JP2012199722A - Image processor, image processing method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an image output with inconspicuous trace pattern (dots).SOLUTION: An image processor comprises: a trace pattern color output prediction part that acquires an image output condition including a condition of color correction for input image data and calculates color difference between a first output color under the image output condition for an input color with a trace pattern not being added and a second output color under the image output condition for an input color with the trace pattern being added; a parameter adjustment part that adjusts a color correction parameter used for the color correction according to the color difference; and a correction part (scanner γ correction part, color adjustment part, hue division masking part, 3D-LUT color conversion part) that generates output image data by correcting the input image data using the adjusted color correction parameter.

Description

  The present invention relates to an image processing apparatus, an image processing method, and a program.

  With recent advances in digital signal processing technology, printing apparatuses and copying machines that print and output images with high quality have been developed. A copying machine or the like that can obtain such a high-quality image may be illegally used for the purpose of counterfeiting banknotes or securities. Conventionally, various techniques for preventing such unauthorized use have been devised.

  For example, there is a technique in which a tracking pattern, which is information for tracking the situation when the image is copied, is input into an output image. The tracking pattern enables tracking of when and by which machine the image was copied. Information such as the machine name, serial number, and copy date / time of the copying machine that copied the image is stored in a certain area. It is expressed as a dot pattern. In general, the tracking pattern needs to be printed difficult to see or invisible. For this reason, yellow, which is difficult for humans to detect visually, is selected as the color of the dots constituting the tracking pattern.

  By the way, some color copying machines capable of copying and outputting color originals have a color conversion function for converting a specified color into another color and outputting it. In such a copying machine, when the conversion from yellow to another color is set by the user, the color of the tracking pattern that is printed in the document is converted to another color by copying, and is a color that is easily recognized by human eyes. And appear as noise.

  Specifically, a specific copy output mode with color processing for a copy original, for example, a designated color 1 (red) other than the black portion of the original, and a black (achromatic) portion of the original designated color 2 (black). Suppose you have a generation copy with two color (red / black) copies reproduced in. In this case, there is a problem that the yellow dots of the tracking pattern hit on the original so as not to be normally recognized by a person are converted (output) to other colors such as red and become conspicuous.

  Therefore, it is detected whether the input manuscript is a generation manuscript, and when a tracking pattern exists in the input manuscript, the tracking pattern included in the input manuscript is detected by detecting a yellow isolated point from the input image, and the image is output. A technique for correcting according to the mode is known. Further, when setting a color conversion process, if it is determined that a pixel in the input image is a pixel constituting a tracking pattern, a technique for prohibiting the color conversion process is considered and already known.

  For example, in Patent Document 1, even when color conversion processing is set when copying an image including specific information, color conversion processing is set for the purpose of outputting an image without degrading image quality. When a pixel constituting the tracking pattern is determined in the input image and the pixel is determined to be a pixel constituting the tracking pattern, the pixel is tracked without performing color conversion. A technique for performing color conversion on a pixel when it is determined that the pixel does not constitute a pattern is disclosed.

  However, in conventional methods such as color conversion switching according to the tracking pattern detection result and correction by tracking pattern detection handling according to the image output mode, detection of yellow dots hitting a specific color or yellow single color Cannot be distinguished from low-line-number halftone dot images. For this reason, it is difficult to completely detect only the tracking pattern, and depending on the image output conditions including color processing, there is a problem that the output image is deteriorated due to recognition of the tracking pattern.

  The present invention has been made in view of the above, and an object of the present invention is to provide an image processing apparatus, an image processing method, and a program for realizing an image output in which a tracking pattern (dot) is not conspicuous in a copy of a copy original. To do.

  In order to solve the above-described problems and achieve the object, the present invention provides a reception unit that receives an image output condition including a color correction condition for input image data, and the image output condition for an input color to which no tracking pattern is added. A calculation unit that calculates a color difference between the first output color and the second output color under the image output condition with respect to the input color to which the tracking pattern is added, and a color correction parameter used in the color correction according to the color difference And an adjustment unit that generates output image data obtained by correcting the input image data using the adjusted color correction parameter.

  According to the present invention, a receiving step for receiving an image output condition including a color correction condition for input image data, a first output color under the image output condition for an input color to which no tracking pattern is added, and a tracking pattern are added. A calculation step of calculating a color difference between the input color and the second output color under the image output condition, an adjustment step of adjusting a color correction parameter used in the color correction according to the color difference, and the adjusted color And a correction step of generating output image data obtained by correcting the input image data with a correction parameter.

  According to another aspect of the present invention, there is provided a computer that receives an image output condition including a color correction condition for input image data, a first output color under the image output condition for an input color to which no tracking pattern is added, and a tracking pattern. A calculation unit that calculates a color difference between the input color with the second output color under the image output condition with respect to the input color added, and an adjustment unit that adjusts a color correction parameter used in the color correction according to the color difference. And a program for causing the output image data to be corrected by the color correction parameter to generate output image data.

  According to the present invention, it is possible to realize an image output in which tracking patterns (dots) are not conspicuous in copying a copy document.

FIG. 1 is a block diagram showing the configuration of the MFP according to this embodiment. FIG. 2 is a block diagram illustrating a configuration example of the image processing unit. FIG. 3 is a block diagram illustrating a configuration example of the image processing unit. FIG. 4 is a block diagram illustrating a functional configuration example of the color conversion processing unit according to the present embodiment. FIG. 5 is a diagram illustrating an example of hue division for RGB data. FIG. 6 is a diagram illustrating an example of a wide-range hue signal. FIG. 7 is a diagram for explaining an example of the grid point output value. FIG. 8 is a diagram showing a tetrahedron stretched by lattice points used in the interpolation tetrahedron. FIG. 9 is a diagram illustrating a rule for determining an interpolation coefficient. FIG. 10 is a diagram illustrating an example of the relationship between the saturation level of the input color and the adjusted saturation. FIG. 11 is a diagram illustrating an example of correspondence between RGB and CMYK. FIG. 12 is a diagram illustrating an example of division points in the color space. FIG. 13 is a diagram illustrating an example of a correspondence between a scanner vector and a printer vector. FIG. 14 is a block diagram illustrating a configuration example of the generation document determination unit. FIG. 15 is a diagram illustrating an example of a pattern used for pattern matching. FIG. 16 is a diagram illustrating an example of coefficients of the MTF correction filter. FIG. 17 is a block diagram illustrating another configuration example of the generation document determination unit. FIG. 18 is a block diagram illustrating a configuration example of the image processing apparatus according to the present embodiment.

  Exemplary embodiments of an image processing apparatus, an image processing method, and a program according to the present invention will be explained below in detail with reference to the accompanying drawings. In the following, an example in which an image processing apparatus is realized as a color digital multifunction peripheral (hereinafter referred to as MFP 100) having at least two functions of a copy function, a printer function, a scanner function, and a facsimile function will be described. It is not limited to this. The present invention can be applied to any image processing apparatus such as a copying machine, a printer, a scanner apparatus, and a facsimile apparatus.

  FIG. 1 is a block diagram showing a configuration of the MFP 100 according to the present embodiment. As shown in FIG. 1, the MFP 100 includes a scanner 1, an image processing unit 2, a bus control unit 3, an image processing unit 4, an HDD 5, a CPU 6, a memory 7, and a plotter I / F (interface) unit. 8, a plotter 9, an operation display unit 10, a line I / F unit 11, an external I / F unit 12, an SB (South Bridge) 13, and a ROM 14.

  The scanner 1 includes a line sensor including a photoelectric conversion element such as a CCD (Charge Coupled Device), an A / D (analog / digital) converter, and a drive circuit for driving the line sensor and the A / D converter. The scanner 1 generates and outputs digital image data of 8 bits for each of RGB from the density information of the document obtained by scanning the set document.

  The image processing unit 2 executes a process for unifying the digital image data output from the scanner 1 to a predetermined characteristic and outputs it. FIG. 2 is a block diagram illustrating a configuration example of the image processing unit 2. As shown in FIG. 2, the image processing unit 2 includes a scanner correction processing unit 30, a γ conversion unit 31, a filter processing unit 32, a color conversion unit 33, a scaling processing unit 34, and an image area separation unit 35. And a separation decoding unit 36.

  The scanner correction processing unit 30 corrects reading unevenness or the like that occurs on the mechanism of the scanner 1 (illuminance distortion or the like), such as shading, on the digital image data output from the scanner 1.

  The γ conversion unit 31 converts the γ characteristic of the RGB image data received from the scanner 1 so as to be a predetermined characteristic (for example, 1 / 2.2).

  The filter processing unit 32 corrects the MTF characteristic of the scanner 1. Further, the filter processing unit 32 changes the frequency characteristics of the read image to make the image clearer and smoother in order to prevent moire.

  The color conversion unit 33 converts the image data value output from the filter processing unit 32 into an RGB image data value having a predetermined characteristic such as sRGB or opRGB.

  The scaling processing unit 34 unifies the size (resolution) of the RGB image data with predetermined characteristics. The scaling processing unit 34 converts, for example, the size (resolution) of RGB image data to 600 dpi.

  Basically, the image data whose characteristics are unified is accumulated in the MFP 100 by the processing in the γ conversion unit 31 and the color conversion unit 33. Thereafter, when the image data is reused, the accumulated image data is converted into an image signal suitable for the characteristics of the output destination, details of which will be described later.

  Further, the image area separation unit 35 extracts a characteristic area of the document. For example, the image area separation unit 35 extracts halftone dots formed by general printing, extraction of edges such as characters, determination of chromatic / achromatic color of the image data, and white background image. A white background is determined as to whether or not.

The separation decoding unit 36 decodes and outputs the image region separation signal output from the image region separation unit 35 to an amount of information necessary for subsequent processing in the image processing unit 4. The image area separation signal is, for example, the following 7-bit signal.
CH2: Character (1) / Non-character (0)
CHR: Character (1) / Non-character (0)
HT: High line number halftone dot (1) / Non-high line number halftone dot (0)
CW: Aya (1) / Non Aya <Aya> (0)
WS: White (1) / Non-white (0)
LHT: Low line number halftone dot (1) / Non-low line number halftone dot (0)
T: tracking pattern (1) / non-tracking pattern (0)

  The separation decoding unit 36, for example, outputs the above 7-bit image region separation signal output from the image region separation unit 35 {black character, color character, character, halftone dot character, high line number halftone dot, Each state of low line number halftone dot, photograph, tracking pattern} is decoded so that each state of 3 bits or {black character, color character, character, non-character} can be expressed by 2 bits.

  The bus control unit 3 is a data bus control unit that exchanges various data such as image data and control commands necessary in the MFP 100. The bus control unit 3 also has a bridge function between a plurality of types of bus standards. In the present embodiment, the bus control unit 3 is connected to the image processing unit 2, the image processing unit 4, and the CPU 6 through a PCI-Express bus, and is connected to the HDD through an ATA bus to form an ASIC.

  The image processing unit 4 is suitable for the output destination specified by the user for the digital image data and the accompanying information (decoded image area separation signal in the present embodiment) whose characteristics predetermined by the image processing unit 2 are unified. Execute the image processing and output. Details thereof will be described later.

  The HDD 5 is a large storage device for storing electronic data that is also used in desktop personal computers. The HDD 5 mainly stores digital image data and accompanying information of the digital image data in the MFP 100. In the present embodiment, as the HDD 5, for example, an ATA bus connection hard disk standardized by expanding IDE is used.

