JP2012085105A - Printer, image forming device, and color processing method and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the discrimination property and the identification property of objects within a designated color reproduction range of two-color printing in a finish after the two-color printing, even if the objects pained in different colors on a document at the time of the two-color printing are converted into the same hue.SOLUTION: A printer converting an input color image into two colors and outputting it comprises: two-color converting means for converting the color image into two colors; object extracting means for extracting a first object and a second object which are superimposed or adjacent to each other among objects constituting the color image; color difference determining means for determining whether a color difference between the first object and the second object which are converted into either one of the two colors is less than or equal to a predetermined threshold value or not; and processing means for increasing at least either one of lightness difference or chroma difference in the first object and the second object which are determined to be less than or equal to the threshold value.

Description

  The present invention relates to the fields of a printing apparatus, an image forming apparatus, a color processing method, and a program.

  There is known an image forming apparatus (hereinafter also referred to as MFP: Multi-Function Peripheral) in which functions of respective apparatuses such as a fax machine, a printer, a copy machine, and a scanner are housed in one casing. This MFP is provided with a display unit, a printing unit, an imaging unit, and the like in one casing, and four types of applications corresponding to a fax, a printer, a copy, and a scanner, respectively. And operate as a copy and scanner.

  For users who use MFP, there is a desire to reduce the cost required for printing as much as possible, so for users who want to print output that is cheaper than full-color printing and expressive than monochrome printing, MFP Has a print service function called two-color printing. The two-color print uses only two colors, such as red and black. For example, as a method for realizing the two-color print, a chromatic color can be designated from among various chromatic colors. Technology that converts achromatic colors to black (for example, red), converts chromatic colors close to the hue of the specified color to specified colors, and converts chromatic and achromatic colors of other hues to black Etc. are known.

  Now, since the two-color print can use only two hues for drawing, an object that has been painted with different hues in the original document is subjected to the conversion process for the two-color conversion as described above. As a result, it may be converted to the same hue. As described above, when objects in different hues that are overlapped or overlapped or are converted to the same hue in the original and the converted saturation and lightness are almost similar, There has been a problem that it is visually difficult for a user to discriminate between objects that can be discriminated.

  Specifically, for example, a character (color) and a background (color) that have been separately painted with different hue colors on the document are converted to the same hue color after two-color printing, and the lightness and saturation are almost similar. If this is the case, the character is buried in the background due to the finish of the two-color print, and it is difficult to visually distinguish the character. The two-color print is mainly used to improve the discriminability due to the color enhancement effect. In this case, the character is printed on the chromatic background. Rather it becomes difficult.

  Further, for example, the same can be said when two-color printing is performed on a graph or a figure that has been painted with different hues on the document. When adjacent areas (for example, areas adjacent to a bar graph or a pie chart) that are separately painted with different hues on the document are converted to the same hue color after two-color printing, and their brightness and saturation are almost similar Therefore, it is difficult to visually discriminate between one area and an adjacent area on the finished two-color print.

  FIG. 1 shows a finished example of a conventional two-color print. (A) shows characters (colors) and backgrounds (colors) that have been painted with different hue colors on the document. If these objects are converted to the same hue color after two-color printing, and the lightness and saturation are almost similar, the two-color print finishes visually as shown in (b). Background discrimination becomes difficult.

  As a technique related to this, Patent Document 1 discloses a case where a character having two or more different color characters is printed in the same color when two-color printing is performed, and the effect of color-coding the characters is reduced. On the other hand, in order to retain the color-coding effect of the characters even after two-color printing, the characters that have been color-coded can be changed by changing them to gradation characters, shaded characters, or shaded characters according to the character color of the original document. An image processing apparatus that makes distinction clear is disclosed.

  However, since Patent Document 1 does not perform processing or color conversion in consideration of the positional relationship between objects, there is a problem in that characters existing on the background, nearby graphs, figures, and the like cannot be clearly identified. It was. In addition, since the characters are processed into gradation characters, shaded characters, shaded characters, etc., there is no denial or leap in the identity of the original characters on the original and the finish after two-color printing.

