JP2013042380A - Image processing apparatus, image processing program, and image processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image processing apparatus, an image processing program, and an image processing method which convert color image data to monochromatic image data from which the color of the original color image can be distinguished.SOLUTION: A printer driver 40 of an image processing apparatus 100 comprises: a pattern type determination part 41 which determines a hatch pattern expressing with monochromatic density a hatch pattern corresponding to the color of a color image; a pattern density determination part 42 which determines a background density to be applied to the background area of the hatch pattern; and a monochromatic image data generation part 43 which generates monochromatic image data in which a hatch pattern having the background density is applied to the background region. The pattern density determination part 42 changes the background density of the hatch pattern in accordance with the color of the color image.

Description

  The present invention relates to an image processing apparatus, an image processing program, and an image processing method for converting color image data into monochrome image data.

Conventionally, in order to convert color image data to monochrome image data, a method of obtaining a monochrome image data represented by a gray value by calculating a gray value from the RGB value of the color image data according to the following equation (1) has been widely used. ing. Since the gray value reflects the lightness information of the original color image, according to this method, it is possible to obtain image data of a monochrome image in which the lightness of the original color image is reflected. Note that “R”, “G”, and “B” in Equation (1) are the red gradation value, the green gradation value, and the blue gradation value of the color image data, respectively, and “Gray” is The gray value, that is, the density of a single black color.
Gray = 0.3R + 0.59G + 0.11B (1)

  In addition, when color image data is converted into monochrome image data by gray conversion according to Expression (1), for example, (R, G, B) = (255, 0, 0), (0, 128, 0), etc. RGB values are converted into equivalent gray values. In this way, two different colors in the color image before conversion are represented by the same gray value in the monochrome image, and the color of the original color image before conversion is distinguished from the converted monochrome image. I couldn't do it.

  Therefore, in Patent Document 1, a color image is converted into each color image of cyan, magenta, and yellow, and a dot pattern of each color is generated by applying a dither matrix that generates a different pattern for each color image. A technique for obtaining monochrome image data by combining dot patterns has been proposed. According to the method described in Patent Document 1, a monochrome image in which different patterns for each color of cyan, magenta, and yellow are superimposed is obtained. For example, (R, G, B) = (255, 0, 0) , (0, 128, 0), etc., even if the color has the same value when converted to a gray value, the color difference in the original color image is reflected in the monochrome image as a different pattern pattern Is done. Therefore, even if a color that cannot be distinguished when gray conversion is used for the color image before conversion, it can be converted into image data of a monochrome image that can distinguish the color difference in the original color image.

JP 2011-23895 A

  However, according to the method described in Patent Document 1, the image of the monochrome image data is obtained by superimposing the dot patterns of each color of cyan, magenta, and yellow. Many kinds of patterns appear in monochrome images. For this reason, in the monochrome image produced | generated by the method of patent document 1, it was difficult for a user to distinguish the pattern of a pattern and the subject that the difference in the color in an original color image was difficult to understand occurred.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

  Application Example 1 An image processing apparatus for converting color image data representing a color image into monochrome image data, a pattern determining unit for determining a single color pattern representing a pattern corresponding to the color of the color image by a single color density; A pattern density determining unit that determines a background density of an area that is a background of the pattern in the image area of the single color pattern, and the monochrome pattern having the background density is applied to an image area corresponding to the color image. A monochrome image data generation unit configured to generate the monochrome image data of the monochrome image, wherein the pattern density determination unit changes the background density according to the color of the color image.

  According to this configuration, the color of the color image is reflected in the monochrome image as a change in the background density in the region that becomes the background of the pattern in addition to the pattern of the single color pattern. Therefore, when the user visually recognizes, it is possible to obtain image data of a monochrome image that can easily distinguish the color difference in the original color image from the pattern of the single color pattern and the density change of the background.

  Application Example 2 In the image processing apparatus, the pattern density determination unit changes the background density according to the brightness of the color image.

  According to this configuration, the background density of the monochrome image data changes according to the brightness of the color image. Therefore, when the user visually recognizes, the monochrome image can be distinguished between colors having different brightness in the original color image. Image data can be obtained.

  Application Example 3 In the image processing apparatus, the pattern density determination unit determines the background density so that the brightness of the monochrome image is equal to the brightness of the color image.

  According to this configuration, since the brightness of the color image is stored in the monochrome image, monochrome image data with excellent brightness reproducibility can be obtained.

  Application Example 4 In the image processing apparatus, the pattern density determination unit is configured to make the monochrome pattern so that an average brightness of an image area to which the monochrome pattern is applied is equal to an average brightness of the monochrome pattern. And determining the background density of the image processing apparatus.

  According to this configuration, since the brightness of a color image is stored in a monochrome image for each image area to which a single color pattern is applied, it is possible to obtain monochrome image data that is superior in brightness reproducibility.

  Application Example 5 In the above image processing apparatus, the pattern determination unit determines the single color pattern representing a pattern corresponding to a hue of a color image of the color image data by a single color density. .

  According to this configuration, the hue of the color image can be reflected in the monochrome image data.

  Application Example 6 In the image processing apparatus, the single-color pattern is a hatch pattern that represents a pattern with a single-color line, and the pattern determination unit has a pattern with a higher line density as the color brightness of the color image is lower. An image processing apparatus, wherein the hatch pattern is determined as a pattern to be applied to the color image.

  According to this configuration, since the line density of hatching increases as the lightness of the color image decreases, image data of a monochrome image that can give an impression closer to the color image to a user who has viewed the monochrome image is obtained. be able to.