  The CPU 6 is a microprocessor that controls the entire control of the MFP 100. In this embodiment, as an example, an integrated CPU in which a + α function is added to a single CPU core that has recently become popular is used. For example, it is possible to use a CPU in which a connection function with a general-purpose standard I / F such as RM11100 of PMC, or a bus connection function using a crossbar switch is integrated.

  The memory 7 is a volatile memory that stores data to be temporarily exchanged in order to absorb a speed difference when bridging between a plurality of types of bus standards and a processing speed difference between connected components themselves. The memory 7 temporarily stores programs and intermediate processing data when the CPU 6 controls the MFP 100. Since the CPU 6 is required to perform high-speed processing, the system is activated by a boot program stored in the ROM 14 at the normal activation. The CPU 6 performs processing by a program developed in the memory 7 that can be accessed at high speed after startup. As the memory 7, for example, a standardized DIMM used in a personal computer can be used.

  When the plotter I / F unit 8 receives digital image data composed of CMYK sent via the general-purpose standard I / F integrated with the CPU 6, the plotter I / F unit 8 performs a bus bridge process for outputting to the dedicated I / F of the plotter 9. The general-purpose standard I / F is, for example, a PCI-Express bus.

  When the plotter 9 receives the digital image data composed of CMYK, the plotter 9 outputs the received image data on the transfer paper using an electrophotographic process using a laser beam.

  The SB (South Bridge) 13 is a general-purpose electronic device used as one of chip sets used in a personal computer. The SB 13 is a general-purpose circuit that bridges a bus used when constructing a CPU system mainly including a PCI-Express and an ISA bridge. In the present embodiment, the SB 13 bridges with the ROM 14. .

  The ROM 14 is a memory that stores a program (including boot) when the CPU 6 controls the MFP 100.

  The operation display unit 10 is a part that performs an interface between the MFP 100 and the user, and includes, for example, an LCD (Liquid Crystal Display) and a key switch. Operation display unit 10 displays various states and operation methods of MFP 100 on the LCD, and detects an input to the key switch by the user. The operation display unit 10 is connected to the CPU 6 via, for example, a PCI-Express bus.

  The line I / F unit 11 connects a PCI-Express bus and a telephone line. The line I / F unit 11 allows the MFP 100 to exchange various data via a telephone line.

  The FAX 15 is a normal facsimile, and exchanges image data with the MFP 100 via a telephone line.

  The external I / F unit 12 connects a PCI-Express bus and an external device. The external I / F unit 12 allows the MFP 100 to exchange various data with an external device. For example, the external I / F unit 12 can use a network (Ethernet (registered trademark)) for the connection I / F. That is, the MFP 100 is connected to the network via the external I / F unit 12.

  The PC 16 is a so-called personal computer. The user performs various controls and input / output of image data to / from the MFP 100 via application software and drivers installed on the PC 16.

  Note that image data sent from the image processing unit 2 and the external I / F unit 12 and the accompanying information such as image data and image area separation signals are all encoded by the CPU 6 and stored in the HDD 5. When processing is performed by the image processing unit 4 and later, the conversion process is executed after the image data and the auxiliary information stored in the HDD 5 are decoded. Here, image data (RGB) whose characteristics are unified is processed at a high compression rate by irreversible JPEG encoding, and incidental information such as an image area separation signal is processed by reversible K8 encoding. Therefore, image quality degradation is minimized.

(Copy operation)
The user sets a document on the scanner 1, and inputs the setting of a desired image quality mode and the like and the start of copying via the operation display unit 10.

  Operation display unit 10 converts information input from the user into control command data inside MFP 100 and issues it. The issued control command data is notified to the CPU 6 via the PCI-Express bus.

  The CPU 6 executes a copy operation process program in accordance with the copy start control command data, and sequentially performs settings and operations necessary for the copy operation. The operation process is described below in order.

  The 8-bit RGB digital image data obtained by scanning the document with the scanner 1 is converted into the above-described scanner correction processing unit 30 and γ conversion unit in FIG. 2 regardless of the set image quality mode. 31, the filter processing unit 32, and the color conversion unit 33 are unified into RGB signals having predetermined characteristics such as sRGB and ROMM-RGB and sent to the bus control unit 3.

In addition, the separation decoding unit 36 decodes the 7-bit image area separation signal generated by the image area separation unit 35 into information necessary for subsequent processing in the image processing unit 4 in accordance with the set image quality mode. And output. For example, the separation decoding unit 36 decodes the 7-bit image area separation signal as described above into 2-bit attribute information (image area separation signal) as shown below according to the set image quality mode.
Text original mode: Black text, color text, text, non-character Text and photo mixed original mode: text / non-character, chromatic / achromatic Photo original mode: chromatic / achromatic, white / non-white Copy original mode: black text, Colored characters, white background, non-characters

  When the bus control unit 3 receives the unified RGB image data output from the image processing unit 2 and attribute information (image area separation signal) having different attributes according to the set image mode, the bus control unit 3 receives the received RGB image data and The attribute information is encoded via the CPU 6 and then stored in the memory 7 and the HDD 5.

  Next, the RGB image data and the attribute information for each pixel accumulated in the memory 7 and the HDD 5 are decoded by the CPU 6 and then sent to the image processing unit 4 via the bus control unit 3.

  The image processing unit 4 converts the received RGB image data into CMYK image data for plotter output based on the attribute information for each pixel and outputs the converted data.

  When the bus control unit 3 receives the CMYK image data output from the image processing unit 4, the bus control unit 3 stores the data in the memory 7 via the CPU 6.

  Next, the CMYK image data stored in the memory 7 is sent to the plotter 9 via the CPU 6 and the plotter I / F unit 8.

  The plotter 9 outputs the received CMYK image data to transfer paper, and a copy of the document is generated.

  FIG. 3 is a block diagram illustrating a configuration example of the image processing unit 4. As shown in FIG. 3, the image processing unit 4 includes a filter processing unit 50, a color conversion unit 51, a pattern generation unit 52, a scaling processing unit 53, a printer γ correction unit 54, and a gradation processing unit 55. And. Hereinafter, the operation of the image processing unit 4 will be described.

  The filter processing unit 50 corrects the sharpness of the unified RGB image data so that the reproducibility when output to the plotter 9 is improved. Specifically, the filter processing unit 50 executes a sharpening process or a smoothing process in accordance with the attribute information (image area separation signal) decoded according to the set image quality mode. For example, the filter processing unit 50 performs a sharpening process in order to make a character clear / clear in the character document mode. Further, the filter processing unit 50 executes a smoothing process in order to smoothly express gradation in the photo mode.

  When the color converter 51 receives the unified RGB image data of 8 bits each, it converts it into 8 bits of CMYK each of which is a color space for the plotter 9. Also at this time, the color conversion unit 51 performs optimum color adjustment according to the attribute information (image area separation signal) decoded according to the set image quality mode information.

  The scaling processing unit 53 converts the size (resolution) of the CMYK image data according to the reproduction performance of the plotter 9. Depending on the performance (resolution) of the plotter 9, the scaling unit 53 may not perform conversion.

  The printer γ correction unit 54 performs table conversion for each CMYK plate by using the CMYK edge γ table and the non-edge γ table generated in advance by the CPU 6 and set for plotter output to perform γ correction. Execute.

  When the gradation processing unit 55 receives 8 bits of CMYK output from the printer γ correction unit 54, the gradation processing unit 55 performs gradation number conversion processing according to the gradation processing capability of the plotter 9. The gradation processing unit 55 performs gradation number conversion processing using, for example, an error diffusion method which is one of pseudo halftone processing for each CMYK 2 bit.

(Fax transmission operation)
The user sets a document on the scanner 1, and performs setting of a desired mode and the like and input of fax start by the operation display unit 10.

  Operation display unit 10 converts information input from the user into control command data inside MFP 100 and issues it. The issued control command data is notified to the CPU 6 via the PCI-Express bus.

  The CPU 6 executes a fax transmission operation process program in accordance with the control command data for starting fax transmission, and sequentially performs settings and operations necessary for the fax transmission operation. The operation process is described below in order.

  RGB 8-bit digital image data obtained by scanning the document with the scanner 1 is converted into RGB values unified with predetermined characteristics by the image processing unit 2 and sent to the bus control unit 3.

  When the bus control unit 3 receives the RGB image data output from the image processing unit 2, the bus control unit 3 stores the RGB image data in the memory 7 via the CPU 6.

  Next, the unified RGB image data stored in the memory 7 is sent to the image processing unit 4 via the CPU 6 and the bus control unit 3.

  The image processing unit 4 converts the received unified RGB image data into monochrome binary image data for fax transmission and outputs it.

  When the bus control unit 3 receives the monochrome binary image data output from the image processing unit 4, the bus control unit 3 stores it in the memory 7 via the CPU 6.

  Next, the monochrome binary image data stored in the memory 7 is sent to the line I / F unit 11 via the CPU 6.

  The line I / F unit 11 transmits the received monochrome binary image data to the FAX 15 connected via the line.

(Scanner delivery operation)
The user sets a document on the scanner 1 and inputs a setting of a desired mode and the like and start of scanner distribution through the operation display unit 10.

  Operation display unit 10 converts information input from the user into control command data inside MFP 100 and issues it. The issued control command data is notified to the CPU 6 via the PCI-Express bus.

  The CPU 6 executes a scanner distribution operation process program in accordance with the scanner distribution start control command data, and the scanner 1 sequentially performs settings and operations necessary for the distribution operation. The operation process is described below in order.

  RGB 8-bit digital image data obtained by scanning the document with the scanner 1 is converted into RGB values unified with predetermined characteristics by the image processing unit 2 and sent to the bus control unit 3.

  Upon receiving the unified RGB image data output from the image processing unit 2, the bus control unit 3 stores the unified RGB image data in the memory 7 via the CPU 6.

  Next, the RGB image data stored in the memory 7 is sent to the image processing unit 4 via the CPU 6 and the bus control unit 3.

  The image processing unit 4 converts the received RGB image data into image data for scanner distribution such as sRGB and outputs the image data (RGB multi-value, gray scale, monochrome binary, etc.).

  When the bus control unit 3 receives the image data output from the image processing unit 4, the bus control unit 3 stores the image data in the memory 7 via the CPU 6.

  Next, the image data stored in the memory 7 is sent to the external I / F unit 12 via the CPU 6.

  The external I / F unit 12 transmits the received image data to the PC 16 connected via the network.

  Next, an operation when image data obtained by scanning a document is accumulated / saved in MFP 100 and then the accumulated / saved image data is reused will be described.

(Copy operation + Accumulation / save operation to HDD)
The user sets a document on the scanner 1, and inputs the setting of a desired image quality mode and the like and the start of copying via the operation display unit 10.

  Operation display unit 10 converts information input from the user into control command data inside MFP 100 and issues it. The issued control command data is notified to the CPU 6 via the PCI-Express bus.

  The CPU 6 executes a copy operation process program in accordance with the copy start control command data, and sequentially performs settings and operations necessary for the copy operation. The operation process is described below in order.

  The 8-bit RGB digital image data obtained by scanning the document with the scanner 1 is converted into the above-described scanner correction processing unit 30 and γ conversion unit in FIG. 2 regardless of the set image quality mode. 31, the filter processing unit 32, and the color conversion unit 33 are unified into RGB signals having predetermined characteristics such as sRGB and ROMM-RGB and sent to the bus control unit 3.

