Image processing device and image processing device control method

Abstract

To provide an image processing device which facilitates color balance adjustment.SOLUTION: An image processing device comprises an image processing unit, an operation unit, and a storage unit. The storage unit stores first and second conversion tables for converting input image data including a first color value to output image data including black and a second color value. When an instruction relating to color balance adjustment is not inputted from the operation unit, the image processing unit performs the conversion based on the first conversion table. When the instruction relating to color balance adjustment is inputted from the operation unit, the image processing unit performs the conversion based on the second conversion table.SELECTED DRAWING: Figure 11

Description

[Technical Field]

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

[0002] In general, when an image forming device such as an MFP (Multi-Function Printer / Peripheral) or a color printer forms an image indicated by input image data on a medium such as paper, image processing is performed to convert the input image data including first color values ​​(e.g., RGB values) into output image data consisting of black and second color values ​​(e.g., CMYK values). The image forming device forms an image on the medium based on the output image data.

[0003] Although it is possible to express achromatic colors (gray and black) by mixing CMY toners, K toner can be used to replace some of the CMY toners. By replacing some of the CMY toners with K toner, the amount of CMY toner consumed during image formation can be reduced. For this reason, a color correction table in which a high proportion of CMY values ​​are replaced with K values ​​is generally used.

[0004] In relation to the present disclosure, Patent Document 1 discloses an image processing device that includes an undercolor removal means 1 that generates black and removes undercolor from colorant signals, a spatial filter 2 that performs smoothing and edge emphasis, an arithmetic circuit 3 that performs a calculation of ax+b using coefficients a and b for colorant signal x, and a color correction control means 4 that performs density adjustment, contrast adjustment, negative-positive reversal, color balance adjustment, etc., and is configured to set the coefficients a and b according to the document type and the results of area identification, and the arithmetic circuit 3 has a plurality of coefficients a and b that can be switched between. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 6-86067 Summary of the Invention [Problem to be solved by the invention]

[0006] When viewing an image formed on a medium based on output image data, users may be dissatisfied with the color tone. In such cases, color balance adjustment is sometimes performed, adjusting the color tone by increasing or decreasing CMYK. Conventional image forming devices perform color balance adjustment based on a single color correction table. As mentioned above, typical color correction tables frequently replace CMY values ​​with K values, which helps reduce CMY toner consumption. However, color balance adjustments are rarely reflected in the output image data, making it difficult for users to adjust the color balance as intended.

[0007] The problem to be solved by the present disclosure is to provide an image processing device that allows easy color balance adjustment. [Means for solving the problem]

[0008] The present disclosure provides an image processing device comprising an image processing unit, an operation unit, and a memory unit, wherein the memory unit stores first and second conversion tables for converting input image data including a first color value into output image data including black and a second color value, and when an instruction related to color balance adjustment is not input from the operation unit, the image processing unit performs conversion based on the first conversion table, and when an instruction related to color balance adjustment is input from the operation unit, the image processing unit performs conversion based on the second conversion table.

