dithering or error diffusion, and gamma correction. The processed image data is output to the printer unit 140. The printer image processing unit 403 also needs to output image data to the printer unit 140 in conjunction with the startup of the printer unit 140 and the feeding of recording material 11 from the paper feed unit 142. For this reason, the printer image processing unit 403 temporarily writes the image data to the RAM 270 via the RAM controller 260 as a buffer to wait until that timing. Then, the printer image processing unit 403 reads the image data from the RAM 270 in synchronization with the timing of the paper feeding of the recording material 11 and outputs it to the printer unit 140.

[0086] <Loopback processing section> Figure 7(b) is a block diagram showing the internal structure of the loopback processing unit 240.

[0087] When the packet input / output interface (PIP) I / F 410 receives packet data, it refers to the chip ID 603 in the header unit 610 and checks whether it is the same as the chip ID assigned to it. If the ID indicated by chip ID 603 is different from the chip ID assigned to it, the packet input / output interface (PIP) I / F 410 determines that the packet data should not be processed by its image processing unit and forwards the packet data to the next image processing unit. On the other hand, if the ID indicated by chip ID 603 is the same as the chip ID assigned to it, and the packet is image data, it passes it through the internal image processing path (from the decompressor 411 to the loopback image processing unit 412) and performs image processing. Then, when the packet input / output interface (PIP) I / F 410 receives the processed image data from the compressor 413, it adds a header to the image data, formats it as packet data, and sends the packet data to the system control unit 210. Furthermore, if the packet input / output interface 410 is a command, it refers to the setting address and setting value stored in the data section 620 and sets the coefficients and modes of the specified image processing unit.

[0088] The decompressor 411 decompresses the compressed image data received from the packet input / output interface 410 and restores it to a pixel state that can be processed by subsequent image processing.

[0089] The compressor 413 compresses the processed image data received from the loopback image processing unit 412 and outputs it to the subsequent packet input / output interface 410. The compression process is performed to recompress the image data that has been decompressed by the decompressor 411.

[0090] The loopback image processing unit 412 receives image data from the decompressor 411 and performs the image processing that is configured to be performed by the loopback processing unit 240. This function can be used for both printing and scanning processes.

[0091] <Scanning Processing Unit> Figure 7(c) is a block diagram showing the internal structure of the scan processing unit 250.

[0092] When the packet input / output interface (I / F) 420 receives packet data, it refers to the chip ID 603 in the header section 610 and checks whether it is the same as the chip ID assigned to it. If the ID indicated by chip ID 603 is different from the chip ID assigned to it, the packet input / output interface (I / F) 420 determines that the packet data is not to be processed by its image processing unit and forwards the packet data to the next image processing unit. On the other hand, if the ID indicated by chip ID 603 is the same as the chip ID assigned to it, and the packet is a command, the I / F 420 refers to the setting address and setting value stored in the data section 620 and sets the coefficient and mode of the specified image processing unit. Note that since image data is input to the scan processing unit 250 only from the scanner unit 110, the only packets received by the packet input / output interface (I / F) 420 are commands.

[0093] The compressor 421 compresses the image data input from the raster packet conversion unit 422 and outputs it to the subsequent packet input / output interface 420. The compression process is performed to compress the image data of the packet data to be transmitted by the packet input / output interface 420.

[0094] The raster packet conversion unit 422 converts the pixel data input from the scan image processing unit 423 into 32x32 pixel rectangular image data. As mentioned above, in this embodiment, the image data within the packet is a 32x32 pixel rectangle. Therefore, the raster packet conversion unit 422 converts the pixel data input from the scan image processing unit 423 into a rectangle for subsequent packet transmission. In other words, the scanning process in the scanner unit 110 is performed in raster order (line sequence) using a line-type image sensor. Therefore, the raster packet conversion unit 422 converts the arrangement of pixels in the image data into a rectangle. In addition, in this embodiment, RAM 270 is used as a temporary buffer for converting the image data from raster order to a 32x32 pixel rectangle, and the raster packet conversion unit 422 accesses RAM 270 via RAM controller 260.

[0095] The scan image processing unit 423 receives image data from the scanner unit 110 and performs image processing such as shading correction, MTF correction, input gamma correction, and filtering (i.e., generates image data). The scan image processing unit 423 also performs edge detection and thickness discrimination to separate image areas and generates attribute data from the image data. The scan image processing unit 423 is a generation unit that generates image data and attribute data indicating the attributes of the image data, including at least whether or not it is text. This image data and attribute data are used in the print function. Furthermore, the image data is compressed using JPEG compression and the attribute data is compressed using packbits compression by the compressor 421, and the compressed data is used for analysis by the fixing temperature calculation unit 325, which will be described later. The compressor 421 is a compression unit that compresses the image data to generate compressed image data and compresses the attribute data to generate compressed attribute data. The image data after image processing is output to the raster packet conversion unit 422. In addition, the scan image processing unit 423 needs to receive the image data in time with the input transfer speed of the input image data in order to not stop the scanning operation using the image sensor in the scanner unit 110. On the other hand, packet transmission via the packet input / output interface 420 may be delayed if the timing of packet transmission from other image processing units overlaps, resulting in unstable transmission speed. Therefore, the scan image processing unit 423 temporarily writes image data to the RAM 270 via the RAM controller 260 as a temporary buffer image until transmission timing. Then, the scan image processing unit 423 reads the image data from the RAM 270 in synchronization with the packet transmission timing and transmits the image data to the raster packet conversion unit 422.