  The present invention has been proposed in view of the above-described problems, and the object of the present invention is when objects that have been separately painted in different colors on a document at the time of two-color printing are converted to the same hue. Even in such a case, an object of the present invention is to provide a printing apparatus or the like that improves the discrimination and discrimination between these objects within the designated color reproduction range of the two-color print in the finish after the two-color print.

  In order to solve the above problems, a printing apparatus according to the present invention is a printing apparatus that converts an input color image into two colors and outputs the two color conversion means for converting the color image into two colors; Object extraction means for extracting first and second objects that overlap or are adjacent to each other among the objects constituting the color image, and the first object converted to one of the two colors Color difference determination means for determining whether or not the color difference between the first object and the second object is equal to or less than a predetermined threshold value, and at least a lightness difference and a chroma with respect to the first object and the second object determined to be equal to or less than the threshold value. And processing means for increasing any of the degree differences.

  As described above, the printing apparatus according to the present invention is an object whose color difference is substantially reduced when two-color printing is performed, and after extracting (detecting) two overlapping or adjacent objects, the color of the designated two-color print When objects that have been painted in different colors on the original are converted to the same hue when printing in two colors to change to colors that can be distinguished within the reproduction range (increased brightness difference and saturation difference) Even so, in the finish after two-color printing, it is possible to improve the discrimination and discrimination between these objects within the specified color reproduction range of the two-color printing.

  In addition, what applied the arbitrary combination of the component of this invention, expression, or a component to a method, an apparatus, a system, a computer program, a recording medium, etc. is also effective as an aspect of this invention.

  According to the present invention, even when objects that have been painted in different colors on a document at the time of two-color printing are converted to the same hue, the designated color of the two-color print in the finish after the two-color printing It is possible to improve the discrimination and discrimination between these objects within the reproduction range.

An example of the finish of a conventional two-color print is shown. 2 is a diagram illustrating an example of a hardware configuration of an MFP 1 according to the embodiment of the present invention. FIG. 3 is a functional block diagram showing main functional configurations of an MFP 1 and a user terminal 2 according to the present embodiment. FIG. FIG. 6 is a diagram illustrating image signal conversion processing by a two-color conversion unit. It is a flowchart (the 1) explaining the color difference determination and adjustment process which concern on a present Example. An example (part 1) of the result of the color difference determination and adjustment processing according to the present embodiment is shown. An example (part 2) of the result of color difference determination and adjustment processing according to the present embodiment is shown. It is a flowchart (the 2) explaining the color difference determination and adjustment process which concern on an Example. An example (part 3) of the result of the color difference determination and adjustment processing according to the second embodiment is shown. 10 is a flowchart illustrating color change processing according to the second exemplary embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings in each embodiment. In the present embodiment, the present invention is applied to an MFP such as a multifunction peripheral. However, the present invention can be applied to any printing apparatus that has a two-color printing function, even if it is not a multifunction peripheral.

[System configuration]
(hardware)
First, a hardware configuration of the MFP 1 according to the present embodiment will be briefly described. FIG. 2 is a diagram illustrating an example of a hardware configuration of the MFP 1 according to the embodiment of the present invention. The MFP 1 according to the present embodiment includes an operation panel 11, a storage medium I / F 12, a controller 13, a data communication I / F 14, a scanner 15, a plotter 16, and an HDD (Hard Disk Drive) 17. Are connected to each other.

  The operation panel 11 includes an input device 11a and a display device 11b. The input device 11a includes hard keys and the like, and is used to input each operation signal to the MFP 1. The display device 11b is configured by an LCD (Liquid Crystal Display) or the like, and displays, for example, various types of information regarding image forming operations. The data communication I / F 14 includes an interface device 14a, and is an interface that connects the MFP 1 to a data transmission path such as a network or a fax machine. The HDD 17 stores various data such as received document data and read image data handled by the MFP 1. Further, the HDD 17 manages these various data by a predetermined file system or DB (Data Base).

  Various data stored in the HDD 17 includes data input from the recording medium 12b. The recording medium 12b is set in the drive device 12a included in the storage medium I / F 12, and various data are stored in the HDD 17 from the recording medium 12b via the drive device 12a.