[0009] The present disclosure also provides a control method for an image processing device that stores first and second conversion tables for converting input image data including a first color value into output image data including black and a second color value, and performs conversion based on the first conversion table when an instruction related to color balance adjustment is not input from the operation unit, and performs conversion based on the second conversion table when an instruction related to color balance adjustment is input from the operation unit. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide an image processing device that allows easy color balance adjustment. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is an external perspective view of an MFP according to a first embodiment of the present disclosure. [Figure 2] 1 is a functional block diagram of an MFP according to a first embodiment of the present disclosure. [Figure 3] FIG. 2 is a diagram for explaining an image processing unit of an MFP according to a first embodiment of the present disclosure. [Figure 4] 10 is an example of an operation screen for a color balance function displayed on a display unit of an MFP (Multi-Function Printer / Peripheral) according to the first embodiment of the present disclosure. [Figure 5] These are examples of conversion curves for increasing or decreasing CMYK (Cyan, Magenta, Yellow, Black) that are set on the operation screen of Figure 4, where Figure 5(A) is an example of a conversion curve for C toner, Figure 5(B) is an example of a conversion curve for M toner, Figure 5(C) is an example of a conversion curve for Y toner, and Figure 5(D) is an example of a conversion curve for K toner. [Figure 6] 1 is a conceptual schematic diagram for explaining the relationship between CMYK toners used in printing and the colors reproduced on paper. [Figure 7] FIG. 10 is a conceptual schematic diagram for explaining that ideal subtractive color mixture CMY toners can be substituted with K toner. [Figure 8] This is a conceptual diagram to explain that in ideal subtractive color mixture, equal amounts of CMY toner and K toner can be substituted for each other, and therefore, even if some of the CMY toners are substituted with the corresponding amount of K toner, the color produced on paper does not change. [Figure 9] FIG. 10 is a conceptual schematic diagram for explaining that when the amount of K toner is large, the amount of change in color tone is small even when the amount of CMY toner is increased in color balance adjustment, compared to when the amount of K toner is small. [Figure 10] FIG. 10 is a conceptual schematic diagram for explaining the difference between color conversion using a normal color correction table and color conversion using a color correction table for color balance adjustment in an MFP according to a first embodiment of the present disclosure. [Figure 11] 11A and 11B are conceptual schematic diagrams for explaining the flow of data processing in an MFP according to a first embodiment of the present disclosure, in which FIG. 11A is a diagram for explaining a case where color conversion is performed using a normal color correction table, and FIG. 11B is a diagram for explaining data processing when color conversion is performed using a color correction table for color balance adjustment. [Figure 12] 4 is a flowchart for explaining the operation of the MFP according to the first embodiment of the present disclosure. [Figure 13] 10A and 10B are diagrams for explaining input image data that is color converted in an MFP according to a second embodiment of the present disclosure. [Figure 14] 10 is a flowchart for explaining the operation of an MFP according to a second embodiment of the present disclosure. [Figure 15] 15A and 15B are conceptual schematic diagrams for explaining the flow of data processing in an MFP according to a third embodiment of the present disclosure, in which FIG. 15A is a diagram for explaining the case where color conversion is performed using a normal color correction table, FIG. 15B is a diagram for explaining data processing when color conversion is performed using a first color correction table (LUT, Look-Up Table) for color balance adjustment, and FIG. 15C is a diagram for explaining data processing when color conversion is performed using a second color correction table (LUT, Look-Up Table) for color balance adjustment. [Figure 16] 10 is a flowchart for explaining the operation of the MFP according to the third embodiment of the present disclosure. [Figure 17] 5 is an example of a screen in which an LUT change notification for notifying the user that the color correction table has been changed is superimposed on the operation screen of the color balance function of FIG. 4. DETAILED DESCRIPTION OF THE INVENTION

[0012] [1. First embodiment] FIG. 1 is an external perspective view of an MFP 51 according to a first embodiment of the present disclosure. FIG. 2 is a functional block diagram of the MFP 51 according to the first embodiment of the present disclosure. An MFP (Multi-Function Printer / Peripheral), also known as a multifunction peripheral, is a type of image forming device and typically includes a copy function, an image scanner function, a facsimile function, and a printer function. The MFP 51 may also include other functions, such as an email sending / receiving function, a file server function, etc. The MFP 51 includes a control unit 53, a storage unit 55, a display unit 57, an operation unit 59, an image input unit 61, an image forming unit 63, a communication unit 65, a connection unit 67, and an image processing unit 71.

[0013] The control unit 53 controls the entire MFP 51. The control unit 53 is configured with one or more control devices and control circuits, and is configured with, for example, a CPU (Central Processing Unit) which is a processor that executes various types of arithmetic processing, an SoC (System on a Chip), etc.

[0014] Furthermore, the control unit 53 can implement each function by reading out a program stored in the storage unit 55 and executing the process.

[0015] The storage unit 55 stores various programs and various data necessary for the operation of the MFP 51. The storage unit 55 includes one or more storage devices capable of temporary storage, such as a dynamic random access memory (DRAM), and non-temporary storage devices, such as a solid state drive (SSD) configured with semiconductor memory or a hard disk drive (HDD) configured with a magnetic disk. For convenience of explanation, the storage unit 55 is shown as a single unit, but it may be configured as separate units for different purposes, such as an area used for executing programs (main storage area), an area for saving programs and data (auxiliary storage area), an area used for caching, etc.

[0016] Display unit 57 displays images and characters. For example, it is configured with a liquid crystal display (LCD), an organic EL (Electro-Luminescence) panel, etc. Display unit 57 may be a standalone display device, or may further include an externally connected display device.