Application Example 7 In the image processing apparatus,
The pattern density determination unit is configured to set the density of the pattern of the monochrome pattern corresponding to the first color among the first color and the second color adjacent to each other in a plurality of color regions that define a hue circle. An image processing apparatus, characterized in that the density of the pattern of the monochromatic pattern corresponding to the second color is made smaller than the background density.

  According to this configuration, one of the first color and the second color of the color images adjacent to each other in the plurality of color regions that define the hue circle has a density larger than the background density and the other is smaller than the background density. A monochrome image pattern is displayed. Accordingly, the difference in color between the first color and the second color that are included in adjacent color regions among a plurality of color regions that define the hue circle of the original color image and are difficult to distinguish in the color image. It is possible to obtain image data of a monochrome image that can be more easily distinguished.

  Application Example 8 In the image processing apparatus, the single color pattern that the pattern determination unit corresponds to the fourth color that is complementary to the third color is the single color pattern that corresponds to the third color. An image processing apparatus that represents a pattern obtained by rotating the pattern.

  According to this configuration, the pattern of the single color pattern corresponding to the fourth color that is complementary to the third color is obtained by rotating the pattern of the single color pattern corresponding to the third color. Thereby, it can be recognized from the monochrome image that the third color and the fourth color are complementary colors in the original color image.

  Application Example 9 In the image processing apparatus, the pattern determination unit changes the pattern of the single-color pattern according to the saturation of the color image.

  According to this configuration, since the pattern of the single color pattern appearing in the monochrome image changes according to the saturation of the color image, it is possible to obtain monochrome image image data that can distinguish the saturation difference in the original color image. it can.

  Application Example 10 The image processing apparatus includes an image type determination unit that determines the type of the color image, and the monochrome image data generation unit corresponds to a determination result of the image type determination unit, and has a monochrome density. An image processing apparatus that converts the image into a monochrome image represented by:

  According to this configuration, even when object images of the same color overlap each other, object images having different types of object image attributes can be easily distinguished from each other without being buried in each other. Monochrome image data can be obtained.

  Application Example 11 In the image processing apparatus, the monochrome image data generation unit includes a prohibited image determination unit that determines whether or not the color image includes a prohibited image predetermined so as not to apply the monochrome pattern. The image processing apparatus converts the prohibited image included in the color image into a monochrome image represented by a monochrome density without applying the monochrome pattern.

  According to this configuration, for a predetermined image, monochrome image image data to which a monochrome pattern is not added is generated. Therefore, for images that need to be faithfully expressed, for example, company logos, and for which inconvenience occurs when a pattern is added, monochrome image data that faithfully represents the original color image can be obtained without adding the pattern. Can do.

  Application Example 12 The image processing apparatus includes correspondence information in which the color of the color image is associated with the background density in advance, and the pattern density determination unit refers to the correspondence information to determine the color image. An image processing apparatus that determines the background density according to color.

  According to this configuration, since the background density of the single-color pattern is determined according to the correspondence information, monochrome image data expressing the color difference in the original color image can be obtained from the color image data by simple processing.

  Application Example 13 In the image processing apparatus, the pattern determining unit includes the single color pattern representing a vertical line pattern, the single color pattern representing a horizontal line pattern, the single color pattern representing a grid line pattern, and a diagonal line pattern. The monochromatic pattern corresponding to the color image according to the color of the color image from among the plurality of monochromatic patterns including any two or more of the monochromatic pattern representing the pattern of the diagonal grid lines An image processing apparatus characterized by selecting.

  According to this configuration, it is possible to obtain monochrome image data in which the color of a color image is expressed by any two or more of vertical lines, horizontal lines, grid lines, diagonal lines, and diagonal grid lines.

  Application Example 14 An image processing program for converting color image data representing a color image into monochrome image data, wherein the computer determines a single-color pattern representing a pattern corresponding to the color of the color image by a single-color density A pattern determining unit that determines a background density of an area that is the background of the pattern among the image areas of the monochrome pattern, and the monochrome that has the background density in the image area corresponding to the color image. A monochrome image data generation unit that generates the monochrome image data of a monochrome image to which a pattern is applied, and the pattern density determination unit changes the background density according to the color of the color image. An image processing program.

  According to this image processing program, it is possible to obtain from the color image data monochrome image data that makes it easy to distinguish the color difference in the original color image when the user visually recognizes it.

  Application Example 15 An image processing method for converting color image data representing a color image into monochrome image data, the step of determining a monochromatic pattern representing a pattern corresponding to the color of the color image by a monochromatic density; Determining a background density of an area that is a background of the pattern among image areas of a single color pattern; and the monochrome of a monochrome image in which the monochrome pattern having the background density is applied to an image area corresponding to the color image. Generating the image data, and changing the background density in accordance with the color of the color image.

  In this way, the color of the color image is reflected in the monochrome image as a change in background density in addition to the pattern of the single color pattern, so that the color difference in the original color image is distinguished when the user visually recognizes it. It is possible to obtain image data of a monochrome image that is easy to perform.

1 is a diagram illustrating a schematic configuration of a printing system according to a first embodiment. FIG. 2 is a diagram illustrating a software configuration of an image processing apparatus. It is the figure which showed an example of the pattern selection table. It is explanatory drawing explaining allocation of a hatch pattern. It is the figure which showed the example of a response | compatibility with the hue on a hue ring, and a hatch pattern. It is the flowchart which showed the flow of the process which an image processing apparatus performs. It is explanatory drawing explaining allocation of the hatch pattern with respect to an attention pixel. It is the figure which showed the structure of the image processing apparatus in 2nd Embodiment. It is the figure which showed the structure of the image processing apparatus in 3rd Embodiment. It is explanatory drawing of the modification 1. It is explanatory drawing of the modification 4.