  The controller 13 includes a ROM (Read Only Memory) 13a, a RAM (Random Access Memory) 13b, and a CPU (Central Processing Unit) 13c. The ROM 13a is a program executed when the MFP 1 is activated. Stores various data. The RAM 13b temporarily stores various programs and data read from the ROM 13a and the HDD 17. Further, the CPU 13c executes a program temporarily stored in the RAM 13b. For example, when the print data is received via the data communication I / F 14, the controller 13 reads a program (PDL parser) that can read PDL (Page Description Language) read from the ROM 13a onto the RAM 13b by the CPU 13c. Execute and interpret the print data to generate a bitmap image.

  The data communication I / F 14 includes a communication interface device 14a, and is a communication device connected to an external network including wired and wireless. In the present embodiment, for example, a color document (print data) can be received from a user terminal (not shown) on the network.

  The scanner 15 includes an image reading device 15a, and optically reads a document placed on a reading surface and generates image data. In the present embodiment, a color original on a paper medium can be read via the scanner 15. The plotter 16 has a printing device 16a and prints a bitmap image on a recording sheet by, for example, an electrophotographic process method.

  As described above, the MFP 1 according to the present embodiment realizes a plurality of functions such as a copy, a printer, a facsimile, and a scanner by the above hardware configuration.

(function)
FIG. 3 is a functional block diagram showing main functional configurations of the MFP 1 and the user terminal 2 according to the present embodiment. The MFP 1 includes a storage unit 101, a color conversion unit 102, an object extraction unit 103, an object color difference determination unit 104, a processing unit 105, a preview unit 106, and an image output unit 107. More specific description will be given later and will be described briefly here.

  The storage unit 100 stores a two-color print conversion LUT (look up table) and a Lab conversion LUT in advance. The two-color print conversion LUT is a look-up table (hereinafter referred to as LUT) that defines conversion from input full-color RGB values to CMYK values of a printing apparatus (for example, the MFP 1). The Lab conversion LUT is a printing apparatus. This LUT defines the conversion from CMYK values to Lab values. A conversion value (output value) corresponding to the input value is defined in advance by the developer of the MFP 1 and stored in advance as the LUT in the storage unit 100.

  The two-color conversion unit 102 converts a full-color input color (Ci) into a CMYK value corresponding to the designated two-color print by using a LUT that converts two-color prints from full-color RGB data into usable two colors. I do. Further, the two-color conversion unit 102 converts the obtained CMYK value of the MFP 1 into a Lab value using the Lab conversion LUT.

  The object extraction unit 103 extracts two objects that overlap or are adjacent to each other among the objects constituting the color image in the full-color document. In addition, the object attributes of characters, graphics, and images are determined for these objects.

  The object color difference determination unit 104 is converted into one of the two specified colors by the two-color conversion unit 102, and the color difference (calculated based on the Lab value) of the two objects extracted by the object extraction unit 103 is predetermined. It is determined whether it is below the threshold value. When the color difference between the two objects is small, these two objects overlap or are adjacent to each other, so that it is difficult to visually distinguish them.

  The processing unit 105 performs a process of increasing at least one of the lightness difference and the saturation difference with respect to the two objects determined to be equal to or less than the threshold value. For example, when the two objects overlap and the color difference is small, the processing unit 105 increases the color difference of the two objects having a small color difference by adjusting the lightness and saturation, thereby visually distinguishing the two objects. It will be improved (details will be described later).

  The preview unit 106 may transmit to the display device 11b (the user terminal 2) the finish of the two-color print that has been processed by the processing unit 105 and the finish of the two-color print that has not been performed. ). The user can compare the finish of the two-color print and select a desired two-color print.

  The image output unit 107 converts the input full-color document (image) into two colors and outputs (prints) it. That is, the two-color print selected by the user is output. The image output unit 107 can be realized by the plotter 16, for example.