[0017] The operation unit 59 accepts operation inputs from a user. For example, the operation unit 59 is configured with hardware keys and / or software keys. The operation unit 59 also includes operation keys such as task keys for issuing instructions to execute tasks such as sending a fax or scanning an image, and a stop key for issuing an instruction to cancel an operation.

[0018] The image input unit 61 reads an image (original) and outputs it as image data. The image input unit 61 is configured with a general color scanner (image input device). The image input unit 61 may input image data from an external storage medium such as a USB memory, or may receive an image via a network.

[0019] The image forming unit 63 forms (prints) an image on a medium such as copy paper based on image data. The printing method of the image forming unit 63 is arbitrary, and may be, for example, an inkjet printer, a laser printer, a thermal transfer printer, or the like. The image forming unit 63 is a color printer. The image forming unit 63 may also include a paper feed mechanism that supplies the medium, a transport mechanism that transports the medium, a sorter mechanism that sorts the medium after the image has been formed, and the like.

[0020] The communication unit 65 connects to a network. For example, it is configured with an interface that can connect to a wired LAN (Local Area Network), a wireless LAN, or an LTE (Long Term Evolution) network. When the communication unit 65 is connected to a network, it is connected to other devices or an external network. In addition, the communication unit 65 may be an interface that performs short-range wireless communication, such as NFC (Near Field Communication) or Bluetooth (registered trademark).

[0021] Connection unit 67 connects MFP 51 to other devices. For example, connection unit 67 is a USB interface to which a USB memory or the like is connected. Connection unit 67 may also be an interface other than a USB interface, such as HDMI (registered trademark).

[0022] 3 is a diagram for explaining an image processing unit 71 of the MFP according to the first embodiment of the present disclosure. The image processing unit 71 includes, as pre-processing units 73, an A / D (Analog / Digital) conversion unit 73a, an input correction unit 73b, an input gradation correction unit 73c, and a segmentation processing unit 73d. The image processing unit 71 also includes, as post-processing units 77, a spatial filter processing unit 77a, an output gradation correction unit 77b, and a gradation reproduction processing unit 77c. An analog signal read by the image input unit 61 is sent within the image processing unit 71 in the order of the A / D conversion unit 73a, the input correction unit 73b, the input gradation correction unit 73c, the segmentation processing unit 73d, the color conversion unit 75, the spatial filter processing unit 77a, the output gradation correction unit 77b, and the gradation reproduction processing unit 77c, and is output to the image forming unit 63 as a CMYK digital color signal.

[0023] The A / D conversion unit 73a converts analog signals into digital signals. The input correction unit 73b performs shading correction, gamma correction, line delay correction, MTF (Modulation Transfer Function) correction, etc. on the digital RGB signals sent from the A / D conversion unit 73a. The input gradation correction unit 73c performs image quality adjustment processing such as removing background density and adjusting contrast.

[0024] The region separation processing unit 73d separates each pixel in the input image into a character region, a halftone region, or a photograph region based on the RGB signal. Based on the separation result, the region separation processing unit 73d outputs a region identification signal indicating which region the pixel belongs to to the color conversion unit, the spatial filter processing unit, and the tone reproduction processing unit, and also outputs the input signal output from the input tone correction unit directly to the color conversion unit at the subsequent stage.

[0025] The color conversion unit 75 performs processing to remove color impurities based on the spectral characteristics of CMYK (cyan, magenta, yellow, black) color materials containing unnecessary absorption components, in order to achieve faithful color reproduction.

[0026] The spatial filter processing unit 77a performs spatial filtering using a digital filter on the image data of the CMYK signal input from the color conversion unit 75 based on the segmentation classification signal, and processes the image data to prevent blurring and deterioration of graininess in the output image by correcting the spatial frequency characteristics. Furthermore, for the regions separated into halftone dot regions by the segmentation processing unit 73d, the spatial filter processing unit 77a performs low-pass filtering to remove input halftone dot components.

[0027] The output tone correction unit 77b performs output tone correction processing to convert signals such as density signals into dot area ratios, which are characteristic values ​​of the image forming unit 63, and then the tone reproduction processing unit 77c performs tone reproduction processing (halftone generation) to finally separate the image into pixels and process the image so that each tone can be reproduced. For the regions separated into photographs by the region separation processing unit 73d, binarization or multi-value processing is performed using a screen that places importance on tone reproduction.

