Image processing device, image processing method, and program

Abstract

To provide an image processing device, a method, and a program that can rotate an image and output it without causing a difference in image quality compared with an image output without rotation.SOLUTION: An image processing device includes a storage serving as a memory unit for storing a plurality of dither matrices, an acquisition unit for acquiring an image, and a control unit for selecting one of the plurality of dither matrices on the basis of information regarding dot arrangement, performing halftone processing, and generating an output image when performing a process for rotating the image acquired by the acquisition unit.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to an image processing device and the like. [Background technology]

[0002] For example, as shown in Patent Document 1, there is known an image processing apparatus that is set to reduce the difference in dot gain that occurs between the printed image based on the print image data after rotation processing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5061144 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present disclosure is to provide an image processing device or the like that, for example, rotates an image before outputting it, but does not result in a difference in image quality compared to an image that is output without being rotated. [Means for solving the problem]

[0005] The image processing device of the present disclosure includes a memory unit that stores a plurality of dither matrices, an acquisition unit that acquires an image, and a control unit that, when performing a process of rotating the image acquired by the acquisition unit, selects one of the plurality of dither matrices based on information regarding dot arrangement, performs halftoning, and generates an output image.

[0006] The image processing method of the present disclosure includes a storage step for storing a plurality of dither matrices, an acquisition step for acquiring an image, and a control step for selecting one of the plurality of dither matrices based on information regarding dot arrangement, performing halftoning processing, and generating an output image when performing a process for rotating the image acquired in the acquisition step.

[0007] The image processing program of the present disclosure provides a computer with a storage function for storing a plurality of dither matrices, an acquisition function for acquiring an image, and a control function for selecting one of the plurality of dither matrices based on information regarding dot arrangement, performing halftoning processing, and generating an output image when executing a process for rotating the image acquired by the acquisition function. [Effects of the Invention]

[0008] According to the present disclosure, for example, it is possible to provide an image processing device or the like in which even if an image is rotated and output, there is no difference in image quality compared to an image output without rotation. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a diagram illustrating the overall configuration of an image processing device according to a first embodiment. [Figure 2] FIG. 1 is a diagram illustrating a hardware configuration of an image processing device according to a first embodiment. [Figure 3] FIG. 2 is a diagram illustrating a software configuration according to the first embodiment. [Figure 4] 1A and 1B are diagrams illustrating an example of job setting information, an example of a normal dither matrix, an example of a specific dither matrix, and an example of screen processing information in the first embodiment. [Figure 5] FIG. 2 is a diagram illustrating the configuration of an image processing unit in the first embodiment. [Figure 6] FIG. 3 is a diagram illustrating halftone processing in the first embodiment. [Figure 7] FIG. 3 is a diagram illustrating halftone processing in the first embodiment. [Figure 8] FIG. 2 is a diagram illustrating a processing flow in the first embodiment. [Figure 9] FIG. 2 is a diagram illustrating an example of operation in the first embodiment. [Figure 10] FIG. 2 is a diagram illustrating an example of operation in the first embodiment. [Figure 11] FIG. 2 is a diagram illustrating an example of operation in the first embodiment. [Figure 12] FIG. 10 is a diagram for explaining a software configuration in a second embodiment. [Figure 13] 10A is a diagram illustrating an example of a normal sub-matrix, FIG. 10B is a diagram illustrating an example of a specific sub-matrix, and FIG. 10C is a diagram illustrating an example of screen processing information in the second embodiment. [Figure 14] FIG. 10 is a diagram illustrating a processing flow in the second embodiment. [Figure 15] FIG. 10 is a diagram illustrating an example of operation in the second embodiment. [Figure 16] FIG. 10 is a diagram for explaining a software configuration in a third embodiment. [Figure 17] 13A is a diagram illustrating an example of a dither matrix DB according to a third embodiment, and FIG. 13B is a diagram illustrating an example of gap determination information according to a third embodiment. [Figure 18] FIG. 10 is a diagram illustrating a processing flow in the third embodiment. [Figure 19] FIG. 10 is a diagram illustrating an example of operation in the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Generally, when an image processing device performs halftone processing in image processing, it reads various screens from a storage unit and performs screen processing. Screen processing includes binarization processing and multi-value processing (multi-bit processing). Here, for example, in screen processing using multi-bit processing, it is known that a difference in image quality occurs when the image processing device rotates an image by 180 degrees and outputs the image and the original image, for example, when the image forming device prints and outputs the image.

[0011] When an image forming apparatus equipped with an image processing apparatus reads a double-sided document or a plurality of documents and performs double-sided copying, there is a problem that the image quality of the front and back sides of the printed material may differ.

[0012] The image processing device of the present disclosure will be described below with reference to the drawings. Note that the following embodiments are merely examples of the invention described in the claims, and the technical scope of the present invention is not limited to the description of the following embodiments.

[0013] [1. First embodiment] A first embodiment will be described below. Note that the first embodiment will be described using the following as an example. In the following embodiment, a case will be described in which the image processing device of the present disclosure is applied to an image forming device, but it can also be applied to other devices.

[0014] [1.1 Overall structure] FIG. 1 is a perspective view of an image forming apparatus 10. As shown in FIG.

[0015] The image forming apparatus 10 is, for example, a device called a multifunction peripheral or an MFP (Multifunction Peripheral / Printer / Product). For example, when the image forming apparatus 10 executes a job (print job), it can form an image on a recording medium, that is, paper. The image forming apparatus 10 can execute jobs for a plurality of processes, such as copy processing, fax processing, scan processing, and print processing.

[0016] For example, in a copy process, the image forming apparatus 10 can read a double-sided document or multiple single-sided documents and output double-sided printed materials. The image forming apparatus 10 may have, for example, an ADF (Automatic Document Feeder) that can read a double-sided document or multiple single-sided documents.

[0017] The image forming apparatus 10 can be connected to a network. The network (NW) connected to the image forming apparatus 10 may be any communication line or communication system, such as a wired or wireless LAN (Local Area Network), a VLAN (Virtual Local Area Network), the Internet, a public line network, mobile communications (e.g., mobile communications such as 4G / 5G / 6G), or a next-generation telephone network.

[0018] [1.2 Hardware Configuration] The image forming apparatus will be described below with reference to the drawings. Figure 2 shows an example of an image forming apparatus 10.

[0019] As shown in FIG. 2, the image forming apparatus 10 has a control unit 100, a storage 110 as a storage device (storage unit), a ROM 120, and a RAM 130, a display unit 140, an operation unit 150, an image forming unit 160, an image reading unit 165, and a communication unit 170.

[0020] The control unit 100 controls the entire image forming apparatus 10. The control unit 100 realizes various functions by reading and executing various programs stored in a storage device (for example, storage 110 or ROM 120). The control unit 100 may be realized by one or more control devices / arithmetic units (CPUs (Central Processing Units), SoCs (System on a Chip)). The control unit 100 may also be configured by a control circuit.

[0021] The storage 110 is a non-volatile storage device capable of storing programs and data. For example, the storage 110 may be configured as one or more storage devices such as a hard disk drive (HDD) or a solid state drive (SSD). The storage 110 may also be configured as an external device such as a USB memory that can be connected to the image forming apparatus 10. The storage 110 may also be a storage area on a cloud, for example.

[0022] The ROM 120 is a non-volatile memory that can retain programs and data even when the power is turned off.

[0023] The RAM 130 is a main memory that is mainly used when the control unit 100 executes processing. The RAM 130 is a rewritable memory that temporarily stores programs read from the storage 110 or the ROM 120, and data including execution results.

