JP2011211287A - Image forming apparatus and image processing program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of converting an inputted image to an image more natural than before at high speed.SOLUTION: A multifunction machine includes a storage unit for storing a representative color, and a controller for preparing a Voronoi diagram where the representative color stored by the storage unit is a generatrix on an Lab color space, and converting the respective pixels of the inputted image to the closest representative color on the basis of the Voronoi diagram. The controller receives a color selected by a user, and calculates one or more colors between the received color and white. The storage unit stores the color received by the controller as the representative color, and stores the color calculated by the controller as the representative color. The controller changes the representative color corresponding to the pixel (S223) so that the adjacent pixel is within a predetermined range on the Voronoi diagram.

Description

  The present invention relates to an image forming apparatus and an image processing program capable of converting an input image into an image composed of only representative colors and outputting the image.

  In recent years, energy conservation has been emphasized for ecology and cost reduction. Also in image forming apparatuses such as copiers and printers, in order to save energy, printing is performed by converting an input image such as a single color print or a two-color print into an image composed only of representative colors. .

  Conventionally, when an input image is converted into an image composed of only representative colors and then output, each pixel of the input image is converted to the closest representative color in the RGB color space or the CMYK color space It has been known. However, since this method is a color space in which the RGB color space and the CMYK color space depend on the image output device, there is a problem in that an actually output image varies depending on the output device.

  As a method for solving this problem, each pixel of the input image is displayed on the Lab color space expressed by the human sense without depending on the image output device from the values on the RGB color space or the CMYK color space. There is known a method of converting to the closest representative color in the Lab color space after conversion to the value (for example, see Patent Document 1). However, in this method, when each pixel is converted to the nearest representative color, the distance between all the representative colors is obtained for each pixel of the input image, and the representative color having the shortest distance is determined as that pixel. Therefore, there is a problem that the processing amount for conversion is large and the processing time is long.

  As a method for solving this problem, a method is known in which each pixel is converted to the closest representative color using a Voronoi diagram (see, for example, Patent Documents 2 and 3).

  By the way, humans are sensitive to changes in hue. Therefore, when a photographic image of sky, sea, vegetation, etc. is converted into an image composed only of representative colors, the converted image may become an unnatural image depending on how the hue changes. . As a technique for smoothing a change in hue, one that generates output image data by performing color error diffusion in the Lab color space for each pixel with respect to original image data is known (for example, (See Patent Document 4).

Japanese Patent No. 4083311 Japanese Patent Laid-Open No. 7-85251 Japanese Patent No. 3492115 Japanese Patent No. 3737149

  In the techniques described in Patent Documents 2 and 3, depending on the selected representative color, pixels having greatly different densities in the input image may be converted to the same representative color. There is a problem that sometimes becomes an unnatural image.

  In the technique described in Patent Document 4, since color error diffusion is performed in the Lab color space for each pixel, there is a problem that the processing speed is slow.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of converting an input image into a more natural image than before.

  An image forming apparatus according to the present invention includes a representative color storage unit that stores a representative color, and a Voronoi diagram generation that generates a Voronoi diagram using the representative color stored in the representative color storage unit as a base point in a uniform color space. An image comprising: means; color conversion means for converting each pixel of the input image to the nearest representative color based on the Voronoi diagram; and a color changing means for changing the representative color corresponding to the pixel. In the forming apparatus, the color changing unit changes the representative color corresponding to the pixel so that the adjacent pixel is within a predetermined range on the Voronoi diagram.

  With this configuration, the image forming apparatus of the present invention changes the representative color corresponding to a pixel so that the adjacent pixel is within a predetermined range on the Voronoi diagram. Can be converted to Further, since the image forming apparatus of the present invention uses the Voronoi diagram, the image can be converted at high speed.

  The image forming apparatus according to the present invention includes a selection color reception unit that receives a color selected by a user, and a color calculation that calculates one or more colors between the color received by the selection color reception unit and white. The representative color storage means preferably stores the color received by the selected color receiving means and the color calculated by the color calculation means as the representative color.