[0096] <Attribute Data> Next, attribute data in this embodiment will be described. Digital document data created by an application on a host computer (such as a client PC) 500 connected via the network 150 is generally represented by a command system called PDL. PDL is broadly composed of three types of objects. The first is character objects. The second is graphic objects such as vector data including shapes and free curves. The third is natural image (bitmap) objects such as image data obtained by scanning photographs or printed materials. If an object is a character, it consists of data such as a character code to identify which character it is, a font that defines the shape of the character, size information that represents the size of the character, and color information that represents the color of the character. This information cannot be interpreted by the printer unit 140 as is. Therefore, the printer driver on the host computer 500 manages the interface with the printer unit 140. In other words, the printer driver sends a sequence of commands representing objects such as characters, graphics, and natural images (bitmaps) to the rendering unit 352, while performing roles such as synchronization to ensure that the correct image is output. The rendering unit 352 converts the received command sequence into two-dimensional bitmap data that can be properly interpreted by the printer unit 140, and also outputs an attribute map. An attribute map is two-dimensional information in which attribute data for each pixel is assigned to each pixel.

[0097] Figure 8(a) is an explanatory diagram showing an example of the attribute data format used in this embodiment. As shown in Figure 8(a), in this embodiment, the attribute data consists of 4 bits of information.

[0098] The 0th bit of the attribute data is the Bitmap flag. If it is 1, it indicates that the pixel was created from a Bitmap object; if it is 0, it indicates that the pixel was created from a Vector object.

[0099] The first bit of the attribute data is the Character flag. A value of 1 indicates that the pixel is a character, while a value of 0 indicates that it is not a pixel.

[0100] The second bit of the attribute data is the Object flag. A value of 1 indicates that the pixel was generated from an object, while a value of 0 indicates that the pixel was generated from something other than an object.

[0101] The third bit of the attribute data is the color flag. A value of 1 indicates a color pixel, while a value of 0 indicates a grayscale pixel.

[0102] For example, if the 4 bits of attribute data are "0010 (=0 (3rd bit) 0 (2nd bit) 1 (1st bit) 0 (0th bit))", it indicates a background pixel. Similarly, "0110" indicates a character pixel, "0100" indicates a graphic pixel, "0101" indicates an image pixel, and "0111" indicates a line pixel. In these examples, the most significant 3rd bit is 0, indicating that all are grayscale pixels.

[0103] Note that the attribute flags shown here are merely examples; you can simplify the classification by reducing the bit width to separate characters from non-characters, or further subdivide the classification by expanding the bit width to include things like thin lines and lowercase letters.

[0104] In this embodiment, when the rendering unit 352 converts an object into two-dimensional bitmap data, it ultimately determines, pixel by pixel, whether the object was generated from text, graphics, or natural images (bitmaps, images). The rendering unit 352 then generates an attribute map that can be associated with the two-dimensional image data.

[0105] Figure 8(b) is an explanatory diagram showing an example of an attribute map in this embodiment. Figure 8(b) shows an image in which the character object, the number "1", is superimposed on a bitmap object.

[0106] When the rendering unit 352 converts an object into two-dimensional bitmap data, it outputs an attribute data format for each pixel in accordance with the attribute data format shown in Figure 8(a). For example, if the pixel is the character "0110", it outputs 6 (the decimal number corresponding to "0110"), and if the pixel is the background "0010", it outputs 2 (the decimal number corresponding to "0010"), thereby generating an attribute map as shown in Figure 8(b).

[0107] The attribute map can be structured in any way, as long as it stores the attributes of each pixel in a way that allows them to be associated with two-dimensional image data. For example, using an attribute map makes the following possible:

[0108] Figure 8(c) is a schematic diagram showing an example of an image with different attribute ranges. The example image shown in Figure 8(c) will be explained. Range 801 has different attributes, such as a text image, range 802 has different attributes, such as an electronically generated graphic image such as a circle or rectangle, and range 803 has different attributes, such as a natural image such as a photograph read by a scanner. Here, it is also possible that the printer unit 140 can only reproduce binary dots. For example, in this case, the rendering unit 352 expands the object into multi-level bitmap data of Y, M, C, and K. The print processing unit 230 that receives this bitmap data then performs a well-known binarization process such as error diffusion or dithering to convert the multi-level image signal into a binary image signal. After that, printing is performed. At this time, the optimal binarization method varies depending on the attribute of the image. That is, for graphics such as text and figures, it is preferable to use a binarization method that prioritizes resolution by reducing the dither matrix size. On the other hand, for natural images such as photographs, it is preferable to use a larger matrix size that prioritizes gradation reproduction.

[0109] Therefore, using the attribute map described above, it can be seen that the attribute data of each image area is "0110" for the character image in image area 801, "0100" for the graphic image in image area 802, and "0111" for the natural image (bitmap) in image area 803. Accordingly, natural images, character images, and graphic images can be easily separated for each pixel, enabling image processing in accordance with the characteristics of each pixel.

[0110] <packbits compression> Next, the algorithm for packbits compression will be described. The description given here uses the 4-bit attribute data described above.

[0111] In packbits compression, input data is divided into "same data sequence", which is a portion where identical data continues, and "different data sequence", which is a portion where different data continues. Then, a "length" representing the length is added to each sequence. Then, with respect to "same data sequence", runlength compression is performed to combine the data portion into a single data. For example, when the input data is "0,0,0,0,1,2,3,4,4,4,4,4,4,4,4,5,5,6,7,8,8,9,10,10" Consider the following case. First, the above data string is "0,0,0,0, 1,2,3, 4,4,4,4,4,4,4,4, 5,5, 6,7, 8,8, 9, 10,10" As described above, the data is divided into "same data sequence" and "different data sequence". Then, after adding "length" to each part, and further performing runlength compression on "same data sequence", the result is as follows. "(-4),0, (3),1,2,3, (-8),4, (-2),5, (2),6,7, (-2),8, (1),9, (-2),10"