(First embodiment)
Embodiments of the present invention will be described below with reference to the drawings. In the first embodiment, a printing system including a host computer as an example of an image processing apparatus will be described.

  FIG. 1 is a diagram illustrating a schematic configuration of a printing system according to the first embodiment. As shown in FIG. 1, the printing system 1 includes a host computer 10 and a printer 20, and the host computer 10 and the printer 20 are connected to each other so that data communication is possible.

  The printer 20 includes a print engine 21 that prints on a medium such as paper, and a controller 22 that controls the operation of the print engine 21. The printer 20 performs processing for receiving a print job from the host computer 10 and processing for causing the print engine 21 to execute printing according to the print job under the control of the controller 22.

  The host computer 10 is a general-purpose personal computer in which a printer driver is installed, for example, and is a host device of the printer 20 that transmits a print job to the printer 20. The host computer 10 includes a CPU 11, a ROM 12, a RAM 13, a hard disk drive 14, a reading device 15, and a communication I / F 16. These components of the host computer 10 are connected to the bus 17 so that data communication is possible via the bus 17.

  The CPU 11 is a control device that controls each component of the host computer 10. The ROM 12 is a non-volatile memory in which a predetermined program for controlling the host computer 10 is recorded, and the RAM 13 is a general-purpose memory used as a working memory.

  The hard disk drive 14 stores in advance a driver program DP for the printer 20, a pattern selection table (corresponding information) PT described later, and a pattern image database PDB. The driver program DP is supplied to the host computer 10 by the recording medium M on which the driver program DP is recorded, and the hard disk drive 14 stores a program read by the reading device 15 from the recording medium M. Examples of the recording medium M include a flexible disk, a magneto-optical disk, a USB memory, a memory card, and the like in addition to an optical disk such as a CD-ROM and a DVD-ROM. A pattern selection table PT and a pattern image database PDB are further recorded on the recording medium M, and the pattern selection table PT and the pattern image database PDB are stored in the hard disk drive 14 together with the driver program DP. However, the form in which the driver program DP, the pattern selection table PT, and the pattern image database PDB are supplied to the host computer 10 is not limited to this. For example, the driver program DP, the pattern selection table PT, and the pattern image database PDB are supplied from a predetermined server via an electric communication line or an optical communication line. You may be made to do.

  The communication I / F 16 is an interface portion that is connected to the printer 20 by a cable or wireless communication. Communication between the printer 20 and the host computer 10 is performed via the communication I / F 16.

  Further, the CPU 11 of the host computer 10 reads and executes the driver program DP stored in the hard disk drive 14 so that the printer driver is installed, and the host computer 10 functions as the image processing apparatus 100. Hereinafter, the image processing apparatus 100 will be described.

  FIG. 2 is a diagram illustrating a software configuration of the image processing apparatus 100. As illustrated in FIG. 2, the image processing apparatus 100 includes an application 30 and a printer driver 40.

  The application 30 is software serving as a print request source for the printer 20, such as document creation software or a web browser. The application 30 generates a print request and color image data to be printed and passes it to the printer driver 40.

  The printer driver 40 is software for controlling printing by the printer 20. The printer driver 40 generates print data in a data format that can be processed by the printer 20 from the print request and color image data received from the application 30, and the communication I / F 16. The print data is transmitted to the printer 20 via. As a result, the printer driver 40 causes the printer 20 to execute printing.

  Further, the printer driver 40 according to the present embodiment converts a color image data into monochrome image data with a hatch pattern, so that a monochrome image that can distinguish a color difference in the original color image by a hatch pattern is printed on the printer. 20 has a function of printing. In order to realize the monochrome printing function with the hatch pattern, the printer driver 40 includes a pattern type determination unit (pattern determination unit) 41, a pattern density determination unit 42, and a monochrome image data generation unit 43. . Note that these configurations of the printer driver 40 function by the CPU 11 executing the driver program DP.

  The pattern type determination unit 41 performs a process of determining a hatch pattern to be applied to the image area of the color image data according to the color of the color image data, particularly the hue. In the present embodiment, a plurality of types of hatch patterns (monochromatic patterns) in which hatch patterns such as vertical lines, horizontal lines, grid lines, diagonal lines, and diagonal grid lines are represented by a single color density are used. The pattern type determination unit 41 selects a hatch pattern of a hatch pattern to be applied to a color image from a plurality of types of hatch patterns.

  The pattern density determination unit 42 performs a process of determining the density of the hatch pattern according to the color of the color image of the color image data, particularly the brightness. Note that the hatch pattern of the present embodiment includes a background region that is a background of the hatch pattern and a foreground region of the hatch pattern itself that is a foreground with respect to the background. The pattern density determination unit 42 determines the monochrome density in the background area (hereinafter referred to as “background density”) and the monochrome density in the foreground area (hereinafter referred to as “foreground density”).

  The monochrome image data generation unit 43 has the hatch pattern determined by the pattern type determination unit 41 and applies the hatch pattern having the background density and the foreground density determined by the pattern density determination unit 42 to the image area of the color image. Perform the process. Accordingly, the monochrome image data generation unit 43 generates monochrome image data with a hatch pattern.