  With this configuration, the image forming apparatus of the present invention not only sets the color selected by the user as the representative color, but also automatically adds one or more colors between the color and white as the representative color. The input image can be converted into a more natural image.

  The image processing program according to the present invention includes a representative color storage unit that stores a representative color, and a Voronoi diagram that creates a Voronoi diagram using the representative color stored in the representative color storage unit as a base point in a uniform color space. The computer functions as a diagram creation means, a color conversion means for converting each pixel of the input image to the nearest representative color based on the Voronoi diagram, and a color change means for changing the representative color corresponding to the pixel An image processing program for performing the processing, wherein the color changing unit changes the representative color corresponding to the pixel so that the adjacent pixel is within a predetermined range on the Voronoi diagram. To do.

  With this configuration, the computer that executes the image processing program of the present invention changes the representative color corresponding to a pixel so that adjacent pixels are within a predetermined range on the Voronoi diagram. It can be converted into a more natural image. Further, since the computer that executes the image processing program of the present invention uses the Voronoi diagram, the image can be converted at high speed.

  The image forming apparatus of the present invention can convert an input image into a more natural image than before.

It is a block diagram which shows the control structure of the multifunctional device which concerns on one embodiment of this invention. 2 is a flowchart of the operation of the control unit shown in FIG. 1 when a copy instruction is given by a user. (A) is a figure which shows the copy operation | movement screen displayed on the monitor shown in FIG. 1 before a representative color is selected by the user. (B) is a figure which shows the copy operation | movement screen displayed on the monitor shown in FIG. 1 after a representative color is selected by the user. It is a flowchart of the representative color selection process shown in FIG. It is a figure which shows the representative color selection screen displayed on the monitor shown in FIG. 3 is a flowchart of a copy process shown in FIG. 7 is a flowchart of Voronoi diagram creation processing shown in FIG. 6. It is a figure which shows the Voronoi diagram produced in the Voronoi diagram creation process shown in FIG. It is a flowchart of the color conversion process shown in FIG. It is a flowchart of the specific area image extraction process shown in FIG. It is a flowchart of the color change process shown in FIG.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  First, the configuration of a multifunction peripheral as an image forming apparatus according to the present embodiment will be described.

  FIG. 1 is a block diagram showing a control configuration of the multifunction machine 10 according to the present embodiment.

  As shown in FIG. 1, the multifunction machine 10 includes a control unit 11 for controlling the entire multifunction machine 10, a storage unit 12 for storing various information, and various operations input by a user. An operation unit 13 on the operation panel (not shown), a monitor 14 on the operation panel for displaying various information, a printer unit 15 for executing printing on paper, and a reading device for reading an original and generating image data. The scanner unit 16 and a network I / F (interface) unit 17 for communicating with an external device (not shown) such as a host computer via a LAN (Local Area Network).

  The control unit 11 includes a CPU (Central Processing Unit), a ROM (Read Only Memory) preliminarily storing programs such as an image processing program of the present invention and various data, and a RAM (Random) used as a work area of the CPU. Access Memory) and the like. The CPU is an arithmetic processing unit that operates the control unit 11 by executing a program stored in the ROM. The RAM temporarily stores programs and various data when the programs are executed by the CPU.

  Here, by executing the image processing program, the control unit 11 receives the color selected by the user as a representative color, as will be described later, and functions as the selected color receiving unit 11a. It has become. Further, the control unit 11 calculates one or more colors between a color selected by the user and white as a representative color by executing an image processing program, as will be described later. It functions as the color calculation means 11b. In addition, the control unit 11 creates a Voronoi diagram with the representative color stored in the storage unit 12 as a generating point in the Lab color space by executing the image processing program, as will be described later. And functions as Voronoi diagram creation means 11c. The control unit 11 executes the image processing program to convert each pixel of the input image into the closest representative color based on the Voronoi diagram, as will be described later. It functions as 11d. Further, the control unit 11 changes the representative color corresponding to the pixel by executing an image processing program, and functions as the color changing unit 11e.