[0028] Like the spatial filter processor 77a, the tone reproduction processor 77c also performs predetermined processing on the image data of the CMYK signal based on the segmentation signal. For example, in the region separated into characters by the segmentation processor 73d, the spatial filter processor increases the amount of emphasis on high frequencies through sharpness enhancement processing in spatial filtering to improve the reproducibility of black and color characters in particular. At the same time, the tone reproduction processor 77c selects binarization or multi-value processing using a high-resolution screen suitable for reproducing high frequencies.

[0029] The image data that has undergone each of the processes by the image processing unit 71 described above is temporarily stored in the storage unit 55, and is read out at a predetermined timing and input to the image forming unit 63. For example, using the copy function of the MFP 51, an RGB image obtained by scanning an original document with the image input unit 61 is converted into a CMYK image by processing in the color conversion unit 75, and the image is formed on a medium by the image forming unit 63.

[0030] 4 is an example of an operation screen for the color balance function displayed on the display unit 57 of the MFP (Multi-Function Printer / Peripheral) according to the first embodiment of the present disclosure. Note that in this figure, K is represented by Bk. This operation screen provides three slide bars for low, medium, and high densities for each of C, M, Y, and K. This allows the density of, for example, the low, medium, and high densities of C to be increased or decreased. The same applies to MYK.

[0031] Figure 5 shows examples of conversion curves for increasing or decreasing CMYK (Cyan, Magenta, Yellow, Black) that are set on the operation screen in Figure 4. Figure 5(A) is an example of a conversion curve for C toner, Figure 5(B) is an example of a conversion curve for M toner, Figure 5(C) is an example of a conversion curve for Y toner, and Figure 5(D) is an example of a conversion curve for K toner. As shown in Figure 4, the positions of the slide bars for low, medium, and high densities of CMYK are shown as being moved to positions that make the low density of Y toner darker, the medium density of M toner slightly lighter, the high density of C toner slightly darker, and leave K toner unchanged. Correspondingly, conversion curves that change the densities of the low, medium, and high densities for each of the CMYK toners are set, as shown in Figure 5.

[0032] Figure 6 is a conceptual diagram illustrating the relationship between the CMYK toners used in printing and the colors reproduced on paper (medium). By printing by overlapping CMYK toners on paper, colors corresponding to the amounts of each CMYK are reproduced on the paper. By varying the amounts of CMYK, the desired color can be reproduced. Figure 6 shows that when CMYK toners represented by a C toner amount of 11C, an M toner amount of 11M, a Y toner amount of 11Y, and a K toner amount of 11K are overlapped on the same area on paper, a greenish color is reproduced on the paper as a result of subtractive color mixture of these toners.

[0033] FIG. 7 is a conceptual diagram illustrating the substitutability of ideal subtractively mixed CMY toners with K toner. The C toner amount 13C, the M toner amount 13M, and the Y toner amount 13Y are all equal. When equal amounts of CMY toners are ideally mixed subtractively, a gray 15K is reproduced on paper. Therefore, equal amounts of CMY toners can be replaced with equal amounts of K toner. In other words, C toner, M toner, and Y toner in a 1:1:1 ratio can be replaced with the same amount of K toner. Because actual toners have different characteristics from ideal toners, the substitutable amounts of CMY toner and K toner do not equal C:M:Y:K=1:1:1:1. However, a person skilled in the art would be able to similarly determine the substitutable ratio of CMY toner and K toner amounts for actual toners.

[0034] Figure 8 is a conceptual diagram illustrating how, in ideal subtractive color mixing, equal amounts of CMY toner can be substituted for equal amounts of K toner, and therefore, replacing a portion of the CMY toner with the corresponding amount of K toner does not change the color on paper. As shown, toner amount 17 and toner amount 19 have different amounts of CMYK toner. However, toner amount 17 reduces toner amount 17K and increases CMYK toner amounts 17C, 17M, and 17Y by the same amount, resulting in toner amount 19 of 19C, 19M, 19Y, and 19K. Therefore, the same color is reproduced on paper whether an image is formed using toner amount 17 or toner amount 19.