  Here, the processing by the pattern type determination unit 41 and the pattern density determination unit 42 described above is performed according to the contents of the pattern selection table PT and the pattern image database PDB. Next, the pattern selection table PT and the pattern image database PDB will be described in order to explain a method for converting color image data into monochrome image data with hatch patterns. In the following description, the color image data represents each color of R (red), G (green), and B (blue) with an 8-bit gradation value “0 to 255” for each pixel of the color image. It shall have RGB values. The monochrome image data has a K value representing the K (black) color with an 8-bit gradation value “0 to 255”, that is, a density of K single color, for each pixel of the monochrome image. Further, regarding the RGB values of the color image data, (R, G, B) = (255, 255, 255) corresponds to white, (R, G, B) = (0, 0, 0) corresponds to black, and K Regarding values, K = 255 corresponds to black, and K = 0 corresponds to white.

  FIG. 3 is a diagram showing an example of the pattern selection table PT. As shown in FIG. 3, in the pattern selection table PT, a pattern type, a background density, and a foreground density are associated in advance with RGB values that are color values.

  In the pattern type column of the pattern selection table PT, as described above, a hatch pattern corresponding to a color value is selected from a plurality of types of hatch patterns such as a vertical line, a horizontal line, a grid line, a diagonal line, and a diagonal grid line. A type is specified. In the background density column, a background density value corresponding to the color value is designated. In the foreground density column, a foreground density value corresponding to a color value is designated.

  The pattern selection table PT determines a hatch pattern, background density and foreground density corresponding to the RGB values of the color image. Specifically, when color image data is converted into monochrome image data, the pattern type determination unit 41 refers to the pattern selection table PT and sets the pattern type of the pattern selection table PT for the image area of the color image data. Select the hatch pattern specified in the field. The pattern density determination unit 42 refers to the pattern selection table PT, determines the background density of the hatch pattern to the density specified by the background density column of the pattern selection table PT, and sets the foreground density of the hatch pattern to the pattern The foreground density specified in the foreground density column of the selection table PT is determined.

  In the pattern image database PDB, image data of a corresponding hatch pattern is stored in advance for each pattern type such as a vertical line, a horizontal line, a grid line, a diagonal line, and a diagonal grid line. The hatch pattern is an image of a predetermined size such as 32 × 32 pixels, for example, and includes at least information indicating the background area and the foreground area in the image area of the hatch pattern. Therefore, as described later, when the hatch pattern is applied to the image area by referring to the pattern image database PDB, the pattern density determination unit 42 determines that the pixel of interest in the image area is the background area and the foreground. It is possible to determine which of the areas corresponds.

  Next, an outline of processing using the pattern selection table PT and the pattern image database PDB will be described. Here, a color image CP having a color value of (R, G, B) = (0, 0, 239) over the entire image will be described as an example.

  As shown in FIG. 4A, the hatch pattern is assigned to each unit area UA obtained by dividing the image area of the color image CP with the same size as the hatch pattern. The type of hatch pattern assigned to the unit area UA is determined according to the pattern selection table PT. According to the pattern selection table PT shown in FIG. 3, the pattern type corresponding to the RGB value of the color image, that is, the color value of (R, G, B) = (0, 0, 239) is “oblique grid line”. Therefore, the hatch pattern P of “oblique grid lines” is applied to the color image CP. Therefore, as shown in FIG. 4B, the hatched pattern of diagonal lattice lines registered in the pattern image database PDB is applied to the unit area UA in the monochrome image MP obtained by converting the color image CP.

  Further, according to the pattern selection table PT shown in FIG. 3, the background density corresponding to (R, G, B) = (0, 0, 239) is determined as K = 19, and the foreground density is determined as K = 51. Therefore, the density of the background area BA of the monochrome image MP is K = 19, and the density of the foreground area FA is K = 51.

  Thus, the hatch pattern P determined by the pattern selection table PT and the pattern image database PDB is applied to each unit area UA. In FIG. 4, the hatch pattern P is applied only to one unit area UA, but in reality, the hatch pattern P is applied to each unit area UA.

The pattern selection table PT used as described above is set in advance so as to satisfy the following requirements (1) to (5).
(1): Requirements for assigning hatch patterns according to hue (2): Requirements for changes in background density according to lightness (3): Requirements for line density of hatch patterns according to lightness (4): Complementary color relationship (5): Requirements for the allocation of hatch patterns between adjacent colors

(1): Requirement Regarding Assignment of Hatch Pattern According to Hue A predetermined hatch pattern hatch pattern is assigned to each color region obtained by dividing the hue circle of the color with respect to the hue. FIG. 5 shows an example of correspondence between hues and hatch patterns on the hue circle. In the example of FIG. 5, the hue on the hue circle is divided into color areas A1 to A12, and hatch patterns P1 to P12 are assigned corresponding to the color areas A1 to A12. Note that the color regions A1 and A12 correspond to red colors, the color region A1 corresponds to a hue angle of 0 ° to less than 30 °, and the color region A12 corresponds to a hue angle of 330 ° to less than 360 °. The color areas A2 and A3 correspond to yellow colors, the color area A2 corresponds to a hue angle of 30 ° to less than 60 °, and the color region A3 corresponds to a hue angle of 60 ° to less than 90 °. The color areas A4 and A5 correspond to green colors, the color area A4 corresponds to a hue angle of 90 ° to less than 120 °, and the color region A5 corresponds to a hue angle of 120 ° to less than 150 °. The color regions A6 and A7 correspond to cyan colors, the color region A6 corresponds to a hue angle of 150 ° to less than 180 °, and the color region A7 corresponds to a hue angle of 180 ° to less than 200 °. The color areas A8 and A9 correspond to blue colors, the color area A8 corresponds to a hue angle of 200 ° to less than 240 °, and the color region A9 corresponds to a hue angle of 240 ° to less than 280 °. The color areas A10 and A11 correspond to magenta colors, the color area A10 corresponds to a hue angle of 280 ° to less than 300 °, and the color region A11 corresponds to a hue angle of 300 ° to less than 330 °.