  The scanner correction processing unit 30 corrects reading unevenness or the like that occurs on the mechanism of the scanner 1 (illuminance distortion or the like), such as shading, on the digital image data output from the scanner 1.

  The γ conversion unit 31 converts the γ characteristic of the RGB image data received from the scanner 1 so as to be a predetermined characteristic (for example, 1 / 2.2).

  The filter processing unit 32 unifies the sharpness of the RGB image data to a predetermined characteristic. For example, when the reference chart is scanned, the filter processing unit 32 converts the number of lines so as to have a predetermined MTF characteristic value for each set image quality mode. At that time, the filter processing unit 32 performs processing using parameters based on the image region separation signal generated by the image region separation unit 35.

  The color conversion unit 33 converts the image data value output from the filter processing unit 32 into an RGB image data value having a predetermined characteristic such as sRGB or opRGB.

  The scaling processing unit 34 unifies the size (resolution) of the RGB image data to a predetermined characteristic (for example, 600 dpi).

In addition, the separation decoding unit 36 decodes the 7-bit image area separation signal generated by the image area separation unit 35 into information necessary for subsequent processing in the image processing unit 4 in accordance with the set image quality mode. And output. For example, the separation decoding unit 36 decodes the 7-bit image area separation signal as described above into 2-bit attribute information (image area separation signal) as shown below according to the set image quality mode.
Text original mode: Black text, color text, text, non-character Text and photo mixed original mode: text / non-character, chromatic / achromatic Photo original mode: chromatic / achromatic, white / non-white Copy original mode: black text, Colored characters, white background, non-characters

  When the bus control unit 3 receives the unified RGB image data output from the image processing unit 2 and attribute information (image area separation signal) having different attributes according to the set image mode, the bus control unit 3 encodes the data via the CPU 6. Are stored in the memory 7.

  The unified RGB image data stored in the memory 7 is transmitted to the HDD 5 via the CPU 6 and the bus control unit 3, and is stored and stored in the HDD 5 together with image input conditions (in this case, scanner input, image quality mode, etc.).

  After that, as described above, the unified RGB image data in the memory 7 interprets the scanner read image and the image quality mode set at the time of input, and an output signal suitable for the plotter 9 by the image processing unit 4. Is output to the plotter 9, and a copy of the document is generated.

  Here, the operation | movement at this time is demonstrated using FIG.

  The filter processing unit 50 corrects the sharpness of the unified RGB image data so that the reproducibility when output to the plotter 9 is improved. Specifically, the filter processing unit 50 executes a sharpening process or a smoothing process in accordance with the attribute information (image area separation signal) decoded according to the set image quality mode. For example, the filter processing unit 50 performs a sharpening process in order to make a character clear / clear in the character document mode. Further, the filter processing unit 50 executes a smoothing process in order to smoothly express gradation in the photo mode.

  When the color converter 51 receives the unified RGB image data of 8 bits each, it converts it into 8 bits of CMYK each of which is a color space for the plotter 9. Also at this time, the optimum color adjustment is executed according to the attribute information (image area separation signal) decoded according to the set image quality mode information.

  The scaling processing unit 53 converts the size (resolution) of the CMYK image data according to the reproduction performance of the plotter 9. Depending on the performance (resolution) of the plotter 9, the scaling unit 53 may not perform conversion.

  The printer γ correction unit 54 performs table conversion for each CMYK plate by using the CMYK edge γ table and the non-edge γ table generated in advance by the CPU 6 and set for plotter output to perform γ correction. Execute.

  When the gradation processing unit 55 receives 8 bits for each of CMYK, the gradation processing unit 55 performs gradation number conversion processing according to the gradation processing capability of the plotter 9.

  As another operation at the time of image storage, the CPU 6 can detect the usage rate of the memory 7 and the HDD 5 and can encode and store the decoded attribute information after the change.

  For example, when an image is input in a state where the usage rate of the HDD 5 exceeds a specified value, the CPU 6 discards a part of the attribute information (image area separation signal) output from the separation decoding unit 36 (for example, lower order) All pixels of the bit are set to 0) and then encoded and stored.

  When operating under this condition, for example, the attribute information (image area separation signal) as described below is interpreted according to the set image quality mode.

(Printer operation + Accumulation / saving operation to HDD)
The user operates DTP (Desk Top Publishing) application software on the PC 16 to create and edit various texts and graphics, and instructs setting of a desired printer output mode and printing start. The PC 16 converts the created / edited document or figure into information such as commands and data described in a page description language (PDL), and then translates the PDL data and converts it into raster image data. (RIP) is performed. The PC 16 sends the raster image data to the CPU 6 via the external I / F unit 12.

At the time of raster image processing (RIP), the PC 16 converts to uniform RGB image data having predetermined characteristics, and also generates 4-bit attribute information as shown below.
CHR: Character / line drawing (1) / Non-character / line drawing (0)
CW: Aya (1) / Non Aya <Aya> (0)
WS: White (1) / Non-white (0)
HS: saturated color (1) / unsaturated color (0)

Further, the PC 16 decodes 2-bit attribute information as shown below according to the set printer output mode, and then sends the decoded attribute information to the CPU 6 via the external I / F unit 12.
General document output: achromatic colors other than images, chromatic colors other than images, images, white background Graphic output: achromatic colors, chromatic colors, white background, saturated colors Photo image output: white background / non-white background

  When the CPU 6 receives the unified RGB image data output from the image processing unit 2 and attribute information having different attributes according to the set image output mode, the CPU 6 encodes the data and stores them in the memory 7.

  The unified RGB image data stored in the memory 7 is transmitted to the HDD 5 via the CPU 6 and the bus control unit 3, and is stored and stored together with image input conditions (in this case, printer output, image output mode, etc.) in the HDD 5. The

  After that, as described above, the unified RGB image data in the memory 7 interprets that it is a printer output image and the image output mode set at the time of input, and the image processor 4 makes an output suitable for the plotter 9. After being converted into a signal, it is output to the plotter 9 and a printer output image is generated.

  When the color converter 51 receives the unified RGB image data of 8 bits each, it converts it into 8 bits of CMYK each of which is a color space for the plotter 9. Also at this time, the color conversion unit 51 performs optimal color adjustment according to the attribute information decoded according to the set image quality mode information.

  The scaling processing unit 53 converts the size (resolution) of the CMYK image data according to the reproduction performance of the plotter 9. Depending on the performance (resolution) of the plotter 9, the scaling unit 53 may not perform conversion.

  The printer γ correction unit 54 performs table conversion for each CMYK plate by using the CMYK edge γ table and the non-edge γ table generated in advance by the CPU 6 and set for plotter output to perform γ correction. Execute.

  Upon receiving 8 bits for each of CMYK, the gradation processing unit 55 performs an optimal gradation number conversion process on the gradation processing capability of the plotter 9 and the attribute information decoded in accordance with the set image quality mode information.

  As another operation at the time of image storage, the CPU 6 can detect the usage rate of the memory 7 and the HDD 5 and can encode and store the decoded attribute information after the change.

  Next, an operation for reusing image data stored and stored in the HDD 5 will be described.

(Fax transmission operation)
The user uses the operation display unit 10 to input desired mode setting and fax transmission start for the image data stored in the HDD 5 when the copy operation is performed earlier.

  Operation display unit 10 converts information input from the user into control command data inside MFP 100 and issues it. The issued control command data is notified to the CPU 6 via the PCI-Express bus.

  The CPU 6 executes a fax transmission operation process program in accordance with the control command data for starting fax transmission, and sequentially performs settings and operations necessary for the fax transmission operation. The operation process is described below in order.

  The bus control unit 3 outputs the RGB image data stored in the HDD 5 to the memory 7 via the CPU 6.

  Thereafter, as described above, the RGB image data in the memory 7 is output to the line I / F unit 11 via the image processing unit 4, and FAX transmission is executed. The operation at this time will be described in order with reference to FIG.

  The filter processing unit 50 corrects the sharpness of the RGB image data so as to improve reproducibility in the case of FAX transmission. Specifically, the filter processing unit 50 performs a sharpening process or a smoothing process according to desired mode information. For example, the filter processing unit 50 executes a sharpening process in order to make a character clear / clear in the character mode, and performs a smoothing process in order to smoothly express gradation in the photo mode.

  When the color conversion unit 51 receives 8-bit RGB data, the color conversion unit 51 converts the data into a single monochrome (monochrome) 8-bit data using a FAX apparatus.

  The scaling processing unit 53 converts the size (resolution) of the monochrome image data into the size (resolution) transmitted / received by the FAX apparatus. For example, the scaling processing unit 53 converts main scanning: 200 dpi × sub scanning: 100 dpi.

  The printer γ correction unit 54 executes γ correction using a γ table for FAX transmission set in advance by the CPU 6.

  When the gradation processing unit 55 receives monochrome 8 bits, the gradation processing unit 55 performs gradation number conversion processing according to the gradation processing capability transmitted / received by the FAX apparatus. For example, the gradation processing unit 55 converts the number of gradations into a binary value using an error diffusion method which is one of pseudo halftone processes.

(Scanner delivery operation)
The user uses the operation display unit 10 to input a desired mode setting and scanner distribution start for the image data stored in the HDD 5 when the copying operation is performed earlier.

  Operation display unit 10 converts information input from the user into control command data inside MFP 100 and issues it. The issued control command data is notified to the CPU 6 via the PCI-Express bus.

  The CPU 6 executes a scanner distribution operation process program in accordance with the scanner distribution start control command data, and sequentially performs settings and operations necessary for the scanner distribution operation. The operation process is described below in order.

  The bus control unit 3 outputs the RGB image data stored in the HDD 5 to the memory 7 via the CPU 6.

  Thereafter, as described above, the RGB image data in the memory 7 is output to the external I / F device (11) via the image processing unit 4, and scanner distribution is executed. The operation at this time will be described in order with reference to FIG.

  The filter processing unit 50 corrects the sharpness of the RGB image data so that the reproducibility in the case of scanner distribution is improved. Specifically, the filter processing unit 50 performs a sharpening process or a smoothing process according to desired mode information. For example, the filter processing unit 50 executes a sharpening process in order to make a character clear / clear in the character mode, and performs a smoothing process in order to smoothly express gradation in the photo mode.

  When the color converter 51 receives RGB 8-bit data, it converts it into a designated color space. For example, the color conversion unit 51 converts each color into an sRGB color space that is common in scanner distribution with 8 bits for each color.

  The scaling processing unit 53 converts the size (resolution) of the sRGB image data into the size (resolution) transmitted / received by the designated scanner distribution. For example, the scaling processing unit 53 converts main scanning: 200 dpi × sub scanning: 200 dpi.

  The printer γ correction unit 54 performs γ correction using a distribution γ table preset by the CPU 6.

  The gradation processing unit 55 performs gradation number conversion processing according to the gradation processing capability transmitted / received by the designated scanner distribution. The gradation processing unit 55 is not particularly required to perform gradation processing, assuming that 160,000 colors of 8 bits for each of RGB are designated.

  As described above, when the output destination different from the input time is desired for the data stored / stored in the MFP 100, the image quality changes at the time of normal operation (operation when the output destination is designated from the beginning). It is possible to change the output destination, and reusability is remarkably improved.

