JP2021062553A - Image processing apparatus, image processing method, and program - Google Patents

Abstract

To output gray having improved distinctiveness for data described in a page description language capable of using a plurality of color spaces.SOLUTION: An image forming apparatus 100 includes an image processing unit 103 including acquisition means for acquiring data described in a PDL (page description language) and expressed in a plurality of color spaces, first conversion means for converting a color value specified to draw a page in the data into a color value to be defined in a common color space as a predetermined one color space, and second conversion means for converting color information converted by the first conversion means into a gray value such that distinctiveness is improved.SELECTED DRAWING: Figure 5

Description

The present disclosure relates to an image processing apparatus, an image processing method, and a program that perform monochrome conversion to improve discrimination.

Documents or presentation documents may be printed in black and white (monochrome black), even if they are generated in color. When printing a document generated in color in this way in monochrome, a monochrome conversion process for converting color data into grayscale data is required. However, when the color data is converted into grayscale data, different colors may be converted into the same or similar gray values in the color data, which may reduce the discrimination property.

Patent Document 1 describes a method of generating a table for converting color data into grayscale data so that gray values converted from color data are assigned to values that are separated from each other.

JP-A-2017-38242

There are page description languages such as PostScript (registered trademark) and PDF (registered trademark) that can specify color values in a plurality of color spaces such as CMYK in addition to RGB. However, Patent Document 1 only describes a method of converting a color value specified in a single color space into a gray value. Therefore, for example, there is a possibility that processing for appropriately improving the discrimination between the gray value converted from the color value in one color space and the gray value converted from the color value in another color space cannot be performed. There is.

An object of the technique of the present disclosure is to output gray with improved discrimination for data described in a page description language that can use a plurality of color spaces.

The image processing apparatus of the present disclosure is described by PDL (Page Description Language), and obtains an acquisition means for acquiring data expressed in a plurality of color spaces and a color value specified for drawing a page in the data. , The first conversion means that performs the process of converting to the color value of the common color space that is a predetermined one color space, and the color value converted by the first conversion means so as to improve the discrimination. It is characterized by having a second conversion means for performing a process of converting to a gray value.

According to the technique of the present disclosure, it is possible to output gray with improved discrimination for data described in a page description language that can use a plurality of color spaces.

It is a block diagram which shows the structure of an image processing system. It is a block diagram which shows the functional structure of an image processing system. This is an example of a PDL type drawing command that can be used only in a single color space. This is an example of a PDL type drawing command that can use a plurality of color spaces. It is a flowchart which shows the process of selecting a color conversion method. It is a figure which shows an example of a color value list. It is a schematic diagram explaining the process which improves the discriminative property. It is a flowchart which shows the monochrome conversion of a single color space which improves the discriminative property. It is a figure which shows an example of a color value list. It is a schematic diagram explaining the process which improves the discriminative property. It is a flowchart which shows the monochrome conversion of a plurality of color spaces which improves the discriminative property. This is an example of a PDL type drawing command that can use a plurality of color spaces. It is a figure which shows an example of a color value list. It is a schematic diagram explaining the process which improves the discriminative property. This is an example of a PDL type drawing command that can use a plurality of color spaces. It is a figure which shows an example of a color value list.

Hereinafter, embodiments will be described with reference to the drawings. The configuration shown in the following embodiments is only an example, and the embodiments are not limited to the illustrated configurations. Moreover, not all combinations of features described in the present embodiment are essential for the means of solving the present invention. The same configuration will be described with the same reference numerals.

<First Embodiment>
In the process of improving the discrimination of the gray value converted from the color value of the color, when different color combinations are converted to the same or similar gray values in the color data, the difference between the gray values of the combinations is widened. Correct the gray value to. On the other hand, it is preferable that a combination of colors having the same or similar tint in the color data is output as the same or similar gray values even when converted to a gray value for improving discrimination.

In print data in which color values are specified in multiple color spaces, an object specified as a color value indicating red in the RGB color space and an object specified as a color value indicating blue in the CMYK color space are included in the page. There may be. In this case, if the color value of each object is converted to a gray value, the same gray value may be output. Therefore, when the difference between the converted gray values is small, it is conceivable to improve the discrimination of gray by modifying the gray value so as to widen the difference.

On the other hand, in the RGB color space, the gray value when the color value indicating red is converted and the gray value when the color value indicating red in the CMYK color space is converted may be output as the same gray value. In this case, it is preferable to output the converted gray value as it is.

Therefore, it is conceivable to determine whether the colors before being converted to the gray value are similar and correct the gray value only when they are not similar. However, the judgment as to whether the two colors are similar depends on the content of the original, the light source that illuminates the output recorded matter, and the person who judges. Further, even if the color values in the RGB color space and the color values in the CMYK color space are compared, it cannot be determined whether they are similar because the color spaces are different.

Therefore, in the present embodiment, all the color values included in the print data are converted into the color values of one color space (called a common color space). Then, it is determined whether the colors are similar based on the result of comparing the color values of the converted common color space. Then, an image processing device that performs processing for improving discrimination based on the determination result will be described.

In the following embodiments, the colors corresponding to each color space are represented by alphabetic characters such as R, G, and B. For example, R represents a red component (signal value) in the RGB color space, and CMYK represents each color of C (Cyan), M (Magenta), Y (Yellow), and K (Black).

[About the image formation system]
FIG. 1 is a diagram showing an image processing system 117 according to the present embodiment. The image processing system 117 includes an image forming apparatus 100 and a host PC 110. The configuration of the image processing system 117 in FIG. 1 is an example, and is not limited to this configuration.

The image forming apparatus 100 is, for example, a multifunction device (MFP: Multi-Faction Peripheral) in which a plurality of functions such as an image processing apparatus function, a scanning function, and a printer function are integrated.

The image forming apparatus 100 includes a control unit 101, an operation unit 104, an image reading unit 108, and an image output unit 109. The control unit 101 includes a CPU 105, a RAM 106, a storage unit 107, a device control unit 102, and an image processing unit 103, and controls the image forming device 100 in an integrated manner.

The CPU 105 controls the operation of the image forming apparatus 100 by expanding the program stored in the storage unit 107 into the RAM 106 and executing the program. The RAM 106 is a temporary storage memory, and can temporarily store image data, programs, and the like. The storage unit 107 is, for example, a hard disk, and stores parameters for controlling the image forming apparatus 100, applications, programs, an OS, and the like for realizing image processing according to the present embodiment.

The parameters for controlling the image forming apparatus 100 stored in the storage unit 107 include an input profile and an output profile used by the image processing unit 103. The input profile is a color conversion table for converting the color values of the RGB color space and the CMYK color space into the L * a * b * color space or the XYZ color space. Further, the output profile is for converting from the L * a * b * color space or the XYZ color space to the device color space of the image output unit 109 (CMYK color space if the image output unit 109 is a printer, RGB color space if the image output unit 109 is a display). It is a color conversion table. By holding these parameters, the image forming apparatus 100 can convert data in an arbitrary color space into another color space. Therefore, the image processing unit 103 can convert the data in the acceptable color space corresponding to the processing of the image output unit 109, or can combine the data in the plurality of color spaces into one color space. ..

The device control unit 102 is a device controller and controls each unit connected to the control unit 101 such as the operation unit 104, the image reading unit 108, and the image output unit 109. The image reading unit 108 is, for example, a scanner, and the image output unit 109 is, for example, a printer or a monitor. By executing the above program, the CPU 105 has a scanning function for acquiring image data of the document read by the image reading unit 108, recording the image on the recording medium via the image output unit 109, and outputting the image to a monitor or the like. The output function is realized.

In the present embodiment, the image output unit 109 supports not only gray color space but also image processing in RGB color space and CMYK color space, and these color spaces will be described as being acceptable. For example, if the image output unit 109 is a printer, when an image in a gray color space is acquired, the color values are inverted and printing is performed using only Black toner. When the image output unit 109 acquires an image in the RGB color space, it performs appropriate color conversion from RGB to CMYK and prints with CMYK toner. Further, when the image output unit 109 acquires an image in the CMYK color space, printing is performed with CMYK toner without performing color conversion.

However, the acceptable data corresponding to the processing of the image output unit 109 is defined on one side in the same color space. When data including a plurality of color spaces is input to the image forming apparatus 100, the image processing unit 103 converts the data into an image having a single color space and then outputs the data to the image output unit 109. The image processing unit 103 reads, for example, the image data stored in the storage unit 107, and performs various image processing according to the parameters. In addition, image processing is also performed based on the setting information notified from the operation unit 104 or the host PC 110.

The operation unit 104 includes a touch panel, hardware keys, and the like that also function as a display unit, and receives instructions and setting operations from the user. The touch panel displays device information of the image forming apparatus 100, job progress information, and various user interface screens. The setting information and the like received by the operation unit 104 are stored in the storage unit 107 via the device control unit 102. In the present embodiment, the user can instruct the setting of the color output, the simple monochrome output that does not consider the discrimination, or the monochrome output that improves the discrimination through the operation unit 104. These settings specified via the operation unit 104 are stored in the RAM 106 or the storage unit 107.

The image processing unit 103 has a function of an image processing device. The image processing unit 103 reads the settings before starting the color processing and switches the color processing method (conversion method) according to the settings to perform color output, simple monochrome output that does not consider discrimination, or monochrome that improves discrimination. Switch the image processing method for output etc.

The host PC 110 is an information processing device connected to the image forming apparatus 100 via the network 116. The host PC 110 includes a control unit 111, an image processing unit 112, a CPU 113, a RAM 114, and a storage unit 115. The control unit 111 controls the host PC 110 in an integrated manner, and uses the CPU 113 and the RAM 114 to control the application 201 and the printer driver 202 (see FIG. 2) mounted on the host PC 110.

In addition to the configurations shown in FIG. 1, the image forming apparatus 100 and the host PC 110 may include configurations necessary for executing the functions of the image forming apparatus 100 and the host PC 110.