[0112] Here, the value of length is enclosed in parentheses, such as "(-4)", to distinguish it from the data. A negative value for length indicates that the sequence is the "same data sequence," while a value of 0 or positive indicates that the sequence is a "different data sequence." Furthermore, length is converted to a "length code" with a width of 8 bits, just like the data. Figure 9(a) is an explanatory diagram showing the correspondence between length and length code. According to the correspondence table in Figure 9(a), compressing the input data sequence in the above example using packbits results in the following output code. “(0xFD),0,(0x02),1,2,3,(0xF9),4,(0xFF),5,(0x01),6,7,(0xFF),8,(0x00),9,(0xFF),10”

[0113] If we convert the data values ​​to hexadecimal notation and concatenate them all, we get the following: “FD 00 02 01 02 03 F9 04 FF 05 01 06 07 FF 08 00 09 FF 0A”

[0114] In this embodiment, the bit width of the "length code" is assumed to be 8 bits, including the sign, so the maximum value of length is 128. If length is 129 or greater, it is divided into a sequence with length=128 and a sequence with length=(length-128). Similarly, if length≦-129, it is divided into a sequence with length=-128 and a sequence with length=(length+128). However, it should be noted that if length is -129 (129 consecutive data points of the same value), the "same data sequence" is divided into a "same data sequence" with length=-128 and a "different data sequence" with length=1. This "different data sequence" with length=1 then combines with any subsequent "different data sequences" to form a single sequence. Of course, assuming the bit width of the "length code" is 8 bits is just an example, and the "length code" may have a larger bit width.

[0115] Using a portion of the image shown in Figure 8(c) as an example, we will further explain packbits compression using Figure 9(b). Figure 9(b) is an explanatory diagram illustrating an example of packbits compression. In this embodiment, compression is performed using 32x32 pixels per packet, but for the sake of simplicity, we will explain an example of packbits compression of an 8x8 pixel attribute map. The attribute map consists of a character portion, a graphic portion, and a natural image (bitmap, image) portion, and the data arranged from the top left to the right of the 8x8 pixels is compressed up to the bottom right of the 8x8 pixels.

[0116] First, looking at the image shown in Figure 9(b), if we list the attribute data of the three highlighted areas in order from top left to bottom right, we get the following data columns. The data columns are shown in the order of the highlighted areas of the text, graphic, and natural image. *22222222_66662222_6666622_222266222_22266222_22222222_22222222_22222222* '44444444_44444444_44444444_44444444_44444444_44444444_44444444_44444444_44444444_44444444_44444444_44444444_44444444_ "77777222_77777222_77777222_77777222_77777222_22222222_22222222_22222222""

[0117] When converted to consecutive numbers and data values, they are as follows: "(-8)2,(-4)6,(-4)2,(-4)6,(-6)2,(-2)6,(-27)2" “(-64)4” "(-4)7,(-3)2,(-5)7,(-3)2,(-5)7,(-3)2,(-5)7,(-3)2,(-5)7,(-27)2"

[0118] Converting the above "length" to a "length code" according to the table shown in Figure 9(a) and then to a data sequence code results in the following: ““0xF9,0x02,0xFD,0x6,0xFD,0x2,0xFD,0x06,0xFB0x2,0xFF,0x6,0xD5,0x2” “0xC1,0x04” “0xFD,0x07,0xFE,0x02,0xFC,0x07,0xFE,0x2,0xFC,0x07,0xFE,0x02,0xFC,0x07,0xFE,0x02,0xFC,0x7,0xD5,0x2”

[0119] The attribute data corresponding to the 8x8 pixels of the three highlighted areas in Figure 9(b) can each be represented by the code shown above. As can be seen from the example above, the more consecutive identical data there are, the smaller the size of the compressed code becomes.

[0120] In this way, by compressing attribute data using packbits, it becomes possible to reduce the data size when storing it in memory.

[0121] In this embodiment, analyzing the compressed attribute data reduces the processing load compared to analyzing uncompressed attribute data. In this embodiment, the CPU 310 of the system control unit 210 performs this analysis, but a dedicated hardware circuit may be configured to perform the same analysis. Even when processing in hardware, the processing load can be reduced using the method of this embodiment.

[0122] Here, the attribute data is not limited to using attribute data that shows all of the above attributes; it is sufficient to be able to determine the characteristics of the image in which it is desirable to lower the fixing temperature from the normal fixing temperature, for example, to reduce power consumption. Typically, the attribute data used is data that shows the attributes of the image data, including at least whether or not it contains text.

[0123] <Firing temperature control based on attribute data analysis results> Next, we will explain the fixing temperature control based on the analysis results of attribute data in this embodiment. As an example, we will explain a method of controlling the fixing temperature to two types of fixing temperatures lower than the normal fixing temperature, depending on the characteristics of the image data. In other words, the fixing temperature is set to one of three temperatures: a first fixing temperature, a second fixing temperature higher than the first fixing temperature, and a third fixing temperature higher than the second fixing temperature, with the third fixing temperature being the normal fixing temperature. Here, as an example, if "all the data on the page consists of background or text (i.e., the data on the page consists only of background or text), and the text size is less than or equal to a predetermined size," the fixing temperature will be set to the first temperature. Also, here, as an example, if "all the data on the page consists of background or text," but "the text size is larger than a predetermined size," the fixing temperature will be set to the second temperature. Furthermore, here we also determine the fixing temperature based on the density and continuity of the image. This will be explained in detail below.

[0124] {Fixing temperature control} The control of the fixing temperature in this embodiment will be explained using Figure 10. Figure 10(a) is a flowchart showing the process executed by the control of the CPU 310 of the system control unit 210, and Figure 10(b) is a flowchart showing the process executed by the control of the CPU 391 of the printer control unit 280.