  The user terminal 2 includes an application 201 and a printer driver 202. When the user issues a two-color print command to the MFP 1 for a full-color document created by the application 201, the printer driver 202 generates print data (including PJL and PDL) and transfers it to the MFP 1 as a print job. The transferred print data is output from the MFP 1 as a two-color print as described above.

  The functional configuration shown in the figure is the main functional configuration for explaining the present invention. Since the MFP 1 is an image forming apparatus, it naturally has an image forming function in addition to this. Needless to say. Each of these functions is actually realized by a computer (for example, MFP 1) by a program executed by the CPU 13c of the apparatus.

[Example 1]
An information processing operation of the MFP 1 according to the present embodiment will be described.

(Step 1)
FIG. 4 is a diagram illustrating the image signal conversion processing of the two-color conversion unit 102. As shown in the figure, the two-color conversion unit 102 uses the two-color print conversion LUT and the Lab conversion LUT to convert the sRGB in the document into CMYK after the two-color print conversion and the Lab after the two-color print conversion. The Lab value is obtained as the output color (Co). A LUT prepared in advance in the storage unit 100 is used as described above.

  First, the two-color conversion unit 102 designates the full-color input color (Ci) using the LUT for converting the print data transmitted from the user terminal 2 into two usable colors from the full-color RGB data. Conversion to CMYK values corresponding to color printing is performed. For example, when a two-color print is specified in which a color other than black is converted to red from a full-color original and output in black, and black is output in black, the input color (Ci) is black by the two-color print conversion LUT. In the case of colors other than those, conversion to CMYK values of the MFP 1 corresponding to all red hues is performed. As described above, the two-color conversion unit 102 performs processing of converting full-color RGB (sRGB) data into two-color CMYK data using an LUT. Similarly, the two-color converter 102 converts the obtained CMYK value of the MFP 1 into a Lab value by using the Lab conversion LUT.

(Step 2)
The object extraction unit 103 analyzes the print data, and first extracts objects constituting the color image. In general, objects can be classified into attributes of characters, graphics (graphics), and images (images and photographs). The attributes of the extracted objects are determined by determining the object attributes of characters, graphics, and images.

  Next, for the extracted objects, two overlapping objects and two adjacent objects are extracted based on the positions of the objects. Here, the two overlapping objects refer to two objects in which one object region has a relationship including at least part of the other object region. Two adjacent objects refer to two objects in which the outer edge of one object region and the other object region are in contact with each other (or the relationship in which the outer edge is very close). Therefore, as an example of two overlapping objects, a character is placed on the background (colored rectangle), and as an example of two adjacent objects, a fan-shaped area divided into several parts in a pie chart is given. It is done.

(Step 3)
The object color difference determination unit 104 determines whether the color difference (calculated based on the Lab value) of two overlapping objects and two adjacent objects is equal to or less than a predetermined threshold value. When the color difference between the two objects is small, these two objects overlap each other or are adjacent to each other, so that it is very difficult to visually distinguish them. Therefore, in this case, the processing unit 105 performs a process of increasing at least one of the brightness difference and the saturation difference for the two objects determined to be equal to or less than the threshold value. By adjusting the brightness and saturation, the color difference between the two objects having a small color difference is increased, and the discriminability between the two objects is visually improved.

  FIG. 5 is a flowchart (part 1) for explaining the color difference determination and adjustment processing according to the present embodiment. Here, as an example of two overlapping objects, a case where a character (character object) is placed on a background (background graphic object) will be specifically described. That is, for a character object whose color difference from the background graphic object is less than a certain value and difficult to discriminate, the color of the background graphic object and the character object is changed in the following flow.

  The object color difference determination unit 104 calculates the color difference between the background graphic object and the character object based on the Lab value, and determines whether or not the color difference between the background graphic object and the character object is equal to or less than a certain value (threshold) (S501). . That is, it is determined whether or not it is difficult to discriminate the background graphic object and the character object after two-color printing. Here, the color difference can be calculated based on the Lab value. For example, the difference between L is squared, the difference between a is squared, and the difference between b is squared. (√) can be calculated (it can also be said to be a distance between two colors in the Lab three-dimensional space). Further, as a constant value (threshold value) standard that makes it difficult to discriminate between the background and the character, for example, if the color difference in the Lab space is 6 or less (or around 6), the discrimination may be difficult.