(2): Requirement Regarding Change of Background Density According to Lightness Regarding the correspondence between the color value and the background density, the background density is set to change according to the lightness of the color value. Thereby, for example, even if the hatch pattern P determined by other requirements is the same between two colors included in the color image, the color difference in the original color image is a monochrome image as a change in background density. It is reflected in. The requirement (2) can be set using a gray value reflecting lightness or lightness in the L * a * b * color system, and the background density changes as these values change. Color value and background density are set.

  Further, the average brightness of the RGB values of the color image in the unit area UA before the hatch pattern P is applied, and the average brightness of the background density and foreground density of the hatch pattern P in the unit area UA after the hatch pattern P is applied. It is set to be equal. That is, for the hatch pattern P of a predetermined size, the brightness when the RGB values of the color image are averaged over the pattern area is equal to the brightness when the K value of the monochrome image is averaged over the pattern area. In addition, the lightness being equal means that the lightness is substantially equal, and is not limited to the same lightness. Includes different cases. Thereby, when color image data is converted into monochrome image data, the brightness is stored for each unit area UA to which the hatch pattern P is applied. For example, when the brightness of the color image changes spatially, the brightness of the monochrome image also changes for each unit area UA following the change in brightness of the color image. The change is reflected in the monochrome image.

(3): Requirement for line density of hatch pattern according to lightness Regarding the lightness of the color on the hue ring and the line density of the hatch pattern of hatch pattern P, the line density is set so that the color with lower lightness has a higher line density. Yes. For example, as shown in the yellow color area A3 and the blue color area A9 in FIG. 5, the yellow color area A3 is assigned a “vertical line” hatch pattern, and the blue color area A9 is added to the vertical line. A “grid line” hatch pattern including horizontal lines is assigned. That is, a hatch pattern P having a higher linear density is assigned to blue, which is lighter than yellow. Thereby, the difference in brightness in the original color image is reflected in the monochrome image as a difference in the line density of the hatch pattern in the hatch pattern P.

(4): Requirements for assigning hatch patterns between colors that are complementary colors Relationships between two colors that are complementary colors are the same when the same hatch pattern is rotated, that is, hatch patterns P that differ only in the angle of the hatch pattern It is set to be. As shown in FIG. 5, for example, the hatch pattern P5 corresponding to a hue angle of 120 ° to 150 ° is a diagonal line drawn from the upper right to the lower left. On the other hand, the hatch pattern of the hatch pattern P11 corresponding to a hue angle of 300 ° to 330 ° which is complementary to this is a diagonal line drawn from the upper left to the lower right. In this way, between the colors complementary to each other, there is a relationship of the hatch pattern P obtained by rotating the hatch patterns with each other, so that the two colors that are complementary to each other in the original color image are complementary to each other. Will be reflected in the monochrome image. In the present embodiment, as shown in FIG. 5, the requirement 4 is not applied to all the color regions A1 to A12, and the color region A4 and the color region A10 that are complementary colors, and further the color region. Although it is applied only between A5 and the color area A11, it may be applied to all the color areas A.

(5): Requirements for assigning hatch patterns between colors that are adjacent color areas For two color areas A that are adjacent to each other, the hatch pattern P corresponding to one color area A has a lower foreground density than a background density. In the hatch pattern P corresponding to the other color area A, the foreground density is set to be larger than the background density. In FIG. 5, for example, a hatch pattern P1 corresponding to a color region A1 having a hue of 0 ° to 30 ° has a “grid line” pattern type, a foreground density is higher than a background density, and a line constituting a hatch pattern The density of is closer to black than the background. On the other hand, the hatch pattern P12 corresponding to the hue 330 ° to 360 ° of the color area A12 adjacent to the color area A1 corresponding to the same color (red) as the color area A1 has a “grid line” pattern type. The foreground density is smaller than the background density, and the density of the lines constituting the hatching is closer to white than the background. In this way, between the colors that are adjacent to the color area A, the foreground density is opposite to the background density, so that the difference between the two colors that are adjacent to the color area A is a monochrome image. Reflected.

  Next, processing performed by the image processing apparatus 100 described above will be described in detail according to the flowchart of FIG.

  For example, when the printer driver 40 receives a print instruction for monochrome printing of color image data from the application 30, the process of FIG. 6 is started. When the process is started, the pattern type determination unit 41 sets a target pixel for the image area of the color image data (Step S10), and acquires the RGB value of the target pixel from the color image data (Step S11). The pattern type determination unit 41 determines the pattern type corresponding to the acquired RGB value with reference to the pattern selection table PT (step S12).

Next, the pattern density determination unit 42 determines whether the coordinates of the target pixel correspond to the background area of the hatch pattern P (step S13). As described in FIG. 4, the hatch pattern P is assigned to the unit area UA having a predetermined size in the image area of the color image, and here, the target pixel is assigned to each unit area UA. It is determined whether the pattern P is at a position corresponding to the background or a position corresponding to the foreground. Specifically, as shown in FIG. 7, when the coordinates of the target pixel are (a, b) and the size of the hatch pattern P is N × N pixels, the relative coordinates (x, y) of the target pixel in the hatch pattern P ) Is obtained by the following equations (2) and (3). In the following formula, “mod” is an operator that returns the remainder after division. The pattern density determination unit 42 refers to the image data of the hatch pattern P registered in the pattern image database PDB to determine whether the relative coordinates (x, y) correspond to the background or the foreground in the hatch pattern P. .
x = a mod N (2)
y = b mod N (3)

  When the target pixel corresponds to the background (step S13: Yes), the pattern density determination unit 42 refers to the pattern selection table PT and acquires the K value of the background density corresponding to the RGB value of the target pixel (step S14). ). On the other hand, when the target pixel corresponds to the foreground region (step S13: No), the pattern density determination unit 42 refers to the pattern selection table PT and acquires the K value of the foreground density corresponding to the RGB value of the target pixel. (Step S15). In the example of FIG. 7, since the relative coordinates (x, y) corresponding to the target pixel (a, b) correspond to the background area BA of the hatch pattern P, the background density is acquired for the target pixel. It will be.