[Functional configuration related to print processing]
FIG. 2 is a diagram illustrating the functional configurations of the image forming apparatus 100 and the host PC 110 during the print processing in the image processing system 117.

The host PC 110 has an application 201 and a printer driver 202. Application 201 is an application used to generate electronic data such as document documents and presentation documents.

The printer driver 202 is a driver for outputting print data to the image forming apparatus 100 for printing. The setting via the operation unit 104 may be set via the printer driver. The print data output from the printer driver 202 is sent to the image forming apparatus 100 for printing. This print data is processed by the image processing unit 103 of the image forming apparatus 100.

Next, the functional configuration of the image processing unit 103 of the image forming apparatus 100 will be described. The image processing unit 103 includes a command determination unit 203, a command analysis unit 204, a command execution unit 205, and an image adjustment unit 206.

The command determination unit 203 determines the PDL type of the print data output from the host PC 110. PDL (Page Description Language) is an abbreviation for page description language. In addition, PDL types include PostScript (PS), PDF, PrinterCommandLanguage (PCL), and the like. The PDL type can be switched by switching the setting of the printer driver 202 or by switching the printer driver 202 itself to be used.

The available color space differs depending on the PDL type. For example, in PCL, an RGB color space is available. On the other hand, in PS, device color spaces such as DeviceGray, DeviceRGB, and DeviceCMYK can be used. Further, in PS, a plurality of color spaces such as a CIEBased color space using a color conversion LUT embedded in PS data and a Named color space in which a color is specified by a color name can be used.

The command analysis unit 204 exists for each PDL type and executes extraction and analysis of the command of the PDL type specified by the command determination unit 203. The command analysis unit 204 performs graying processing and the like according to the contents of the analyzed command.

The command analysis unit 204 functions as a first conversion unit that converts the color information included in the command into the color information defined in the common color space. Further, the command analysis unit 204 functions as a second conversion unit that converts the color information included in the command into the color information of the gray value that improves the discriminability. A description of these functions will be described later.

The command execution unit 205 executes a drawing command according to the analysis result of the command analysis unit 204 to generate a raster image. The image adjustment unit 206 applies image processing such as color conversion and a filter to the raster image. The processing in the image processing unit 103 is performed page by page. The functions of the command determination unit 203, the command analysis unit 204, the command execution unit 205, and the image adjustment unit 206 of the image processing unit 103 shown in FIG. 2 are stored in the CPU 105. This is realized by expanding the program code stored in the unit 107 into the RAM 106 and executing it. Alternatively, some or all the functions of each part of FIG. 2 may be realized by hardware such as an ASIC or an electronic circuit.

[About PDL drawing commands that can use a single color space]
FIG. 3 is a diagram showing an example of a drawing command that can use a single color space included in the print data acquired by the image forming apparatus 100 and a drawing result based on the drawing command. The commands included in the print data include drawing commands and control commands, and FIG. 3A is a diagram showing an example of drawing commands 300. FIG. 3B is a diagram showing an image 307 drawn based on the drawing command 300.

The drawing command 300 includes a color mode setting command 301 indicating the color mode of the job and a color setting command 302 for setting the color of the RGB color space. Further, there are an object drawing command 303 for drawing an object, a character size setting command 304 for setting a character size, a font setting command 305 for setting a character font, and a character drawing command 306 for drawing a character. The structure of these series of commands is the same for other objects and character strings. In addition to this, commands for setting coordinates and line thickness, commands for drawing an image, etc. are also included, but they are omitted.

The contents of the drawing command 300 will be briefly described. The color value data in the subsequent drawing commands is assumed to be an 8-bit image. The second command of the drawing command 300, "Set Page Color (CL)" of the color mode setting command 301, indicates that the following commands are expanded in color.

The third color setting command 302 "Set Color (146, 208, 80)" indicates that the RGB values are green with R = 146, G = 208, and B = 80. The fourth command, the object drawing command 303 "Draw Polygon", indicates that a figure is drawn. As a result, as shown in FIG. 3B, the object 308 is drawn in green with R = 146, G = 208, and B = 80 in the image 307. The area indicated by the reference numeral “308” in FIG. 3A indicates that the area is for drawing the object 308 in the image 307. As described above, the area in the drawing command 300 indicated by the same code as the code indicating the object in the image 307 indicates that the area in which the command for drawing the object of the code is described is described.

Next, the fifth to twelfth commands will be described. The character size setting command 304 "Set Text Size (6)" indicates that the character size is 6 points. Further, the font setting command 305 "Set Font (Arial)" indicates that the font of the character is Arial. Of the character drawing commands 306, for example, "Draw Text (" x ")" indicates that the character "x" is drawn. As a result, in the image 307 of FIG. 3B, "1.xxx" of the character string object 309 is an Arial font, a character size of 6 points, and a light red color of R = 255, G = 138, B = 138. It is drawn.

Similarly, by the 13th to 16th commands, in the image 307 of FIG. 3B, the sun object 310 is drawn in light red (R = 255, G = 135, B = 135). Further, by the 17th to 24th commands, in the image 307 of FIG. 3B, "2.xxx" of the character string object 311 is drawn in black with an Arial font and a character size of 6 points.

Although the background color is not specified in the drawing command 300, it is defined as the PDL specification that the portion where the object is not drawn is white (R = G = B = 255). Similarly, it is assumed that black (R = G = B = 0) is defined when the drawing color is not specified.

In the present embodiment, it is assumed that the color value specified for drawing the page in the print data is the print data of the color data including the color value of the color.

[About drawing commands in PDL that can use multiple color spaces]
FIG. 4 is a diagram showing an example of a drawing command according to a PDL type that can use a plurality of color spaces included in the print data acquired by the image forming apparatus 100 according to the first embodiment, and a drawing result based on the drawing command. Is. FIG. 4A shows an example of a drawing command 400 that can use a plurality of color spaces, and FIG. 4B shows an image 413 drawn using the drawing command 400.

The drawing command 400 has a comment 401 that clearly indicates that the PDL type is a PS that can use a plurality of color spaces. Further, in the drawing command 400, a color setting command is described using a plurality of color spaces. Specifically, it includes a color setting command 402 that uses an RGB color space, a color setting command 404 that uses a CMYK color space, a color setting command 410 that uses a CIEBasedABC color space, and a color setting command 412 that uses a gray color space. It has been.

There are object command groups 403 and 411 for drawing graphic objects such as quadrilaterals. Character drawing includes a font setting command 405 for setting a character font, a character size setting command 406 for setting a character size, a drawing position specification command 407 for specifying a drawing position, and a character drawing command 408 for drawing a character. The structure of these series of commands is the same for other objects and character strings. In addition to this, commands for setting coordinates and line thickness, commands for drawing an image, etc. are also included, but they are omitted.

Next, the contents of the drawing command 400 will be specifically described. In the drawing command 400, the color value data is defined as a decimal number between 0 and 1.

Comment 401 is a comment line because "%! PS" starts with "%". Since there are image forming devices that can use multiple PDL types, the comment line indicating the PDL type is used to indicate to the image forming device that has acquired the drawing command that the drawing command is PS data. It is said.

The second to third commands of the drawing command 400 will be described. The color setting command 402 "/ DeviceRGB setcolorspace 0.57 0.82 0.31 setcolor" specifies that the color space is drawn in DeviceRGB. When each signal value of the color value is represented by 8 bits, R = 0.57 × 255 = 146, G = 0.82 × 255 = 208, and B = 0.31 × 255 = 80.

Object command group 403 "{setbbox" to "} ufill" indicates that a figure is drawn by designating a closed area and filling the inside. As a result, the object 414 of FIG. 4B is drawn in green with the color values of R = 146, G = 208, and B = 80.

The fourth to eighth commands of the drawing command 400 will be described. The color setting command 404 "/ DeviceCMYK setcolorspace 0 0.46 0.46 0 setcolor" specifies that the color space is drawn with a color value of DeviceCMYK. The color values are C = 0 × 255 = 0, M = 0.46 × 255 = 117, Y = 0.46 × = 117, and K = 0 × 255 = 0. The font setting command 405 "/ Arial findfont" indicates that the character font is Arial, and the character size setting command 406 "6 scalefont setfont" indicates that the character size is 6 points. Further, the drawing position designation command 407 "move to" indicates a position for drawing a character, and the character drawing command 408 "(1.xxx)" indicates that the character string "1.xxx" is drawn. As a result, "1.xxx" of the object 415 of the character string in FIG. 4B is an Arial font, the character size of 6 points, and the color values of C = 0, M = 117, Y = 117, and K = 0. It is drawn in light red.

The 9th to 11th commands of the drawing command 400 will be described. Color conversion information command 409 The color conversion information command 409 from "[/ CIEBasedABC" to "] setcolorspace" defines a color conversion method for converting from the input color space of three channels of ABC to the XYZ color space. When the color value of the CIEBasedABC color space is specified by another command after this command, it is converted to the XYZ color space by the color conversion method defined by the color conversion information command 409. In the example of FIG. 4, the color conversion information command 409 defines only the range of the input color value (RangeABC), the range of the output XYZ color value (RangeLMN), and the white point (WhitePoint) of the output XYZ, and the color conversion method. Is not defined. Therefore, the input color value is output as it is by the color conversion information command 409, and as a result, it is shown that the input color space is the XYZ color space.

The color setting command 410 "/ CIEBasedABC setcolorspace 0.56 0.41 0.21 setcolor" sets the color value in the CIEBasedABC color space. The signal values of each channel are A = 0.56 × 255 = 143, B = 0.41 × 255 = 105, and C = 0.21 × 255 = 54. In the example of FIG. 4, the CIEBasedABC color space defines XYZ, and the color value of this ABC is light red. The object command group 411 shows drawing of a figure in the same manner as the object command group 403. As a result, the sun object 416 is drawn in light red as shown in FIG. 4 (b).