[0024] The display unit 140 is a display device capable of displaying various types of information and execution screens. The display unit 140 may be, for example, a liquid crystal display (LCD), an organic electroluminescence (EL) display, an electrophoretic display, or other display device. The display unit 140 also includes an interface to which a display device can be connected. For example, the display unit 140 may be configured as an external display device connected via an HDMI (registered trademark) High-Definition Multimedia Interface, a DVI (Digital Visual Interface), or a Display Port.

[0025] The operation unit 150 is an operation device that allows a user to input operations. For example, it may be software keys displayed on a touch panel integrated with the display unit 140, or hardware keys such as operation buttons. The operation unit 150 may also be an operation device such as a keyboard or a mouse. The operation unit 150 may also include an interface (for example, a Universal Serial Bus (USB)) to which an operation device can be connected. For example, the image forming apparatus 10 may be connected to a different operation device (such as a keyboard or a mouse) via an interface.

[0026] The image forming unit 160 forms an image, for example, on recording paper. The image forming unit 160 includes, for example, an image carrier, a charging device that uniformly charges the image carrier, an image writing device that forms an electrostatic latent image on the image carrier, such as an LSU (Laser Scanning Unit), and a developing device that converts the electrostatic latent image into a toner image, and forms an image by transferring the toner image on the image carrier onto recording paper. The image forming unit 160 may be configured as an image forming device such as a printer. Alternatively, the image forming unit 160 may form an image electronically as an image file.

[0027] Image reading unit 165 reads an original (image) and outputs it as image data. Image reading unit 165 is, for example, a scanner, and may be a reading device using a CCD (Charge Coupled Device), a CIS (Contact Image Sensor), or a CMOS (Complementary Metal-Oxide-Semiconductor) image sensor.

[0028] The communication unit 170 is a communication interface for communicating with other devices. For example, it may be a network interface that can provide a wired connection or a wireless connection. In this embodiment, communication with other devices is possible via a network NW.

[0029] [1.3 Software Configuration] [1.3.1 Image forming device] The main software configuration of the image forming apparatus 10 will be described with reference to Fig. 3. Fig. 3 is a diagram showing the software configuration of the image forming apparatus 10. Note that the software configuration shown in Fig. 3 mainly describes the configuration required in this embodiment, and other configurations are omitted.

[0030] First, we will explain the main software configuration of the image forming apparatus 10. For example, the control unit 100 can realize an image rotation processing unit 1010 and an image processing unit 1020 by reading and executing programs stored in a memory unit (storage 110, ROM 120).

[0031] The image rotation processing unit 1010 performs image rotation processing. The image rotation processing unit 1010 may perform image rotation processing using, for example, an affine transformation. The image rotation processing unit 1010 may also perform rotation processing using an algorithm such as a nearest neighbor method or a bilinear interpolation method. The image rotation processing unit 1010 may also be included in the image processing unit 1020, which will be described later.

[0032] Image processing unit 1020 controls image processing of the image forming apparatus. Image processing unit 1020 performs various types of image processing, such as sharpness processing, region separation processing, and gradation reproduction processing, as general image processing, on image data input from image reading unit 165. Image processing unit 1020 outputs the processed image data to image forming unit 160.

[0033] The image processing unit 1020 may be included as hardware in the image forming apparatus 10. In this case, the image processing unit 1020 may include, for example, a control unit and a storage unit (storage, ROM, RAM). The image processing unit 1020 will be described later.

[0034] The storage 110 also reserves an area for a job setting information storage area 1100 that stores job setting information. Here, the job setting information is information for executing jobs for multiple processes, such as copy processing, fax processing, scan processing, and print processing, in the image forming apparatus 10. The job setting information stores setting items and setting values. For copy processing (copy job), an example of the job setting information is information such as paper size, copy magnification, and number of copies.

[0035] 4(a) will be used to explain an example of job setting information stored in the job setting information storage area 1100. Setting items (e.g., "double-sided printing") and setting values ​​(e.g., "enabled") of the job settings of the image forming apparatus 10 are stored.

[0036] Furthermore, storage 110 reserves an area for normal dither matrix storage area 1110 for storing normal dither matrices. A normal dither matrix refers to, for example, a dither matrix selected in screen processing for normal output. In this embodiment, normal output refers to output without rotation. For example, when image forming apparatus 10 outputs double-sided printouts, this corresponds to the output of the front printing surface and the output of the back printing surface without rotation. The normal dither matrix stores the positions of the smallest dots that make up the dither matrix and the order in which dots grow to form a dither pattern. Dither matrices and dither patterns will be described later.

[0037] 4(b) will be used to explain an example of a normal dither matrix stored in the normal dither matrix storage area 1110. The position of the smallest dot in the normal dither matrix (e.g., "c2") and the dot growth order (e.g., "1") are stored.

[0038] Furthermore, the storage 110 allocates an area for a specific dither matrix storage area 1120 that stores a specific dither matrix. A specific dither matrix refers to, for example, a dither matrix selected in screen processing for a specific output. In this embodiment, when outputting a double-sided print, the specific output refers to the output of the back printing surface after 180-degree rotation processing. The specific dither matrix differs from a normal dither matrix in that, for example, the LPI (screen ruling: lines per inch) and rotation angle are the same as a normal dither matrix, but the dot growth order is changed. Note that the specific dither matrix may be, for example, a dither matrix for 180-degree rotation. The specific dither matrix stores the position of the smallest dot that constitutes the specific dither matrix and the dot growth order for forming a dither pattern.

[0039] 4(c) will be used to explain an example of a specific dither matrix stored in the specific dither matrix storage area 1120. The position of the smallest dot of the specific dither matrix (e.g., "c2") and the order of dot growth for forming the dither pattern (e.g., "6") are stored.

[0040] Furthermore, the storage 110 allocates an area for a screen processing information storage area 1130 for storing screen processing information. The screen processing information is information related to laser writing for forming a dither pattern. The screen processing information stores laser writing positions and pixel values ​​corresponding to the writing positions.

[0041] 4(d) will be used to explain an example of the screen processing information stored in the screen processing information storage area 1130. The laser writing position (e.g., "c2") and the pixel value (e.g., "15") corresponding to the writing position are stored.

[0042] [1.3.2 Image processing section] The image processing unit 1020 will be described below with reference to the drawings.

[0043] As shown in FIG. 5, the image processing unit 1020 includes an A / D (analog / digital) conversion unit 202, a shading correction unit 204, a region separation processing unit 206, a first color space conversion unit 208 that converts the color space from RGB to YCbCr, a YCbCr correction unit 210, a spatial filter processing unit 212, a second color space conversion unit 214 that converts the color space from YCbCr to RGB, a color correction unit 216, a black generation and undercolor removal unit 218, an output tone correction unit 220, and a tone reproduction processing unit 222.

[0044] For example, the image processing unit 1020 outputs image data input from the image reading unit 165 to the image forming unit 160 as image data ultimately represented by digital color signals corresponding to each of CMYK (C: cyan, M: magenta, Y: yellow, K: black).

[0045] The A / D conversion unit 202 converts image data composed of analog RGB (R: red, G: green, B: blue) signals input from the image reading unit 165 into image data of analog signals corresponding to each of the RGB components into image data of digital signals. The A / D conversion unit 202 outputs the image data to the shading correction unit 204.

[0046] The shading correction unit 204 performs processing on the image data of the digital signal corresponding to RGB sent from the A / D conversion unit 202 to remove various distortions that occur in the illumination system, imaging system, and imaging system of the image reading unit 165. The shading correction unit 204 also adjusts the color balance.

[0047] Furthermore, the shading correction unit 204 outputs RGB density signals (hereinafter, unless otherwise specified, density signals represent signals that represent pixel values) to the segmentation processing unit 206 as image data.