  When the K value of background density or foreground density is acquired in step S14 or step S15, the monochrome image data generation unit 43 applies the acquired K value of density to the pixel corresponding to the target pixel in the image area of the monochrome image. (Step S16). Thereby, the pixel corresponding to the target pixel in the monochrome image has the K value of the density corresponding to the type of hatch pattern P determined in step S12.

  Next, the monochrome image data generation unit 43 determines whether or not the processing of steps S10 to S16 has been performed for all pixels of the color image (step S17). If the processing has not been completed for all pixels (step S17: No), the process returns to step S10, for example, a new pixel of interest is set by scanning the pixel of interest in the raster direction, and the step is performed for the new pixel of interest. The process after S11 is performed. When the processing is completed for all the pixels (step S17: Yes), all the pixels of the monochrome image have a K value of density corresponding to the type of hatch pattern P determined in step S12, and monochrome image data generation is performed. The unit 43 generates monochrome image data of this monochrome image (step S18). The generated monochrome image data is output to the printer 20 by the printer driver 40 (step S19). Accordingly, a monochrome image with a hatch pattern corresponding to the color of the color image is printed as monochrome printing of the color image data delivered from the application 30.

  Hereinafter, effects of the first embodiment will be described.

  (1) According to the image processing apparatus 100 of the present embodiment, in accordance with the requirement (1) of the pattern selection table PT, monochrome image data in which hatching hatching corresponding to the hue of the color image is performed from the color image data. Generated. Therefore, it is possible to obtain monochrome image data from which the color of the original color image can be distinguished from the pattern of the hatch pattern P, and this monochrome image can be printed.

  (2) According to the requirement (2) of the pattern selection table PT, even if the pattern type of the hatch pattern P applied according to other requirements is the same, a color difference in the original color image is a monochrome image as a difference in background density. It is reflected in. Therefore, it is possible to obtain monochrome image data that can distinguish colors in the original color image from the background density of the hatch pattern.

  Further, the brightness of the color image is stored in a monochrome image for each unit area UA to which the hatch pattern P is applied. For example, when the brightness of a color image changes spatially, the brightness of a monochrome image also changes for each unit area UA following the change in brightness of the color image, so that the brightness reproducibility of the color image is excellent. A monochrome image can be obtained.

  (3) Due to the requirement (3) of the pattern selection table PT, the difference in lightness in the original color image is reflected in the monochrome image as the difference in the line density of the hatch pattern. A high hatch pattern is added. According to this monochrome image, an impression closer to a color image can be given to a user who has visually recognized the monochrome image.

  (4) Due to the requirement (4) of the pattern selection table PT, the hatch patterns are in a relationship of being rotated with respect to each other between the two colors which are in a complementary color relationship. As a result, the user who has visually recognized the monochrome image can recognize from the monochrome image that the two colors in the original color image have a complementary color relationship.

  (5) According to the requirement (5) of the pattern selection table PT, the foreground density has a relationship opposite to the background density between the colors that are adjacent to each other, so that the adjacent color area A is obtained. The color difference between colors is reflected in the monochrome image. Therefore, even in the case of two colors that are adjacent to each other in the color area A and are difficult to distinguish in the color image, it is easy to distinguish the color difference in the monochrome image.

(Second Embodiment)
In the first embodiment described above, the color image of the color image data is converted into the image data of a monochrome image with a hatch pattern. However, in the second embodiment, one or more objects included in the color image data are described. For each image (color image), determine the type of object image such as text attribute indicating character or symbol data, graphic attribute indicating vector data, graphic attribute indicating bitmap data, etc. A hatch pattern is given according to the type. In the following, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  FIG. 8 shows the configuration of the image processing apparatus 200 in the second embodiment. As shown in FIG. 8, the printer driver 40 of the image processing apparatus 200 includes an image type determination unit 44, a pattern type determination unit 41, a pattern density determination unit 42, and a monochrome image data generation unit 43. Yes.

  The image type determination unit 44 determines the type of object image included in the color image data. For example, it is determined whether the type of the object image is a text attribute or a graphic attribute. This determination is performed by referring to the attribute information of the object image included in the color image data, for example.

  For example, among the object images included in the color image data, the pattern type determining unit 41 and the pattern density determining unit 42 perform hatch pattern processing on object images other than text attributes and graphic attributes, that is, object images having graphic attributes. Is converted into a monochrome object image with a hatch pattern.

  On the other hand, the monochrome image data generation unit 43 converts the object image having the text attribute or the graphic attribute into a monochrome object image by gray conversion.

  The monochrome image data generation unit 43 generates monochrome image data including a gray-converted object image for text attributes and graphic attributes, and a hatched object image for object images other than text attributes and graphic attributes.

  According to the second embodiment, among the object images included in the color image data, the graphic attribute object image is converted into a monochrome image with a hatch pattern, so that the same effect as in the first embodiment is obtained. be able to. Furthermore, since the color image data is converted into a monochrome object image with a hatch pattern corresponding to the type of object image included in the color image data, even if the object images of the same color overlap each other, It is possible to obtain monochrome image data that can easily distinguish original color images without burying object images having different attribute types of object images.