Finally, the 12th to 16th commands of the drawing command 400 will be described. The color setting command 412 "/ Device Gray setcolorspace 0 set color" specifies that the device gray is used to draw with a color value of Gray = 0 × 255 = 0. The commands after the color setting command 412 are the same as the commands described in the fifth to eighth commands. As a result, as shown in FIG. 4B, "2.xxx" of the object 417, which is a character string, is drawn in black with an Arial font and a character size of 6 points.

Although the background color is not specified in the drawing command 400 as in the drawing command 300, it is defined as the PDL specification that the part where the object is not drawn is white (C = M = Y = K = 0). Suppose you are. Similarly, when the drawing color is not specified, it is defined as black (C = M = Y = 0, K = 255).

[Color conversion method selection process]
As described above, the acceptable print data corresponding to the processing of the image output unit 109 is defined on one side in the same color space. When print data including a plurality of color spaces is input to the image forming apparatus 100, the image processing unit 103 converts the print data into a single color space and then outputs the print data to the image output unit 109. Further, the image processing unit 103 converts the color value specified by the drawing command into a color value according to the setting of the image forming apparatus 100. Therefore, the image processing unit 103 needs to select and determine the color conversion method according to the PDL type or the setting of the image forming apparatus 100.

FIG. 5 is a flowchart showing a series of processes for determining a color conversion method when performing color conversion of a drawing command in an image forming apparatus. The series of processes shown in the flowchart of FIG. 5 is performed by the CPU of the image forming apparatus 100 expanding the program code stored in the ROM into the RAM and executing it. Further, some or all the functions of the steps in FIG. 5 may be realized by hardware such as an ASIC or an electronic circuit. The symbol "S" in the description of each process means that the step is a step in the flowchart, and the same applies to the subsequent flowcharts.

In the flowchart of FIG. 5, in S501, conditional branching is performed based on the PDL type of the input drawing command. In S502 to S505, conditional branching is performed according to the setting. Then, the color conversion method is selected in S506 to S511.

In S501, the command analysis unit 204 determines whether or not the input data is a PDL type that can use a plurality of color spaces. Specifically, the command determination unit 203 determines the PDL type of the data input to the image forming apparatus 100 before the processing of this flowchart is started. Then, if the discrimination result of the command discrimination unit 203 is PS or PDF, the command analysis unit 204 determines that a plurality of color spaces are available PDL types, and if the discrimination result of the command discrimination unit 203 is PCL or the like. It is determined that the PDF type can be used only in a single color space.

When the PDL type of the input data is a PDL type that can use a plurality of color spaces (YES in S501), the command analysis unit 204 in S502 sets the image output set via the operation unit 104 or the host PC 110. Determines if is a color output. When the image output is set via the operation unit 104, the setting information is stored in the RAM 106 or the storage unit 107. The command analysis unit 204 reads the saved image output setting and determines whether the image output setting is color output. The same applies to the processing based on other setting information set via the operation unit 104.

When the color output is determined in S502 (YES in S502), the command analysis unit 204 selects CMYK conversion as the color conversion method in S506 and ends the processing of this flowchart.

On the other hand, when the monochrome output is determined in S502 (NO in S502), the command analysis unit 204 in S503 determines whether or not the image output setting is a setting for improving discrimination. In the case of the setting for improving the discriminability (YES in S503), the command analysis unit 204 selects "monochrome conversion of a plurality of color spaces for improving the discriminability" as the color conversion method in S507, and ends the process of this flowchart. On the other hand, in the case of a setting that does not consider discrimination (S503 is NO), the command analysis unit 204 selects "simple monochrome conversion of a plurality of color spaces" as the color conversion method in S508 and ends the processing of this flowchart.

On the other hand, when the PDL type of the input data is a PDL type that can use only a single color space (S501 is NO), the command analysis unit 204 in S504 determines whether or not the image output setting is color output. judge.

When the color output is determined in S504 (YES in S504), the command analysis unit 204 selects "no conversion" as the color conversion method in S509 and ends the process of this flowchart. On the other hand, if it is determined in S504 that the output is monochrome (NO in S504), the process proceeds to S505.

In S505, the command analysis unit 204 determines whether or not the image output setting is a setting that improves discrimination. In the case of the setting for improving the discriminability (YES in S505), the command analysis unit 204 selects "monochrome conversion of a single color space for improving the discriminability" as the color conversion method in S510, and ends the process of this flowchart. In the case of a setting that does not consider discrimination (S505 is NO), the command analysis unit 204 selects "simple monochrome conversion of a single color space" as the color conversion method in S511 and ends the processing of this flowchart.

In this way, the command analysis unit 204 selects an appropriate color conversion method by performing conditional branching according to the PDL type of the input data and the image output setting.

[About color conversion processing by the selected color conversion method]
The contents of each color conversion process according to the color conversion method selected in the process of FIG. 5 will be described. First, the contents of the color conversion method when the image output setting is color output will be described.

(S509: No conversion)
The color conversion method selected in S509 will be described based on the drawing command 300. It is assumed that all the color values of the drawing command 300 are specified in the RGB color space, and the image output unit 109 also corresponds to the data in the RGB color space. In this case, the command analysis unit 204 does not perform color conversion. When the input drawing command includes data in the gray color space, the gray value value Gray is converted to the color value in the RGB color space by setting R = G = B = Gray.

(S506: CMYK conversion)
The processing content of the color conversion based on the color conversion method selected in S506 will be described by taking the drawing command 400 as an example. The drawing command 400 expresses color values in a plurality of color spaces. Of the color spaces, for example, the CIEBasedABC color space indicated by the color setting command 410 is not a color space corresponding to processing in the image output unit 109. Therefore, the command analysis unit 204 performs color conversion that converts the color value of each drawing command into one type of color space that can correspond to the processing of the image output unit 109. For example, it is assumed that the image output unit 109 is a printer and the color space that the printer can output is a CMYK color space. In this case, the command analysis unit 204 performs a process of converting the color value of each drawing command into the color value of the CMYK color space.

A method of converting the color value of each color space into the color value of the CMYK color space will be described. When a color value is specified in the Device RGB color space as in the color setting command 402 of the drawing command 400 in FIG. 4, the color value is the color value of the general display RGB space, here the sRGB color space. It is interpreted as specifying. Therefore, the command analysis unit 204 uses a profile for converting the sRGB color space to the XYZ color space and a profile for converting the XYZ color space to the CMYK color space stored in the storage unit 107. Using these profiles, the command analysis unit 204 performs color conversion in the order of input color value → color value in XYZ color space → color value in CMYK color space.

When a color value is specified in the DeviceCMYK color space as in the color setting command 404 of the drawing command 400, it is interpreted that the color value in the output color space of the image output unit 109, which is an output device, is directly specified. To do. Therefore, the color value of the color setting command 404 is output as a color value in the CMYK color space without color conversion.

When a color value is specified in the CIEBasedABC color space like the color setting command 410 of the drawing command 400, the information for converting the CIEBasedABC color value specified by the color conversion information command 409 to the XYZ color value is used. .. Therefore, using the information of the color conversion information command 409 and the profile for converting the XYZ color space to the CMYK color space, the color value of the color setting command 410 is the input color value → the color value of the XYZ color space → CMYK. Color conversion is performed in the order of color values in the color space.

When a color value is specified in the Device Gray color space as in the color setting command 412 of the drawing command 400, profile conversion is performed in the same manner as for Device RGB. Alternatively, since gray is simple information only for brightness, it may be processed by algebraic operation. For example, in algebraic operation, assuming that the gray value is Gray, conversion to the CMYK color space is performed by inverting the gray values such as C = M = Y = 0 and K = 255-Gray.

In this way, the command analysis unit 204 performs calculations using the built-in profile, calculations using some profiles, simple algebraic operations such as inversion, and color conversion according to the color space such as outputting the input color value without processing. Use the processing method of. Then, the command analysis unit 204 performs color conversion to a color value in the color space corresponding to the processing of the image output unit 109 according to the color space processing method.

Note that this color conversion is an example, and the color value of the PDL type drawing command that can use multiple color spaces by another color conversion method is converted into the color value of the color space corresponding to the processing of the image output unit 109. You may. Further, the user may set a conversion method from each color space to a color space corresponding to the processing of the image output unit 109 via the operation unit 104 or the operation unit (not shown) of the host PC 110. For example, the input profile of the Device RGB color space may be set according to the output color space of the display device (not shown) connected to the host PC 110. In this case, the setting information is stored in the RAM 106 or the storage unit 107, and the command analysis unit 204 acquires this setting and executes the color conversion process designated for the color value of each color space. In the above example, all the color values are converted into the color values of the CMYK color space, but it may be converted into a color space corresponding to the processing of the image output unit 109 such as the RGB color space.

(S5111: Simple monochrome conversion of a single color space)
Color conversion when the image output setting is monochrome output will be described. As described above, the print data of the present embodiment is print data of color data including color values of colors. Therefore, unlike the case of color output, a process of converting a color value indicated by color into a color value (gray value) in a gray color space is included. First, a general monochrome conversion formula will be described. When monochrome output is specified for the print data of the color image by the user, the command analysis unit 204 converts the color value of the drawing command into a gray value in both the drawing command 300 and the drawing command 400.

Equations 1, 2, and 3 are examples of equations for converting each signal value of R, G, and B into a gray value Gray. Equation 1 is a color value conversion formula defined by NTSC, Equation 2 is a color value conversion formula defined by sRGB, and Equation 3 is a conversion in which the color values defined in the RGB color space are evenly weighted. It is an expression.
Gray = 0.30 × R + 0.59 × G + 0.11 × B (Equation 1)
Gray = 0.21 × R + 0.72 × G + 0.07 × B (Equation 2)
Gray = (R + G + B) ÷ 3 (Equation 3)

In Equations 1 and 2, the weights of the respective signal values of R, G, and B are changed and converted into gray values. The reason for this is that when looking at each of the red, green, and blue lights of the same brightness, the color is converted according to the human visual characteristic that green looks relatively bright and blue looks dark.