(Configuration of color conversion processor)
FIG. 4 is a block diagram illustrating a functional configuration example of the color conversion processing unit 200 according to the present embodiment. The color conversion processing unit 200 performs color conversion processing on a series of image data from scanner input to copy output. As will be described below, the color conversion processing unit 200 includes the same functions as the components included in the image processing unit 2 and the image processing unit 4 described above. The color conversion processing unit 200 may be configured to share such a similar function with the image processing unit 2 and the image processing unit 4, or may be configured independent of the image processing unit 2 and the image processing unit 4. You may comprise as a part.

  As shown in FIG. 4, the color conversion processing unit 200 includes a scanner γ correction unit 210, a color adjustment unit 220, a hue division masking unit 230, a 3D-LUT color conversion unit 240, a parameter adjustment unit 250, and a tracking function. A pattern color output prediction unit 260.

  In order to unify the digital image data output from the scanner 1 into predetermined characteristics, the scanner γ correction unit 210 converts each of the RGB image reading data into, for example, 1 using a one-dimensional lookup table. / Γ transform so that it becomes the power of 2.2. The scanner γ correction unit 210 corresponds to the γ conversion unit 31 in FIG.

  The color adjustment unit 220 performs color adjustment before color conversion to unified RGB. For example, as shown below, the color adjustment unit 220 converts RGB image data into Yuv image data, and executes saturation adjustment by correcting the uv signal.

<RGB → Yuv conversion>
Y = R1 + 2 × G1 + B1 (Y: 0 to 1020)
U = R1-G1 (U: -255 to 255)
V = B1-G1 (V: -255 to 255)

<Saturation distance calculation>
The saturation distance (sat) is the sum of the absolute values of uv.
sat = | U | + | V | (sat: 0 to 510)

<Conversion from saturation distance to table index>
The saturation distance (sat) is halved.
INDEX = sat >> 1

<Saturation conversion rate setting>
The conversion table is subtracted from the obtained index to obtain the saturation conversion rate (conv_sat [INDEX]). The conversion rate preset in the conversion table is 0/64 to 255/64 at the minimum, and the coefficient resolution is 1/64 (8 bits). Therefore, the conversion rate 1 is 64.
Table write value = unsigned char (conversion rate x 64)

<Saturation adjustment>
Saturation adjustment is performed by multiplying uv by a saturation conversion rate (conv_sat [INDEX]) corresponding to the distance of uv.
U ′ = (U × conv_sat [INDEX]) / 24
V ′ = (V × conv_sat [INDEX]) / 24

<Yuv → RGB conversion>
The chroma-converted YUV data is converted into RGB data. Clip outRGB as follows.
G ′ = Y − ((U ′ + V ′) / 22)
However, (G ′ <0: outG = 0), (G ′ ≧ 1024: outG = 255), (0 ≦ G ′ <1024: outG = G ′ >> 2)
R '= U' + G '
However, (B ′ <0: outB = 0), (B ′ ≧ 1024: outB = 255), (0 ≦ B ′ <1024: outB = B ′ >> 2)
B '= V' + G '
However, (R ′ <0: outR = 0), (R ′ ≧ 1024: outR = 255), (0 ≦ R ′ <1024: outR = R ′ >> 2)

  The hue division masking unit 230 calculates a hue component for the RGB data after γ conversion in order to unify the predetermined characteristics, and uses a masking coefficient set for each area divided for each hue. Perform linear transformation. The hue division masking unit 230 corresponds to the color conversion unit 33 in FIG.

  As shown in FIG. 5, the hue division for the RGB data divides the color space by a plane extending radially around the achromatic color axis (Dr = Dg = Db).

  Specifically, the hue determination is performed by converting an image signal (snpr, snpg, snpb) into a hue signal (HUE) and comparing it with a hue boundary value (HUE00 to 11), and determining the hue region (12 divisions) based on the result. This is realized by outputting a hue area signal (Huejo).

<Color difference signal generation>
Color difference signals (X, Y) are generated from the image signals (snpr, snpg, snpb).
X = snpg-snpr
Y = snpb-snpg

<Wide area hue detection>
A wide-range hue signal (HUEH) is generated from the color difference signal (X, Y). The wide area hue signal (HUEH) indicates a position when the XY signal plane is divided into eight (see FIG. 6). The wide-range hue is detected by the following conditional expression.
! HT1 and HT0: HUEH = 0
! HT2 and HT1: HUEH = 1
! HT3 and HT2: HUEH = 2
! HT4 and HT3: HUEH = 3
! HT5 and HT4: HUEH = 4
! HT6 and HT5: HUEH = 5
! HT7 and HT6: HUEH = 6
! HT0 and HT7: HUEH = 7
Other than above (Y = X = 0): HUEH = 7

However, HT0 to HT7 are as follows.
HT0 = (Y ≧ 0)
HT1 = (Y ≧ X)
HT2 = (X ≦ 0)
HT3 = (Y ≦ −X)
HT4 = (Y ≦ 0)
HT5 = (Y ≦ X)
HT6 = (X ≧ 0)
HT7 = (Y ≧ −X)

<Color difference signal rotation>
Color difference signals (XA, YA) are generated according to the wide-range hue signal (HUEH). The color difference signals (XA, YA) are coordinates when the color difference signal plane (X, Y) is rotated and moved to the area of “HUEH = 0”.
When HUEH = 0: XA = X, YA = Y
When HUEH = 1: XA = X + Y, YA = −X + Y
When HUEH = 2: XA = Y, YA = −X
When HUEH = 3: XA = −X + Y, YA = −X−Y
When HUEH = 4: XA = −X, YA = −Y
When HUEH = 5: XA = −XY, YA = XY
When HUEH = 6: XA = −Y, YA = X
When HUEH = 7: XA = X−Y, YA = X + Y

<Narrow hue detection>
A narrow-range hue signal (HUEL) is generated from the color difference signals (XA, YA). The narrow-range hue signal (HUEL) is the slope of the color difference signal plane coordinates (HUEL / 32 = YA / XA).
XA is 0: HUEL = 0x1F
Other than the above: Huel = (YA << 5) / XA

<Hue boundary register>
Hue boundary registers (HUE00 to HUE11) set values are output.

<Hue area determination>
The hue boundary signal (HUE00 to HUE11: 8 bits) is compared with the hue signal (HUEHL {HUEH, HUEL}) to generate a hue region (HUE).
HUE00 <HUEHL ≦ HUE01: HUE = 1
HUE01 <HUEHL ≦ HUE02: HUE = 2
HUE02 <HUEHL ≦ HUE03: HUE = 3
HUE03 <HUEHL ≦ HUE04: HUE = 4
HUE04 <HUEHL ≦ HUE05: HUE = 5
HUE05 <HUEHL ≦ HUE06: HUE = 6
HUE06 <HUEHL ≦ HUE07: HUE = 7
HUE07 <HUEHL ≦ HUE08: HUE = 8
HUE08 <HUEHL ≦ HUE09: HUE = 9
HUE09 <HUEHL ≦ HUE10: HUE = 10
HUE10 <HUEHL ≦ HUE11: HUE = 11
Other than above: HUE = 0

  The last condition is equivalent to (HUE11 <HUEHL) && (HUEHL ≦ HUE00).

<Hue division masking>
Based on the hue HUE determined for the hue area, a masking operation corresponding to the hue is performed. In this embodiment, a masking operation from the scanner RGB to the unified RGB is performed.

Here, when performing a product-sum operation for linear masking with 12 hue divisions, each operation is processed independently for each color of RGB. Based on the hue determination signal HUE calculated by the hue area determination, a color correction coefficient and a color correction constant are selected and calculated.
sum_X = coef_r [HUE] × bcr + coef_g [HUE] × bcg + coef_b [HUE] × bcb + const × 256 + 128 (X: RGBK)
Msk_X = sum_X >> 8 (X: RGBK)

  In the case of a copy operation, the 3D-LUT color conversion unit 240 in FIG. 4 converts CMYK image data for plotter control based on the unified RGB image data. The 3D-LUT color conversion unit 240 corresponds to the color conversion unit 51 in FIG.

  In the case of a copy (plotter) output operation, three-dimensional LUT conversion is executed, and conversion to the output color (CMYK) of the plotter 9 is executed. For the conversion algorithm based on the three-dimensional LUT, for example, a memory map interpolation method widely used conventionally can be used.

  Three-dimensional memory map interpolation is performed on the input u_8-bit unified RGB image data (In_r, In_g, In_b).

  In memory map interpolation, the three-dimensional input color space is divided into a plurality of unit cubes, each divided unit cube is divided into six tetrahedrons that share the axis of symmetry, and output by linear operation for each unit cube. Find the value. In the linear operation, data of division boundary points (= lattice points) are used as parameters (hereinafter referred to as lattice point parameters). The actual processing procedure is as follows (the same processing is executed for each output version). In this three-dimensional memory map interpolation, the length of one side of the unit cube is 32 because it is divided into eight.

  When the input data is X (X, Y, z), first, a unit cube containing the coordinate X is selected. Here, X (X, Y, z) = (In_r, In_g, In_b).

  The lower coordinates (Δx, Δy, Δz) of the coordinate P in the selected unit cube are obtained, the unit tetrahedron is selected by comparing the lower coordinates, the linear interpolation is performed for each unit tetrahedron, and the coordinates P The output value Pout at is obtained. Pout is an integer value obtained by multiplying the entire expression by the length of one side of the unit cube.

  P0 to P7 in FIG. 7 are grid point output values (here, corresponding to the device CMYK of the plotter 9 corresponding to the unified RGB color). The interpolation coefficients K0, K1, K2, and K3 are determined in accordance with the magnitude relationship between Δx, Δy, and Δz and the above-described separation signal.

  FIG. 8 is a diagram showing a tetrahedron stretched by lattice points used in the interpolation tetrahedron. FIG. 9 is a diagram illustrating a rule for determining an interpolation coefficient.

Finally, based on the output values on the four preset vertices of the selected tetrahedron and the position (distance from each vertex) in the input tetrahedron, linear interpolation is performed by the following formula: Executed.
Pout_c = (K0_c × Δx + K1_c × Δy + K2_c × Δz + K3_c) << 5
Pout_m = (K0_m × Δx + K1_m × Δy + K2_m × Δz + K3_m) << 5
Pout_y = (K0_y × Δx + K1_y × Δy + K2_y × Δz + K3_y) << 5
Pout_k = (K0_k × Δx + K1_k × Δy + K2_k × Δz + K3_k) << 5

  The operation display unit 10 in FIG. 4 is a part that performs an interface between the MFP 100 and the user, as in FIG. In the present embodiment, in the copying operation, image output conditions including conditions relating to the document type, desired finish (density setting, etc.) and color processing conditions are set using the operation display unit 10. The set image output conditions are sent to the CPU 6 via the bus.

  The tracking pattern color output prediction unit 260 receives the image output condition set in the operation display unit 10 (receiving unit). Then, the tracking pattern color output prediction unit 260 receives the input color under the received image output condition and each of the processing units (scanner γ correction unit 210, color adjustment unit 220, hue division masking unit 230, 3D-LUT color conversion unit). 240) A change in color when a tracking pattern is added to a representative input color forming the color correction parameter of 240) is predicted, and a normal output color under a set image output condition and a tracking pattern are added. The color difference (ΔE) between the input color and the output color is calculated (calculation unit). The tracking pattern color output prediction unit 260 sends the calculated color difference to the parameter adjustment unit 250. The normal output color means an output color for an input color to which no tracking pattern is added. Further, the color correction parameter refers to adjustment and processing (RGB → R′G′B ′, etc.) for color signals handled in the MFP 100 and each coefficient used in conversion formulas of color attributes (RGB and CMYK) and coefficient calculation. This is a generic term for the base parameters.