(Third embodiment)
In the third embodiment, it is determined whether the color image of the color image data includes a prohibited image for which hatching is prohibited in advance, and the area of the prohibited image is grayed without adding a hatch pattern. Convert to monochrome image by conversion. Examples of prohibited images include images with a specific mark such as a company logo or a specific pattern such as a hatch pattern.

  FIG. 9 shows the configuration of the image processing apparatus 300 according to the third embodiment. As shown in FIG. 9, the printer driver 40 of the image processing apparatus 300 includes a prohibited image determination unit 45, a pattern type determination unit 41, a pattern density determination unit 42, and a monochrome image data generation unit 43. Yes.

  The prohibited image determination unit 45 determines whether a prohibited image is included in the color image of the color image data. This determination is performed, for example, by previously registering a prohibited image template as the prohibited image data PRD in the hard disk drive 14 and performing template matching between the registered template and the color image.

  In addition, in the color image of the color image data, a monochrome image to which a hatch pattern is added by the pattern type determination unit 41 and the pattern density determination unit 42 for the image region that is not a prohibited image, as in the first embodiment. Converted to an image.

  On the other hand, for the image area of the prohibited image, the monochrome image data generation unit 43 converts the image into a monochrome image by gray conversion. Furthermore, the monochrome image data generation unit 43 generates monochrome image data in which a monochrome image in the image area of the prohibited image and a monochrome image in which a hatch pattern is added to the image area that is not the prohibited image are combined.

  According to the third embodiment, the area of the prohibited image in the color image is converted into a monochrome image by gray conversion without adding a hatch pattern. Therefore, the provision of a hatch pattern eliminates the inconvenience of losing the representation of a logo or other mark representing a company name or an image with a specific pattern such as a hatch pattern, improving convenience for users. .

  However, as a processing method that does not add a hatch pattern to the prohibited image, for example, when a plurality of object images are included in the color image data, the object image including the prohibited image is not limited to the area of the prohibited image. The hatch pattern may not be applied to the entire area.

  Although the first to third embodiments according to the present invention have been described above, the present invention is not limited to these embodiments, and can be changed and improved without departing from the spirit and scope of the claims. Of course, the present invention includes equivalents thereof. Hereinafter, modified examples will be described.

  (Modification 1) In the first to third embodiments, the hue and brightness of the color image are correlated in determining the type of the hatch pattern P to be applied to the color image. The method for determining the type of P is not limited to this. The type of hatch pattern P may be determined according to the hue, or the type of hatch pattern P may be determined according to the brightness.

  Further, the type of the hatch pattern P may be determined according to the saturation. In this case, for example, as shown in FIG. 10, it is desirable to change the line density of the hatch pattern in accordance with the level of saturation of the color image. That is, a hatch pattern Ph having a low black line density for high saturation, a hatch pattern Pm having a medium black line density for medium saturation, and a hatch pattern Pm having a high black line density for low saturation. Assign Pl. However, when the foreground density of the hatch pattern P is lower than the background density, it is desirable to increase the line density as the saturation increases. In this way, since the saturation of the color image is reflected in the monochrome image, it is possible to print a monochrome image in which the difference in saturation in the original color image can be distinguished.

  (Modification 2) In the above embodiment, the requirements (1) to (5) are satisfied by performing the process of converting color image data into monochrome image data with hatching according to the pattern selection table PT. The calculation may be performed without using a table. That is, brightness, hue, and the like corresponding to the RGB values of the color image data may be calculated by calculation, and hatching that satisfies the requirements (1) to (5) may be performed using the calculation result. However, the processing speed can be increased when the pattern selection table PT is used as compared with the case where the brightness, hue, and the like are obtained by calculation.

  (Modification 3) In the above embodiment, the color image data will be described by taking, as an example, data having an 8-bit gradation value for each color of RGB, and monochrome image data having data having an 8-bit gradation value for a single K color. However, the color and the number of gradations specified by the image data are not limited to this. In the above embodiment, the color image data in the bitmap format having RGB values for each of a large number of pixels arranged in a matrix has been described. However, the color image data is not limited to this. For example, the printer driver 40 receives color image data in an image format other than a bitmap, such as a vector format, and develops it into a bitmap by internal processing of the printer driver 40, and then performs the same processing as in the above embodiment. May be. Also, the monochrome image data is not limited to K monochrome image data, and may represent a monochrome image other than K.

  (Modification 4) In the above embodiment, the color image data is converted into the monochrome image data with hatching by the processing on the host computer 10 side. However, the color image data is converted into the monochrome image data by the internal processing of the printer. You may do it. As shown in FIG. 11, the printer controller 22 functions as an image processing apparatus having a pattern type determination unit 41, a pattern density determination unit 42, a monochrome image data generation unit 43, and a print processing unit 23. The pattern type determination unit 41, the pattern density determination unit 42, and the monochrome image data generation unit 43 perform the same processing as in the first embodiment on the color image data transmitted from the host computer. The print processing unit 23 performs halftone processing or the like on the monochrome image data with the hatch pattern and causes the print engine 21 to print, so that a monochrome image that can distinguish the color difference in the original color image is printed. The

  Further, the host computer and the printer may cooperate to convert to monochrome image data with a hatch pattern. In the system shown in FIG. 11, the printer driver 40 of the host computer refers to the pattern selection table PT and transmits color image data to which the designation information designating parameters such as pattern type, background density, and foreground density is added to the printer. To do. The pattern type determination unit 41 of the printer may determine the pattern type according to the designation information added to the color image data, and the pattern density determination unit 42 may determine the background density and the foreground density according to the designation information.