[0035] There are multiple combinations of CMYK toner amounts that will reproduce the same color on paper, as shown in Figure 8. These toner amount combinations differ in terms of ease of color balance adjustment.

[0036] 9 is a conceptual diagram illustrating that when the amount of K toner is large, the amount of change in color tone is small even when the amount of CMY toner is increased through color balance adjustment, compared to when the amount of K toner is small. Toner amounts 21 and 23 are CMYK toner amounts that reproduce the same color on paper.

[0037] Toner amount 25 is obtained by increasing only the C toner amount in toner amount 21. In other words, C toner amount 25C is larger than C toner amount 21C. M toner amount 25M, Y toner amount 25Y, and K toner amount 25K are equal to M toner amount 21M, Y toner amount 21Y, and K toner amount 21K, respectively.

[0038] Similarly, toner amount 27 is obtained by increasing only the C toner amount in toner amount 23. In other words, C toner amount 27C is greater than C toner amount 23C. M toner amount 27M, Y toner amount 27Y, and K toner amount 27K are equal to M toner amount 23M, Y toner amount 23Y, and K toner amount 23K, respectively.

[0039] Here, the difference between C toner amount 25C and C toner amount 21C is equal to the difference between C toner amount 27C and C toner amount 23C, and both have changed by amount D. Then, the ratio of amount of change D in the C toner amount to the K toner amount is compared between toner amount 25 and toner amount 27. For toner amount 25, K toner amount 25K is greater than K toner amount 27K. Therefore, the ratio of amount of change D in the C toner amount to the K toner amount is smaller for toner amount 25 and greater for toner amount 27.

[0040] This means that when the amount of C toner is changed by the same amount, the saturation of the color reproduced on paper is greater with toner amount 27. With toner amount 25, the K toner amount 25K is greater than the change in C toner amount D, so the change due to the change in C toner amount D is overshadowed by the influence of the K toner, and no change in color occurs. On the other hand, with toner amount 27, the K toner amount 27K is smaller than the change in C toner amount D, so the change due to the change in amount D is less affected by the K toner, and as a result, the saturation of the color reproduced on paper can be changed significantly.

[0041] Taking this into consideration, the image processing device according to the present disclosure includes a color correction table for color balance adjustment in addition to a normal color correction table. When performing processing other than color balance adjustment, the former table is used for color conversion, and when performing color balance adjustment, the latter table is used for color conversion.

[0042] 10 is a conceptual schematic diagram for explaining the difference between color conversion using a normal color correction table and color conversion using a color correction table for color balance adjustment in the MFP 51 according to the first embodiment of the present disclosure. Toner amounts 29 and 31 are a combination of CMYK toner amounts that reproduce the same color on paper.

[0043] In the case of processing other than color balance adjustment, the image processing unit 71 performs color conversion using a normal color correction table and obtains CMYK toner amounts 29C, 29M, 29Y, and 29K as indicated by the toner amount 29. In this case, the amount of CMY toner used can be reduced.

[0044] On the other hand, in the case of color balance adjustment, the image processing unit 71 performs color conversion using a color correction table for color balance adjustment to obtain CMYK toner amounts 31C, 31M, 31Y, and 31K as indicated by the toner amount 31. In this case, the amount of CMY toner used increases and the amount of K toner used decreases. As a result, the amount of change in CMY toner relative to the amount of K toner increases, making it easier to change the color tone.

[0045] 11 is a conceptual schematic diagram for explaining the flow of data processing in the MFP 51 according to the first embodiment of the present disclosure. The color correction unit 75 stores a normal LUT (Look-Up Table) 75a used for processing other than color balance adjustment, and a color balance adjustment LUT 75b used for color balance adjustment. The normal LUT 75a is also referred to as a first conversion table. The color balance adjustment LUT 75b is also referred to as a second conversion table.

[0046] 11A is a diagram for explaining a case where color conversion is performed using a normal color correction table. In the case of processing other than color balance adjustment, the color correction unit 75 performs color conversion based on the normal LUT 75a.

[0047] 11(B) is a diagram for explaining data processing when color conversion is performed using a color correction table for color balance adjustment. In the case of color balance adjustment, the color correction unit 75 performs color conversion based on the color balance adjustment LUT 75b. The normal LUT 75a is a table with a smaller amount of CMY and a larger amount of K than the color balance adjustment LUT 75b. On the other hand, the color balance adjustment LUT 75b is a table with a larger amount of CMY and a smaller amount of K than the normal LUT 75a.