[0048] The region separation processing unit 206 performs region separation processing to determine whether each pixel in the input image data input from the shading correction unit 204 belongs to a background region, a photographic region (continuous tone region), a character region, or a halftone region, based on the RGB density signal. The region separation processing unit 206 also generates a region identification signal indicating which region each pixel belongs to based on the result of the region separation processing, and outputs this to the spatial filter processing unit 212, the color correction unit 216, the black generation and under color removal unit 218, and the tone reproduction processing unit 222, and also outputs the RGB signal input from the shading correction unit 204 directly to the downstream first color space conversion unit 208.

[0049] The first color space conversion unit 208 (color space conversion (RGB to YCbCr) unit) converts the RGB image data input from the region separation processing unit 206 into YCbCr image data. The first color space conversion unit 208 outputs the YCbCr image data to the YCbCr correction unit 210.

[0050] The YCbCr correction unit 210 performs background density removal processing (for example, processing to change the background density to white density) and image quality adjustment processing such as contrast adjustment processing on the YCbCr image data input from the first color space conversion unit 208. The YCbCr correction unit 210 outputs the image data of the YCbCr signal to the spatial filter processing unit 212.

[0051] The spatial filtering processing unit 212 performs spatial filtering using a digital filter that is preset for each type of region in accordance with the region classification signal input from the region separation processing unit 206, thereby correcting the spatial frequency characteristics of the image data of the YCbCr signal input from the YCbCr correction unit 210, in order to prevent blurring and deterioration of graininess in the output image.

[0052] Here, for example, with respect to a region separated into a halftone dot region by the region separation processing unit 206, the spatial filter processing unit 212 performs low-pass filtering to remove input halftone dot components. Also, for example, with respect to a region separated into a character region by the region separation processing unit 206, the spatial filter processing unit 212 increases the amount of enhancement of high frequencies by sharpness enhancement processing in order to improve the reproducibility of black characters or color characters. The spatial filter processing unit 212 outputs the YCbCr image data to the second color space conversion unit 214.

[0053] The second color space conversion unit 214 (color space conversion (YCbCr to RGB) unit) converts the YCbCr image data input from the spatial filter processing unit 212 into RGB image data. The second color space conversion unit 214 outputs the RGB image data to the color correction unit 216.

[0054] The color correction unit 216 converts the RGB signals input from the second color space conversion unit 214 into CMY signals in accordance with the segmentation classification signal input from the segmentation processing unit 206. Furthermore, in order to achieve faithful color reproduction, the color correction unit 216 performs processing to remove color impurities based on the spectral characteristics of the CMY colorants, including unnecessary absorption components. The color correction unit 216 outputs the CMY signals to the black generation and undercolor removal unit 218.

[0055] The black generation and under color removal unit 218 performs black generation processing to generate a black (K) signal from the CMY signals after color correction by the color correction unit 216, and under color removal processing to generate new CMY signals by subtracting the K signal obtained in the black generation processing from the original CMY signals. As a result, the CMY signals are converted into four color signals of CMYK (hereinafter referred to as CMYK signals). The black generation and under color removal unit 218 outputs the CMYK signals to the output gradation correction unit 220.

[0056] The output tone correction unit 220 performs output tone correction processing on the image data of the CMYK signals input from the black generation and under color removal unit 218 based on the output characteristics of the image forming unit 160. The output tone correction unit 220 outputs the image data of the CMYK signals to the tone reproduction processing unit 222.

[0057] The tone reproduction processing unit 222 performs tone reproduction processing (halftone processing) on ​​the image data of the CMYK signal input from the output tone correction unit 220, dividing the pixels in accordance with the area classification signal input from the area separation processing unit 206 so that the tone of each pixel can be reproduced.

[0058] The tone reproduction processing unit 222 performs halftone processing to reproduce the tone of each pixel. Here, the halftone processing generates a dither pattern using a dither screen (dither matrix), and performs binarization processing (1-bit processing) or multi-value processing (multi-bit processing). The halftone processing will be described later.

[0059] Furthermore, for regions separated into character regions by the region separation processing unit 206, the tone reproduction processing unit 222 performs, for example, 1-bit processing or multi-bit processing using a high-resolution screen suitable for reproducing high frequencies. Also, for regions separated into photographic regions (continuous tone regions) by the region separation processing unit 206, the tone reproduction processing unit 222 performs, for example, 1-bit processing or multi-bit processing using a screen that places importance on tone reproducibility.

[0060] The tone reproduction processing unit 222 outputs the image data to be output, for example, image data that has been subjected to each of the above-mentioned screen processes, to the image forming unit 160. Here, for example, the image data output by the tone reproduction processing unit 222 may be temporarily stored in the storage 110, and then read out and output to the image forming unit 160 at a predetermined timing.

[0061] [1.3.3 Halftoning] FIG. 6 is a diagram showing an example of halftone processing in this embodiment.

[0062] Fig. 6 shows an example of a dither matrix and dither pattern used in halftone processing. For example, Fig. 6 shows an example of a dither matrix used when the tone reproduction processing unit 222 performs halftone processing using 1-bit processing. In order to reproduce halftones, the tone reproduction processing unit 222 can reproduce the gradation of an image by performing screening processing that forms a dither pattern using a dither matrix and threshold values ​​in an LUT (Look Up Table) based on the density signals of the CMYK signals, for example.

[0063] FIG. 6(a) shows a dither matrix used in screen processing. The dither matrix M100 may be composed of, for example, a plurality of minimum dots. Here, the minimum dot is, for example, the smallest unit of a dot (pixel) that makes up a dot. The tone reproduction processing unit 222 plots the minimum dots (by filling in the minimum dots) to form a dither pattern. In this embodiment, the dither matrix M100 is composed of, for example, 18 minimum dots.

[0064] Here, each smallest dot in the dither matrix M100 may be assigned a position. In this embodiment, the positions are defined, for example, by defining the columns of the smallest dots from left to right as column a, column b, column c, column d, column e, and column f, and the rows of the smallest dots from top to bottom as row 1, row 2, row 3, row 4, and row 5. The positions are then defined by combining rows and columns, such that the smallest dots are defined from top to bottom as b1, b2, and b3 in column b. However, the positions of the smallest dots may be described in any way as long as the positions can be identified. In this embodiment, the shape of the dither matrix is ​​shown as a rhombus, but it may also be a matrix of a square, rectangle, parallelogram, or other shape.

[0065] The tone reproduction processor 222 plots the smallest dots in the dither matrix M100 one by one to form a dither pattern. Here, the tone reproduction processor 222 outputs pixel values ​​based on the density signals of the CMYK signals, for example, as pixel values ​​required to form the dither pattern using an LUT. Here, the pixel values ​​required to form the dither pattern may be, for example, the number of plotted smallest dots.

[0066] 6(b) shows an example of an LUT used to form a dither pattern. Here, the LUT stores, for example, input pixel values ​​and output pixel values. Here, the input pixel values ​​refer to, for example, the pixel values ​​of dots, and are input to the LUT. The output pixel values ​​refer to, for example, the pixel values ​​that the LUT outputs as threshold values ​​for the input pixel values.

[0067] When the LUT receives an input pixel value, for example, a pixel value based on the density signal of a CMYK signal, it outputs a pixel value corresponding to the output pixel value. Specifically, if the input pixel value is "73," it outputs "2" as the output pixel value. The tone reproduction processing unit 222 forms a dither pattern by plotting, for example, the number of minimum dots corresponding to the output pixel value, i.e., two dots.

[0068] Figure 6(c) is a diagram showing an example of forming a dither pattern using a dither matrix. Hereinafter, unless otherwise specified, the main scanning direction of the laser is from the top (upstream) to the bottom (downstream) of the figure. The sub-scanning direction of the laser is from the left (upstream) to the right (downstream) of the figure. In Figure 6(c), the smallest dots that make up the dither matrix M102 are filled with the plotted smallest dots D100.