  If it is determined that the color difference is equal to or less than a certain value (difficult to determine), the processing unit 105 first compares the brightness of the character and the background for the background graphic object and the character object that are difficult to determine (S502). If the lightness of the background is greater than the lightness of the character, the lightness of the background is increased (S503). On the contrary, if the brightness of the character is larger than the brightness of the background, the brightness of the character is increased (S504). This process increases the brightness difference between the character and the background. Note that the lightness of the object on the side with the smaller lightness may be further lowered.

  Similarly, regarding the saturation, the saturation of the object on the higher saturation side is increased. You may make it further reduce the saturation of the object of the side with small saturation. That is, the saturation of the character and the background is compared (S505), and if the saturation of the background is greater than the saturation of the character, the saturation of the background is increased (S505), and on the contrary, the saturation of the character is higher than the saturation of the background. If so, the saturation of the character is increased (S507). This process increases the saturation difference between the character and the background. Based on the Lab value, for example, the lightness is L, the saturation is a square of a, the square of b is added, and the sum can be calculated by the square root (√) (the distance from the origin in the ab two-dimensional space is also I can say).

  As described above, even when the character and background that were originally painted in different colors on the document are converted to the same hue, lightness, and saturation by the saturation and lightness adjustment processing, the lightness difference and saturation difference are converted. Since the color difference also increases by adding, it becomes possible to distinguish between the character and the background. In other words, character recognition on the background is facilitated.

  FIG. 6 shows a result example (part 1) of the color difference determination and adjustment processing according to the present embodiment. (A) shows an example in which it is difficult to discriminate between a character and a background that have been painted with different hues on a document due to the conventional two-color printing. Then, by adjusting the lightness and saturation of the background and characters according to the above-described embodiment, the color difference between the background and characters increases as shown in FIG. Can be distinguished.

  The finish of the two-color print that has been subjected to the above-described processing by the processing unit 105 and the finish of the two-color print when the above-described processing is not performed are displayed on the display device 11b (may be transmitted to the user terminal 2). It is good to make it. For example, since the images of FIGS. 6A and 6B are displayed on the display device 11b as a finished preview image of two-color print, the user confirms and compares the finish of the two-color print, and finally A desired two-color print can be selected. The image output unit 107 outputs (prints) the two-color print selected by the user.

  In addition, when displaying on the display device 11b, the difference from the Lab value to the RGB value by using the two-color print conversion LUT and the Lab conversion LUT, and the output (printing) difference is similarly determined from the Lab value. What is necessary is just to carry out reverse conversion to the CMYK value of MFP1.

  FIG. 7 shows a result example (part 2) of the color difference determination and adjustment processing according to the present embodiment. (A) shows a pie chart, and shows an example in which it is difficult to discriminate between the adjacent graphic object 1 and graphic object 2 by performing different colors on the document due to the conventional two-color printing. ing. By performing color difference determination and adjustment processing for the adjacent graphic object 1 and graphic object 2 in accordance with the procedure of the above-described flowchart, the discrimination between the graphic object 1 and the graphic object 2 can be improved.

  FIG. 8 is a flowchart (part 2) for explaining the color difference determination and adjustment processing according to the embodiment. This is obtained by replacing the background and characters in the flowchart described above with the graphic object 1 and the graphic object 2.

  The object color difference determination unit 104 calculates the color difference between the graphic object 1 and the graphic object 2 based on the Lab value, and determines whether or not the color difference between the graphic object 1 and the graphic object 2 is equal to or less than a certain value (threshold value) (S801). ). If it is determined that the color difference is equal to or less than a predetermined value (difficult to determine), the processing unit 105 first compares the brightness of the graphic object 1 and the graphic object 2 for the graphic object 1 and graphic object 2 that are difficult to determine (S802). . If the brightness of the graphic object 1 is greater than the brightness of the graphic object 2, the brightness of the graphic object 1 is increased (S803). On the contrary, if the brightness of the graphic object 2 is larger than the brightness of the graphic object 1, the brightness of the graphic object 2 is increased (S804). By this processing, the brightness difference between the graphic object 1 and the graphic object 2 is increased.