The tracking pattern color output prediction unit 260 calculates the color difference ΔE as follows, for example.
ΔE = {(L1-L2) ² + (a1-a2) ² + (b1-b2) ² } ^0.5
However,
L1a1b1: CIELAB value of the output color under the image output condition with respect to the normal input color L2a2b2: CIELAB value of the output color under the image output condition with respect to the input color to which the tracking pattern is added

  The parameter adjustment unit 250 performs an operation as described later on the color correction parameters of the above-described processing units (scanner γ correction unit 210, color adjustment unit 220, hue division masking unit 230, 3D-LUT color conversion unit 240). And adjustment is executed and set in the register of each processing unit.

  For example, in the two-color copy mode, the parameter adjustment unit 250 outputs the vivid color (saturated color of each hue) portion of the document image read by the scanner 1 in yellow and moves it to the achromatic (gray) side of the document image. The gradation change is expressed in black, and the achromatic (gray) of the original image is reproduced with one black color. The two-color copy mode is a mode in which a portion other than the black portion of the document is reproduced in yellow (Yellow) and a black portion (achromatic color) portion of the document is reproduced in black (Black).

  Therefore, when the document read by the scanner 1 is a copy document, yellow dots (patterns) are written on the entire image as a tracking pattern. For this reason, for example, if a high-saturation blue-based (particularly Cyan) region exists in the document, the saturation (brilliance) decreases due to the influence of yellow (yellow) dots (patterns), and the green (Green) direction. As a result of the color shift, the tracking pattern appears as a black dot in the two-color copy and is recognized by a person.

  The tracking pattern color output prediction unit 260 outputs the CIELAB value of the output color in the normal two-color copy mode to the representative color in the input color space and 2 for the representative color in the input color space to which the tracking pattern is added. The aforementioned color difference (ΔE) is calculated from the CIELAB value of the output color in the color copy mode. When the calculated color difference (ΔE) is larger than a preset allowable color difference, the parameter adjustment unit 250 performs the above-described processing units (scanner γ correction unit 210, color adjustment unit 220, hue division masking unit 230, 3D). The color correction parameter of the -LUT color conversion unit 240 is adjusted and set in the register of each processing unit (details will be described later).

  In the two-color copy mode that is the image output condition, the color difference is increased due to a decrease in saturation due to the addition of the tracking pattern. Therefore, the parameter table (conv_sat [INDEX]) described above is changed so that the parameters of the color adjustment unit 220 described above have the saturation conversion characteristics shown in FIG.

  Note that S1 in FIG. 10 represents a saturation level at which the saturation is saturated with respect to the saturation of the input color (in this embodiment, the sum of UVs). As a setting method of S1, for example, the saturation of an input color to which a tracking pattern in which the above-described color difference exceeds an allowable color difference due to a decrease in saturation due to the addition of the tracking pattern is added to the representative color in the input color space (the embodiment) Then, the method of UV sum) is an example.

  Here, the color after the tracking pattern is added to the representative color in the input color space of the tracking pattern color output prediction unit 260 (in this embodiment, the value is R′G′B ′ after scanner γ correction in FIG. 4). May be obtained in advance and stored in a table as a representative color. Further, the color after adding the tracking pattern may be estimated using a color mixing simulator for CMY (K) constructed in advance using a neural network.

  The CIELAB values (L1a1b1 and L2a2b2) handled in the calculation of the color difference ΔE are the typical representative input color R1G1B1 (in this embodiment, the RGB values after the scanner γ correction in FIG. 4), and the representative to which the tracking pattern is added. For the input color R2G2B2 (in this embodiment, the RGB value after the scanner γ correction in FIG. 4), the hue division masking unit 230 uses a hue division masking coefficient for two-color copy mode, which will be described later, to use a unified RGB value. Is converted into a color separation result into two colors shown in FIG.

The result of color separation into these two color-converted colors is unified RGB. For this reason, assuming that the unified RGB is sRGB, the above-described L1a1b1 and L2a2b2 are color-converted via the tristimulus values (CIEXYZ) as follows.
X1 = 0.4124 × r1 + 0.3576 × g1 + 0.1805 × b1
Y1 = 0.2126 × r1 + 0.7152 × g1 + 0.0722 × b1
Z1 = 0.0193 × r1 + 0.1192 × g1 + 0.9505 × b1
X2 = 0.4124 * r2 + 0.3576 * g2 + 0.1805 * b2
Y2 = 0.2126 * r2 + 0.7152 * g2 + 0.0722 * b2
Z2 = 0.0193 * r2 + 0.1192 * g2 + 0.9505 * b2

here,
r1 = (R1 / 1023) ^2.2
g1 = (G1 / 1023) ^2.2
b1 = (B1 / 1023) ^2.2
r2 = (R2 / 1023) ^2.2
g2 = (G2 / 1023) ^2.2
b2 = (B2 / 1023) ^2.2

L1 = 116 × (Y1 / Y0) ^1/3 −16
a1 = 500 × {(X1 / X0) ^1/3 − (Y1 / Y0) ^1/3 }
B1 = 500 × {(Y1 / Y0) ^1/3 − (Z1 / Z0) ^1/3 }
L2 = 116 × (Y2 / Y0) ^1/3 −16
a2 = 500 × {(X2 / X0) ^1/3 − (Y2 / Y0) ^1/3 }
B2 = 500 × {(Y2 / Y0) ^1/3 − (Z2 / Z0) ^1/3 }

(Color correction operation of the color conversion processing unit 200)
The masking coefficients for each hue used in the hue division masking unit 230 in FIG. 4 are (Dr, Dg, Db) → (Dc, 2 points on the achromatic color axis and 2 points on both boundary planes (4 points in total). Dm, Dy, Dk) can be determined if the corresponding relationship is known.

  Here, the input color is defined as RGB (scanner vector) and the output color (corresponding color) is defined as CMYK (printer vector). However, the input / output data attributes can be set arbitrarily, and general-purpose color conversion is possible. It is.

  In the present embodiment, RGB after scanner γ correction corresponds to a scanner vector, and unified RGB (sRGB or the like) corresponds to a printer vector. In addition, the printer vector (corresponding color) for the scanner vector (input color) can be switched according to the image output mode, or changed according to color correction (color adjustment or color processing), and then the masking coefficient can be obtained. It corresponds to various color corrections.

In FIG. 11, it is assumed that the correspondence between the four points (Dr, Dg, Db) and (Dc, Dm, Dy, Dk) is expressed by the following equation (1).

In this case, the correspondence of each of the colors 1 to 4 is put together as shown in the following equation (2).

The masking coefficient that links the correspondence of the equation (2) is as the following equation (3).

The masking coefficient to be finally obtained is expressed by the following equation (4) using an RGB inverse matrix.

  If the relationship between two points on the achromatic axis (white and black) and two points on both boundary planes (four points in total) is determined in this way, a masking coefficient can be obtained. Therefore, as a parameter design for color conversion, the right side of equation (1) is defined as the scanner vector and the left side is defined as the printer vector regardless of the input / output data attributes, and the scanner vector and printer vector at each division point are obtained. become.

  In the hue division masking color conversion, R, G, B, C, M, and Y are divided at two division points in a total of 12 color spaces (see FIG. 12). Therefore, after setting 14 final scanner vectors and printer vectors including white and black points on the achromatic color axis shown in FIG. 13, a masking coefficient is calculated for each hue region.

<Setting of corresponding color (printer vector) for single color output operation>
When the basic scanner vector and the basic printer vector for full color are set as shown in FIG. 13, the printer vectors (Xr ′, Xg ′, Xb ′, Xk ′) are set as the set colors for single color as follows: Sort by hue. After that, the lightness calculated based on the basic scanner vector is multiplied by each component (R, G, B, K) to set as a final single color printer vector, and the masking coefficient is calculated as described above. . The calculated masking coefficient is set in the hue division masking unit 230.

(non-colored)
W (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Wr−Wr) × sr + (Wg−Wg) × sg + (Wb−Wb) × sb} / (sr + sg + sb) / 1024]
K (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Kr−Wr) × sr + (Kg−Wg) × sg + (Kb−Wb) × sb} / (sr + sg + sb) / 1024]
(Chromatic color)
Rm (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Rmr−Wr) × sr + (Rmg−Wg) × sg + (Rmb−Wb) × sb} / (sr + sg + sb) / 1024]
Ry (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Ryr−Wr) × sr + (Ryg−Wg) × sg + (Ryb−Wb) ×× sb} / (sr + sg + sb) / 1024]
Yr (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Yrr−Wr) × sr + (Yrg−Wg) × sg + (Yrb−Wb) × sb} / (sr + sg + sb) / 1024]
Yg (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Ygr−Wr) × sr + (Ygg−Wg) × sg + (Ygb−Wb) × sb} / (sr + sg + sb) / 1024]
Gy (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Gyr−Wr) × sr + (Gyg−Wg) × sg + (Gyb−Wb) × sb} / (sr + sg + sb) / 1024]
Gc (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Gcr−Wr) × sr + (Gcg−Wg) × sg + (Gcb−Wb) × sb} / (sr + sg + sb) / 1024]
Cg (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Cgr−Wr) × sr + (Cgg−Wg) × sg + (Cgb−Wb) × sb} / (sr + sg + sb) / 1024]
Cb (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Cbr−Wr) × sr + (Cbg−Wg) × sg + (Cbb−Wb) × sb} / (sr + sg + sb) / 1024]
Bc (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Bcr−Wr) × sr + (Bcg−Wg) × sg + (Bcb−Wb) × sb} / (sr + sg + sb) / 1024]
Bm (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Bmr−Wr) × sr + (Bmg−Wg) × sg + (Bmb−Wb) × sb} / (sr + sg + sb) / 1024]
Mb (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Mbr−Wr) × sr + (Mbg−Wg) × sg + (Mbb−Wb) × sb} / (sr + sg + sb) / 1024]
Mr (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Mrr−Wr) × sr + (Mrg−Wg) × sg + (Mrb−Wb) × sb} / (sr + sg + sb) / 1024]

  The above sr, sg, and sb are set as parameters as weighting factors in consideration of color sensitivity.