[0048] 12 is a flowchart for explaining the operation of MFP 51 according to the first embodiment of the present disclosure. Control unit 53 determines whether an operation instructing execution of color balance adjustment (an instruction related to color balance adjustment) has been performed from operation unit 59 (step S1). If an operation instructing execution of color balance adjustment has been performed (step S1, Yes), control unit 53 instructs image processing unit 71 to perform color conversion processing using color balance adjustment LUT 75b (step S3). If an operation instructing execution of color balance adjustment has not been performed (step S1, No), control unit 53 instructs image processing unit 71 to perform color conversion processing using normal LUT 75a (step S5).

[0049] According to this embodiment, in processes other than color balance adjustment, color conversion is performed using the normal LUT 75a. The normal LUT 75a is a table with small CMY amounts and large K amounts, so consumption of CMY toner can be suppressed. On the other hand, in color balance adjustment, color conversion is performed using the color balance adjustment LUT 75b. The color balance adjustment LUT 75b is a table with large CMY amounts and small K amounts, so the amount of change in CMY amounts is large relative to the amount of K, which makes it easier to change color shades and make the user's intended adjustments.

[0050] [2. Second Embodiment] A second embodiment will now be described. In the first embodiment, either the normal LUT 75a or the color balance adjustment LUT 75b was selected depending on whether an operation to instruct execution of color balance adjustment had been performed. In contrast, in the second embodiment, either the normal LUT 75a or the color balance adjustment LUT 75b was selected based on input image data in addition to whether an operation to instruct execution of color balance adjustment had been performed. The following description will focus on differences in configuration and processing from the first embodiment.

[0051] Generally, colors with high brightness or high saturation have small overall CMY amounts, or even if the overall CMY amounts are large, the minimum toner amount among the CMY toner amounts is small. When the overall CMY amounts are small, the amount of CMY toner that can be substituted with K toner is also inevitably small. Furthermore, when the minimum toner amount among the CMY toner amounts is small, the CMY toner is replaced with K toner based on that minimum toner amount, so the amount of CMY toner that can be substituted with K toner is small. For this reason, there is no need to perform color conversion using the color balance adjustment LUT 75b, as described in the first embodiment, for images with high brightness pixels or high saturation. This embodiment takes this into consideration.

[0052] 13 is a diagram for explaining input image data that is color converted in MFP 51 according to the second embodiment of the present disclosure. Input image data 101 has an area where text is drawn (text area) and a non-text area 103 where objects other than text, such as photographs, are drawn. In the second embodiment, when an operation to instruct execution of color balance adjustment is performed and the number of gray pixels in non-text area 103 exceeds a threshold, color conversion is performed using color balance adjustment LUT 75b.

[0053] 14 is a flowchart for explaining the operation of the MFP 51 according to the second embodiment of the present disclosure. The control unit 53 determines whether an operation to instruct execution of color balance adjustment has been performed from the operation unit 59 (step S11). If an operation to instruct execution of color balance adjustment has been performed (step S11, Yes), the control unit 53 determines for each pixel of the input image data whether it is a pixel in a character area or a non-character area (step S13). Next, the control unit 53 counts the number of pixels in the non-character area whose saturation is less than threshold 1 and whose brightness is less than threshold 2 (step S15). Threshold 1 is, for example, 5, and threshold 2 is, for example, 80. Next, the control unit 53 determines whether the number of pixels counted in step S15 is greater than threshold 3 (step S17). Threshold 3 is, for example, 10% of the total number of pixels (4,905,587 pixels for A4 size at 600 dpi). If the number of pixels counted in step S15 is greater than threshold 3 (step S17, Yes), the image processing unit 71 is instructed to execute color conversion processing using the color balance adjustment LUT 75b (step S9). Even if an operation to instruct execution of color balance adjustment has not been performed (step S1, No), and even if an operation to instruct execution of color balance adjustment has been performed (step S11, Yes), if the number of pixels counted in step S15 is equal to or less than threshold 3 (step S17, No), the control unit 53 instructs the image processing unit 71 to execute color conversion processing using the normal LUT 75a (step S21).