  Similarly, regarding the saturation, the saturations of the graphic object 1 and the graphic object 2 are compared (S805). If the saturation of the graphic object 1 is greater than the saturation of the graphic object 2, the saturation of the graphic object 1 is determined. On the contrary, if the saturation of the graphic object 2 is larger than the saturation of the graphic object 1, the saturation of the graphic object 2 is increased (S807). By this processing, the saturation difference between the graphic object 1 and the graphic object 2 is increased.

  As described above, even if the graphic object 1 and the graphic object 2 that are originally painted in different colors on the original by the saturation and lightness adjustment processing are converted to the same hue, lightness, and saturation color, the lightness difference is obtained. Since the color difference is increased by adding the saturation difference, the graphic object 1 and the graphic object 2 can be discriminated. That is, it becomes easy to recognize boundaries and areas between graphic objects.

  Refer to FIG. 7 again. By adjusting the brightness and saturation of the graphic object 1 and the graphic object 2 according to the above-described embodiment, the color difference between the graphic object 1 and the graphic object 2 increases as shown in FIG. Can be distinguished.

[Example 2]
FIG. 9 illustrates a result example (part 3) of the color difference determination and adjustment processing according to the second embodiment. (A) shows a pie chart, and shows an example in which it is difficult to discriminate between the adjacent graphic object 1 and graphic object 2 by performing different colors on the document due to the conventional two-color printing. ing. In (b), the color difference between the graphic object 1 and the graphic object 2 is increased as shown in (b) by adjusting the brightness and saturation of the graphic object 1 and the graphic object 2 according to Example 1 described above. As a result, it is possible to visually distinguish easily.

  However, in (b), the color difference is increased by adjusting the brightness and saturation of the graphic object 1 and the graphic object 2. As a result, the visual difference can be easily determined. This time, it is difficult to distinguish between the graphic object 2 and the adjacent graphic object 3. In other words, when three or more graphic objects such as a pie chart and a bar graph are adjacent to each other, the brightness and saturation of a certain graphic object can be adjusted before the adjustment. If the color difference from the third object is lowered, visual discrimination may be difficult.

  In such a case, in this embodiment, the graphic object 2 is changed to a color having a different hue that can be used within the range of two-color printing. For example, when the designated color is a two-color print of red and black, after adjusting the brightness and saturation within the range of the red hue assigned the color of the graphic object 2, the graphic object 2 after adjustment, The color difference with the adjacent graphic object 3 is compared, and if it is difficult to discriminate from the adjacent graphic object 3, the color is changed to black, which is another color that can be used for the graphic object 2.

  FIG. 10 is a flowchart illustrating the color change process according to the second embodiment. This flowchart is executed based on the above-mentioned meaning when the adjustment processing according to the flowchart of FIG. 8 is performed on two adjacent objects and there is an object further adjacent to the adjusted object. .

  First, the object color difference determination unit 104 determines whether or not the color difference between all objects adjacent to the object whose brightness and saturation are adjusted is equal to or smaller than a certain value (S1001). In the example of FIG. 9, the color difference between the adjusted graphic object 2 and the adjacent graphic object 3 is calculated, and it is determined whether or not the color difference is equal to or less than a certain value (for example, the color difference 6 or less).

  Next, for example, the processing unit 105 changes the object whose brightness and saturation have been adjusted to another color that can be used for two-color printing (S1002). In the example of FIG. 9, when the color difference is equal to or less than a certain value and it is difficult to discriminate between the adjusted graphic object 2 and the adjacent graphic object 3, the graphic object 2 is changed from red to black. Change the color.

  Refer to FIG. 9 again. By changing the color of the graphic object 2 from red to black, the color of the graphic object 2 is changed from red to black as shown in (c), and the graphic object 1 and the graphic object 2 or the graphic object 2 are changed. The graphic object 3 can be easily visually determined.