<Setting of corresponding color (printer vector) for 2-color output operation>
After distributing the printer vectors as follows, the lightness calculated based on the basic scanner vector is multiplied by each achromatic component and set as the basic printer vector for two colors as follows, and the masking coefficient is set Calculate as described above. Then, the calculated masking coefficient is set in the hue division masking unit 230.
Printer vector of designated color 1 (set other than the black part of the document): (Yr, Yg, Yb, Yk)
Printer vector of designated color 2 (set to the black part of the document): (Xr, Xg, Xb, Xk)

(non-colored)
W (Xr ′, Xg ′, Xb ′, Xk ′) × {(Wr−Wr) × sr + (Wg−Wg) × sg + (Wb−Wb) × sb / (sr + sg + sb) / 1024}
K (Xr ′, Xg ′, Xb ′, Xk ′) × {(Kr−Wr) × sr + (Kg−Wg) × sg + (Kb−Wb) × sb / (sr + sg + sb) / 1024}
(Chromatic color)
Rm (Yr ′, Yg ′, Yb ′, Yk ′)
Ry (Yr ′, Yg ′, Yb ′, Yk ′)
Yr (Yr ′, Yg ′, Yb ′, Yk ′)
Yg (Yr ′, Yg ′, Yb ′, Yk ′)
Gy (Yr ′, Yg ′, Yb ′, Yk ′)
Gc (Yr ′, Yg ′, Yb ′, Yk ′)
Cg (Yr ′, Yg ′, Yb ′, Yk ′)
Cb (Yr ′, Yg ′, Yb ′, Yk ′)
Bc (Yr ′, Yg ′, Yb ′, Yk ′)
Bm (Yr ′, Yg ′, Yb ′, Yk ′)
Mb (Yr ′, Yg ′, Yb ′, Yk ′)
Mr (Yr ′, Yg ′, Yb ′, Yk ′)

<Corresponding color (printer vector) settings for color conversion output operation>
The printer vector conversion corresponding to color conversion is shown. As an operation, a scanner vector and a printer vector (12 hues (Ry, Yr, Yg, Gy, Gc, Cg, Cb, Bc, Bm, Bm) corresponding to a selected color selected from 8 colors (basic 6 hues + black and white) are used. , Mb, Mr, Rm) + W, K), the scanner vector table is selected and replaced with the printer vector value corresponding to the color set on the operation panel.

Assume the following printer vectors for color conversion:
Color to be converted (set color before conversion) 1: Pchf1 (Pchf1_r, Pchf1_g, Pchf1_b, Pchf1_k)
Color to be converted (pre-conversion setting color) 2: Pchf2 (Pchf2_r, Pchf2_g, Pchf2_b, Pchf2_k)
Color to be converted (set color after conversion) 1: Pcha1 (Pcha1_r, Pcha1_g, Pcha1_b, Pcha1_k)
Color to be converted (set color after conversion) 2: Pcha2 (Pcha2_r, Pcha2_g, Pcha2_b, Pcha2_k)

In this case, the printer vector of the color to be converted has the following configuration.
Pchf1 (Pcha1_r, Pcha1_g, Pcha1_b, Pcha1_k)
Pchf2 (Pcha2_r, Pcha2_g, Pcha2_b, Pcha2_k)

For example, when converting yellow to green, the yellow printer vector is replaced with the green printer vector as follows.
Yr: (Gyr, Gyg, Gyb, Gyk)
Yg: (Gcr, Gcg, Gcb, Gck)

However, it is assumed that a normal printer vector is set as follows.
Yellow printer vector Yr: (Yrr, Yrg, Yrb, Yrk)
Yg: (Ygr, Ygg, Ygb, Ygk)
Green printer vector:
Gy: (Gyr, Gyg, Gyb, Gyk)
Gc: (Gcr, Gcg, Gcb, Gck)

  Here, the tracking pattern color output prediction unit 260 treats the above-described scanner vector forming the color correction parameter of the hue division masking unit 230 as a representative color in the input color space.

  That is, the tracking pattern color output prediction unit 260 performs scanner γ correction corresponding to a total of 12 color document patches using two colors surrounding each of R, G, B, C, M, and Y of the target document. A color difference between an output color under an image output condition including color processing for a later RGB value and an output color under an image output condition including color processing for the same color to which a tracking pattern is added is calculated. Then, the tracking pattern color output prediction unit 260 sends the calculated color difference to the parameter adjustment unit 250.

For example, the color difference calculated as the influence of the tracking pattern on the white background during the above-described single color output operation is obtained when the printer vector (Xr ′, Xg ′, Xb ′, Xk ′) is used as the set color for single color. This is the difference between A (unified RGB value) and color B (unified RGB value). Color A is the following corresponding color (printer vector) corresponding to the white scanner vector: W (Wr, Wg, Wb).
W (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Wr−Wr) × sr + (Wg−Wg) × sg + (Wb−Wb) × sb} / (sr + sg + sb)]

  The color B is a color (Wr ′, Wg ′, Wb ′) obtained by adding a tracking pattern (yellow dot) to white (Wr, Wg, Wb), using the parameter masking coefficient calculated for the set single color output. This is the color of the output color W (+ y) obtained by executing the hue division masking operation.

  The white scanner vectors (Wr ′, Wg ′, Wb ′) are obtained in advance and tabulated as representative colors, and the input color is obtained by adding a tracking pattern (yellow dots) to a white background indicated by a unified RGB value. When obtaining a color difference between a single color output color and a white background, the color difference may be calculated from the above-described unified RGB definition formula. Further, the color difference may be calculated after the 3D-LUT color conversion unit 240 in FIG. 4 obtains the CIELAB value via the CMYK value. The conversion from the CMYK value to the CIELAB value may be obtained by executing color measurement on the representative color in advance, forming a three-dimensional table, and performing interpolation calculation. Also, the CIELAB value may be estimated using a color mixing simulator for CMY (K) that is built in advance using a neural network.

  The parameter adjustment unit 250 selects the color difference between the color obtained by single-color output with respect to the input color obtained by adding the tracking pattern (yellow dot) to the white background obtained by the tracking pattern color output prediction unit 260 and the operation display unit 10. The allowable color difference set in accordance with the output application (image output device) set is compared. When the color difference becomes larger than the allowable color difference, the parameter adjustment unit 250 causes the RGB value (after scanner γ correction) of the white scanner vector (Wr ′, Wg ′, Wb ′) to which the tracking pattern (yellow dot) is added. On the other hand, the printer vector calculation formula for the hue area determined when the above-described hue division masking process is executed is adjusted.

Specifically, the parameter adjustment unit 250 adjusts the weighting coefficients (sr, sg, sb) in consideration of the color sensitivity for the Y region shown below.
Yr (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Yrr−Wr) × sr + (Yrg−Wg) × sg + (Yrb−Wb) × sb} / (sr + sg + sb)]
Yg (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Ygr−Wr) × sr + (Ygg−Wg) × sg + (Ygb−Wb) × sb} / (sr + sg + sb)]

  This adjustment is achieved by reducing the sb relative to the sum of the weighting coefficients (sr, sg, sb), thereby providing a single color output color of the input color in which the tracking pattern (yellow dots) is added to the white background and the white background. This is executed until the color difference becomes smaller and falls within the allowable color difference.

  For example, it is possible to use a method of preparing a combination of weighting factors for color sensitivity as described below and executing the above-described color difference calculation until it falls within the allowable color difference. By adjusting the weighting coefficients (sr, sg, sb), it is possible to perform color adjustment that makes the dots of the tracking pattern inconspicuous according to the single color setting color (printer vector: Xr ′, Xg ′, Xb ′, Xk ′). It becomes.

(Color sensitivity parameter for single color (for Yr, Yg hue))
sr sg sb
Parameter 0: 4 6 2
Parameter 1: 3 6 1
Parameter 2: 3 7 1
Parameter 3: 4 8 1
Parameter 4: 5 9 1
Parameter 5: 6 10 1

  The color difference calculated as the effect of the tracking pattern on the white background during the two-color output operation is determined by the printer vector (Yr, Yg, Yb, Yk) of the designated color (set other than the black part of the document). In the two-color output of this embodiment, the reproduction density of the designated color is determined according to the strength of the color including the saturation component regardless of the lightness (brightness component) of the color before conversion (scanner vector). . For this reason, if a tracking pattern (yellow dots) on a white background is replaced with a dark color such as blue, the color difference from the white background may increase.

  Therefore, the hue when the above-described hue division masking process is executed on the RGB values (after the scanner γ correction) of the white scanner vector (Wr ′, Wg ′, Wb ′) to which the tracking pattern (yellow dot) is added. The printer vector calculation formula for the hue area to be area-determined is changed to one that takes into account the lightness component of the target color as shown below. Then, combinations of weighting factors for color sensitivity are prepared as follows, and the printer vector is adjusted by the parameter adjustment unit 250 until the above-described color difference calculation falls within the allowable color difference.

Yr (Yr ′, Yg ′, Yb ′, Yk ′) →
Yr (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Yrr−Wr) × sr + (Yrg−Wg) × sg + (Yrb−Wb) × sb} / (sr + sg + sb) / 1024]
Yg (Yr ′, Yg ′, Yb ′, Yk ′) →
Yg (Xr ′, Xg ′, Xb ′, Xk ′) × [{(Ygr−Wr) × sr + (Ygg−Wg) × sg + (Ygb−Wb) × sb} / (sr + sg + sb) / 1024]

(Color sensitivity parameter for two color (for Yr, Yg hue))
sr sg sb
Parameter 0: 2 4 10
Parameter 1: 2 4 8
Parameter 2: 2 4 6
Parameter 3: 2 4 4
Parameter 4: 2 4 2
Parameter 5: 2 4 1

  The same applies to the influence of the tracking pattern on the white background during the color conversion output (Y → red) operation. That is, regardless of the lightness (brightness component) of the color before conversion (scanner vector), the reproduction density of the converted color is determined according to the strength of the color including the saturation component. For this reason, if the tracking pattern (yellow dots) on a white background is replaced with a dark color, the color difference from the white background may increase.

In the case of converting yellow to green, as described below, when replacing the yellow printer vector with the green printer vector, the adjustment parameter (A) is decreased from 16 to suppress the color strength of the converted color. In this way, the parameter adjustment unit 250 adjusts the printer vector calculation formula until the above-described color difference calculation falls within the allowable color difference.
Yr: (Gyr, Gyg, Gyb, Gyk) × A / 16
Yg: (Gcr, Gcg, Gcb, Gck) × A / 16

However, it is assumed that a normal printer vector is set as follows.
Yellow printer vector:
Yr: (Yrr, Yrg, Yrb, Yrk)
Yg: (Ygr, Ygg, Ygb, Ygk)
Green printer vector:
Gy: (Gyr, Gyg, Gyb, Gyk)
Gc: (Gcr, Gcg, Gcb, Gck)

  Next, the adjustment of the color difference and the color correction parameter calculated as the influence of the tracking pattern on various color grounds during the two-color output operation will be described.

  For the scanner vector of 14 representative colors including the white and black points on the achromatic color axis shown in FIG. 13 (RGB values after scanner γ correction), the tracking pattern color output prediction unit 260 uses the tracking pattern (yellow). A color (RGB value after scanner γ correction) to which dots are added is extracted. Then, as described above, the tracking pattern color output prediction unit 260 divides the output color (unified RGB value) in the two-color output operation when the extracted color is the input color into the normal two-color mode. Calculation is performed using the masking coefficient set by the masking unit 230. The tracking pattern color output prediction unit 260 obtains the color difference between the calculated output color (unified RGB value) and the printer vector (unified RGB value) set for the two-color mode, and sends it to the parameter adjustment unit 250.

  Predicted values when tracking patterns (yellow dots) are added to the scanner vectors for each color used here are obtained in advance and tabulated as representative colors, and color differences are calculated from the above-described unified RGB definition formula. Also good. The 3D-LUT color conversion unit 240 may calculate the CIELAB value via the CMYK value and then calculate the color difference. The conversion from the CMYK value to the CIELAB value may be obtained by executing color measurement on the representative color in advance, forming a three-dimensional table, and performing interpolation calculation. Also, the CIELAB value may be estimated using a color mixing simulator for CMY (K) that is built in advance using a neural network.