Explaining the processing content of the color conversion based on the color conversion method selected in S511 by taking the drawing command 300 as an example, the colors of all the objects 308 to 311 are described by using the gray conversion formula of the NTSC method shown in Equation 1. Convert color values to gray values. In this way, in the monochrome conversion that does not consider the discrimination, the color value of each object is uniformly converted to the gray value by using any mathematical formula (conversion method) for converting to the gray value. Therefore, there is a feature that it is easy to guess the converted monochrome image from the color data input by the user. On the other hand, if the conversion to the gray value is performed uniformly, the colors different from each other in the color data may become close to each other or the same gray value after the gray conversion, and the discrimination property may be lost.

It should be noted that uniformly converting the color value of the color specified in the drawing command to a gray value without considering the discrimination may be called simple monochrome conversion or simply simple conversion.

(S508: Simple monochrome conversion of multiple color spaces)
Regarding the processing contents of the color conversion based on the color conversion method selected in S508, a method of converting the color value of each color space into a gray value will be described by taking the drawing command 400 of FIG. 4 as an example.

When a color value is specified in the Device RGB color space as in the color setting command 402 of the drawing command 400, the color value of the object is used by using the NTSC graying conversion formula shown in Equation 1 as in the drawing command 300. To convert.

When a color value is specified in the DeviceCMYK color space as in the color setting command 404 of the drawing command 400, Equation 1, Equation 2, and Equation 3 cannot be applied as they are. However, when the colors of the CMYK color space and the RGB color space are qualitatively compared, Cyan (C) is the complementary color of Red (R), Magenta (M) is the complementary color of Green (G), and Yellow (Y) is Blue ( It is a complementary color of B). Black (K) is the inverted version of Gray. When converting the color value of the DeviceCMYK color space into a gray value by utilizing this feature, the following equations 4, 5, and 6 are used.
Gray = 255 --min (255, 0.30 × C + 0.59 × M + 0.11 × Y + K) (Equation 4)
Gray = 255 --min (255, 0.21 × C + 0.72 × M + 0.07 × Y + K) (Equation 5)
Gray = 255 --min (255, (C + M + Y) ÷ 3 + K) (Equation 6)

Here, in Equations 4, 5, and 6, "min" is a function that outputs the smaller of the two input values. For example, if the input values are 10 and 20, then min (10, 20). ) = 10 is output.

When a color value is specified in the CIEBasedABC color space like the color setting command 410 of the drawing command 400, the color value is once converted to the XYZ color space using the information specified by the color conversion information command 409. Then, using the profile that converts the XYZ color space to the gray color space, the color conversion is performed in the order of the input color value → the color value of the XYZ color space → the gray value. As an output profile for converting from the XYZ color space to the gray color space, for example, there is a profile that outputs only the Y component of the XYZ color space.

When a color value is specified in the DeviceGray color space, since it indicates a gray value, the input color value is output as a gray value without color conversion.

(S510: Monochrome conversion of a single color space to improve discrimination)
The monochrome conversion of a single color space for improving discrimination, which is the color conversion method selected in S510, will be described by taking the drawing command 300 as an example. In the color conversion method selected in S510, the color value of the color is uniformly converted into the clay value by the same method as the monochrome conversion of the single color space, which is the color conversion method selected in S511. Next, a process for improving the discriminability of correcting the converted gray value is performed.

FIG. 6 is a diagram showing an example of a color value list 600 for applying a monochrome conversion of a single color space that improves discrimination to color values in the RGB color space included in the drawing command 300. Since the drawing command 300 has a command for describing four objects 308 to 311 having different color values, the color value list 600 has four lines corresponding to the objects 308 to 311. In the color value list of the present specification, the line corresponding to the object is given the same code as the code of the object.

Column 601 of the color value list 600 is a column that holds the type of the color space. Column 602 is a column that holds the color values of the color space held in column 601 as signal values of each color component. Column 603 is a column that holds the gray value when the color value of column 602 is simply gray-converted by the method selected in S511. Column 604 is a column that holds the gray values after the simply converted gray values have been modified to improve discrimination. Since all the drawing commands 300 are color values in the RGB color space, the values in column 601 of the color space hold values indicating all RGB, and the color values in column 602 are the three channels of R, G, and B. The signal value is retained.

FIG. 7 is a diagram for explaining how to adjust the gray value when the simple gray conversion is performed in order to improve the discrimination. On the number line 700, the simply converted gray values in column 603 are arranged in descending order. That is, the gray values 702 to 705 indicate the gray values held in column 603 of the color value list 600. Further, on the number line 710, gray values after processing for improving discrimination with respect to the simply converted gray values are arranged. Both the number line 700 and the number line 710 show a gray value of 0 to 255, indicating that the higher the gray value, the larger the gray value and the lighter the gray.

Here, it is defined that the non-drawn background portion of the drawing command 300 is white (R = G = B = 255). The portion of the image 307 of FIG. 3 in which the object is not drawn is white. Since it is necessary to distinguish between white and the gray value of the object, white (gray value 255) is not included in the color value list 600, but is added to the number line 700. Similarly, even if the default drawing color black (gray value is 0) is not in the color value list 600, black is added on the number line 700. The intervals 706 to 709 indicate the intervals (differences) of the gray values 701 to 705 on the number line 700.

FIG. 8 is a flowchart for explaining the color conversion process by the color conversion method selected in S510. In addition to FIGS. 6 and 7, FIG. 8 will be used to describe the monochrome conversion process of the single color space for improving the discriminability performed by the command analysis unit 204.

In S801, the command analysis unit 204 reads the input drawing command 300 from the beginning to the end, and inputs the color space of the color value list 600 to the column 601 and the color values to the column 602, respectively. Specifically, the drawing command 300 of FIG. 3 is read in order from the first row, a new row is added to the color value list 600 for each SetColor command, "RGB" is input to the column 601 of the color space, and the color is displayed. Enter the argument of the SetColor command in the value column 602. By continuing this process until the Page End command, the command analysis unit 204 inputs all the RGB color values in the drawing command 300 to the color value list 600. For example, line 308 of the color value list 600 is the “Set Color (146, 208, 80)” of the color setting command 302 of FIG. 3 (a) that specifies the color value of the object 308 of FIG. 3 (b). The argument has been entered.

In S802, the command analysis unit 204 uniformly performs simple gray conversion on the color values input to the column 602 of the color value list 600, and inputs the result to the column 603 of the color value list 600. The color values of the object 308, R = 146, G = 208, and B = 80, have a gray value of 175 when the gray conversion is performed by Equation 1. Similarly, the gray value of object 309 is 173, the gray value of object 310 is 171 and each gray value is entered in column 603.

In S803, the command analysis unit 204 arranges the simply converted gray values 701 to 705 in ascending or descending order as shown by the number line 700 in FIG. 7, and the interval between adjacent gray values 706 to 709 is less than a predetermined value. Determine if there is an interval between. The predetermined value is determined based on the interval from other gray values required for discriminating the gray object output by the image output unit 109. For example, if the gray values need to be 16 apart to discriminate objects, the predetermined value is determined to be 16.

In the example of FIG. 7, the interval 707 is an interval indicating the difference between the gray value 702 of the object 308 and the gray value 703 of the object 309, and the interval value is 2. The interval 708 is an interval indicating the difference between the gray value 703 of the object 309 and the gray value 704 of the object 310, and the interval value is 2. Therefore, the command analysis unit 204 determines that the gray value interval is smaller than the predetermined value for the interval 707 and the interval 708.

When there is an interval less than a predetermined value (YES in S803), the command analysis unit 204 determines in S804 whether the gray values constituting the interval determined to be smaller than the predetermined value have a similar color relationship. Judgment of similar colors is performed based on the color value of the color before it is converted to the gray value.

When the colors in the color data before conversion are similar, it becomes unnatural if the color data is improved in discrimination against the converted gray. Therefore, when the colors are similar, this determination process is performed so as not to perform the process for improving the discrimination.

Whether or not the two colors are similar depends on the content of the original, the light source that illuminates the output recorded matter, and the person who makes the judgment. Therefore, it is uniformly determined whether or not the two colors are similar colors by using the difference between the color values in the RGB color space before the conversion to the gray value. The signal values of the two RGB color spaces before being converted into gray values are R1, G1, B1 on one side and R2, G2, B2 on the other side. The diff based on the difference between the two color values is calculated as in Equation 7.
diff = sqrt (pow (R1 --R2, 2) + pow (G1 --G2, 2) + pow (B1 --B2, 2)) (Equation 7)

Here, power is a function indicating a power, and among the values separated by commas in parentheses, the value on the right side is used as an exponent, and the value obtained by multiplying the value on the left side by a power is returned. Also, sqrt is a function indicating the square root.

diff is a value indicating the degree of similarity. If the diff value is equal to or less than a certain threshold value, it is determined that the two input RGB values are similar colors, and if it is larger than the threshold value, it is determined that the two input RGB values are different colors. Here, as an example, the threshold value will be described as 20. The relationship between the color values of the two RGB color spaces is always determined to be either a similar color or a different color, and even if the input color values of the two RGB color spaces are the same, it is assumed that the colors are similar.

For example, the diff of the color value of the object 308 and the object 309 before conversion is 142, and the object 308 and the object 309 are determined to be different colors. Since the diff of the color values of the object 309 and the object 310 before conversion is 4 and is equal to or less than the threshold value of 20, it is determined that the colors are similar. The diff of the color value before conversion between the object 310 and the object 308 is 142, which is determined to be a different color and is determined to be a target for discrimination. In this way, by deriving the diff indicating the degree of similarity using Equation 7, it is possible to determine whether the color values of the respective RGB color spaces are similar colors or different colors. Therefore, it is possible to determine whether or not to improve the discrimination in the subsequent processing.

When the combination of gray values whose intervals are less than a predetermined value is determined to be different (NO in S804), the command analysis unit 204 in S805 widens the intervals smaller than the predetermined values by the gray conversion process for improving discrimination. Correct the gray value so that. For example, the gray value is modified so that the interval is greater than or equal to a predetermined value. If the combination of gray values is determined to be similar, the interval is maintained.