[0125] First, using Figure 10(a), we will explain the process executed by the control of the CPU 310 of the system control unit 210.

[0126] In S101, the CPU 310 receives a print job input from the scanner unit 110 or an external device such as a host computer 500 connected via the network 150, and starts the print process.

[0127] In S102, under the direction of the CPU 310, the fuser temperature calculation unit 325 calculates the target fuser temperature for printing the pages to be printed included in the print job. The specific processing performed by the fuser temperature calculation unit 325 in S102 will be described later using the flowcharts in Figures 11 and 12.

[0128] In S103, the CPU 310 notifies the CPU 391 of the printer control unit 280 via the print communication I / F unit 303 of the fixer target temperature information necessary for printing the page to be printed, which was determined in S102.

[0129] In S104, the CPU310 determines whether there is a next page in the print job, and if there is, it repeats the process from S102.

[0130] Next, using Figure 10(b), we will explain the processes executed by the control of the CPU 391 of the printer control unit 280.

[0131] In S201, CPU 391 waits for a print command from CPU 310 of the system control unit 210. If CPU 391 receives a print command from CPU 310 of the system control unit 210, it proceeds to S202.

[0132] In S202, the CPU 391 checks whether it has received the fixation target temperature information necessary for fixing the page to be printed from the CPU 310 of the system control unit 210. If the CPU 391 has received the fixation target temperature information necessary for fixing the page to be printed from the CPU 310 of the system control unit 210 via the system communication I / F unit 396 in S202, the process proceeds to S203. Normally, the fixation target temperature information necessary for fixing the page is received several pages before printing the page in question, but if it has not been received, S202 is executed again after a predetermined time has elapsed to wait for reception. Alternatively, if the fixation target temperature information has not been received, the process may proceed to S203 to prioritize printing and control the system to set the fixation temperature to the fixation temperature corresponding to the maximum toner load (normal fixation temperature) without lowering the fixation target temperature.

[0133] In S203, under the direction of the CPU 391, the fuser temperature control unit 319 controls the fuser device 30 so that the fuser temperature reaches the fuser target temperature received in S202. Specifically, if necessary to reach the fuser target temperature, it controls the power supply to the heaters 34 and 35 to raise the fuser temperature. Also, if it is possible to lower the fuser temperature relative to the fuser target temperature, it controls the fuser temperature to be lowered as necessary. Examples of controls to lower the fuser temperature include waiting until the temperature drops, or using a fan to draw in or exhaust air.

[0134] In S204, CPU391 determines whether the print job is finished or not (whether there is a next page in the print job), and if the print job is not finished, it repeats the process from S202.

[0135] {Determination of fixing temperature} Using Figures 11 and 12, the determination of the fixing temperature using the analysis results of the compressed attribute data in this embodiment will be explained. Figure 11 is a flowchart of the process performed in S102 of Figure 10. Figure 12 is a flowchart of the process performed in S302 of Figure 11.

[0136] First, the determination of the fixing temperature will be explained using Figure 11. The flow shown in Figure 11 is the flow of the fixing temperature determination process that is executed by the CPU 310 of the system control unit 210 in S102 of Figure 10.

[0137] In S301, the CPU 310 determines whether the attribute information contained in the packet data of the page to be printed is compressed. This is done by the CPU 310 referring to the attribute compression flag 611, which is one of the pieces of information in the header portion 650 of the packet of the page to be printed. If the data is compressed, the CPU 310 proceeds to S302. On the other hand, if the data is not compressed, the CPU 310 proceeds to S309. In this embodiment, if the result of the determination in S309 is that the data is not compressed, the analysis is not performed. However, although the processing load will be heavier, the process may proceed to S302 and analyze the uncompressed attribute data.

[0138] In S302, under the direction of the CPU 310, the fixing temperature calculation unit 325 analyzes the compressed attribute information contained in the packet data to be printed and assigns an attribute ID to the packet based on the analysis results. This attribute ID indicates what kind of image features are contained in the packet. The CPU 310 stores the attribute IDs assigned to each packet in the RAM 331.

[0139] Here, we will first explain the process of S302 in Figure 11 using Figure 12. The flow shown in Figure 12 is the flow of the attribute information analysis process executed by the fixing temperature calculation unit 325 at the instruction of the CPU 310 of the system control unit 210 in S302 of Figure 11.

[0140] In S401, the fixing temperature calculation unit 325 determines whether the attribute byte length 609 of the packet is greater than or equal to a predetermined threshold. If it is greater than or equal to the threshold, the unit 325 proceeds to S404; if it is less than (shorter than) the threshold, it proceeds to S402. As per the packbits specifications mentioned above, if there is discontinuous data with different attributes within the packet, the attribute byte length will be larger. For example, if each pixel has a different attribute, there will be multiple data sets with a sequence of "different data sequence" consisting of 128 consecutive attribute data points. This is almost equivalent to analyzing uncompressed data. By checking the attribute byte length in the S401 process, the processing load on the CPU 310 can be reduced.

[0141] In S402, the fixing temperature calculation unit 325 determines whether the attribute data 630 consists only of attributes indicating the background. For example, in the case of the packbits compression method described above, if the data for the length following the sequence is all background, the fixing temperature calculation unit 325 proceeds to the analysis of the next sequence. Then, when an attribute other than the background appears, the fixing temperature calculation unit 325 proceeds to S403. If, after examining all the data, the attribute data 630 consists only of background, the fixing temperature calculation unit 325 proceeds to S405.