  The parameter adjustment unit 250, for example, a color obtained by outputting two colors for the color obtained by adding the tracking pattern (yellow dot) to the representative color (scanner vector) of each hue obtained by the tracking pattern color output prediction unit 260; The color difference with the corresponding color (printer vector) for the two-color output operation is calculated. The parameter adjustment unit 250 compares the calculated color difference with the allowable color difference set according to the output application (image output device) selected by the operation display unit 10. When the color difference becomes larger than the allowable color difference, the parameter adjustment unit 250 adjusts the scanner vector so as to approach the RGB value (after the scanner γ correction) to which the tracking pattern (yellow dot) is added.

  For example, the 14-point scanner vector and printer vector including the white and black points on the achromatic color axis at the time of full-color operation shown in FIG. Explain the case.

Printer vector of designated color 1 (set other than the black part of the document): (Yr, Yg, Yb, Yk)
Printer vector of designated color 2 (set to the black part of the document): (Xr, Xg, Xb, Xk)

(non-colored)
W (Xr ′, Xg ′, Xb ′, Xk ′) × {(Wr−Wr) × sr + (Wg−Wg) × sg + (Wb−Wb) × sb / (sr + sg + sb) / 1024}
K (Xr ′, Xg ′, Xb ′, Xk ′) × {(Kr−Wr) × sr + (Kg−Wg) × sg + (Kb−Wb) × sb / (sr + sg + sb) / 1024}
(Chromatic color)
Rm (Yr ′, Yg ′, Yb ′, Yk ′)
Ry (Yr ′, Yg ′, Yb ′, Yk ′)
Yr (Yr ′, Yg ′, Yb ′, Yk ′)
Yg (Yr ′, Yg ′, Yb ′, Yk ′)
Gy (Yr ′, Yg ′, Yb ′, Yk ′)
Gc (Yr ′, Yg ′, Yb ′, Yk ′)
Cg (Yr ′, Yg ′, Yb ′, Yk ′)
Cb (Yr ′, Yg ′, Yb ′, Yk ′)
Bc (Yr ′, Yg ′, Yb ′, Yk ′)
Bm (Yr ′, Yg ′, Yb ′, Yk ′)
Mb (Yr ′, Yg ′, Yb ′, Yk ′)
Mr (Yr ′, Yg ′, Yb ′, Yk ′)

In the above-described color difference evaluation, for example, when the allowable color difference is exceeded by Cg hue, that is, the printer vector Cg (Yr ′, Yg ′, Yb ′, Yk ′) at the time of designated two-color mode output and the scanner vector Cg_s. Colors Cg ″ (Yr ″, Yg ″, Yb ″, and Cg_s ′ (Cgr ′, Cgg ′, Cgb ′) obtained by adding a tracking pattern (yellow dots) to (Cgr, Cgg, Cgb) after hue division masking calculation. When the color difference from Yk ″) is larger than the allowable color difference, the adjustment parameter (A) of each component of the Cg hue scanner vector is decreased from 16 as follows. Adjust the scanner vector until the color value approaches the RGB value (after scanner γ correction) with (yellow dot) added, and the color difference is within the allowable color difference, and calculate the masking coefficient. To. Parameter adjustment unit 250, the calculated masking coefficient is set as the color correction parameters hue division masking unit 230.
Cgr ″ = Cgr ′ + (Cgr−Cgr ′) × A / 16
Cgg ″ = Cgg ′ + (Cgg−Cgg ′) × A / 16
Cgb ″ = Cgb ′ + (Cgb−Cgb ′) × A / 16

  In the present embodiment, a tracking pattern specific to the color copier output image is detected using the unified RGB image data converted into the unified RGB image data and stored in the memory 7 via the image processing unit 2 in FIG. . This is to prevent abuse of copying of banknotes and securities. That is, measures are taken so that some pattern is printed when banknotes or securities are copied. Such a tracking pattern is detected with high accuracy by local image processing utilizing the fact that it is isolated on the white ground and printed in yellow.

(Generation manuscript judgment)
A configuration example of a generation document determination unit that detects whether an input document is a generation document will be described below. FIG. 14 is a block diagram illustrating a configuration example of the generation document determination unit 300.

  The generation document determination unit 300 includes an MTF correction unit 306, a binarization processing unit 307, pattern matching circuits (hereinafter referred to as PM) 308a, 308b, and 308c, an overall determination unit 309, a counter 310, and a comparator. 311.

  In order to determine whether or not the document is a generation document, in this embodiment, attention is paid to the trace pattern that is always printed on the color copier output image, and the trace pattern is detected by using pattern matching.

  Generally, the tracking pattern is printed with yellow toner with a size of about 2 pixels × 2 pixels or 1 pixel × 3 pixels by a 400 dpi printer. Therefore, a tracking pattern can be detected by performing pattern matching as shown in FIG. 15B described later on the b signal which is a complementary color of yellow.

However, the following problems arise.
(1) A printed document is formed from a large number of halftone dots. In the pattern of FIG. 15B, halftone dots are erroneously detected as a tracking pattern, and as a result, the printed document is erroneously determined as a generation document. In a general printed document, dots are concentrated to some extent even in a highlight portion.
(2) Even if the tracking pattern is limited to isolated dots on the white ground as described above, dust (noise) often appears on the original. Because of the noise, there is little possibility that such dust is yellow, and many are achromatic colors. Therefore, the tracking pattern is limited to the yellow area using three signals.

  As described with reference to FIG. 1, the scanner 1 has a photoelectric conversion element such as a CCD camera, reads a document, obtains three color separation signals (analog) of red, green, and blue. Then, A / D conversion is performed, and RGB digital signals (each 8 bits) are output. Here, the resolution of the scanner 1 is 400 dpi. The output signal value is 255 for paper white and 0 for black.

  The MTF correction unit 306 applies an MTF correction filter to each of the RGB signals as preprocessing for the binarization processing at the subsequent stage. FIG. 16 is a diagram illustrating an example of coefficients of the MTF correction filter.

  The binarization processing unit 307 performs binarization processing on the signal after MTF correction. When the target pixel level is X, the binarization processing unit 307 sets the target pixel as a black pixel when X is smaller than the predetermined threshold th, and sets the target pixel as a white pixel when X is equal to or higher than the threshold th.

  The PM 308a performs pattern matching using the r signal and g signal patterns. FIG. 15A is a diagram illustrating an example of the r signal and g signal patterns. By using the PM 308a, it is possible to detect a region where cyan and magenta, which are complementary colors of r and g, do not exist in the vicinity of the target pixel, that is, a yellow region.

  The PM 308b performs pattern matching using the b signal pattern. FIG. 15B is a diagram illustrating an example of a b signal pattern. As described above, since the tracking pattern is at most 400 dpi and 3 pixels × 3 pixels or less, matching is performed using a pattern as shown in FIG. However, since this pattern alone matches yellow dot dots, it is necessary to prepare PM 308c for determining whether or not the area is surrounded by a white background, which will be described next.

  The PM 308c performs pattern matching using the b signal pattern for determining whether or not the target pixel is a truly isolated region surrounded by a white background. FIG. 15C is a diagram showing an example of the b signal pattern in this case. The halftone dot for printing is a highlight area, but there is no halftone dot that matches the pattern as shown in FIG. That is, the halftone dots are a little denser.

  In order to simplify the explanation, the b signal is used. However, in the case where a region surrounded by a white background is more accurately detected, a signal obtained by binarizing min (r, g, b) after MTF correction is used. This pattern matching may be performed using.

  When the outputs from the four pattern matching circuits (two PM 308a, PM 308b, and PM 308c) are all on, that is, when all match, the comprehensive determination unit 309 determines the target pixel as a tracking pattern pixel.

  The counter 310 counts the number of pixels of the tracking pattern described above over the entire surface of the document.

  The comparator 311 compares the count value (V) of the tracking pattern pixels described above with a predetermined threshold value (THgen), and outputs a signal that the document is a generation document if V> THgen.

  For the sake of simplicity, the RGB signal is used as a signal used for generation document determination. However, in order to improve the accuracy, the color correction for generation is performed on the RGB signal to obtain a cmy signal. Thus, it is also effective to make a similar determination using this cmy signal. FIG. 17 is a block diagram illustrating a configuration example of the generation document determination unit 300-2 configured as described above. FIG. 17 is different from the generation document determination unit 300 of FIG. 14 in that it further includes a color correction circuit 12 that corrects RGB signals to cmy signals.

  Further, the actual output from the scanner 1 may include noise, and it is also effective to apply a smoothing filter to the signal output from the scanner 1 to remove noise.

(Image playback device using generation manuscript judgment)
Here, an example of an apparatus that reproduces an image using the generation document determination unit 300 of FIG. 14 described above (hereinafter referred to as an image processing apparatus 400) will be described.

  FIG. 18 is a block diagram illustrating a configuration example of the image processing apparatus 400 according to the present embodiment. As illustrated in FIG. 18, the image processing apparatus 400 includes a scanner 1, a log conversion unit 401, a color correction circuit 402, a plotter 9, a generation document determination unit 300, and a color correction count storage unit 403. ing.

  Hereinafter, in order to simplify the explanation, the color correction means to be prepared has two types, one for halftone photographs (printing) and one for generation documents. By using the technique described in Patent Document 2, color correction means for silver halide photography (photographic paper) and color correction means for mixing them may be prepared. This ensures color fidelity for a wide range of documents.

  The Log conversion unit 401 converts the output signal of the scanner 1 which is a substantially linear reflectance signal into an advantageous density signal (RGB signal) by color correction processing.

  The color correction circuit 402 performs color correction using the following linear linear expression. That is, R, G, B are signals after log conversion (each 8 bits), Y, M, C are printer drive signals, and a0-a3, b0-b3, c0-c3 are color correction coefficient groups. The color correction by the color correction circuit 402 is expressed by the following equation.

C = a0 + a1 × R + a2 × G + a3 × B
M = b0 + b1 × R + b2 × G + b3 × B
Y = c0 + c1 × R + c2 × G + c3 × B

  Here, the plotter 9 is a printer that creates an image with three colors of cyan, magenta, and yellow. The plotter 9 receives the drive signals (C, M, Y) and creates an image. In the case of four-color reproduction with black added, for example, a black signal is created with min (C, M, Y), a drive signal is created by so-called UCR processing that subtracts that amount from C, M, Y, and printed out. do it.

  As described with reference to FIG. 14, the generation document determination unit 300 determines a generation document (electrophotographic printer document) and other documents. That is, the generation document determination unit 300 identifies a print document and outputs the result.

  The generation document determination unit 300 is provided, for example, in the image processing unit 2 of FIG. Only when the generation document determination unit 300 determines that the document is a generation document, the image processing unit 4 in FIG. 1 uses the color correction coefficient calculated by performing the above-described adjustment of the image output condition, and performs color correction processing. I do.

  In the present embodiment, when obtaining the color difference from the above-described unified RGB, the color difference may be converted into a perceptual amount for predicting the appearance of the color under the observation condition via the image signal color-converted to the tristimulus value (CIEXYZ). Absent.