[0069] Here, the numbers shown for each minimum dot indicate, for example, the order in which the minimum dots are plotted, i.e., the order in which the dots grow. For example, if the output pixel value is 2, the order in which the tone reproduction processing unit 222 plots the minimum dots at the minimum dots indicated as 1 and 2 in the dither matrix M102.

[0070] Here, only one minimum dot is plotted in dither matrix M102. Here, dither matrix M104 shows a case where the input pixel value input to dither matrix M102 is, for example, 74. The tone reproduction processing unit 222 inputs 74 as the input pixel value to the LUT. The LUT outputs 2 as the output pixel value. Then, based on the dot growth order, the tone reproduction processing unit 222 plots minimum dot D100 and minimum dot D102 adjacent to minimum dot D100 to form a dither pattern.

[0071] Here, a case where the input pixel value is, for example, 115 is shown in dither matrix M106. As with dither matrix M104, the tone reproduction processing unit 222 plots minimum dot D100, minimum dot D102, and minimum dot D104 adjacent to minimum dot D100 to form a dither pattern. Further, a case where the input pixel value is, for example, 117 is shown in dither matrix M108. Similarly, the tone reproduction processing unit 222 plots minimum dot D100, minimum dot D102, minimum dot D104, and minimum dot D106 adjacent to minimum dot D104 to form a dither pattern.

[0072] (multi-bit processing) Figure 7(a) shows an example of a dither pattern formed by halftone processing using multi-bit processing. The dither matrix M110 in Figure 7(a) contains dither patterns (smallest dot D100, smallest dot D102, smallest dot D104, smallest dot D106, smallest dot D108) formed by multi-bit processing. The difference between multi-bit processing and 1-bit processing is that, for example, the smallest dot can be further divided to represent multiple gradations.

[0073] Here, the tone reproduction processing unit 222 may use, for example, PWM (Pulse Width Modulation) as a method for dividing the minimum dot. The tone reproduction processing unit 222 divides the minimum dot into multiple parts along the laser writing direction using PWM to perform area gradation. Specifically, the tone reproduction processing unit 222 writes, for example, the minimum dot D108 using PWM from upstream in the main scanning direction of the laser with a right-justified laser (a laser positioned upstream in the main scanning direction) by controlling the duty ratio. By this laser writing process from one side (right-justified), for example, the tone reproduction processing unit 222 divides the minimum dot D108, and multiple gradations can be realized by area gradation.

[0074] Figure 7(b) is an enlarged view of the smallest dot D108 in Figure 7(a). The tone reproduction processing unit 222, for example, plots small dots as part of the smallest dot to form the smallest dot D108. For example, in the case of 4-bit processing, the smallest dot D108 may be area-gradated by dividing one smallest dot into 16 gradations (15 divisions including 0).

[0075] For example, if the output pixel values ​​of the LUT are divided into integers and fractions, such as "1, 1+1 / 15, . . . 1+14 / 15, 2, . . . ," the tone reproduction processing unit 222 plots the smallest dot corresponding to the integer output pixel value. The tone reproduction processing unit 222 then controls the PWM duty cycle so that it becomes the fractional ratio of the output pixel value, and plots the remaining fractional output pixel value by area-modulating the smallest dot with a duty cycle of less than 100%. In this way, the tone reproduction processing unit 222 can express multiple gradations using small dots, for example, by area-modulating the smallest dot with a duty cycle of less than 100%.

[0076] As a specific example, if the fraction of the output pixel value is 1 / 15, the tone reproduction processing unit 222 may plot small dots only in region R102 to form a dither pattern for the minimum dot D108. Here, if the fraction of the output pixel value is 2 / 15, for example, the tone reproduction processing unit 222 may plot small dots in region R102 and up to region R104 adjacent to region R102 to form a dither pattern for the minimum dot D108. Here, if the fraction of the output pixel value is 8 / 15, for example, the tone reproduction processing unit 222 may plot small dots in adjacent regions up to region R106, including region R102 and region R104, to form a dither pattern for the minimum dot D108.

[0077] That is, by plotting the smallest dot, which is plotted last in the order of dot growth, as a small dot, for example, in this embodiment, 1-bit processing can reproduce 18 gradations, while 4-bit processing can express 18 x 16 = 288 gradations. Note that although 4-bit processing is used as an example in this embodiment, multi-bit processing with different bit counts, such as 2-bit processing or 8-bit processing, may also be used.

[0078] [1.4 Processing flow] The processing flow in this embodiment will be described below with reference to FIG.

[0079] 8 is a diagram showing the flow of the screen processing of this embodiment. Note that each component described in FIG. 2 or FIG. 3 may execute the processing of each step.

[0080] First, the control unit 100 reads out the job setting information (S102). The control unit 100 reads out, for example, information on the setting items and setting values ​​of the job setting information related to the job to be executed from the job setting information storage area 1100.

[0081] Next, the control unit 100 determines whether multi-bit processing is to be performed (S104). The control unit 100, for example, compares the setting values ​​of the setting items related to multi-bit processing in the read job setting information. For example, if the setting value is other than 1-bit processing, the control unit 100 may determine that multi-bit processing is to be performed.

[0082] If the control unit 100 determines that the job is multi-bit processing, it determines whether double-sided printing is to be performed (S104; Yes → S106). The control unit 100, for example, compares the setting value of the setting item related to double-sided printing in the read job setting information. For example, if the setting value is double-sided printing, the control unit 100 may determine that double-sided printing is to be performed.

[0083] If the control unit 100 determines that double-sided printing is to be performed, it then determines whether back-side printing is to be performed (S106; Yes → S108). The control unit 100, for example, compares the setting value of the setting item related to the number of pages to be output in the read job setting information. For example, if the setting value indicates output of even-numbered pages, the control unit 100 may determine that back-side printing is to be performed.

[0084] If the control unit 100 determines that the printing is on the back side, it determines whether the printing is on the short side (S108; Yes → S110). The control unit 100, for example, compares the setting value of the setting item related to the binding direction to be output in the read job setting information. For example, if the setting value indicates short side binding, the control unit 100 may determine that short side binding is to be performed.

[0085] If the control unit 100 determines that the printing is short-edge bound, it determines whether the printing is portrait orientation (S110; Yes → S112). The control unit 100, for example, compares the setting value of the setting item related to the printing direction to be output from the read job setting information. For example, if the setting value indicates portrait orientation printing, the control unit 100 may determine that portrait orientation printing is to be executed.

[0086] If the control unit 100 determines that the printing is vertical, it selects a specific dither matrix (S112; Yes → S116). The control unit 100 selects a specific dither matrix by, for example, reading information about the position and growth order to be stored in the specific dither matrix storage area 1120.

[0087] On the other hand, if the control unit 100 determines that the printing is not short-edge bound, it determines whether the printing is landscape orientation (S110: No → S114). The control unit 100, for example, compares the setting value of the setting item related to the printing direction to be output in the read job setting information. For example, if the setting value indicates landscape orientation, the control unit 100 may determine that landscape orientation printing will be performed.

[0088] If the control unit 100 determines that the printing is in landscape orientation, it selects a specific dither matrix (S114; Yes→S116).

[0089] On the other hand, if the control unit 100 determines that it is not multi-bit processing (S104; No), that it is not double-sided printing (S106; No), that it is not reverse-side printing (S108; No), that it is not portrait printing (S112; No), or that it is not landscape printing (S114; No), it selects a normal dither matrix (S118). The control unit 100 selects a normal dither matrix by, for example, reading information about the position and growth order stored in the normal dither matrix storage area 1110.