Explaining with the example of FIG. 7, the gray value 702 of the object that was green in the color data before conversion and the gray value 703 of the object that was light red in the color data before conversion are gray values in order to improve discrimination. To change. Here, as an example, the interval (difference) of gray values to be discriminated is changed so as to have a difference of 16 or more, which is a predetermined value.

The gray values 711 to 715 of the number line 710 indicate the gray values modified from the simply converted gray values 701 to 705. The intervals 716 to 719 indicate the intervals of the gray values 711 to 715 on the number line 710.

The gray value 702 of object 308 is modified from 175 to 182 in the modified gray value 712. The gray value 703 of the object 309 is modified from 173 to 166 in the modified gray value 713. The gray value 704 of the object 310 is modified from 171 to 164 in the modified gray value 714 so that the interval remains 2.

Therefore, by this process, the gray value is corrected so that the gray value can be discriminated even when the green color of the object 308 to be discriminated from and the light red color of the objects 309 and 310 are converted into gray values. However, for the light red color of the object 309 and the object 310, which do not need to be discriminated, the gray value is not positively separated. Therefore, although the interval is smaller than the predetermined value, the process of improving the discriminability is not performed. Can be.

If there is no interval less than the predetermined value (S803 is NO), or if the combination of gray values whose interval is less than the predetermined value is determined to be similar colors (S804 is YES), the discrimination improvement process is not performed. Ends the processing of this flow with. The order of determination of S803 and S804 may be reversed.

As described above, when a color value in a single color space is input, not only the gray value can be compared but also the color value of the color can be compared. Therefore, it is judged based on the color data whether the color is different and discriminated. It is possible to realize a sexual graying.

(S507: Monochrome conversion of multiple color spaces to improve discrimination)
The content of the color conversion method selected in S507 will be described by taking a drawing command 400 including color values in a plurality of color spaces as an example.

In a PDL type drawing command in which a plurality of color spaces can be used, such as the drawing command 400, a color value may be specified by a plurality of color spaces. Whether the colors indicated by the color values in different color spaces are similar colors or different colors cannot be determined by directly comparing the input color values. That is, it is not possible to determine whether the colors are similar using Equation 7.

Therefore, in the present embodiment, the color values of the plurality of color spaces are converted into a common color space and then converted into a gray value. The common color space is a predetermined one color space, and for example, any one of the color spaces such as RGB, CMYK, L * a * b *, and XYZ is the common color space. In this embodiment, the CMYK color space will be described as an example as a common color space. Further, the conversion method from the color value of each color space to the color value of the CMYK color space will be described as the same method as the conversion method to the CMYK color space when the color selected in S506 is output.

A method of deriving a diff indicating the degree of similarity in the conversion method selected in S507 will be described. Equation 8, Equation 9 and Equation 10 with one of the signal values of the two CMYK color spaces to be compared converted from the color values of each color space as C1, M1, Y1, K1 and the other as C2, M2, Y2, K2. Is used to calculate the diff.
C1 = min (255, C1 + K1), M1 = min (255, M1 + K1), Y1 = min (255, Y1 + K1) (Equation 8)
C2 = min (255, C2 + K2), M2 = min (255, M2 + K2), Y1 = min (255, Y2 + K2) (Equation 9)
diff = sqrt (pow (C1 --C2, 2) + pow (M1 --M2, 2) + pow (M1 --M2, 2)) (Equation 10)

If the diff value is less than or equal to the threshold value, the color is similar, and if it is larger than the threshold value, the color is different. In the CMYK color space, when expressing black, not only the signal value K is expressed by a single color, but also black can be expressed by using C, M, and Y. After adding the signal value of K to each of the signal values of M and Y, the diff is calculated using Equation 10. When the RGB color space is used as the common color space, the diff may be calculated using Equation 7.

The squared value of Equations 10 and 7, that is, the value at which the sqrt function for calculating the square root does not act may be diff. In this case, the threshold value may be adjusted by squared and used.

The method of determining whether the color values of the two CMYK color spaces are similar colors or different colors using the diff value is the same as the process of S804. If the diff is equal to or less than the threshold value, the color values of the two CMYK color spaces are similar colors, while if the diff is larger than the threshold value, the color values of the two CMYK color spaces are different colors. By converting the color value of the drawing command to the color value of the common color space in this way, it is possible to compare the color values defined in different color spaces before the conversion.

FIG. 9 is a diagram showing an example of a color value list 900 for applying a monochrome conversion for improving discrimination to color values in a plurality of color spaces included in the drawing command 400. Since the drawing command 400 has four objects 414 to 417 having different color values, the color value list 900 has four lines 414 to 417 corresponding to the objects. Column 901 of the color value list 900 holds the color space of the color values held in column 902. Column 902 is a column that holds the color values of the color space held in column 901 as signal values of each color component. Column 903 is a column that holds the signal value of each color component of the color value converted into the color value of the common color space. Column 904 is a column that holds a simply converted gray value, and column 905 is a column that holds a gray value that has been corrected as a result of processing for improving discrimination.

FIG. 10 is a diagram for explaining adjustments for improving discrimination with respect to the simply converted gray value as in FIG. 7. On the number line 1000, the simply converted gray values 1002 to 1005 in column 904 in the color value list 900 and the gray values 1001 on a white background (background of the original) are arranged in descending order. The intervals 1006 to 1009 indicate the intervals (differences) between adjacent gray values 1001 to 1005 arranged in ascending or descending order.

FIG. 11 is a flowchart showing a color conversion process by the color conversion method selected in S507. A monochrome conversion process of a plurality of color spaces for improving discriminability performed by the command analysis unit 204 will be described with reference to FIG.

S1101 is the same process as S801. For example, by the process of this step, the information of "setcolorspace" of the drawing command 400 is extracted, the signal values of the respective color values are converted into the values of 0 to 255, and the columns 901 and 902 of the color value list 900 are displayed. The value is entered.

In S1102, the command analysis unit 204 converts the color value of the drawing command input in S1101 into the color value of the CMYK color space which is a common color space. In the present embodiment, the color value of each color space is converted into the color value of the CMYK color space by the same conversion method as the conversion method for color output selected in S506.

For example, since the color value of the object 414 is described in the RGB color space, it is converted into the color value in the CMYK color space by using profile conversion. Since the color value of the object 415 is originally described in the CMYK color space, no color conversion is performed. Since the color value of the object 416 is described in the CIEBasedABC color space, it is converted into a color value in the CMYK color space by using the color conversion information command 409 and the profile conversion. Since the color value of the object 417 is shown in the Gray color space, the color value is inverted and converted to the K value in the CMYK color space.

In this way, the command analysis unit 204 converts the color values in the CMYK color space, which is a common color space, into the color values in the CMYK color space based on the color value information in columns 901 and 902 of the color value list 900. The signal values of each of these are input to column 903.

In S1103, the command analysis unit 204 performs simple gray conversion on the color value of the object converted into the color value of the common color space. That is, simple gray conversion is performed on the color values in the common color space input in column 903 of the color value list 900. Regarding the color values of the objects 414 to 417 in the drawing command 400, the gray values after the gray conversion using the equation 4 are 179, 173, 167, and 0, respectively, and are input to the column 904 of the color value list 900.

The process of S1104 is the same process as that of S803. In the case of the gray value on the number line 1000 in FIG. 10, in this step, it is determined that the gray interval is less than the predetermined value for the interval 1007 and the interval 1008 where the gray value interval is less than 16 which is a predetermined value.

The processing of S1105 is different from that of S804, and the determination of similar colors is determined by comparing the color values in the color space of the common color converted in S1102. In the case of the gray value on the number line 1000 in FIG. 10, the command analysis unit 204 determines that the interval between the gray values is smaller than the predetermined value. Determine if it is a different color. Similarly, it is determined whether the combination of the gray values 1003 and the gray values 1004 constituting the interval 1008 has a similar color or a different color. The determination of similar colors or different colors was derived using Equations 8, 9, and 10 with respect to the color values of the CMYK color space, which is a common color space held in column 903 of the color value list 900. It is determined whether the color is similar or different based on the diff. The threshold value used for determining whether the colors are different or similar will be described as being 20 as in S804.

Here, the diff between the gray value 1002 of the object 414 and the gray value 1003 of the object 415 is 139, and since it is larger than the threshold value of 20, it is determined that there is a different color relationship. Since the diff between the gray value 1003 of the object 415 and the gray value 1004 of the object 416 is 13 and is equal to or less than the threshold value of 20, it is determined that the colors are similar.

In S1106, the command analysis unit 204 performs a process of correcting the gray value so as to widen the interval of the combination of the gray values determined to be different colors to improve the discrimination. For example, the gray value is modified so that the interval between combinations of gray values to be discriminated is 16 or more, which is a predetermined value.

In the number line 1010 of FIG. 10, gray values that have been processed to improve discrimination by the processing of this step are arranged in descending order. The gray values 1011 to 1015 on the number line 1010 are gray values after the gray values 1001 to 1005 have been processed to improve the discriminability. The intervals 1016 to 1019 are intervals (differences) of the gray values 1011 to 1015 on the number line 1010.

As a result of the processing by this step, the gray value 1002, which was the green color value before the conversion, and the gray value 1003, which was the light red color value before the conversion, are different from each other even in the gray color. It will be fixed. As a result, the gray value 1002 in the object 414 is modified from 179 to 184 in the modified gray value 1012.

The gray value 1003 in the object 415 is modified from 173 to 168 in the modified gray value 1013. The gray value 1004 in the object 416 is modified from 167 to the modified gray value 914 to 162.

Therefore, even if the green object 414 to be discriminated and the light red object 415 are converted to gray by the processing by this step, discrimination is possible. However, for the light red objects 415 and 416 that do not need to be discriminated, it is possible to prevent the process of widening the difference between the gray values from being performed.