As described above, the target color is unified RGB obtained by color conversion from the read value. For this reason, when the unified RGB is assumed to be sRGB, the color conversion to the tristimulus value (CIEXYZ) is expressed by the following equations (5) and (6).
r = (R / 1023) ^2.2 ,
g = (G / 1023) ^2.2 ,
b = (B / 1023) ^2.2 (5)
X = 0.4124 × r + 0.3576 × g + 0.1805 × b,
Y = 0.2126 × r + 0.7152 × g + 0.0722 × b,
Z = 0.0193 × r + 0.1192 × g + 0.9505 × b (6)

  Here, the converted tristimulus values (CIEXYZ) of the background (white) of the recording paper are used as the reference white tristimulus values (Xw, Yw, Zw) defined by the color appearance model (CIECAM) recommended by the CIE. ), And the following processing is executed to convert it into a perceptual amount (JCH).

In this embodiment,
Test color: X, Y, Z → Tristimulus value of image signal input from scanner 1 Reference white: Xw, Yw, Zw → Tristimulus value of recording paper background (white) (calculated from reading value)
The operation is executed as follows.

Rc = (D × (1.0 / Rw) + 1−D) × R,
Gc = (D × (1.0 / Gw) + 1−D) × G,
if (B <0)
Bc = (D × (1.0 / pow (Bw, p)) + 1−D) × fabs (pow (B, p)) × (−1.0)
else

Bc = (D × (1.0 / pow (Bw, p)) + 1−D) × pow (B, p)
... (10)
Rcw = (D × (1.0 / Rw) + 1−D) × Rw,
Gcw = (D × (1.0 / Gw) + 1−D) × Gw,
Bcw = (D × (1.0 / pow (Bw, p)) + 1−D) × pow (fabs (Bw), p) (11)
However,
p = pow ((Bw / 1.0), 0.0834) (12)
D = F−F / (1 + 2 × pow (La, 1/4) + La × La / 300)
... (13)

  Note that La is the luminance of the adaptation field of view, and F is a coefficient representing the degree of adaptation.

  The D factor (adaptation coefficient) defined here is basically calculated based on this defining formula. When an output image viewing condition is set as a parameter from the operation display unit 10 at the time of image output, it is reflected in the D factor (adaptation coefficient).

Rda = (40 × pow ((F1 × Rd / 100), 0.73)) / (pow ((F1 × Rd / 100), 0.73) +2) +1
Gda = (40 × pow ((F1 × Gd / 100), 0.73)) / (pow ((F1 × Gd / 100), 0.73) +2) +1
Bda = (40 × pow ((F1 × Bd / 100), 0.73)) / (pow ((F1 × Bd / 100), 0.73) +2) +1 (16)
Rdaw = (40 × pow ((F1 × Rdw / 100), 0.73)) / (pow ((F1 × Rdw / 100), 0.73) +2) +1
Gdaw = (40 × pow ((F1 × Gdw / 100), 0.73)) / (pow ((F1 × Gdw / 100), 0.73) +2) +1
Bdaw = (40 × pow ((F1 × Bdw / 100), 0.73)) / (pow ((F1 × Bdw / 100), 0.73) +2) +1 (17)

k = 1 / (5 × La + 1) (19)
Fl = 0.2 × pow (k, 4) × (5 × La) + 0.1 × (1-pow (k, 4)) × (1-pow (k, 4)) × pow (5 × La, 1/3) (20)
n = Yb / Yw (21)
Nbb = 0.725 × pow (1 / n, 0.2) (22)
Ncb = Nbb (23)
z = 1 + Fll × pow (n, 0.5) (24)

Yb is a background luminance rate, Fl is a coefficient corresponding to adaptation brightness, Fll is a lightness contrast coefficient, and n is a coefficient representing the degree to which the background affects the appearance of the stimulus.
Ca = Rda-12.0 × Gda / 11.0 + Bda / 11.0,
Cb = (1/9) × (Rda + Gda−2 × Bda),
h = (180 / M_PI) × atan2 (b, a),
if (h <0) h = 360−fabs (h) (25)
e = e1 + (e2−e1) × (h−h1) / (h2−h1) (26)
H = h1 + 100 × (h−h1) / e1 / ((h−h1) / e1 + (h2−h) / e2) (27)

However,
if (h <= 20.14) {
e1 = 0.8565
e2 = 0.8
h1 = 0.0
h2 = 20.14
}
else if (h <= 90.0) {
e1 = 0.8
e2 = 0.7
h1 = 20.14
h2 = 90.0
}
else if (h <= 164.25) {
e1 = 0.7
e2 = 1.0
h1 = 90.0
h2 = 164.25
}
else if (h <= 237.53) {
e1 = 1.0
e2 = 1.2
h1 = 164.25
h2 = 237.53
}
else {
e1 = 1.2
e2 = 0.8565
h1 = 237.53
h2 = 360.0
} (28)

A = (2 × Rda + Gda + (1/20) × Bda−2.05) × Nbb (29)
Aw = (2 × Rdaw + Gdaw + (1/20) × Bdaw−2.05) × Nbb (30)
J = 100 × pow (A / Aw, c × z) (31)
Q = (1.24 / c) × pow ((J / 100), 0.67) × pow ((Aw + 3), 0.9) (32)
s = (50 × pow ((a × a + b × b), 0.5) × 100 × e × (10/13) × Nc × Ncb) / (Rda + Gda + (21/20) × Bda) (33 )
C = 2.44 × pow (s, 0.69) × pow ((J / 100), 0.67 × n) × (1.64-pow (0.29, n)) (34)
M = C × pow (F1, 0.15) (35)

  Here, c is a coefficient related to the magnitude of the influence of the surroundings, Nc is a chromatic induction coefficient, A is an achromatic response, Aw is an achromatic response to white, J is lightness, Q is brightness, s is saturation, and C is chroma. , M represents colorfulness.

  Various parameters in the present embodiment are set by the operator from the operation display unit 10 as observation conditions corresponding to the environment where the hard copy is actually observed. If not set in particular, it is set as follows according to the definition of unified RGB (sRGB).

(XtYtZt → JtCtHt)
Brightness of adaptation field of view: La = 4 (cd / m ² )
Coefficient representing the degree of adaptation: F = 1.0 (Average)
Background luminance ratio: Yb = 20
Lightness contrast coefficient: Fll = 1.0 (Average)
Coefficient for magnitude of influence of surroundings: c = 0.69 (Average)
Chromatic induction coefficient: Nc = 1.0 (Average)

  The Euclidean distance of the image data color-converted to the perceptual amount (JCH) based on the color appearance model obtained here is a color difference that is a condition for the color correction parameter.

  As described above, according to this embodiment, the input color is set so that the color difference between the normal output color under the set image output condition and the output color with respect to the input color to which the tracking pattern is added is equal to or less than the allowable color difference. The parameter used when the color is corrected to the output color is adjusted. This makes it possible to reproduce colors close to the image output conditions including the original color processing without depending on the characteristics of the input image, regardless of the characteristics of the input image, regardless of the image output condition settings including the color processing. Can realize image output that is inconspicuous. In addition, even if the image input conditions with low tracking pattern detection accuracy are copied with the image output conditions including any color processing, color reproduction faithful to the image output conditions including the original color processing is realized for general documents. it can.

  In addition, even if a tracking pattern is struck on the color ground in the input image, color reproduction faithful to the image output conditions including the original color processing is realized for the image area that is not affected by the tracking pattern. Only for the image area affected by the above, it is possible to realize an image output in which the dots of the tracking pattern are inconspicuous, close to the image output conditions including the original color processing.

  In addition, even if an input document with a tracking pattern on a white ground is copied with image output conditions including any color processing, color reproduction close to the original image output conditions including color processing is achieved. Thus, it is possible to realize an image output in which the dots of the tracking pattern are not conspicuous.

  Moreover, even if the image output conditions including any color processing are set, it is relatively easy to approximate the image output conditions including the original color processing without using information on the spectral characteristics in the actual observation environment. Color reproduction can be realized, and image output in which the dots of the tracking pattern are not conspicuous can be realized.

  Note that the program executed by the image processing apparatus of the present embodiment is provided by being incorporated in advance in a ROM or the like.

  The program executed in the image processing apparatus of the present embodiment is a file in an installable format or an executable format, and is a computer such as a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disk). The program may be recorded on a readable recording medium and provided as a computer program product.

  Furthermore, the program executed by the image processing apparatus of the present embodiment may be provided by being stored on a computer connected to a network such as the Internet and downloaded via the network. The program executed by the image processing apparatus according to the present embodiment may be configured to be provided or distributed via a network such as the Internet.

  The program executed by the image processing apparatus of the present embodiment includes the above-described units (scanner γ correction unit, color adjustment unit, hue division masking unit, 3D-LUT color conversion unit, parameter adjustment unit, tracking pattern color output prediction unit, etc. ), And as actual hardware, the CPU (processor) reads the program from the ROM and executes the program, so that the respective units are loaded onto the main storage device, and the respective units are installed on the main storage device. To be generated.

DESCRIPTION OF SYMBOLS 1 Scanner 9 Plotter 10 Operation display part 200 Color conversion process part 210 Scanner gamma correction part 220 Color adjustment part 230 Hue division masking part 240 3D-LUT color conversion part 250 Parameter adjustment part 260 Tracking pattern color output prediction part

JP 2001-103279 A Japanese Patent Laid-Open No. 06-197218

Claims (8)

A receiving unit for receiving an image output condition including a condition for color correction for input image data;
A calculation unit that calculates a color difference between the first output color under the image output condition for the input color to which no tracking pattern is added and the second output color under the image output condition for the input color to which the tracking pattern is added;
An adjustment unit for adjusting a color correction parameter used in the color correction according to the color difference;
A correction unit that generates output image data obtained by correcting the input image data using the adjusted color correction parameter;
An image processing apparatus comprising: The adjusting unit adjusts the color correction parameter until the color difference is within a predetermined allowable color difference;
The image processing apparatus according to claim 1. A detection unit for detecting a tracking pattern from the input image data;
The adjusting unit adjusts the color correction parameter when the tracking pattern is detected;
The image processing apparatus according to claim 1. The adjusting unit adjusts the input color until the color difference is within a predetermined allowable color difference, and calculates the color correction parameter based on the adjusted input color;
The image processing apparatus according to claim 1. The color correction parameter is a parameter for adjusting the color sensitivity of the yellow hue to the input color;
The image processing apparatus according to claim 1. The reception unit further receives an observation condition of the output image data,
The calculation unit includes the first output color under the observation condition and the image output condition for an input color to which no tracking pattern is added, and the observation condition and the image output condition for an input color to which a tracking pattern is added. Calculating a color difference from the second output color of
The image processing apparatus according to claim 1. An accepting step for accepting an image output condition including a condition for color correction for input image data;
A calculation step of calculating a color difference between the first output color under the image output condition for the input color to which no tracking pattern is added and the second output color under the image output condition for the input color to which the tracking pattern is added;
An adjustment step of adjusting a color correction parameter used in the color correction according to the color difference;
A correction step of generating output image data obtained by correcting the input image data with the adjusted color correction parameter;
An image processing method comprising: Computer
A receiving unit for receiving an image output condition including a condition for color correction for input image data;
A calculation unit that calculates a color difference between the first output color under the image output condition for the input color to which no tracking pattern is added and the second output color under the image output condition for the input color to which the tracking pattern is added;
An adjustment unit for adjusting a color correction parameter used in the color correction according to the color difference;
A correction unit that generates output image data obtained by correcting the input image data using the adjusted color correction parameter;
Program to function as.

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