[0142] In S403, the fixing temperature calculation unit 325 determines whether the attribute data 630 consists of only two types of attributes: an attribute indicating the background and an attribute indicating the text. If the attribute data 630 consists of only two types of attributes, background and text, the fixing temperature calculation unit 325 proceeds to S406. On the other hand, if the attribute data 630 contains attributes other than background and text, the fixing temperature calculation unit 325 proceeds to S407. In this example, if the attribute data 630 consists only of an attribute indicating the text, the process also proceeds to S407. Thus, if the attribute data 630 consists only of the background attribute, the process proceeds to S405. If the attribute data 630 consists of two types of attributes, background and text, the process proceeds to S406. If the attribute data 630 consists only of the text attribute, or contains attributes other than the two types of attributes background and text, the process proceeds to S407.

[0143] In S404, the fixing temperature calculation unit 325 sets the packet attribute ID to 1. Data with an attribute ID of 1 is data whose attribute data length is greater than or equal to a predetermined threshold. Data with a longer attribute data length has a lower compression ratio and lower continuity of areas with the same attribute, indicating that areas with two or more different attributes are scattered. In other words, it indicates that there are no areas of large characters or images where toner density tends to be high. Therefore, packets with an attribute ID of 1 are areas where toner can be fixed even if a fixing temperature lower than the fixing temperature corresponding to the expected maximum toner load (normal fixing temperature) is set. As this attribute data length threshold, for example, the minimum packet length at which fixing failure may occur if the fixing temperature is not corresponding to the maximum toner load can be set.

[0144] In S405, the fixing temperature calculation unit 325 sets the packet's attribute ID to 2. A packet with attribute ID 2 indicates that it is a packet containing only the background. In other words, there are no graphic areas where toner density tends to be high. Therefore, packets with attribute ID 2 are areas where toner can be fixed even if a fixing temperature lower than the fixing temperature corresponding to the expected maximum toner load (normal fixing temperature) is set.

[0145] In S406, the fixing temperature calculation unit 325 sets the packet's attribute ID to 3. A packet with attribute ID 3 indicates that it is a packet in an area where background and text are mixed. In other words, it indicates that there are no graphic areas where toner density tends to be high. Therefore, a packet with attribute ID 3 can be determined to be an area where toner can be fixed even if a fixing temperature lower than the fixing temperature corresponding to the expected maximum toner load (normal fixing temperature) is set.

[0146] In S407, the fixing temperature calculation unit 325 sets the packet attribute ID to 4. Packets with attribute ID 4 are areas containing only text, or areas containing text and background elements. In other words, they indicate the possibility of areas containing large text or graphics where toner density tends to be high. Therefore, packets with attribute ID 4 are areas where the fixing temperature corresponding to the expected maximum toner load (normal fixing temperature) should be set.

[0147] By performing the above S401-S407 processes on all packets, it becomes possible to determine whether or not the data on the page consists entirely of background or text, which is one of the aforementioned analysis conditions: "all data on the page consists entirely of background or text, and the text size is less than or equal to a predetermined size."

[0148] In this example, packets with attribute data 630 consisting only of characters are assigned attribute ID 4, but the following is also possible. That is, in S306, which will be described later, it is possible to detect large characters by determining whether or not a packet consisting only of characters exists in isolation based on information about the position and continuity of packets within the page. In this case, in S403, packets with attribute data 630 consisting only of characters may be assigned attribute ID 3. Then, if large characters are detected in S306, which will be described later, the temperature should be set to the normal fixing temperature.

[0149] Let's return to the explanation of the fixing temperature determination flow in Figure 11.

[0150] In S303, if the attribute ID assigned by the attribute information analysis in S302 is 1, 2, or 3, the CPU 310 proceeds to S304. On the other hand, if the attribute ID is anything else (i.e., attribute ID is 4), the CPU 310 proceeds to S309. This process allows the CPU 310 to reduce its processing load by deciding not to lower the fixing temperature (fixing target temperature, fixing temperature control setting temperature) from the normal fixing temperature in the case of attributes other than background and text, and by not analyzing the remaining packets.

[0151] In S304, the CPU310 determines, based on the Thumbnail data612, whether the average density is below a predetermined threshold. The higher the average density, the higher the toner density. Therefore, if the average density is greater than the threshold, it is necessary to set the fixing temperature (normal fixing temperature) corresponding to the expected maximum toner load, regardless of the attribute ID value. As this average density threshold, for example, the minimum average density at which fixing failure may occur if the fixing temperature is not corresponding to the maximum toner load can be set. If the average density is below the threshold, the CPU310 proceeds to S305. On the other hand, if the average density is greater than the threshold, the CPU310 proceeds to S309. This process reduces the processing load on the CPU310 by determining that the fixing temperature (fixing target temperature, fixing temperature control setting temperature) should not be lowered from the normal fixing temperature if there are packets with high density, and by not analyzing the remaining packets. In other words, by performing the density determination described above for all packets on one page, the CPU 310 (fixing temperature calculation unit 325) can obtain information on the average density of the image across the entire image-forming area of ​​one page without decompressing the compressed attribute data. Then, if the average density is greater than a predetermined threshold, the CPU 310 (fixing temperature calculation unit 325) can determine that the fixing temperature should not be lowered from the normal fixing temperature, regardless of the compressed attribute data.

[0152] In S305, CPU310 determines whether the analysis of all packets for one page has been completed. If it has been completed, it proceeds to S306; otherwise, it repeats the process from S302.