When there is no interval smaller than the predetermined value (NO in S1104), or when a combination of gray values whose interval is smaller than the predetermined value is determined to be similar colors (YES in S1105), processing for improving discrimination is performed. End the processing of this flow without. The order of determination of S1104 and S1105 may be reversed.

As an example of a common color space, a method of converting to a CMYK color space by the same method as color output has been described, but other color spaces having brightness and hue saturation information such as XYZ or L * a * b * can be used. It may be converted using a profile or numerical conversion. When the XYZ color space is a common color space, a method of converting the Y signal value into a gray value may be used as a method of converting the color value of the XYZ color space into a gray value. When the L * a * b * color space is used as a common color space, the method of using the L * value can be used as a method of converting the color value of the L * a * b * color space to the gray value. Good.

Further, the common color space may be changed according to the input color space. For example, when a color value is specified only in the RGB color space for a PDL type that can use a plurality of color spaces, the RGB color space may be used as a common color space. Alternatively, if a color value is specified only in the RGB color space for a PDL type that can use multiple color spaces, the color value in the RGB color space is not converted to a common color space. Simple gray conversion may be performed to determine whether or not the colors are similar from the color values in the RGB color space.

As described above, in the present embodiment, the color values of all the objects are once converted into a common color space and then converted into gray values. This makes it possible to compare color values even when data in a page description language of a type that allows color values to be specified in multiple color spaces is input. Therefore, according to the present embodiment, the gray value of the object should be widened even when the monochrome conversion for improving the discrimination is selected for the print data in which the color value is specified in a plurality of color spaces. It is possible to determine whether or not the processing is performed.

In the present embodiment, PS has been illustrated as an example in which a plurality of color spaces can be used in the PDL language, but a PDL type in which a plurality of other color spaces such as PDF and XPS can be used is used. You may. Further, although the color spaces of DeviceGray, DeviceRGB, DeviceCMYK, and CieBasedABC are illustrated as the input color space, the method of the present embodiment may be applied to a color space such as another color space (CieBasedA, Named) of the PS command. Good. When the color value of ICCBased is input when the PDF is input, the same color conversion as the conversion method from the color value of the CIEBasedABC color space described in the embodiment may be performed.

In the present embodiment, an example of processing by the image processing unit 103 of the image forming apparatus 100 is shown, but in addition, the host PC 110 which has the same function as the image processing unit 103 and also functions as an image processing apparatus The printer driver 202 may convert the color values into a common color space. In this case, the image forming apparatus 100 executes only the process of improving the discrimination. Alternatively, the printer driver 202 of the host PC 110 converts the color value into a common color space and converts it into a gray value including a process for improving discrimination, and generates a drawing command based on the result. It may be transmitted to the image forming apparatus 100.

<Second embodiment>
In the first embodiment, a method of using a conversion method to a CMYK color space for color output when converting a drawing command that can use a plurality of color spaces to a common color space has been described. In the present embodiment, a method of converting to a color value in the CMYK color space will be described by a method different from the method of converting to the CMYK color space when performing color output.

Even if the original data is generated by specifying the color value only in the RGB color space in the application 201, the PDL type of the print data may be different due to the difference in the type or setting of the printer driver 202.

The drawing command 1200 of FIG. 12A is a PDL type in which a plurality of color spaces can be used, but the color spaces indicated by the color setting commands 1201 to 1204 are all color-designated in the Device RGB color space. These RGB signal values are converted to values from 0 to 255, and RGB is represented by (R signal value, G signal value, B signal value). The color values of the color setting commands 1201 to 1204 are (146,208,80), (255,138,138), (255,135,135), and (0,0,0), respectively. As shown in the image 1205 of FIG. 12B, the objects 1206 to 1209 are drawn with the color values specified by the color setting commands 1201 to 1204, respectively. This is the same as the color value specified by the color setting command in the drawing command 300 described in the PDL type that can use the single color space shown in FIG. 3A.

That is, the PDL type drawing command 1200 that can use the plurality of color spaces of FIG. 12A is the same drawing as the PDL type drawing command 300 that can use the single color space shown in FIG. 3A. It is a drawing command that expresses the command of. The difference between the drawing command 300 and the drawing command 1200 is that the same original data on the host PC is converted into a drawing command that supports a single color space, or a drawing command that supports multiple color spaces. It's the difference.

Therefore, if the output setting specified by the user is monochrome output and the setting for improving discrimination is made, the conversion method in S510 is selected if the drawing command is 300 in the flow of FIG. On the other hand, if the drawing command is 1200, the conversion method in S507 is selected. However, even when either conversion method is selected, it is preferable that the drawing command 300 and the drawing command 1200 are drawn and output in the same manner. Similarly, it is the same whether it is a monochrome output that does not improve without considering discrimination and a color output.

Here, it will be described that the drawing command 300 and the drawing command 1200 output the same color value for normal color output. When the drawing command 300 using a single color space is input to the image processing unit 103, the color value of the RGB color space is input to the image output unit 109. If the image output unit 109 is a printer, it is converted into a color value in the CMYK color space, which is the color of the color material. The conversion method to the CMYK color space at this time is the same as the case where the drawing command 1200 in which the color output is specified is converted from the Device RGB color space to the CMYK color space by the method selected in S506. Specifically, the CMYK color space is created by using a profile for converting the sRGB color space stored in the storage unit 107 to the XYZ color space and a profile for converting the XYZ color space to the CMYK color space of the image output unit 109. Conversion is done to color values. As a result, the color value of the RGB color space of the drawing command 300 is converted into the same CMYK value (the amount of color material of the image output unit 109) as the color value of the Device RGB color space of the drawing command 1200, and the output of the same color value is obtained. be able to.

Next, it will be described that the drawing command 300 and the drawing command 1200 output the same color value for a simple monochrome output which is a monochrome output without considering discrimination. When a drawing command 300 using a single color space is input to the image processing unit 103, the color values in the RGB color space are converted to monochrome according to Equation 1 by the conversion method selected in S511. Similarly, when a drawing command 1200 using a plurality of color spaces is input to the image processing unit 103, the Device RGB data is monochrome-converted by the equation 1 by the conversion method selected in S508. As a result, the color value of the RGB color space of the drawing command 300 and the color value of the Device RGB color space of the drawing command 1200 are converted into the same gray value, and the output of the same color value can be obtained from the image output unit 109.

Next, the process of converting the color value of the drawing command 1200 by the monochrome conversion of the plurality of color spaces for improving the discriminability described in the first embodiment will be described.

The color value list 1300 of FIG. 13A is a comparative example of a color value list for performing monochrome conversion for improving discrimination against a drawing command 1200 that can use a plurality of color spaces. Since columns 1301 to 1305 are columns having the same values as columns 901 to 905 in the color value list 900 of FIG. 9, description thereof will be omitted. That is, the color information of the drawing command 1200 is held in the input color space of column 1301 and the color value of column 1302. The color value list 1300 and the color value list 600 of FIG. 6, which is a color value list of the drawing command 300, will be compared and described.

Comparing the values of column 603 of the color value list 600 and column 1304 of the color value list 1300, which hold the simply converted gray values, even if the color values are in the same RGB color space before conversion, It can be seen that the gray values are different. In the PDL type drawing command 1200 that can use a plurality of color spaces, it is converted into a color value in the CMYK color space and then converted into a gray value. On the other hand, in the PDL type drawing command 300 that can use only a single color space, the color value in the RGB color space is directly converted into the gray value. The difference in gray value between the color value list 600 and the color value list 1300 is due to the difference in the conversion method to this gray value. In column 1304 of the color value list 1300 that holds the retained simple converted gray values, the gray value of the green object 1206 is smaller than the gray value of the light red objects 1207 and 1208, resulting in a darker color. Note that it has become.

FIG. 14 is a diagram for explaining the adjustment of the simply converted gray value in column 1304 of the color value list 1300. On the number line 1400, the simply converted gray values 1402 to 1405 and the white gray values 1401 held in column 1304 of the color value list 1300 are arranged. The intervals 1406 to 1409 are intervals of each gray value 1401 to 1405 on the number line 1400.

Here, it is considered that the gray values 1401 to 1405 on the number line 1400 are subjected to a process for improving the discriminability of the simply converted gray values based on S1104 to S1106 of FIG. The intervals of less than 16 which are predetermined values among the intervals 1406 to 1409 are the interval 1407 and the interval 1408. Of these, the only combination of gray values having a diff exceeding the threshold value of 20 is a combination of a gray value 1403 having a diff of 138 and a gray value 1404, and the colors of the gray value 1403 and the gray value 1404 before conversion are different. Is determined. Therefore, the values of the gray values 1402 to 1404 are modified so as to widen only the interval 1408 composed of the gray value 1403 and the gray value 1404.

On the number line 1410, gray values 141 to 1415 after being processed to improve discrimination with respect to gray values 1401 to 1405 are arranged. The intervals 1416 to 1419 are intervals of each gray value 1411 to 1415 on the number line 1410. The gray values 1412 to 1415 thus obtained are input to column 1305 of the color value list 1300.

Comparing FIG. 14 with FIG. 7 showing the adjustment of the gray value in the color value list 600, the gray value 702 corresponding to the object 308, which was green in the drawing command 300 in FIG. 7, becomes lighter (brighter). It has been corrected to a gray value of 712. On the other hand, as shown in FIG. 14, the gray value 1404 corresponding to the object 1206 which was the same green in the drawing command 1200 of the PDL type in which a plurality of color spaces can be used is changed to the gray value 1414 so as to be dark (dark). It has been fixed.

Similarly, in FIG. 7, the gray values 703 and 704 corresponding to the objects 309 and 310, which were light red in the drawing command 300, are corrected to the gray values 713 and 714 so as to be dark (dark). On the other hand, in FIG. 14, the gray values 1402 and 1403 corresponding to the objects 1207 and 1208, which were light red even in the drawing command 1200, are corrected to the gray values 1412 and 1413 so as to be light (bright).