  The storage unit 12 is configured by a RAM or the like that constitutes the control unit 11. Here, the storage unit 12 is configured to store a representative color as will be described later when the control unit 11 executes the image processing program, and constitutes a representative color storage unit of the present invention.

  The operation unit 13 includes input devices such as buttons that form a touch panel together with the monitor 14 and buttons on the operation panel.

  The monitor 14 includes a display device such as an LCD (Liquid Crystal Display).

  The printer unit 15 executes various jobs such as a print data job received from an external device (not shown) via a network I / F unit 17 described later and an image data job generated by the scanner unit 16. A printing device for printing.

  The network I / F unit 17 transmits, for example, image data generated by the scanner unit 16 to an external device via the LAN, or print data to be printed by the printer unit 15 via the LAN. Or receive from the device.

  Next, the operation of the multifunction machine 10 will be described.

  The user can give a copy instruction to the multifunction machine 10 through the operation unit 13. When the user gives a copy instruction to the multifunction device 10, the control unit 11 of the multifunction device 10 starts the processing shown in FIG.

  FIG. 2 is a flowchart of the operation of the control unit 11 when a copy instruction is given by the user.

  As shown in FIG. 2, the control unit 11 first displays the copy operation screen shown in FIG. 3A on the monitor 14 (S101).

  FIG. 3A shows a copy operation screen displayed on the monitor 14 before the representative color is selected by the user. FIG. 3B is a diagram showing a copy operation screen displayed on the monitor 14 after the representative color is selected by the user.

  As shown in FIG. 3, the copy operation screen includes a representative color display area 21 in which the representative color selected by the user is displayed, an image type display area 22 in which the image type selected by the user is displayed, and usage. A “representative color selection” button 23 to be pressed when the user selects a representative color, and a “copy start” button 24 to be pressed when the user starts the multifunction device 10 to copy is included. The user can press the “representative color selection” button 23 and the “copy start” button 24 by the operation unit 13. In the copy operation screen shown in FIG. 3A, nothing is displayed in the representative color display area 21 and the image type display area 22.

  As shown in FIG. 2, the control unit 11 determines whether or not the “representative color selection” button 23 on the copy operation screen has been pressed by the user after the process of S101 (S102).

  If the control unit 11 determines in S102 that the “representative color selection” button 23 on the copy operation screen has been pressed by the user, the control unit 11 executes a representative color selection process shown in FIG. 4 (S103).

  FIG. 4 is a flowchart of representative color selection processing.

  As shown in FIG. 4, in the representative color selection process, the control unit 11 first displays the representative color selection screen shown in FIG. 5 on the monitor 14 instead of the copy operation screen shown in FIG. 3A (S121). .

  FIG. 5 is a diagram showing a representative color selection screen displayed on the monitor 14.

  As shown in FIG. 5, the representative color selection screen includes a color palette 31 for the user to select a representative color, a radio button 32 a for allowing the user to select a photographic image as an image type, and the user. A radio button 32b for selecting a text image as an image type and an “OK” button 33 for pressing when the user finishes selecting a representative color are included. The radio buttons 32a and 32b are always in a state where only one radio button is selected. The user can select an arbitrary color from the color palette 31 using the operation unit 13, select one of the radio buttons 32 a and 32 b, and press the “OK” button 33.

  As shown in FIG. 4, after the process of S121, the control unit 11 determines whether or not a representative color has been selected by the user from the color palette 31 on the representative color selection screen (S122).

  When the selected color receiving means 11a, which is one of the functions of the control unit 11, determines in S122 that the representative color has been selected by the user from the color palette 31 on the representative color selection screen, the representative color selected by the user (hereinafter referred to as “representative color”). After the RGB value of “user selected representative color” is stored in the storage unit 12 (S123), the process returns to S122 again. Therefore, the user can select a plurality of representative colors by repeating the processes of S122 and S123.