[0054] According to the second embodiment, color conversion is performed by selecting either the normal LUT 75a or the color balance adjustment LUT 75b depending on whether an operation to instruct the execution of color balance adjustment has been performed and the number of pixels in the non-text area of ​​the input image that are close to gray, and the process of switching the color correction LUT can be omitted when there are many pixels with a low amount of K toner.

[0055] 3. Third Embodiment A third embodiment will now be described. In the first embodiment, when an operation is performed to instruct the execution of color balance adjustment, color conversion is performed based on a predetermined table (color balance adjustment LUT 75b). In contrast, in the third embodiment, multiple tables are prepared for use when an operation is performed to instruct the execution of color balance adjustment, one of the tables is selected in response to a user operation, and color conversion is performed using the selected table. Hereinafter, only the differences in configuration and processing from the first embodiment will be described.

[0056] FIG. 15 is a conceptual schematic diagram for explaining the flow of data processing in an MFP according to a third embodiment of the present disclosure. In the third embodiment, the color correction unit 75 has two color balance adjustment LUTs, namely, a first color balance adjustment LUT 75c and a second color balance adjustment LUT 75d, in addition to a normal LUT 75a. FIG. 15(A) is a diagram for explaining a case where color conversion is performed using the normal LUT 75a. FIG. 15(B) is a diagram for explaining data processing when color conversion is performed using the first color balance adjustment LUT 75c. FIG. 15(C) is a diagram for explaining data processing when color conversion is performed using the second color balance adjustment LUT 75d. The first color balance adjustment LUT 75c and the second color balance adjustment LUT 75d are also referred to as second conversion tables.

[0057] The normal LUT 75a is a table with a smaller amount of CMY and a larger amount of K than the color balance adjustment LUTs 75c and 75d. The color balance adjustment LUT 75c is a table with a larger amount of CMY and a smaller amount of K than the normal LUT 75a. The color balance adjustment LUT 75d is a table with a larger amount of CMY and a smaller amount of K than both the normal LUT 75a and the color balance adjustment LUT 75c.

[0058] 16 is a flowchart for explaining the operation of MFP 51 according to the third embodiment of the present disclosure. Control unit 53 determines whether an operation to instruct execution of color balance adjustment has been performed from operation unit 59 (step S31). If an operation to instruct execution of color balance adjustment has been performed (step S31, Yes), control unit 53 determines whether the first LUT for color balance adjustment 75c or the second LUT for color balance adjustment 75d has been selected by the operation via operation unit 59 (step S33).

[0059] If it is determined that the first LUT 75c for color balance adjustment has been selected (step S33, 1st LUT), the control unit 53 instructs the image processing unit 71 to execute color conversion processing using the first LUT 75c for color balance adjustment (step S35).If it is determined that the second LUT 75d for color balance adjustment has been selected (step S33, 2nd LUT), the control unit 53 instructs the image processing unit 71 to execute color conversion processing using the second LUT 75d for color balance adjustment (step S37).

[0060] If it is determined in step S31 that no operation has been performed from the operation unit 59 to instruct the execution of color balance adjustment, the control unit 53 instructs the image processing unit 71 to execute color conversion processing using the normal LUT 75a (step S39).

[0061] In the above description, step S33 is described as an operation to select either the first LUT for color balance adjustment 75c or the second LUT for color balance adjustment 75d via the operation unit 59. Alternatively, the control unit 53 may display on the display unit 57 a screen inquiring about the degree of change in hue desired by the user when performing color balance adjustment, and in response, have the user input the magnitude of the change in hue via the operation unit 59. In this case, if the user desires a smaller change in hue, the control unit 53 determines in step S33 that the first LUT has been selected, and if the user desires a larger change in hue, the control unit 53 determines in step S33 that the second LUT has been selected.

[0062] [4. Modifications] The present disclosure is not limited to the above-described embodiments and variations, and various modifications are possible. In other words, embodiments obtained by combining appropriately modified technical means within the scope of the gist of the present disclosure are also included in the technical scope of the present disclosure.

[0063] In the above embodiment, the normal LUT 75a, the color balance adjustment LUT 75b, the first color balance adjustment LUT 75c, and the second color balance adjustment LUT 75d are described as being stored in the color correction unit 75, but these tables may also be stored in the storage unit 55. In this case, the color correction unit 75 reads out a desired table from the storage unit 55 as needed.