In this way, even when the same color value is specified by the RGB color space, the monochrome conversion of a plurality of color spaces for improving discrimination and the monochrome conversion of a single color space for improving discrimination are simple. A difference occurs in the converted gray value. Further, the difference may be increased by the process of improving the discrimination.

[Monochrome conversion of multiple color spaces to improve discrimination]
Therefore, in the present embodiment, when the monochrome conversion in S507 is selected, the color values in the RGB color space are converted into the color values in the CMYK color space, which is a common color space, by a method different from the CMYK conversion for normal color output. To do. In the present embodiment, when converting the color value of the Device RGB color space into the color value of the CMYK color space as a common color space, Equation 11 is used.
C = 255-R, M = 255-G, Y = 255-B, K = 0 (Equation 11)

This formula utilizes the fact that R, G, B and C, M, Y have complementary colors, and simply inverts the color values in the RGB color space to obtain C from each signal value of R, G, and B. , M, and Y signal values are obtained. Further, the signal value of K is always converted as 0.

FIG. 13B is a color value list 1306 when the color values of the drawing command 1200 are converted from the RGB color space to the color values of the CMYK color space by the method of the present embodiment. The input values of the color value list 1300 of the comparative example of FIG. 13 (a) and the color value list 1306 of the present embodiment of FIG. 13 (b) are the same color values of the drawing command 1200. Therefore, the color spaces held in columns 1301 and 1307 and the input signal values in columns 1302 and 1308 are the same.

On the other hand, in the present embodiment, the command analysis unit 204 converts the color values of the RGB color space of column 1308 into the color values of the CMYK color space and inputs them to column 1309 using Equation 11. Since the conversion method to the CMYK color space is different from the color value list 1300 which is a comparative example, the result of conversion to the color value of the common color space is the value in column 1303 of the color value list 1300 and the color value list 1306. It is different from the value in column 1309 of.

The command analysis unit 204 simply converts the color values in the CMYK color space of column 1309 into gray values and assigns them to column 1310. Comparing the gray values of column 603 of the color value list 600 of FIG. 6 and column 13100 of FIG. 13B, it can be seen that they are the same. This is the result of inverting the color value of the RGB color space with the formula 11 to obtain the color value of the CMYK color space and then converting it to the gray value using the formulas 8 to 10, and the color value of the RGB color space with the formula 1. This is because the results converted to gray values are equal.

The command analysis unit 204 determines whether the color before conversion is similar or different for the gray values of the object 1206 and the object 1207 in the color value list 1306 whose gray value interval is smaller than a predetermined value. Similarly, the command analysis unit 204 determines whether the gray values of the object 1207 and the object 1208 are similar colors or different colors before conversion.

For object 1206 and object 1207, the Diff value is 142 by substituting the CMYK values (109, 47, 175, 0) and (0, 117, 117, 0) into Equation 8, Equation 9, and Equation 10. Is calculated. Then, since the diff value exceeds the threshold value of 20, it is determined to be a different color. Similarly, for object 1207 and object 1208, substituting the CMYK values (0,117,117,0) and (0,120,120,0) into equations 8, 9 and 10 will result in a diff. The value is calculated as 4. Therefore, the value of diff is 20 or less, which is the threshold value, and it is determined that the colors are similar. In this way, the determination of whether or not the colors are similar has the same result as when the PDL type drawing command 300, which can use only a single color space, is processed. Therefore, the value in column 1311 of the color value list 1306 of the present embodiment of the drawing command 1200 and the value in column 604 of the color value list 600 of the drawing command 300 are the same, and the result of the process of improving the discrimination is obtained. Will be the same.

As described above, in the present embodiment, the color value in the RGB color space is converted into the color value in the CMYK color space by a method different from the conversion method at the time of color output. When the original data for which color values are specified in the same RGB color space is generated as either PDL type that can use only one color space or PDL type that can use multiple color spaces. is there. Even in such a case, according to the present embodiment, it is possible to make the result of the process for improving the discrimination be the same.

<Third embodiment>
In the first embodiment, a method of using a conversion method to a CMYK color space for color output when converting a drawing command that can use a plurality of color spaces to a common color space has been described. In the present embodiment, a method of converting to a color value in the CMYK color space will be described by a method different from the method of converting to the CMYK color space when performing color output.

First, a case will be described in which even if the user makes a setting for improving the discrimination, the modification for improving the discrimination is not performed for the simply converted gray value. For example, the simply converted gray values are well spaced apart. In addition, there are many colors in one page, and the gray value cannot be corrected to improve the discrimination. In such a case, the simply converted gray value is used as it is for the output even if the discrimination is set to be improved.

The conversion method for converting the color value of a PDL type drawing command that can use multiple color spaces to a gray value is monochrome conversion (called normal monochrome conversion) that is not set to improve discrimination, and discrimination. There are monochrome conversions that are set to improve. It is preferable that the gray value when the normal monochrome conversion is performed and the gray value when the monochrome conversion for improving the discrimination is selected but not corrected to the simple converted gray value are the same. However, in the PDL type in which a plurality of color spaces can be used, the gray value in which the monochrome conversion for improving discrimination is selected but not modified may be different from the normal monochrome converted gray value. Therefore, in the present embodiment, a method of converting the color value of the drawing command into the color value of the common color space by using a parameter different from the case of color output will be described.

First, a case where the monochrome conversion for improving the discrimination according to the first embodiment is selected but not modified and the normal monochrome converted gray value are different will be described.

The drawing command 1500 in FIG. 15A is an example of a drawing command according to the PDL type that can use a plurality of color spaces. In the drawing command 1500, the CIEBasedABC color space is defined by the color conversion information command 1501. Further, the color values specified by the color setting commands 1502 to 1505 for all objects are defined in the CIEBasedABC color space. FIG. 15B is a diagram showing an image 1506 output by the drawing command 1500. In the image 1506, the object 1507 is drawn in dark green, the objects 1508 and 1509 are drawn in light red, and the object 1510 is drawn in black.

The color value of CIEBasedABC is converted into the XYZ color space based on the color conversion information command 1501 in the drawing command 1500. The color conversion information command 1501 indicates that the CIEBasedABC color space is the XYZ color space.

The color value list 1600 of FIG. 16A is a comparative example of a color value list for performing monochrome conversion for improving discrimination against a drawing command 1500 that can use a plurality of color spaces. The color information of the drawing command 1500 is held in the input color space of column 1601 and the color value of column 1602. Based on the color value list 1600, it is considered that the color value of the drawing command 1500 is monochrome-converted (conversion by the conversion method selected in S507) to improve the discrimination by the method of the first embodiment.

All the color spaces shown in the 1601 column are CIEBasedABC, and the color value of the CIEBasedABC color space in the drawing command 1500 is the color value of the XYZ color space. Therefore, as described in the first embodiment, each signal value of C, M, Y, and K is derived from the XYZ color space using the conversion profile of the CMYK color space for color output and input to column 1603. Will be done. Further, the signal value in column 1603 is simply converted into a gray value using Equation 4 and input to column 1604.

The gray value held in column 1604, which is simply converted from the CMYK color space, is corrected to a gray value whose discriminability is improved by the processing by the flow of FIG. In the color value list 1600, the only interval of less than 16 where the difference between the simply converted gray values in column 1604 is a predetermined value is the interval between the gray values of object 1508 and object 1509. Since the CMYK signal values of the object 1508 and the object 1509 held in the column 1603 are the same, they have similar colors. Therefore, the simply converted gray value is not modified in order to improve the discrimination. That is, as the gray values held in column 1605 indicate, according to the color value list 1600, the output gray values of the objects 1507 to 1510 are the same as the gray values simply converted from the color values in the common color space. Become.

FIG. 16C is a list of gray values obtained by converting the color values specified by the drawing command 1500 by normal monochrome conversion (conversion by the conversion method selected in S508) that is not set to improve discrimination. It is a figure which shows 1612.

As illustrated in the first embodiment, the profile that converts the color value of the XYZ color space into the gray value is a profile that outputs the Y value of the XYZ color space as the gray value. In this case, in the drawing command 1500, the output gray value of the color setting command 1502 corresponding to the object 1507 is 0.11 × 255 = 28. The output gray value of the color setting commands 1503 and 1504 corresponding to the objects 1508 and 1509 is 0.41 × 255 = 105. The output gray value of the color setting command 1505 corresponding to the object 1510 is 0 × 255 = 0. These gray values are displayed in column 1613 of the list of FIG. 16 (c).

The gray values in column 1604 of the color value list 1600 converted after being converted to the CMYK color space for the process of improving the discrimination, and the gray values in column 1613 of the list 1612 converted by the normal monochrome conversion. The values are different when compared.

The gray value of the object 1507 becomes 28 in the normal monochrome conversion, but the gray value becomes 37 when the object 1507 is converted into the CMYK color space and then converted into the gray value. Objects 1508 and 1509 have a gray value of 105 in normal monochrome conversion, but when converted to a CMYK color space and then converted to a gray value, the gray value becomes 167.

In normal monochrome conversion, the CIEBasedABC color space is converted to the XYZ color space, and the Y signal value is set to the gray value. On the other hand, in the monochrome conversion for improving discrimination, the CIEBasedABC color space is converted to the CMYK color space, and the color value of the CMYK color space is color-converted to the gray value by Equation 4. The difference in gray value is due to this difference in color conversion processing.

[Monochrome conversion of multiple color spaces to improve discrimination]
Therefore, in the present embodiment, when monochrome conversion for improving discrimination is selected for drawing commands that can use a plurality of color spaces (when proceeding to S507), CMYK output for monochrome conversion for improving discrimination is selected. Convert to CMYK value in profile. The CMYK output profile for monochrome conversion that improves discrimination is hereinafter simply referred to as a "monochrome conversion profile" in the present specification.

The monochrome conversion profile has the same gray value that is simply converted from the CMYK value converted from the color value of the drawing command by the monochrome conversion profile and the gray value that is simply converted from the color value of the drawing command. The profile is adjusted to.