  If the control unit 11 determines in S122 that the representative color is not selected by the user from the color palette 31 on the representative color selection screen, has the image type been selected by the user from the radio buttons 32a and 32b on the representative color selection screen? It is determined whether or not (S124).

  When the control unit 11 determines in S124 that the image type has been selected by the user from the radio buttons 32a and 32b on the representative color selection screen, the control unit 11 stores the image type selected by the user in the storage unit 12 (S125). Then, the process returns to S122 again.

  On the other hand, when the control unit 11 determines in S124 that the image type is not selected by the user from the radio buttons 32a and 32b on the representative color selection screen, the “OK” button 33 on the representative color selection screen is pressed by the user. It is determined whether or not (S126).

  If the control unit 11 determines in S126 that the “OK” button 33 on the representative color selection screen has not been pressed by the user, the control unit 11 returns to the process of S122 again.

  On the other hand, when determining in S126 that the “OK” button 33 on the representative color selection screen has been pressed by the user, the control unit 11 replaces the representative color selection screen shown in FIG. 5 with the copy operation screen shown in FIG. Is displayed on the monitor 14 (S127), and the representative color selection process shown in FIG. In the copy operation screen shown in FIG. 3B, the user selected representative color is displayed in the representative color display area 21, and the image type selected by the user is displayed in the image type display area 22.

  As illustrated in FIG. 2, when the representative color selection process of S103 is completed, the control unit 11 returns to the process of S102 again.

  If the control unit 11 determines in S102 that the “representative color selection” button 23 on the copy operation screen has not been pressed by the user, it determines whether or not the “copy start” button 24 on the copy operation screen has been pressed by the user. Judgment is made (S104).

  If the control unit 11 determines in S104 that the “copy start” button 24 on the copy operation screen has not been pressed by the user, the process returns to S102.

  On the other hand, if the control unit 11 determines in S104 that the “copy start” button 24 on the copy operation screen has been pressed by the user, the control unit 11 executes the copy process shown in FIG. 6 (S105).

  FIG. 6 is a flowchart of the copy process.

  As shown in FIG. 6, in the copy process, the control unit 11 first executes the Voronoi diagram creation process shown in FIG. 7 (S141).

  FIG. 7 is a flowchart of Voronoi diagram creation processing.

  As shown in FIG. 7, in the Voronoi diagram creation process, the color calculation means 11b, which is one of the functions of the control unit 11, first calculates the user-selected representative color stored in the storage unit 12 in S123 and the white color. The m colors in between are calculated as additional representative colors in the RGB color space (S161), and the RGB values of the additional representative colors calculated in S161 are stored in the storage unit 12 (S162).

  As an additional representative color calculation method, for example, there is a method in which m points dividing a line segment connecting the user-selected representative color and white in the RGB color space into (m + 1) equals the additional representative color. When a plurality of user-selected representative colors are stored in the storage unit 12, m additional representative colors are calculated for each of the user-selected representative colors. However, when the user selected representative color is close to white, the number of additional representative colors may be set to less than m according to a predetermined rule. Note that m, which is the number of additional representative colors, can be set by the user in advance using the operation unit 13.

  Next, the Voronoi diagram creation means 11c, which is one of the functions of the control unit 11, converts the representative colors stored in the storage unit 12 in S123 and S162 from RGB values to Lab values (S163), and converts them to Lab values in S163. A Voronoi diagram 40 (see FIG. 8) using the converted representative color as a base point is created in the Lab color space as a uniform color space (S164), and the Voronoi diagram creating process shown in FIG. 7 is terminated.

The Voronoi diagram is a diagram in which a space closest to each generating point existing in the space is divided by a hyperplane such as a line or a surface. That is, the Voronoi diagram shows the Voronoi regions {V (p1), V (p2),..., V (pn)} for the finite subset P = {p1, p2,. It can be defined as a set. Here, the Voronoi region is a region V (pi) configured by the following expression with respect to the distance function d.
V (pi) = {p | d (p, pi) ≦ d (p, pj), i ≠ j}

  FIG. 8 is a diagram showing the Voronoi diagram 40 created in S164.