[0153] In S306, the CPU 310 determines whether the continuity in the main scanning direction (direction approximately perpendicular to the recording material transport direction) and the continuity in the sub-scanning direction (direction of recording material transport direction) of packets with attribute ID 3 assigned by attribute information analysis in S302 are below a predetermined threshold. The greater the continuity of packets with attribute ID 3, i.e., packets containing background and characters, the greater the possibility of large character areas existing. Large characters have a higher toner density. Therefore, if at least one of the continuity in the main scanning direction or the sub-scanning direction is greater than the threshold, it is desirable to set a fixing temperature corresponding to the expected maximum toner load (normal fixing temperature, third fixing temperature) or a fixing temperature relatively close to this (second fixing temperature). The thresholds for continuity in the main scanning direction and the continuity in the sub-scanning direction can be set appropriately in consideration of fixing performance, etc. For example, for characters with a size of 12pt or larger, fixing failure may occur if the fixing temperature is not the same as the fixing temperature corresponding to the maximum toner load (normal fixing temperature, third fixing temperature) or a fixing temperature relatively close to it (second fixing temperature). In this case, the number of consecutive packets corresponding to the size of 12pt can be set as the continuity threshold for the main scanning direction and the continuity threshold for the sub-scanning direction. The continuity threshold for the main scanning direction and the continuity threshold for the sub-scanning direction may be the same value or different values. If the continuity of both the main scanning direction and the sub-scanning direction is below the threshold, the CPU 310 proceeds to S307. On the other hand, if the continuity of at least one of the main scanning direction or the sub-scanning direction is greater than the threshold, the CPU 310 proceeds to S308.

[0154] In this embodiment, one packet consists of 32 x 32 pixels. At a resolution of 600 dpi, one pixel is equivalent to 43 μm; therefore, if one packet consists entirely of characters, its dimensions will be approximately 1.3 mm x 1.3 mm or larger. Thus, the character size can be determined by the number of consecutive scans in the main or sub-scanning direction. Consequently, it becomes possible to determine whether the character size is less than or equal to a predetermined size, fulfilling the aforementioned analysis condition that "all data on the page consists of background or characters, and the character size is less than or equal to a predetermined size."

[0155] Furthermore, if the value in S306 is greater than the threshold, the process may proceed to S309. In other words, the fixing temperature setting may be set to two types, corresponding to the first fixing temperature and the third fixing temperature in this embodiment.

[0156] In S307, the CPU310 sets the fixing target temperature to a first fixing temperature. The first fixing temperature is lower than the second fixing temperature. The first fixing temperature can be set appropriately in consideration of fixing performance, etc. For example, the first fixing temperature can be set to a fixing temperature 9°C lower than the fixing temperature corresponding to the expected maximum toner load (normal fixing temperature, third fixing temperature).

[0157] In S308, the CPU310 sets the fixing target temperature to the second fixing temperature. The second fixing temperature is lower than the third fixing temperature and higher than the first fixing temperature. The second fixing temperature can be set appropriately in consideration of fixing performance, etc. For example, the second fixing temperature can be set to a fixing temperature 5°C lower than the fixing temperature corresponding to the expected maximum toner load (normal fixing temperature, third fixing temperature).

[0158] In S309, the CPU 310 sets the fixing target temperature to the third fixing temperature. The third fixing temperature is higher than the second fixing temperature. The third fixing temperature can be set appropriately in consideration of fixing performance, etc. For example, the third fixing temperature can be set to a fixing temperature corresponding to the expected maximum toner load (normal fixing temperature). Thus, typically, the third fixing temperature (third temperature) is the fixing target temperature when the entire image-forming area of ​​one page is an image with the maximum toner load in the image forming apparatus 100 (image forming unit 160). The second fixing temperature (second temperature) is lower than the third fixing temperature, and the first fixing temperature (first temperature) is lower than the second fixing temperature.

[0159] As described above, in this embodiment, the image forming apparatus 100 includes an image forming unit 160 that forms an image on a recording material 11 with toner based on image data, a fixing unit 30 that applies heat to the recording material 11 on which the image has been formed by the image forming unit 160 to fix the image to the recording material 11, a generation unit (rendering unit) 352 that generates image data and also generates attribute data indicating the attributes of the image data, including at least whether or not it is text, a compression unit (image compression unit) 350 that compresses the image data to generate compressed image data and compresses the attribute data to generate compressed attribute data, a setting unit (fixing temperature calculation unit) 325 that analyzes the compressed image data or compressed attribute data of a one-page image formed on one sheet of recording material 11 in a compressed state and sets a target temperature for the fixing unit 30 when fixing the one-page image to the recording material 11 based on the analysis results, and a control unit (fixing temperature control unit) 319 that controls the fixing unit 30 based on the target temperature set by the setting unit 325.

[0160] In this embodiment, if the analysis result indicates that the image data of the image on the first page consists of two types of attribute data: background and text, the setting unit 325 sets the target temperature to a first temperature lower than the temperature when the entire image-forming area of ​​the first page is an image with the maximum toner load. In this embodiment, if the analysis result indicates that all attribute data of the image data on the first page is background, the setting unit 325 sets the target temperature to a first temperature lower than the temperature when the entire image-forming area of ​​the first page is an image with the maximum toner load. In this embodiment, if the analysis result indicates that the size of the compressed image data or compressed attribute data of the image on the first page is above a predetermined threshold, the setting unit 325 sets the target temperature to a first temperature lower than the temperature when the entire image-forming area of ​​the first page is an image with the maximum toner load. Furthermore, in this embodiment, if the analysis result indicates that the image data of the image on the one page consists of image data with two types of attributes: background and text, the setting unit 325 sets the target temperature to a first temperature lower than the temperature when the entire image-forming area of ​​the one page is an image with the maximum toner load, if the number of consecutive images of background or text attributes in the image on the one page in the transport direction of the recording material 11 is less than or equal to a predetermined threshold, and sets the target temperature to a second temperature higher than the first temperature and lower than the temperature when the entire image-forming area of ​​the one page is an image with the maximum toner load, if the number of consecutive images is greater than the predetermined threshold, the setting unit 325 sets the target temperature to a second temperature higher than the first temperature and lower than the temperature when the entire image-forming area of ​​the one page is an image with the maximum toner load. Furthermore, in this embodiment, if the analysis result indicates that the image data of the image on the one page consists of image data with two types of attributes: background and text, the setting unit 325 sets the target temperature to a first temperature lower than the temperature when the entire image-forming area of ​​the one page is an image with the maximum toner load, if the number of consecutive images of background or text attributes in the image on the one page in a direction substantially perpendicular to the transport direction of the recording material 11 is less than or equal to a predetermined threshold, and if the number of consecutive images is greater than the predetermined threshold, the setting unit 325 sets the target temperature to a second temperature higher than the first temperature and lower than the temperature when the entire image-forming area of ​​the one page is an image with the maximum toner load.