[0090] Finally, the control unit 100 executes screen processing (S120). The control unit 100 executes halftoning indicated in the tone reproduction processing unit 222 of the image processing unit 1020, for example, based on the input pixel value corresponding to the dither matrix, the LUT, the position of the selected dither matrix, and the growth order. Next, the control unit 100 stores the pixel value corresponding to the position in the screen processing information storage area 1130.

[0091] Next, when it is necessary to perform a rotation process, the control unit 100 may perform a 180-degree rotation process of the image using the image rotation processing unit 1010. Finally, the control unit 100 outputs the information on the position and pixel value stored in the screen processing information storage area 1130 to the image forming unit 160.

[0092] It should be noted that the position value of the smallest dot that constitutes the dither matrix does not necessarily have to match the position value written by the laser. For example, a correspondence table that stores the position values ​​before and after the rotation process may be stored in the storage unit (storage 110, ROM 120).

[0093] [1.5 Example of operation] 9, 10, and 11 are diagrams showing examples of image processing as a result of the operation of the image forming apparatus 10 in this embodiment.

[0094] 9(a) is a diagram showing the relationship between the positions of the smallest dots in dither matrices at 0 degrees and 180 degrees, for example. For example, dither matrix M100 shows the position of the smallest dot at 0 degrees. On the other hand, M112 shows the position of the smallest dot after a 180-degree rotation. In this way, when control unit 100 executes the 180-degree rotation process, the position of the smallest dot in the dither matrix also rotates 180 degrees, so the position of the smallest dot and the growth order of the dots corresponding to that position also rotate 180 degrees.

[0095] FIG. 9(b) shows an example of a dither matrix and dither pattern when an image is rotated 180 degrees in multi-bit processing. In this embodiment, the dither pattern is formed using PWM. Dither matrix M114 in FIG. 9(b) shows an example of a dither pattern formed by the control unit 100 performing screening processing when there is no rotation output. Meanwhile, dither matrix M116 shows an example of a dither pattern formed by the control unit 100 performing screening processing.

[0096] The smallest dots constituting the dither pattern shown in dither matrix M114 are a smallest dot (large dot) D110 with a duty ratio of 100% and a smallest dot (small dot) D112 with a duty ratio of less than 100%, which are adjacent to each other. When plotting smallest dots along the main scanning direction using PWM, for example, the control unit 100 plots the large smallest dot D110 on the smallest dot upstream in the main scanning direction in accordance with the order of dot growth. The control unit 100 then plots the small smallest dot D112 on the adjacent smallest dot.

[0097] Here, due to the relationship between the main scanning direction and the order of dot growth, a dither pattern is formed in which there is no gap between the minimum dot D110 and the minimum dot D112 adjacent to the minimum dot D110 downstream in the main scanning direction. In this way, small dots are added adjacent to large dots in the dither pattern, which results in a large dither pattern with good developability, enabling, for example, beautiful and stable reproduction of continuous gradations.

[0098] Next, the control unit 100 performs the same process on the smallest dots that make up the dither matrix M116 after the 180-degree rotation process. Here, the smallest dots that make up the dither pattern shown in the dither matrix M116 are adjacent to each other: a smallest dot (large dot) D114 with a duty ratio of 100% and a smallest dot (small dot) D116 with a duty ratio of less than 100%. When plotting smallest dots along the main scanning direction using PWM, for example, the control unit 100 plots the smallest dot D116 next to the smallest dot upstream in the main scanning direction in accordance with the dot growth order. The control unit 100 then plots the large smallest dot D114 next to the adjacent smallest dot.

[0099] Here, the relationship between the main scanning direction and the dot growth order is reversed. That is, a dither pattern is formed in which there is a gap between the minimum dot D116 and the minimum dot D114 adjacent to the minimum dot D116 downstream in the main scanning direction. In this way, the formed dither pattern has small dots formed at a distance from large dots. That is, the developability becomes unstable, and, for example, a gradation gap occurs.

[0100] Therefore, to perform halftone processing with good reproducibility and no gradation gaps, the rotation angle of the dither matrix, the pixel value of the dot determined by the position of the smallest dot and the dot growth order, and the main scanning direction of the laser are closely related. Based on this information about the dot arrangement, the control unit 100 must select a dither matrix and form a dither pattern with stable developability.

[0101] (Example 1) FIG. 10(a) shows an example in which the image forming apparatus 10 performs double-sided printing with the long edge bound and the printing direction portrait. The control unit 100 performs double-sided printing on the printed matter P100 in the following order: the front printing surface P102 of the first sheet, the back printing surface P104 of the second sheet, and the front printing surface ... of the third sheet. Here, the control unit 100 outputs the front printing surface P102 of the printed matter P100 without performing rotation processing. Here, the arrow A100 on the front printing surface P102 indicates the main scanning direction, which is the laser writing direction. Meanwhile, the arrow A102 indicates the direction in which the control unit 100 plots the smallest dots according to the dot growth order. The main scanning direction and the direction in which the dither pattern grows on the front printing surface P102 are the same. The control unit 100 selects a normal dither matrix, for example, dither matrix M118 as shown in Fig. 11(a), and performs screening. The control unit 100 forms a dither pattern in which there is no gap between the minimum dot D120 and the minimum dot D122 adjacent to the minimum dot D120 downstream in the main scanning direction.

[0102] Next, the back printing surface P104 of the printed material P100 is bound long-side up and printed vertically. Therefore, the control unit 100 outputs it without performing rotation processing. Here, arrow A104 on the back printing surface P104 indicates the main scanning direction, which is the laser writing direction. Meanwhile, arrow A106 indicates the direction in which the control unit 100 plots the minimum dots according to the dot growth order. On the back printing surface P104, the main scanning direction and the direction in which the dither pattern grows are the same. As with the front printing surface P102, the control unit 100 selects a normal dither matrix, for example, dither matrix M118 shown in Figure 11(a), and performs screen processing. The control unit 100 forms a dither pattern with no gap between the minimum dot D120 and the minimum dot D122 adjacent to the minimum dot D120 downstream in the main scanning direction.

[0103] (Example 2) 10(b) is a diagram showing an example in which image forming apparatus 10 performs double-sided printing with short edge binding and portrait orientation. Control unit 100 performs double-sided printing on printed matter P106 in the following order: front printing surface P108 for the first sheet, back printing surface P110 for the second sheet, front printing surface P110 for the third sheet, etc. Here, front printing surface P108 of printed matter P106 is the front printing surface, and control unit 100 outputs it without performing rotation processing. Therefore, control unit 100 selects dither matrix M118 and performs screen processing.

[0104] Next, the printing surface P110 on the back side of the printed material P106 is short-edge bound and printed in portrait orientation. Therefore, the control unit 100 performs a 180-degree rotation process before output. Here, arrow A112 on the printing surface P110 on the back side indicates the main scanning direction, which is the laser writing direction. Meanwhile, arrow A114 indicates the direction in which the control unit 100 plots the smallest dots according to the dot growth order. On the printing surface P110 on the back side, the main scanning direction and the direction in which the dither pattern grows do not match, but are opposite directions.

[0105] Here, suppose that the control unit 100 selects a normal dither matrix, for example, the dither matrix M118 shown in Fig. 11(a), and performs screening. Then, the control unit 100 rotates the dither matrix M118 by 180 degrees, resulting in screening with the dither matrix M120 shown in Fig. 11(b). In this case, the control unit 100 creates a dither pattern with a gap between the minimum dot D124 and the minimum dot D126, which is adjacent to the minimum dot D124 upstream in the main scanning direction.

[0106] Therefore, the control unit 100 selects, for example, dither matrix M122 as shown in Fig. 11(c) as the specific dither matrix. Then, the control unit 100 rotates the dither matrix M122 by 180 degrees, and therefore, as shown in Fig. 11(d), dither matrix M124 is applied and screen processing is performed. The control unit 100 forms a dither pattern in which there is no gap between the minimum dot D120 and the minimum dot D130 adjacent to the minimum dot D128 downstream in the main scanning direction.