  In the Voronoi diagram 40 shown in FIG. 8, the representative color 41 converted into the Lab value in S163 is a generating point of the Voronoi diagram 40. The Voronoi regions 42 each containing the representative color 41 are delimited by Voronoi boundaries 43 and Voronoi points 44 that are intersections of the Voronoi boundaries 43. In FIG. 8, a two-dimensional Voronoi diagram is shown for easy understanding, but the Voronoi diagram 40 created in S164 is actually a three-dimensional Voronoi diagram.

  As shown in FIG. 6, when the Voronoi diagram creation process of S141 is completed, the control unit 11 reads all pixels of the document by the scanner unit 16 (S142), and executes the color conversion process shown in FIG. 9 (S143). .

  FIG. 9 is a flowchart of the color conversion process.

  As shown in FIG. 9, in the color conversion process, the control unit 11 first converts the pixels read in S142 from RGB values to Lab values (S181).

  Next, the color conversion unit 11d, which is one of the functions of the control unit 11, converts the pixel converted into the Lab value in S181 into the closest representative color based on the Voronoi diagram 40 created in S164 (S182). Then, the color conversion process shown in FIG. That is, the control unit 11 obtains one Voronoi region 42 including the pixel converted to the Lab value in S181 from the plurality of Voronoi regions 42 of the Voronoi diagram 40 created in S164, and the pixel converted to the Lab value in S181. Is converted into a representative color 41 included in the Voronoi region 42.

  When the pixel exists on the Voronoi boundary 43 or the Voronoi point 44, the control unit 11 converts the pixel into the representative color 41 according to a predetermined rule. For example, when the pixel exists on the Voronoi boundary 43, the control unit 11 has only one representative color having the highest L value among the representative colors 41 of the plurality of Voronoi regions 42 partitioned by the Voronoi boundary 43. When the pixel is converted to a representative color having the highest L value. Next, when there are a plurality of representative colors having the highest L value, when there is only one representative color having the highest a value among the plurality of representative colors having the highest L value, the representative color having the highest a value. Convert the pixel to. Finally, when there are a plurality of representative colors having the highest L value and a value, the pixel is converted to a representative color having the highest b value among the plurality of representative colors having the highest L value and a value. Although the case where the pixel exists on the Voronoi boundary 43 has been described, the same applies to the case where the pixel exists on the Voronoi point 44.

  As shown in FIG. 6, when the color conversion process of S143 is completed, the control unit 11 executes the specific area image extraction process shown in FIG. 10 (S144).

  FIG. 10 is a flowchart of the specific area image extraction process.

  As shown in FIG. 10, in the specific area image extraction process, the control unit 11 first extracts a specific area image from the entire image converted into the Lab value in S181 (S201). Here, the specific area is an area where the hue change needs to be smoothed, and the specific area image is an image of the specific area. The specific area includes, for example, a natural image area such as an empty area, a sea area, and a vegetation area in a photographic image. What is included in the specific area depends on the setting. Also, what is included in the specific area may be different depending on the image type selected by the user. Note that the image of the specific area is characterized by hue, brightness, saturation, frequency band, and the like as compared with an image other than the specific area. Techniques for distinguishing a specific area image from other images based on these characteristics are described in Japanese Patent Application Laid-Open No. 2004-234409, Japanese Patent Application Laid-Open No. 2004-038481, Japanese Patent Application Laid-Open No. 2004-120092, and the like. Yes. Using such a known technique, the control unit 11 can extract the specific area image from the entire image converted into the Lab value in S181.

  Next, the color conversion unit 11d of the control unit 11 converts each pixel of the specific area image extracted in S201 into the closest representative color based on the Voronoi diagram 40 created in S164 (S202), and FIG. The specific area image extraction process shown in FIG.