[0161] Furthermore, in this embodiment, if the analysis result indicates that all attributes of the image data of the image on the page are text, or if the image data of the image on the page includes image data with attributes other than the two types of attributes, background and text, the setting unit 325 sets the target temperature to a third temperature higher than the first temperature. Furthermore, in this embodiment, if the analysis result indicates that all attributes of the image data of the image on the page are text, or if the image data of the image on the page includes image data with attributes other than the two types of attributes, background and text, the setting unit 325 sets the target temperature to a third temperature higher than the second temperature. Furthermore, in this embodiment, if the average density of the image across the entire image-forming area of ​​the page, which is acquired without decompressing the compressed image data and compressed attribute data, is greater than a predetermined threshold, the setting unit 325 sets the target temperature to a third temperature higher than the first temperature, regardless of the compressed image data and compressed attribute data. The third temperature is, for example, the temperature when the entire image-forming area of ​​the page is an image with the maximum toner amount. Furthermore, the third temperature is, for example, a higher temperature than the second temperature. In this embodiment, the generation unit 352 generates image data and attribute data for each region into which the image of one page has been divided, and generates multiple packets containing the image data and attribute data for each divided region. The compression unit 350 compresses the image data and attribute data for each packet. The control unit 319 analyzes the compressed image data or compressed attribute data for each packet in its compressed state to obtain the analysis results for the image of one page. In this embodiment, the control unit 319 also analyzes the compressed attribute data in its compressed state to obtain the analysis results.

[0162] As explained above, in this embodiment, by analyzing compressed attribute data in its compressed state, the processing load of image analysis can be reduced while determining the fixing temperature. Here, attribute data is data generated in advance for use in image processing to identify backgrounds, text, photographs, etc. Therefore, according to this embodiment, in a configuration that controls the fixing temperature according to the image to be printed, the processing load of image analysis can be reduced while determining the fixing temperature. As a result, power consumption can be reduced by controlling the fixing temperature according to the image characteristics.

[0163] In this embodiment, three types of fixing temperature settings (fixing target temperatures) were used, but the system is not limited to these. Although the processing load will be heavier than with three types, the fixing temperature settings can be further subdivided into four or more types by performing a more detailed analysis, thereby increasing the power saving effect. The types of fixing temperature settings can be appropriately selected from, for example, two to ten types. Conversely, the processing load can be reduced by making the analysis less detailed. For example, the processing in S306 may be omitted, and the fixing target temperature may be set to two types, corresponding to the second and third fixing temperatures in this embodiment. Alternatively, the processing in S304 may be omitted, and the fixing temperature may be set based on whether the image on a page consists only of two types of attributes (background and text) (or only background), or whether it includes images with attributes other than background and text (photographs, graphics). In this case, for example, a lower fixing temperature than the normal fixing temperature can be set for the former type of image, and the normal fixing temperature can be set for the latter type of image. In this case as well, the character size can be determined by the same process as in S306, and the fixing temperature can be changed according to the character size, as in this embodiment.

[0164] Furthermore, although this embodiment describes the attribute data compression method as the packbits method, other compression methods may also be used.

[0165] Furthermore, in this embodiment, the fixing temperature was controlled by analyzing compressed attribute data, but the compressed image data may also be analyzed. For example, if it can be determined from the compression code of the compressed image data that the page contains only black pixels corresponding to characters and pixels of a predetermined color corresponding to the background (and furthermore, the size of the characters is less than or equal to a predetermined size), the fixing temperature can be controlled to be lower than the normal fixing temperature. In this case, the same effects as in the above embodiment can be obtained.

[0166] [others] Although the present invention has been described above with reference to specific embodiments, the present invention is not limited to the embodiments described above.

[0167] In the above-described embodiment, image data and attribute data were generated for each region obtained by dividing a single page image into multiple regions with a predetermined number of pixels, evenly distributed in the main scanning direction and the sub-scanning direction. However, the single page image may be divided unevenly in at least one of the main scanning direction or the sub-scanning direction.

[0168] Furthermore, it is also possible to compress image data and attribute data without dividing a single page of image data, analyze the compressed image data or attribute data, and set and control the fixing temperature based on the analysis results.

[0169] Furthermore, in the above-described embodiment, the system control unit performed attribute analysis, set a target fixing temperature based on the analysis results, and the printer control unit controlled the fixing unit to achieve the set target fixing temperature. However, the system configuration is not limited to this, and any configuration is acceptable as long as it yields results similar to those described in the above-described embodiment. For example, the system control unit may perform attribute analysis, the printer control unit may set a target fixing temperature based on the analysis results, and the fixing unit may be controlled to achieve the set target fixing temperature.

[0170] In the above-described embodiment, the image forming apparatus was a color image forming apparatus, but the present invention can also be applied to a monochrome (e.g., black monochrome) image forming apparatus.

[0171] Furthermore, the present invention may be considered as an image forming apparatus that performs the processing described in the above embodiments, or as an image forming method using such an image forming apparatus, or as a control method for an image forming apparatus.

[0172] Furthermore, the present invention can also be realized by supplying a program that implements one or more of the functions of the above embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions.