[0107] (Example 3) 10(c) is a diagram showing an example in which image forming apparatus 10 performs double-sided printing with the long edge bound and landscape printing direction. Control unit 100 performs double-sided printing on printed matter P112 in the following order: front printing surface P114 of the first sheet, back printing surface P116 of the second sheet, front printing surface P116 of the third sheet, etc. Here, control unit 100 outputs front printing surface P114 of printed matter P112 without performing rotation processing. Therefore, control unit 100 selects dither matrix M118 and performs screen processing.

[0108] Next, the printing surface P116 on the back side of the printed matter P112 is bound long-side and printed in landscape orientation. Therefore, it is rotated 180 degrees before being output. Here, arrow A116 on the printing surface P116 on the back side indicates the main scanning direction, which is the direction in which the laser writes. Meanwhile, arrow A118 indicates the direction in which the control unit 100 plots the smallest dots according to the dot growth order. On the printing surface P116 on the back side, the main scanning direction and the direction in which the dither pattern grows do not match, but are opposite directions.

[0109] The control unit 100 selects, for example, a dither matrix M122 as shown in FIG. 11(c) as the specific dither matrix, and executes screening to form a gapless dither pattern.

[0110] (Example 4) 10(d) is a diagram showing an example in which image forming apparatus 10 performs double-sided printing with short edge binding and landscape printing. Control unit 100 performs double-sided printing on printed matter P118 in the following order: front printing surface P120 for the first sheet, back printing surface P122 for the second sheet, front printing surface P123 for the third sheet, etc. Here, front printing surface P120 of printed matter P118 is the front printing surface, and is output without being rotated. Therefore, control unit 100 selects dither matrix M118 and performs screen processing.

[0111] Next, the printing surface P122 on the back side of the printed matter P118 is double-sided, bound on the short edge, and printed in landscape orientation. Therefore, the control unit 100 outputs the printed matter without performing rotation processing. Therefore, the control unit 100 selects the dither matrix M118 and performs screening processing to form a gapless dither pattern.

[0112] [1.6 Effects, etc.] Thus, according to this embodiment, when executing a process to rotate an image, for example, the control unit 100 can select one of a plurality of dither matrices based on information about the dot arrangement and execute halftone processing. As a result, when the user executes double-sided printing based on an image, if the control unit 100 includes a process to rotate the back side, for example, double-sided printing can be achieved with no difference in image quality depending on the printing side.

[0113] [2. Second Embodiment] The second embodiment will be described below. The second embodiment is an embodiment in which a sub-matrix including a plurality of dither matrices is used.

[0114] In the second embodiment, explanations of the same hardware and software configurations as those in the first embodiment will be omitted, and the explanation will focus on the differences from the first embodiment.

[0115] [2.1 Software Configuration] The main software configuration of the image forming apparatus 10 in the second embodiment will be described with reference to FIG.

[0116] The storage 110 allocates an area for a normal submatrix storage area 1112 that stores a normal submatrix. A normal dither matrix refers to, for example, a submatrix selected in screen processing for normal output. In this embodiment, normal output refers to output of the front printing surface or the back printing surface when outputting a double-sided printout, without rotation. The normal submatrix stores the position of the smallest dot that constitutes the normal submatrix and the order in which dots grow to form a dither pattern. Submatrices will be described later.

[0117] 13(a) will be used to explain an example of a normal submatrix stored in the normal submatrix storage area 1112. The position of the smallest dot that constitutes the normal submatrix (e.g., "Ac2") and the order of dot growth (e.g., "1") for forming a dither pattern are stored.

[0118] Furthermore, the storage 110 reserves an area for a specific submatrix storage area 1122 that stores a specific submatrix. A specific submatrix refers to, for example, a submatrix selected in screen processing for a specific output. In this embodiment, a specific output refers to the output of the printing surface of the back side of a double-sided printed material that has been rotated 180 degrees. The difference between a specific submatrix and a normal submatrix is ​​that the dot growth order of a normal dither matrix is ​​changed. The specific submatrix stores the position of the smallest dot that constitutes the specific submatrix and the dot growth order for forming a dither pattern.

[0119] 13(b) will be used to explain an example of a specific submatrix stored in the specific submatrix storage area 1122. The position of the smallest dot that constitutes the specific submatrix (e.g., "Ac2") and the order of dot growth (e.g., "26") for forming a dither pattern are stored.

[0120] Furthermore, the storage 110 reserves an area for a screen processing information storage area 1130 for storing screen processing information. In this embodiment, for example, the screen processing information stores laser writing positions corresponding to the above-mentioned sub-matrix and pixel values ​​corresponding to the positions.

[0121] 13(c) will be used to explain an example of the screen processing information stored in the screen processing information storage area 1130. The laser writing position (e.g., "Ac2") and the pixel value (e.g., "15") corresponding to the position are stored.

[0122] [2.2 Processing flow] Fig. 14 is a diagram illustrating the flow of processing in this embodiment. Fig. 14 replaces Fig. 8 of the first embodiment. S202 is executed instead of S116 in Fig. 8, and S204 is executed instead of S118.

[0123] The control unit 100 selects a specific sub-matrix (S202) For example, the control unit 100 reads out information on the position and growth order stored in the specific sub-matrix storage area 1122 to select the specific sub-matrix.

[0124] Furthermore, the control unit 100 selects a normal sub-matrix (S204). The control unit 100 selects a normal sub-matrix by, for example, reading out information on the position and growth order stored in the normal sub-matrix storage area 1112.

[0125] [2.3 Example of operation] FIG. 15 is a diagram showing an example of image processing as a result of the operation of the image forming apparatus 10 in this embodiment.

[0126] (Submatrix) 15 shows an example of a sub-matrix and a dither matrix used in halftone processing in this embodiment, for example, when the tone reproduction processing unit 222 performs multi-bit processing.

[0127] 15(a) may be composed of multiple dither matrices. For example, in this embodiment, the submatrix M200 is composed of four dither matrices: dither matrix A, dither matrix B, dither matrix C, and dither matrix D.

[0128] For ease of explanation, each dither matrix is ​​written in capital letters. Furthermore, dither matrix A may be composed of multiple minimum dots, as shown in dither matrix M202. The position of dither matrix M202 may also be defined as, for example, Aa1, Ab1, Ab2, . . ., De2, De3, Df1.

[0129] Fig. 15(b) is a diagram showing an example of a submatrix M204 obtained by rotating the submatrix M200 of Fig. 15(a) by 180 degrees and outputting it. As shown in Fig. 15(b), the positions of the dither matrices that make up the submatrix have been rotated by 180 degrees. Furthermore, the positions of the smallest dots that make up the submatrix have been rotated by 180 degrees, for example, as shown in dither matrix M206 that makes up the submatrix.

[0130] The dot growth order may be, for example, the same as in the first embodiment, where a dither pattern is formed for each dither matrix that makes up the sub-matrix. Specifically, a dither pattern for dither matrix A may be formed first, followed by dither matrix B, dither matrix C, and dither matrix D. Alternatively, the dither patterns may be formed in any of the following ways, such as plotting one smallest dot for dither matrix A, then plotting one smallest dot for dither matrix B.

[0131] (Example 1) As a result of the operation of the image forming device 10 in this embodiment, for example, when the image forming device 10 executes a copy job with double-sided printing bound on the short edge and printing in portrait orientation, and double-sided printing bound on the long edge and printing in landscape orientation, no difference in image quality is observed between the printed surface on the front side and the printed surface on the back side, and printing with finer gradations can be executed.