  As shown in FIG. 6, when the specific area extraction process of S144 is completed, the control unit 11 executes the color change process shown in FIG. 11 (S145).

  FIG. 11 is a flowchart of the color change process.

  As shown in FIG. 11, the color changing unit 11e, which is one of the functions of the control unit 11, first targets one pixel in the specific area image converted into the representative color 41 in S202 in the color changing process. (S221).

  Next, the color changing unit 11e determines whether or not the pixel targeted in S221 is within a predetermined range on the Voronoi diagram 40 created in S164 with respect to the pixel adjacent to the pixel (S222). . Here, the “adjacent pixels” in S222 are selected from only the pixels already targeted in S221. Therefore, the first pixel of the specific region pixels does not have “adjacent pixels” yet, and therefore cannot be determined in S222. In such a case, the color changing unit 11e determines in S222 that it is within the predetermined range. The “predetermined range” means that the Voronoi regions 42 to which the representative colors 41 corresponding to each pixel belong are in a positional relationship within two neighbors, for example. The positional relationship within two neighbors means that the target Voronoi regions 42 are the same Voronoi regions 42, directly adjacent Voronoi regions 42, or adjacent Voronoi regions 42 with another one Voronoi region 42 in between. 42 is any positional relationship. Note that the predetermined range depends on the setting. Further, the predetermined range may be different depending on the image type selected by the user.

  If it is determined in S222 that the color changing unit 11e is not within the predetermined range, the color changing unit 11e changes the representative color 41 corresponding to the target pixel so as to be within the predetermined range (S223). That is, the color changing unit 11e has a Voronoi within a predetermined range with respect to the Voronoi region 42 to which the “adjacent pixel” belongs, among the Voronoi regions 42 where the line segments connecting these two pixels on the Voronoi diagram 40 overlap. The region 42 is selected, and the representative color 41 of the selected Voronoi region 42 is set as the representative color 41 corresponding to the target pixel. For example, when it is “predetermined range” that the Voronoi regions 42 to which the representative color 41 corresponding to each pixel belongs are in a positional relationship within two neighbors, the color changing unit 11e determines that the target Voronoi regions 42 Is not within the predetermined range, the target Voronoi regions 42 are the same Voronoi region 42, directly adjacent to each other, or adjacent to each other with another one Voronoi region 42 interposed therebetween. In this way, the representative color 41 corresponding to the target pixel is changed. It should be noted that whether the target Voronoi regions 42 are the same Voronoi region 42, the directly adjacent Voronoi region 42, or the adjacent Voronoi region 42 across another one Voronoi region 42 depends on the setting. is there. Also, the user determines whether the target Voronoi regions 42 are in the same Voronoi region 42, the directly adjacent Voronoi region 42, or the adjacent Voronoi region 42 with the other one Voronoi region 42 in between. It may differ depending on the selected image type.

  Next, the color changing unit 11e determines whether or not all the pixels in the specific area are targeted (S224). In addition, when it is determined in S222 that the color changing unit 11e is within the predetermined range, the color changing unit 11e performs the process of S224 without changing the representative color 41 corresponding to the target pixel.

  If the color changing unit 11e determines in S224 that there is a pixel that is not yet targeted among the pixels in the specific area, the process returns to S221 for the pixel that is not yet targeted.

  On the other hand, when the color changing unit 11e determines in S224 that all the pixels in the specific area are targeted, the color changing process shown in FIG. 11 is terminated.

  As shown in FIG. 6, when the color changing process in S145 is completed, the control unit 11 changes the representative color 41 to the whole image converted into the representative color 41 in S182 as necessary in the color changing process in S145. The specific area image is overwritten and synthesized (S146). That is, the control unit 11 generates an entire image that is represented by the representative color 41 and in which the representative color 41 of the specific area image is changed as necessary.

  Then, the control unit 11 converts the image synthesized in S146 from the Lab value to the RGB value (S147).

  Next, the control unit 11 converts the pixel converted to the RGB value in S147 from the RGB value to the CMYK value based on the color lookup table stored in advance in the ROM (S148).