[0064] In the above-described embodiment, the user is not explicitly notified that a color balance adjustment LUT has been adopted. However, after changing the selection of the color correction LUT, the change in the table may change the color tone of the image formed on the medium, which may confuse the user. To avoid this confusion, a message warning that the color correction LUT has been changed and a change in color tone may occur may be displayed on the screen, such as the LUT change notification 111 in FIG. 17. In the example of FIG. 17, the LUT change notification 111 is displayed superimposed on the operation screen for the color balance function in FIG. 4. The LUT change notification 111 may also be displayed on a screen separate from the operation screen for the color balance function in FIG. 4. By displaying the LUT change notification 111, the user can be warned that the color tone of the image formed on the medium may change.

[0065] The programs that run on each device in the embodiments 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 storage devices such as ROMs (Read Only Memories) and HDDs, and is read, modified, and written by the CPU as needed.

[0066] 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), MO (Magneto Optical Disc), MD (Mini Disc), CD (Compact Disc), BD (Blu-ray (registered trademark) Disc), etc.), magnetic recording media (e.g., magnetic tape, flexible disk, etc.), etc. Furthermore, not only are the functions of the above-described embodiments realized by executing the loaded program, but the functions of the present disclosure may also be realized by processing in cooperation with an operating system or other application programs, etc., based on instructions from the program.

[0067] Furthermore, when distributing the program on 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 computer is also included in the present disclosure. [Explanation of symbols]

[0068] 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31 Toner amount 11C, 13C, 17C, 19C, 21C, 23C, 25C, 27C, 29C, 31C C toner amount 11K, 15K, 17K, 19K, 21K, 23K, 25K, 27K, 29K, 31K K toner amount 11M, 13M, 17M, 19M, 21M, 23M, 25M, 27M, 29M, 31M toner amount 11Y, 13Y, 17Y, 19Y, 21Y, 23Y, 25Y, 27Y, 29Y, 31Y Y toner amount 11G Color reproduction on paper 51 MFP(Multi-Function Printer / Peripheral) 53 Control Unit 55 Storage section 57 Display section 59 Operation section 61 Image input unit 63 Image forming unit 65 Communications Department 67 Connection 71 Image processing section 73 Pre-processing section 73a A / D conversion section 73b Input correction section 73c Input tone correction section 73d Region separation processing section 75 Color conversion unit 75a Normal LUT (Look-Up Table) 75b Color balance adjustment LUT 75c 1st LUT for color balance adjustment 75d Second LUT for color balance adjustment 77 Post-processing section 77a Spatial filter processing section 77b Output tone correction section 77c Tone reproduction processing section 101 Input image data 103 Non-character area 111 LUT change notification

Claims

1. An image processing unit, an operation unit, and a storage unit are provided, the storage unit stores first and second conversion tables for converting input image data including a first color value into output image data including black and a second color value; the image processing unit performs conversion based on the first conversion table when an instruction related to color balance adjustment is not input from the operation unit; when an instruction for color balance adjustment is input from the operation unit, the image processing unit performs conversion based on the second conversion table. Image processing device.

2. the image processing unit classifies the input image data into a character area and a non-character area; when an instruction for color balance adjustment is input from the operation unit, the image processing unit performs conversion based on one of the first and second conversion tables selected based on the number of pixels in the non-character region. The image processing device according to claim 1 .

3. The image processing device according to claim 2 , wherein the image processing unit performs the selection based on saturation and brightness of pixels in the non-character region.

4. the storage unit stores a plurality of the second conversion tables; when an instruction relating to color balance adjustment is input from the operation unit, the image processing unit performs conversion based on one of the plurality of second conversion tables selected based on the instruction. The image processing device according to claim 1 .

5. when an instruction for color balance adjustment is input from the operation unit, the image processing unit performs conversion based on one of the first and second conversion tables selected based on the number of gray pixels in the non-character area. The image processing device according to claim 2 .

6. storing first and second conversion tables for converting input image data including a first color value to output image data including black and a second color value; If an instruction for color balance adjustment is not input from the operation unit, conversion is performed based on the first conversion table; When an instruction for color balance adjustment is input from the operation unit, conversion is performed based on the second conversion table. A method for controlling an image processing device.

Images