[0132] [2.4 Effects, etc.] In this way, this embodiment can also be applied to sub-matrices made up of multiple dither matrices, making it possible to realize an image processing apparatus that does not cause any difference in image quality even when printing more detailed and complex characters.

[0133] 3. Third Embodiment The third embodiment will be described below. In this embodiment, a plurality of dither matrices are stored, and processing is repeated until an optimal dither matrix that does not cause a tone gap is selected.

[0134] In the third embodiment, the description of the same hardware and software configurations as those of the first embodiment will be omitted, and the description will focus on the differences from the first embodiment.

[0135] [3.1 Software Configuration] The main software configuration of the image forming apparatus 10 will be described with reference to Fig. 16. Fig. 16 is a diagram showing the software configuration of the image forming apparatus 10.

[0136] First, storage 110 allocates a dither matrix DB storage area 1150 for storing a dither matrix DB. In this embodiment, a dither matrix DB refers to a dither matrix DB that includes at least a normal dither matrix and a specific dither matrix. The dither matrix DB stores the ID of the dither matrix, the position of the smallest dot that constitutes the dither matrix, and the order of dot growth for forming the dither pattern.

[0137] 17(a) will be used to explain an example of the dither matrix DB stored in the dither matrix DB storage area 1150. The ID of the dither matrix (e.g., "1"), the position of the smallest dot (e.g., "c2") that constitutes the dither matrix corresponding to the ID, and the order of dot growth (e.g., "1") for forming the dither pattern corresponding to the ID are stored.

[0138] Here, the dither matrix stored in ID "1" is, for example, a normal dither matrix. The dither matrices stored in other IDs may at least be specific dither matrices.

[0139] Furthermore, the storage 110 reserves an area for a gap determination information storage area 1140 that stores gap determination information. Here, the gap determination information is, for example, information for determining whether there is a gap between a large dot and a small dot. The gap determination information stores the position where the gap is determined and the pixel value corresponding to the position.

[0140] 17(b) will be used to explain an example of the gap determination information stored in the gap determination information storage area 1140. The position where the gap is determined (e.g., "c2") and the pixel value corresponding to the position (e.g., "8") are stored.

[0141] [3.2 Processing flow] Fig. 18 is a diagram illustrating the flow of processing in this embodiment. Fig. 18 replaces Fig. 8 of the first embodiment. S302 is executed instead of S102 in Fig. 8, and S304 to S312 are executed between S108 and S120.

[0142] The control unit 100 reads out the job setting information and sets n=1 (S302). The control unit 100 reads out, for example, information on the setting items and setting values ​​of the job setting information related to the job to be executed from the job setting information storage area 1100. Next, the control unit 100 stores n=1 in the storage 110. Here, the value of n is a value corresponding to the ID stored in the dither matrix DB storage area 1150.

[0143] The control unit 100 selects the nth dither matrix (S304). For example, the control unit 100 selects the dither matrix whose ID is nth stored in the dither matrix DB storage area 1150. The control unit 100 reads out information about the position and growth order for the nth dither matrix.

[0144] Next, the control unit 100 generates gap determination information (S306). Here, the control unit 100 performs the same processing as the halftoning shown in the tone reproduction processing unit 222 of the image processing unit 1020 based on the input pixel values ​​corresponding to the dither matrix, the LUT, the position of the nth dither matrix, and the growth order. Next, the control unit 100 stores the pixel values ​​corresponding to the position in the gap determination information storage area 1140. Here, if it is necessary to perform rotation processing, the control unit 100 may perform 180-degree image rotation processing using the image rotation processing unit 1010, for example.

[0145] Next, the control unit 100 determines whether there is a gap (S308). For example, the control unit 100 compares the pixel value with the position stored in the gap determination information storage area 1140, and determines whether there is a gap (gap) between the large dot and the adjacent small dot.

[0146] As a method for determining whether there is a gap between a large dot and an adjacent small dot, for example, the pixel values ​​of the positions stored in the gap determination information storage area 1140 may be compared in order from upstream in the main scanning direction to downstream in the main scanning direction, and if the pixel value downstream in the main scanning direction is greater than the pixel value upstream in the main scanning direction (except when the pixel value is 0), it may be determined whether there is a gap (gap) between the large dot and the adjacent small dot.

[0147] As an example, the pixel value of the position "c2" upstream in the main scanning direction of column c stored in the gap determination information storage area 1140 may be compared with the pixel value of the position "c3" downstream in the main scanning direction, and if "c3" is greater than "c2," it may be determined that a gap exists.

[0148] Note that the above determination is an example in which the pixel values ​​are stored in the gap determination information storage area 1140 after the 180-degree rotation process has been performed, and the determination conditions are reversed if the determination is made without performing the 180-degree rotation process. Therefore, any determination means can be selected as long as it is possible to determine that there is a gap between a large dot and a small dot.

[0149] If the control unit 100 determines that there is no gap (S308; No), that it is not multi-bit processing (S104; No), that it is not double-sided printing (S106; No), or that it is not back-side printing (S108; No), the control unit 100 selects the n-th dither matrix (S310). The control unit 100 selects a dither matrix in the same way as in the processing of S304.

[0150] On the other hand, if the control unit 100 determines that there is a gap, it executes n=n+1 (S308; Yes→S312). Subsequently, the control unit 100 again selects the n-th dither matrix (S304).

[0151] It should be noted that the position value of the smallest dot that constitutes the dither matrix does not necessarily have to match the position value for gap determination stored in the gap determination information storage area 1140. For example, a correspondence table that stores the position values ​​before and after the rotation process may be stored in the storage unit (storage 110, ROM 120).

[0152] [3.3 Example of operation] Fig. 19 is a diagram showing an example of image processing as a result of the operation of the image forming apparatus 10 in this embodiment. Fig. 19 is a diagram showing an example in which the image forming apparatus 10 outputs the reverse side of the printed page that requires multi-bit processing and 180-degree rotation processing for double-sided printing.

[0153] Here, the control unit 100 selects the first dither matrix (normal dither matrix) from the dither matrix DB storage area 1150. The control unit 100 reads the first dither matrix, generates gap determination information, and stores pixel values ​​corresponding to the positions in the gap determination information storage area 1140.

[0154] FIG. 19(a) shows the results of reading the first dither matrix and generating gap determination information. The control unit 100 compares the pixel values ​​of adjacent positions in the main scanning direction stored in the gap determination information storage area 1140, comparing the pixel value of the first row of column b with the pixel value of the second row of column b, comparing the pixel value of the second row of column b with the pixel value of the third row of column b, and so on. Here, the control unit 100 determines that there is a gap between the large dot and the small dot because the pixel value V304 of the second row of column d is "8" and the pixel value V302 of the third row of column d is "15." The control unit 100 reads the second dither matrix and generates gap determination information.

[0155] 19(a) shows the dither pattern formed when the first dither matrix is ​​selected and screen processing is performed. There is a gap between the smallest dot D304 corresponding to pixel value V304 and the smallest dot D302 corresponding to pixel value V302.

[0156] FIG. 19(b) shows the results of reading the nth dither matrix and generating gap determination information. The control unit 100 compares pixel values ​​at adjacent positions in the main scanning direction, just as it did with the first dither matrix. Here, the control unit 100 determines that there is no gap between the large dot and the small dot because the pixel value V306 in the third row of column c is "15" and the pixel value V308 in the fourth row of column c is "8." The control unit 100 repeats the determination, and because the pixel values ​​at other positions are either "0" or "15," it also determines that there is no gap between the large dot and the small dot. The control unit 100 reads the nth dither matrix and performs screen processing.

[0157] 19(b) shows the dither pattern formed when the nth dither matrix is ​​selected and screen processing is performed. There is no gap between the smallest dot D306 corresponding to pixel value V306 and the smallest dot D308 corresponding to pixel value V308.