[0173] Furthermore, each process in each embodiment may be realized by the method by which the computer executes the program. The program may be provided to the computer, for example, via a network or from a computer-readable recording medium that holds data non-temporarily. The program may also be recorded on a computer-readable recording medium. [Explanation of Symbols]

[0174] 30 Fixing device 100 Image forming apparatus 120 Controller section 140 Printer Section 210 System Control Unit 280 Printer Control Unit 310 System Control Unit CPU 319 Fixing Temperature Control Unit 325 Fixing temperature calculation unit 391 CPU of the printer control unit

Claims

1. An image forming unit that forms an image on a recording material with toner based on image data, A fixing unit applies heat to the recording material on which an image has been formed by the image forming unit to fix the image to the recording material, A generation unit that generates the aforementioned image data and also generates attribute data indicating the attributes of the aforementioned image data, including at least whether or not it is text. A compression unit that compresses the aforementioned image data to generate compressed image data, and compresses the aforementioned attribute data to generate compressed attribute data, A setting unit that analyzes the compressed image data or compressed attribute data of a one-page image formed on a single recording material in its compressed state, and sets the target temperature of the fixing unit when fixing the one-page image to the recording material based on the analysis results, A control unit that controls the fixing unit based on the target temperature set by the setting unit, An image forming apparatus characterized by having the following features.

2. The image forming apparatus according to claim 1, wherein the setting unit sets the target temperature to a first temperature lower than the temperature when the entire image-forming area of ​​the one page is an image with the maximum toner amount, if the analysis result indicates that the image data of the one page consists of two types of attributes: background and text.

3. The image forming apparatus according to claim 1, wherein the setting unit sets the target temperature to a first temperature lower than the temperature when the entire image-formable area of ​​the one page is an image with the maximum toner amount, when the analysis result indicates that all attributes of the image data of the one page are background.

4. The image forming apparatus according to claim 1, characterized in that, when the setting unit indicates that the size of the compressed image data or compressed attribute data of the image on one page is greater than or equal to a predetermined threshold, it sets the target temperature to a first temperature lower than the temperature when the entire image-forming area of ​​one page is an image with the maximum toner amount.

5. The image forming apparatus according to claim 1, characterized in that, when the analysis result indicates that the image data of the image on one page consists of two types of attributes, background and text, the setting unit sets the target temperature to a first temperature lower than the temperature when the entire image-forming area of ​​the one page is an image with the maximum toner load, when the number of consecutive images of background or text attributes in the transport direction of the recording material in the image on one page is less than or equal to a predetermined threshold, and when the number of consecutive images is greater than the predetermined threshold, the target temperature is set to a second temperature higher than the first temperature and lower than the temperature when the entire image-forming area of ​​the one page is an image with the maximum toner load.

6. The image forming apparatus according to claim 1, characterized in that, when the analysis result indicates that the image data of the image of the one page consists of two types of attributes, background and text, the setting unit sets the target temperature to a first temperature lower than the temperature when the entire image-forming area of ​​the one page is an image with the maximum toner load, when the number of consecutive images of the background or text attribute in the one page image is less than or equal to a predetermined threshold, and when the number of consecutive images is greater than the predetermined threshold, the target temperature is set to a second temperature higher than the first temperature and lower than the temperature when the entire image-forming area of ​​the one page is an image with the maximum toner load.

7. The image forming apparatus according to any one of claims 1 to 4, wherein the setting unit sets the target temperature to a third temperature higher than the first temperature when the analysis result indicates that all attributes of the image data of the image on the one page are text, or when the image data of the image on the one page includes image data with attributes other than the two types of attributes of background and text.

8. The image forming apparatus according to claim 7, characterized in that the third temperature is the temperature when the entire image-forming area of ​​one page is an image with the maximum amount of toner applied.

9. The image forming apparatus according to claim 5 or 6, wherein the setting unit sets the target temperature to a third temperature higher than the second temperature when the analysis result indicates that all attributes of the image data of the image on the one page are text, or when the image data of the image on the one page includes image data with attributes other than the two types of attributes of background and text.

10. The image forming apparatus according to claim 9, characterized in that the third temperature is the temperature when the entire image-forming area of ​​one page is an image with the maximum amount of toner applied.

11. The image forming apparatus according to any one of claims 1 to 4, characterized in that, if the average density of the image in the entire image-forming region of the one page, which is acquired without decompressing the compressed image data and the compressed attribute data, is greater than a predetermined threshold, the setting unit sets the target temperature to a third temperature higher than the first temperature, regardless of the compressed image data and the compressed attribute data.

12. The image forming apparatus according to claim 11, characterized in that the third temperature is the temperature when the entire image-forming area of ​​one page is an image with the maximum amount of toner applied.

13. The image forming apparatus according to claim 5 or 6, characterized in that, if the average density of the image in the entire image-forming area of ​​the one page, which is acquired without decompressing the compressed image data and the compressed attribute data, is greater than a predetermined threshold, the setting unit sets the target temperature to a third temperature higher than the second temperature, regardless of the compressed image data and the compressed attribute data.

14. The image forming apparatus according to claim 7, characterized in that the third temperature is the temperature when the entire image-forming area of ​​one page is an image with the maximum amount of toner applied.

15. The generation unit generates the image data and attribute data for each region into which the image of one page has been divided, and generates multiple packets containing the image data and attribute data for each divided region. The compression unit compresses the image data and attribute data for each packet. The image forming apparatus according to claim 1, characterized in that the control unit analyzes the compressed image data or compressed attribute data for each packet in a compressed state and obtains the analysis result for the image on one page.

16. The image forming apparatus according to claim 1, characterized in that the control unit analyzes the compressed attribute data in a compressed state and obtains the analysis result.

Images