For example, when the color value of the CMYK color space converted by the monochrome conversion profile from the color value of the CIEBasedABC color space of the drawing command is NTSC-converted using Equation 4, it becomes the Y signal value of XYZ before conversion. The monochrome conversion profile is adjusted so as to be converted into a color value in the CMYK color space in this way. When the color value is specified in the RGB color space in the drawing command, the color value in the CMYK color space may be derived by using Equation 11 instead of the monochrome conversion profile.

The color value list 1606 of FIG. 16B is a color value list of the present embodiment in which the color values of the CMYK color space, which is the result of color conversion by the monochrome conversion profile, are held. The color space shown in column 1607 of the color value list 1606 and the signal values shown in column 1608 are related to the drawing command 1500 and are the same as the color value list 1600 of the comparative example of FIG. 16 (a).

When the command analysis unit 204 extracts the color value in the drawing command 1500, in the present embodiment, the color value of CIEBasedABC is converted into the CMYK color value by the profile for monochrome conversion. This result is the value in column 1609. The signal value in column 1609 is converted to a gray value using Equation 4 and input to column 1610.

For example, in the color value list 1606, the color value of the CIEBasedABC color space of the dark green object 1507 is (20, 28, 8). As described above, in the drawing command 1500, the value of CIEBasedABC is directly converted into the XYZ color space, so that XYZ is converted into (20, 28, 8). When this is color-converted by the monochrome conversion profile of the present embodiment, the color value of the CMYK color space is derived as (238,216,255,0). Further, when the color values (238,216, 255, 0) of this CMYK color space are converted by Equation 4, the gray value becomes 28. In this way, when the color value of the green XYZ color space is converted to the value of the CMYK color space by the CMYK output profile for monochrome conversion that improves discrimination, the C and Y signal values are converted to the large green hue. .. Further, when the NTSC gray conversion of Equation 1 is performed on the color value of this CMYK color space, it becomes the value of Y in the XYZ color space.

Similarly, for the light red objects 1508 and 1509, the color value of CIEBasedABC is (143,105,54), and the color value of the XYZ color space is (143,105,54). When the color value in this XYZ color space is converted into a color value in the CMYK color space using the monochrome conversion profile, it is converted to (0,215,215,0). When the color value of the CMYK color space of the converted column 1609 is gray-converted by Equation 4, it becomes 105. In this way, the gray value becomes 105, which is the Y value of the XYZ color space, while the color value of the CMYK color space is converted into the hue of red (0,215,215,0).

The same conversion to the CMYK color space is performed for the black object 1510. The color value of the CIEBasedABC color space is (0,0,0), and the color value of the XYZ color space is (0,0,0). Using the CMYK output profile for monochrome conversion that improves discrimination, the color value of this CMYK color space is (255,255,255,0) when the color value of this XYZ color space is converted to the CMYK color space. The simply converted gray value becomes 0. In this way, the gray value becomes 0, which is the value of Y in the XYZ color space, while the color value in the CMYK color space is converted into the hue of black (255,255,255,0).

In the color value list 1606 of the present embodiment, the gray value that is simply converted from the color value of the CMYK color space held in column 1610 and the gray value that has been processed to improve the discrimination held in column 16011 are the same. It becomes a value. Specifically, in the color value list 1606, a combination of gray values less than 16 in which the difference between the simply converted gray values in column 1610 is a predetermined value is a combination of gray values of object 1508 and object 1509. .. As shown in column 1609, the signal values of the object 1508 and the object 1509 in the CMYK color space are the same. Therefore, since the diff is 0, the colors indicated by the color values before conversion between the object 1508 and the object 1509 are determined to be similar colors, and the gray values are not modified to improve the discrimination. Therefore, the output color values of the objects 1507 to 1510 are the same as the simply converted gray values. Comparing the color value list 1606 of the present embodiment of FIG. 16 (b) with the gray value list 1612 of FIG. 16 (c), the gray values of column 1611 and the gray values of column 1613, which are output values, are the same values. become.

As described above, according to the present embodiment, the normal monochrome conversion is selected even when the monochrome conversion for improving the discrimination is selected but the gray value for improving the discrimination is not corrected. It is possible to output the same value as the gray value that is converted when it is done.

<Other Embodiments>
If the monochrome conversion profile of the third embodiment is used for conversion to a common color space, the gray value can be output so that the color value of the drawing command becomes the same as the simply converted gray value. Therefore, by converting to the common color space by the method of the third embodiment, the same effect as the conversion method to the common color space described in the second embodiment can be obtained. That is, also by the method of the third embodiment, the print data is generated in the PDL type in which only a single color space can be used, and the print data is generated in the PDL type in which a plurality of color spaces can be used. In some cases, it is possible to prevent a difference in gray values.

The present invention supplies a program that realizes one or more functions of the above-described embodiment to a system or device via a network or storage medium, and one or more processors in the computer of the system or device reads and executes the program. It can also be realized by the processing to be performed. It can also be realized by a circuit (for example, ASIC) that realizes one or more functions.

100 Image forming device 103 Image processing unit 204 Command analysis unit

Claims (17)

An acquisition means for acquiring data described in PDL (Page Description Language) and expressed in a plurality of color spaces, and
A first conversion means for converting a color value designated for drawing a page in the data into a color value in a common color space, which is a predetermined color space,
A second conversion means that performs a process of converting a color value converted by the first conversion means into a gray value so as to improve discrimination.
An image processing device characterized by having. The common color space is
The image processing apparatus according to claim 1, wherein the color space is any one of RGB, CMYK, L * a * b *, and XYZ. The second conversion means is
The color value defined in the common color space converted by the first conversion means is converted into a gray value by the same conversion method.
When the gray values converted by the first conversion means are arranged in ascending or descending order, if the difference between the gray values of adjacent combinations is less than a predetermined value, the gray values are corrected so as to widen the difference. The image processing apparatus according to claim 1 or 2, wherein the image processing apparatus is converted into a gray value so as to improve discrimination. The second conversion means is
The color value defined in the common color space converted by the first conversion means is converted into a gray value by the same conversion method.
The second conversion means is
When the gray values converted by the first conversion means are arranged in ascending or descending order, if the difference between the gray values of adjacent combinations is less than a predetermined value, the difference becomes greater than or equal to the predetermined value. The image processing apparatus according to claim 1 or 2, wherein the gray value is corrected and converted into a gray value so as to improve discrimination. Further, it has a determination means for determining whether or not the relationship is similar colors based on the color values defined in the common color space before being converted into gray values.
The second conversion means is
In the gray value of the combination, when the color values defined in the common color space before being converted into the gray value have a similar color relationship, the difference between the gray values of the combination is less than the predetermined value. However, the image processing apparatus according to claim 3 or 4, wherein the gray value is not modified so as to widen the difference between the gray values of the combination. The determination means
With respect to the respective signal values constituting the color values defined in the common color space before being converted into gray values, the respective signal values in one gray value of the combination and the other gray value of the combination. 5. The fifth aspect of claim 5, wherein if the value based on the difference between the respective signal values and the corresponding signal values in the above is equal to or less than the threshold value, it is determined that the gray values of the combination have a similar color relationship. Image processing equipment. The common color space is a CMYK color space.
The determination means
Derived each value based on the value obtained by adding the signal value of K to each of the signal values of C, M, and Y in the CMYK color space before the gray value is converted to the gray value, and among the above combinations. If the value based on the difference between the respective values in one gray value and the respective values in the other gray value of the combination is equal to or less than the threshold value, the gray value of the combination is The image processing apparatus according to claim 5, wherein it is determined that the relationship is similar in color. Further, it has a discriminating means for discriminating whether the PDL type of the data is a type in which a plurality of color spaces can be used.
The image processing apparatus according to any one of claims 1 to 7, wherein when the PDL type is not a type in which a plurality of color spaces can be used, the first conversion means does not perform processing. If not set to improve discrimination
The first conversion means does not perform any processing.
The image processing according to any one of claims 1 to 8, wherein the second conversion means simply converts a color value designated for drawing a page in the data into a gray value. apparatus. The common color space is a CMYK color space.
The first conversion means is
Any of claims 1 to 9, wherein the color value specified for drawing the page is converted into a color value in the CMYK color space by a conversion method different from the conversion method performed for color output. The image processing apparatus according to item 1. The common color space is a CMYK color space.
The first conversion means is
If the color values specified to draw the page are specified in the RGB color space
The signal value of R is inverted to derive the signal value of C, the signal value of G is inverted to derive the signal value of M, and the signal value of B is inverted to derive each signal value of Y to derive the signal values of Y in the RGB color space. The image processing apparatus according to any one of claims 1 to 10, wherein the color value is converted into a color value in the CMYK color space. The first conversion means is
The gray value when the color value of the common color space converted from the color value specified for drawing the page is simply converted to the gray value, and the color specified for drawing the page. It is characterized by converting the color value specified for drawing the page so that the gray value when the value is simply converted to the gray value is the same gray value as the color value in the common color space. The image processing apparatus according to any one of claims 1 to 10. The image processing apparatus according to any one of claims 1 to 12, wherein the color value designated for drawing a page in the data includes a color value of the color. If color output is set,
The image processing apparatus according to any one of claims 1 to 13, wherein the first conversion means and the second conversion means do not perform processing. The item according to any one of claims 1 to 14, further comprising an execution means for executing a drawing command of the data to generate a raster image based on the gray value converted by the second conversion means. The image processing apparatus described. An acquisition step for acquiring data described in PDL (Page Description Language) and expressed in a plurality of color spaces, and
The first conversion step of converting the color value specified for drawing the page in the data into the color value of the common color space which is one predetermined color space, and the first conversion step.
A second conversion step in which the color value converted in the first conversion step is converted into a gray value so as to improve discrimination, and the second conversion step.
An image processing method characterized by having. A program for causing a computer to function as each means of the image processing apparatus according to any one of claims 1 to 15.

Images