  (Modification 5) In the first to third embodiments, a hatch pattern is used as a single color pattern applied to a color image. However, the single color pattern is not limited to this. The monochromatic pattern may be a pattern other than a hatch pattern as long as the pattern has a predetermined regularity.

  DESCRIPTION OF SYMBOLS 1 ... Printing system, 10 ... Host computer, 20 ... Printer, 21 ... Print engine, 22 ... Controller, 23 ... Print processing part, 30 ... Application, 40 ... Printer driver, 41 ... Pattern type determination part as pattern determination part, 42 ... pattern density determination unit, 43 ... monochrome image data generation unit, 44 ... image type determination unit, 45 ... prohibited image determination unit, 100 ... image processing device, P ... hatch pattern as a single color pattern, PT ... as correspondence information Pattern selection table, PDB ... pattern image database.

Claims (15)

An image processing apparatus for converting color image data representing a color image into monochrome image data,
A pattern determining unit that determines a monochromatic pattern representing a pattern corresponding to the color of the color image by a monochromatic density;
A pattern density determining unit that determines a background density of an area that is a background of the pattern in the image area of the monochrome pattern;
A monochrome image data generation unit that generates the monochrome image data of a monochrome image in which the monochrome pattern having the background density is applied to an image region corresponding to the color image;
The image processing apparatus, wherein the pattern density determination unit changes the background density according to a color of the color image. The image processing apparatus according to claim 1.
The image processing apparatus, wherein the pattern density determination unit changes the background density according to the brightness of the color image. The image processing apparatus according to claim 1 or 2,
The pattern density determination unit
An image processing apparatus, wherein the background density is determined so that the brightness of the monochrome image is equal to the brightness of the color image. In the image processing device according to any one of claims 1 to 3,
The pattern density determination unit
An image processing apparatus, wherein the background density of the monochrome pattern is determined so that an average brightness of an image area to which the monochrome pattern is applied to the color image is equal to an average brightness of the monochrome pattern. In the image processing device according to any one of claims 1 to 4,
The image processing apparatus, wherein the pattern determining unit determines the monochrome pattern that represents a pattern corresponding to a hue of a color image of the color image data by a monochrome density. In the image processing device according to any one of claims 1 to 5,
The monochromatic pattern is a hatch pattern that represents a pattern with a monochromatic line;
The image processing apparatus, wherein the pattern determination unit determines the hatch pattern having a higher line density as the color brightness of the color image is lower as a pattern to be applied to the color image. The image processing apparatus according to any one of claims 1 to 6,
The pattern density determination unit is configured to set the density of the pattern of the monochrome pattern corresponding to the first color among the first color and the second color adjacent to each other in a plurality of color regions that define a hue circle. An image processing apparatus, characterized in that the density of the pattern of the monochromatic pattern corresponding to the second color is made smaller than the background density. In the image processing device according to any one of claims 1 to 7,
The single color pattern corresponding to the fourth color that is complementary to the third color and the pattern determining unit represents a pattern obtained by rotating the pattern of the single color pattern corresponding to the third color. A featured image processing apparatus. The image processing apparatus according to any one of claims 1 to 8,
The image processing apparatus, wherein the pattern determination unit changes the pattern of the monochromatic pattern according to the saturation of the color image. The image processing apparatus according to any one of claims 1 to 9,
An image type determination unit for determining the type of the color image;
The monochrome image data generation unit converts the image into a monochrome image represented by a single color density corresponding to the determination result of the image type determination unit. The image processing device according to any one of claims 1 to 10,
A prohibited image determination unit that determines whether or not the color image includes a prohibited image determined in advance so as not to apply the monochrome pattern;
The monochrome image data generation unit converts the prohibited image included in the color image into a monochrome image represented by a single color density without applying the monochrome pattern. . The image processing apparatus according to any one of claims 1 to 11,
Correspondence information in which the color of the color image and the background density are associated in advance;
The pattern density determining unit determines the background density according to the color of the color image with reference to the correspondence information. The image processing apparatus according to any one of claims 1 to 12,
The pattern determining unit includes the monochrome pattern representing a vertical line pattern, the monochrome pattern representing a horizontal line pattern, the monochrome pattern representing a grid line pattern, the monochrome pattern representing a diagonal line pattern, and the diagonal grid line pattern. An image processing apparatus that selects the single color pattern corresponding to the color image according to the color of the color image from a plurality of the single color patterns including any two or more of the single color patterns representing . An image processing program for converting color image data representing a color image into monochrome image data,
Computer
A pattern determining unit that determines a monochromatic pattern representing a pattern corresponding to the color of the color image by a monochromatic density;
A pattern density determining unit that determines a background density of an area that is a background of the pattern in the image area of the monochrome pattern;
Functioning as a monochrome image data generation unit that generates the monochrome image data of a monochrome image in which the monochrome pattern having the background density is applied to an image region corresponding to the color image;
The image processing program characterized in that the pattern density determination unit changes the background density according to the color of the color image. An image processing method for converting color image data representing a color image into monochrome image data,
Determining a monochromatic pattern representing a pattern corresponding to the color of the color image by a monochromatic density;
Determining a background density of an area to be a background of the pattern in the image area of the monochrome pattern;
Generating monochrome image data of a monochrome image in which the monochrome pattern having the background density is applied to an image region corresponding to the color image; and
An image processing method, wherein the background density is changed according to a color of the color image.