  As an exception, if the color difference between the background graphic object and the character adjacent to the background graphic object becomes small as a result of adjusting the brightness and saturation of the background graphic object that is the background color of the character, the color is not changed. Shall. This is because ensuring the distinguishability of the character is the top priority when printing with two colors, so that the distinguishability between adjacent graphic objects is secured within a range where the distinguishability of the character is not impaired.

[Summary]
As described above, the MFP 1 according to the present embodiment is an object whose color difference is substantially reduced when two-color printing is performed, and after extracting (detecting) two overlapping or adjacent objects, it is within the color reproduction range of the designated two-color printing. Even if objects that were painted in different colors on the document during two-color printing are converted to the same hue to change to colors that can be discriminated with (Adjust brightness difference and saturation difference) In the finish after two-color printing, it is possible to improve the discrimination and discrimination between these objects within the specified color reproduction range of the two-color printing.

  The present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the gist of the present invention described in the claims. For example, in the present embodiment, the present invention is applied to an image forming apparatus as an example of an information processing apparatus, and can be widely applied to other systems and apparatuses.

1 MFP
2 User terminal 11 Operation unit (operation panel)
11a Input device 11b Display device 12 Storage media I / F
12a Drive device 12b Recording medium 13 Controller (part)
13a ROM
13b RAM
13c CPU
14 Data communication I / F
14a Interface device 15 Scanner 15a Image reading device 16 Plotter 16a Printing device 17 HDD
DESCRIPTION OF SYMBOLS 101 Memory | storage part 102 2 color conversion part 103 Object extraction part 104 Object color difference determination part 105 Processing part 106 Preview part 107 Image output part 201 Application 202 Printer driver

JP 2007-68127 A

Claims (7)

A printing apparatus that converts an input color image into two colors and outputs the color image,
Two-color conversion means for converting the color image into two colors;
An object extracting means for extracting a first object and a second object that overlap or are adjacent to each other among the objects constituting the color image;
Color difference determination means for determining whether a color difference between the first object and the second object converted into one of the two colors is equal to or less than a predetermined threshold;
Processing means for increasing at least one of a lightness difference and a saturation difference with respect to the first object and the second object determined to be equal to or less than the threshold;
A printing apparatus comprising: The color difference determination means is configured such that a color difference between the first object or the second object and the third object that is further adjacent to the first object or the second object that is increased by either the lightness difference or the saturation difference by the processing means is equal to or less than a predetermined threshold value. Whether or not
The first object or the second object determined to be equal to or less than the threshold is changed to the other color different from the color converted by the two-color conversion unit among the two colors.
The printing apparatus according to claim 1. A first lookup table that defines conversion from RGB values of the input color image to CMYK values of the printing apparatus; and a second lookup table that defines conversion of CMYK values to Lab values of the printing apparatus; Storage means for storing in advance,
Conversion means for converting the RGB values into the CMYK values with reference to the first lookup table, and for converting the CMYK values into the Lab values with reference to the second lookup table;
With
The color difference, brightness difference and saturation difference are calculated based on the converted Lab values;
The printing apparatus according to claim 1 or 2. The converting means refers to the second look-up table and the first look-up table, and inversely converts Lab values based on the increased brightness difference and saturation difference to the CMYK values and RGB values,
4. The printing apparatus according to claim 3, further comprising preview means for generating a preview image based on the inversely converted RGB values and displaying the preview image on the display means.   An image forming apparatus comprising the printing apparatus according to claim 1. A color processing method in a printing apparatus that converts an input color image into two colors and outputs the color image,
A two-color conversion procedure for converting the color image into two colors;
An object extraction procedure for extracting a first object and a second object that overlap or are adjacent to each other among the objects constituting the color image;
A color difference determination procedure for determining whether a color difference between the first object and the second object converted into one of the two colors is equal to or less than a predetermined threshold;
A processing procedure for increasing at least one of a brightness difference and a saturation difference with respect to the first object and the second object determined to be equal to or less than the threshold;
A color processing method characterized by comprising:   A program for causing a computer to execute the color processing method according to claim 6.