  Next, the control unit 11 causes the printer unit 15 to perform printing on a sheet based on all the pixels converted into CMYK values in S148 (S149), and ends the copy process illustrated in FIG.

  As shown in FIG. 2, when the copy process of S105 is finished, the control unit 11 closes the copy operation screen shown in FIG. 3B on the monitor 14 (S106), and finishes the process shown in FIG.

  As described above, the multifunction machine 10 changes the representative color 41 corresponding to the pixel so that the adjacent pixel is within a predetermined range on the Voronoi diagram 40, so that the input image is more natural than before. Can be converted into a simple image.

  Further, the multifunction device 10 not only sets the color selected by the user as a representative color, but also automatically adds one or more colors between the color and white as the representative color, so that the input image Can be converted into a more natural image.

  Further, since the multifunction machine 10 converts each pixel to the nearest representative color using the Voronoi diagram 40, the distance between all the representative colors is obtained for each pixel of the input image, and each pixel is nearest. Compared with the configuration for converting to a representative color, processing can be performed at high speed.

  In addition, the multifunction device 10 converts each pixel of the image input from the scanner unit 16 from a value in the RGB color space to a value in the Lab color space expressed by a human sense without depending on the image output device. Then, the image is converted to the closest representative color in the Lab color space, so that the image actually printed by the printer unit 15 can be prevented from being different depending on the apparatus.

  In the present embodiment, a copy job has been described. However, any other job may be used as long as it is a job for executing printing. For example, a print data job received from an external device (not shown) via the network I / F unit 17 may be used.

  In this embodiment, the color space of the input image is the RGB color space, and the color space of the output image is the CMYK color space. However, the color space of the input image and the output image are the same. The color space is not limited to these.

  In this embodiment, the Lab color space is used as the uniform color space. However, a uniform color space other than the Lab color space may be used. For example, the Luv color space may be used as the uniform color space.

  In this embodiment, the image types that can be selected by the user are a photographic image and a text image, but other image types may be selectable by the user.

  The image forming apparatus according to the present invention has been described with respect to a multifunction peripheral in the present embodiment, but may be an image forming apparatus other than a multifunction peripheral such as a copier or a printer.

  Further, although the image forming apparatus has been described in the present embodiment as a computer that executes the image processing program of the present invention, a computer other than the image forming apparatus may be used. For example, a general-purpose personal computer may execute the image processing program of the present invention.

10 MFP (image forming device)
11a Selected color receiving means 11b Color calculating means 11c Voronoi diagram creating means 11d Color converting means 11e Color changing means 12 Storage section (representative color storing means)
40 Voronoi diagram 41 Representative colors

Claims (3)

Representative color storage means for storing representative colors, Voronoi diagram creation means for creating a Voronoi diagram with the representative color stored in the representative color storage means as a base point in a uniform color space, and input image An image forming apparatus comprising: a color conversion unit that converts each pixel to the closest representative color based on the Voronoi diagram; and a color change unit that changes the representative color corresponding to the pixel,
The image forming apparatus, wherein the color changing unit changes the representative color corresponding to the pixel so that the adjacent pixel is within a predetermined range on the Voronoi diagram. A selection color reception unit that receives a color selected by a user; and a color calculation unit that calculates one or more colors between the color received by the selection color reception unit and white,
The image forming apparatus according to claim 1, wherein the representative color storage unit stores the color received by the selected color reception unit and the color calculated by the color calculation unit as the representative color. . Representative color storage means for storing representative colors, Voronoi diagram creation means for creating a Voronoi diagram with the representative color stored in the representative color storage means as a base point in a uniform color space, and input image An image processing program for causing a computer to function as a color conversion unit that converts each pixel into the closest representative color based on the Voronoi diagram, and a color change unit that changes the representative color corresponding to the pixel,
The image processing program, wherein the color changing unit changes the representative color corresponding to the pixel so that the adjacent pixel is within a predetermined range on the Voronoi diagram.

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