[0158] In this way, in this embodiment, gap determination is performed by selecting multiple dither matrices, so it is possible to perform screen processing without any difference in image quality under various conditions. It is also possible to handle not only rotation processing but also complex processing such as inversion processing.

[0159] [3.4 Effects, etc.] In this way, according to this embodiment, it is possible to select the optimum dither matrix from multiple dither matrices and execute screen processing. For example, it is possible to support not only rotated output but also reversed output, and it is possible to provide an image processing device that does not cause a difference in image quality between the front and back sides of double-sided printed material.

[0160] [4. Fourth Embodiment] A fourth embodiment will be described below. In the fourth embodiment, the image forming apparatus 10 is applied to an image other than an image read from a document.

[0161] For example, in the above-described first to third embodiments, an example was described in which an original document is read by image reading unit 165, and image rotation processing unit 1010 and image processing unit 1020 process the image data output by image reading unit 165.

[0162] In this embodiment, image data is acquired by an image acquisition unit (not shown) instead of the image reading unit 165. Here, the image acquisition unit acquires image data from, for example, the following acquisition sources. (1) The control unit 100 acquires image data based on print data from a terminal device connected to the image forming apparatus 10. For example, when a print job is executed to output an image, the control unit 100 executes any one of the processes of the first to third embodiments when rotating the image.

[0163] (2) The control unit 100 acquires image data recorded on a recording medium such as a USB memory. For example, when a file print job is executed to output an image, the control unit 100 executes any one of the processes of the first to third embodiments when rotating the image.

[0164] When processing print data, the image processing unit 1020 can perform optimal image and color conversion processing using a processing procedure not shown, depending on the input data format, for example, when the input data is color specification data other than RGB, or when the input data includes area information.

[0165] As described above, according to this embodiment, the processes described in the first to third embodiments can be performed on data other than image data read from a document by the image reading unit 165. That is, the control unit 100 can apply the processes of each embodiment to jobs other than copy jobs.

[0166] [5. Modifications] The present disclosure is not limited to the above-described embodiments, and various modifications are possible. In other words, embodiments obtained by combining technical means that are appropriately modified within the scope of the present disclosure are also included in the technical scope.

[0167] In the above-described embodiment, an image forming apparatus has been described as an example of an image processing apparatus. However, the image processing apparatus can be applied to other devices. For example, an example of an image processing apparatus may be an information processing apparatus such as a smartphone or a tablet. It may also be a home appliance equipped with an IoT function (e.g., a label printer). It is not limited to a stationary device, and may also be, for example, a portable device.

[0168] Although the above-mentioned embodiments are described separately for convenience of explanation, they can be combined to the extent possible. Furthermore, the present invention intends to obtain rights to any of the technologies described in the specification through amendments or divisional applications, etc.

[0169] In addition, the programs that run on each device in each embodiment are programs that control the CPU, etc. (programs that make a computer function) so as to realize the functions of the above-described embodiments. Information handled by these devices is temporarily stored in a temporary storage device (e.g., RAM) during processing, and then stored in various ROMs and HDDs, and is read, modified, and written by the CPU as needed.

[0170] Here, the recording medium for storing the program may be any of semiconductor media (e.g., ROM, non-volatile memory card, etc.), optical recording media / magneto-optical recording media (e.g., DVD (Digital Versatile Disc), CD (Compact Disc), BD (Blu-ray (registered trademark) Disc), etc.), magnetic recording media (e.g., magnetic tape, flexible disk, etc.), etc.

[0171] Furthermore, when distributing the program in the market, the program can be stored in a portable recording medium and distributed, or transferred to a server computer connected via a network such as the Internet. In this case, the storage device of the server device is also included in the present disclosure.

[0172] Furthermore, the above-mentioned data may not be stored within the device, but may be stored in an external device and called up as needed. For example, the data may be stored in a network attached storage (NAS) or on the cloud.

[0173] The scope of the present disclosure is not limited to the configurations explicitly described in the specification, but also includes combinations of the technologies disclosed in the specification. The configurations of the present disclosure for which a patent is sought are set forth in the appended claims, but it is not intended to exclude them from the technical scope on the grounds that they are not set forth in the claims.

[0174] Furthermore, in the above-mentioned specification, the statements "in the case of" and "when" are given as examples and are not intended to limit the configuration to the described contents. The disclosure also includes configurations that are not in these cases or situations, even if they would be obvious to a person skilled in the art, and the applicant intends to obtain rights to them.

[0175] Furthermore, the processes and data flows described in the specification are not limited to the order in which they are described. For example, the patent also discloses configurations in which some processes are deleted or the order is changed, and the patent holder intends to obtain the rights to such configurations.

[0176] Furthermore, although the functions described in the embodiments are executed by each device, they may be realized by one device or may further utilize an external server.

[0177] Furthermore, each functional block or feature of the device used in the above-described embodiments may be implemented or performed by an electrical circuit, for example, an integrated circuit or multiple integrated circuits. The electrical circuit designed to perform the functions described herein may include a general-purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or a combination thereof. The general-purpose processor may be a microprocessor, or a conventional processor, controller, microcontroller, or state machine. The electrical circuit may be composed of digital circuits or analog circuits. Furthermore, as advances in semiconductor technology emerge, one or more aspects of the present disclosure may utilize new integrated circuits based on that technology. [Explanation of symbols]

[0178] 10 Image forming device 100 control section 110 Storage 120 ROM 130 RAM 140 Display section 150 Operation section 160 Image forming unit 165 Image reading unit 170 Communications Department

Claims

1. a storage unit that stores a plurality of dither matrices; an acquisition unit that acquires an image; a control unit that, when executing a process of rotating the image acquired by the acquisition unit, selects one of the plurality of dither matrices based on information about dot arrangement, executes halftoning, and generates an output image; An image processing device comprising:

2. 2. The image processing apparatus according to claim 1, wherein the information relating to the dot arrangement is information relating to a rotation angle of the dither matrix, pixel values ​​of the dots, and a main scanning direction.

3. 3. The image processing device according to claim 2, wherein the control unit executes multi-bit processing in the halftone processing, dividing the dots to express multiple gradations.

4. 4. The image processing device according to claim 3, wherein the control unit executes the multi-bit processing by area gradation using pulse width modulation.

5. 5. The image processing device according to claim 4, wherein when a dot with a duty ratio of less than 100% is adjacent to a dot with a duty ratio of 100% downstream in the main scanning direction, the control unit selects the dither matrix that places the dot with a duty ratio of less than 100% upstream in the main scanning direction of the dot with a duty ratio of 100%, and performs the halftone processing.

6. 3. The image processing device according to claim 2, further comprising a dither matrix for 180-degree rotation, the dither matrix having a rotation angle of 180 degrees.

7. 7. The image processing apparatus according to claim 6, wherein the 180-degree rotation dither matrix includes a dither pattern in which the dot arrangement constituting the dither pattern is changed based on the pixel values ​​of the dots and information on the main scanning direction.

8. The image processing device according to claim 1 , wherein the control unit performs the image rotation process on the back side of the output image.

9. a storing step of storing a plurality of dither matrices; an acquisition step of acquiring an image; a control step of selecting one of the plurality of dither matrices based on information about dot arrangement when performing a process of rotating the image acquired in the acquisition step, performing halftoning, and generating an output image; An image processing method comprising:

10. On the computer, a storage function for storing a plurality of dither matrices; an acquisition function for acquiring an image; a control function for selecting one of the plurality of dither matrices based on information about dot arrangement when executing a process of rotating the image acquired by the acquisition function, performing halftoning, and generating an output image; A program to achieve this.

Images