JP2008042545A - Image processing apparatus and its program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus and its program by which a limited colorization process can be performed where a lack of information and allochroism are suppressed through the replacement to representative colors. <P>SOLUTION: A representative color obtaining unit 11 obtains a plurality of the representative colors. A difference vector calculation unit 21 in a pixel value replacement unit 12 determines an average color in a peripheral region of a processing target pixel in an input image to calculate the difference vector which is directed from the average color to a color of the processing target pixel and is on a color space. A representative color selector 22 determines the length of the difference vector calculated in a difference vector calculation unit 21. Then, when the length of the difference vector is longer than a given threshold, in the difference vector direction a representative color nearest to a straight line which passes the difference vector is selected. On the contrary, when being shorter, a representative color nearest to the color of the processing target pixel on the color space is selected. A replacement unit 23 replaces the color of the processing target pixel by the representative color selected by the representative color selection unit 22. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  Conventionally, limited color processing for reducing the number of colors used in an image has been performed. With this limited color processing, when various noises and unevenness included in the image, for example, when the image is a document image read by an image reading device, the document printing unevenness, scanning noise at the time of reading and MTF are read. When there is a deterioration or handwritten portion, handwriting unevenness can be reduced. Further, when the image is compressed, compression noise can be reduced and the compression rate can be improved.

  The limited color processing is performed by extracting a representative color from the image and replacing the color of each pixel with one of the representative colors. As a method of replacing with a representative color, for example, as in Non-Patent Document 1, a method of calculating a difference between the color of a pixel to be replaced and each representative color and replacing it with a representative color that minimizes the difference is known. Yes.

P. Heckbert, “Color-Image-Quantation-for-frame-buffer-Display”, Computer-Graphics, Vol. 16, no. 3, p297-304, 1982

  The present invention has been made in view of the above-described circumstances, and provides an image processing apparatus and an image processing program capable of performing limited color processing that suppresses information loss and discoloration by replacement with a representative color. It is the purpose.

  The invention according to claim 1 of the present invention selects one of the representative color acquisition means for acquiring a plurality of representative colors and the representative color acquired by the representative color acquisition means for the color of each pixel of the input image. A pixel value replacement unit that replaces a pixel color with a selected representative color, and the pixel value replacement unit includes a difference from an average color of a peripheral region of the pixel to be processed in the input image to a color of the pixel to be processed A difference vector calculation means for calculating a vector; a representative color selection means for selecting a representative color closest to a straight line passing through the difference vector in the direction of the difference vector; and a color of the pixel to be processed by the representative color selection means. An image processing apparatus having a replacement unit that replaces a selected representative color.

  According to the second aspect of the present invention, when the representative color selecting means in the configuration according to the first aspect has a length of the difference vector equal to or less than a predetermined threshold value, the representative color selecting means An image processing apparatus is characterized in that a closest representative color is selected.

  The invention according to claim 3 of the present application selects one of the representative color acquisition means for acquiring a plurality of representative colors and the representative color acquired by the representative color acquisition means for the color of each pixel of the input image. A pixel value replacement unit that replaces a pixel color with a selected representative color, and the pixel value replacement unit includes a difference from an average color of a peripheral region of the pixel to be processed in the input image to a color of the pixel to be processed A difference vector calculation means for calculating a vector, and a first representative color closest to a straight line passing through the difference vector in a direction of the difference vector and a second representative color closest to the color of the pixel to be processed Representative color selection means for selecting based on the length of the difference vector as a representative color to be replaced, and replacement means for replacing the pixel to be processed with the representative color to be replaced selected by the representative color selection means. An image processing apparatus according to claim.

  The invention according to claim 4 selects one of the representative color acquisition means for acquiring a plurality of representative colors and the representative color acquired by the representative color acquisition means for the color of each pixel of the input image. A pixel value replacement unit that replaces the pixel color with the selected representative color, and the pixel value replacement unit is a distance between a line passing through the background color and each representative color in the input image and the color of the pixel to be processed. An image processing apparatus comprising: a distance calculating unit that calculates a color; and a replacing unit that replaces the color of the pixel to be processed with a representative color corresponding to a straight line having the smallest distance calculated by the distance calculating unit. is there.

  The invention according to claim 5 of the present application is characterized in that the representative color acquisition means in the configuration according to any one of claims 1 to 4 extracts the representative color from an input image. It is.

  The invention according to claim 6 of the present application is characterized in that the representative color acquisition means in the configuration according to any one of claims 1 to 4 acquires a color designated by a user as the representative color. An image processing apparatus.

  A seventh aspect of the present invention is an image processing program that causes a computer to execute the function of the image processing apparatus according to any one of the first to sixth aspects.

  According to the invention described in claim 1 of the present application, it is possible to perform limited color processing that suppresses information loss and discoloration by replacement with a representative color as compared with the case where the configuration of the present invention is not provided. .

  According to the invention described in claim 2 of the present application, discoloration caused by replacement with a representative color can be further suppressed as compared with the invention described in claim 1 of the present application.

  Also in the inventions according to claims 3 and 4 of the present application, compared to the case where the configuration of the present invention is not provided, the limited colorization processing that suppresses information loss and discoloration by replacement with a representative color is performed. It can be carried out.

  According to the invention described in claim 5 of the present application, in addition to the effect of the invention described in any one of claims 1 to 4, the representative color to be replaced can be automatically extracted. According to the invention described in claim 6, in addition to the effect of the invention described in any one of claims 1 to 4, the user can arbitrarily set a representative color to be replaced. .

  According to the invention described in claim 7 of the present application, the effect of the invention described in any one of claims 1 to 6 of the present application can be obtained.

  FIG. 1 is a block diagram showing a first embodiment of the present invention. In the figure, 11 is a representative color acquisition unit, 12 is a pixel value replacement unit, 21 is a difference vector calculation unit, 22 is a representative color selection unit, and 23 is a replacement unit.

  The representative color acquisition unit 11 acquires a plurality of representative colors. The method for obtaining the representative color is arbitrary. For example, the representative color can be extracted from the input image, or the color designated by the user can be obtained as the representative color.

  The pixel value replacement unit 12 sequentially sets each pixel of the input image as a processing target pixel, selects one of the representative colors acquired by the representative color acquisition unit 11 for the color of the processing target pixel, and sets the color of the processing target pixel. Replace with selected representative color. In this example, the pixel value replacement unit 12 includes a difference vector calculation unit 21, a representative color selection unit 22, and a replacement unit 23.

  The difference vector calculation unit 21 obtains an average color of the peripheral region of the processing target pixel in the input image, and calculates a difference vector in the color space from the average color to the color of the processing target pixel.

  The representative color selection unit 22 determines the length of the difference vector calculated by the difference vector calculation unit 21. If the length of the difference vector is longer than a predetermined threshold, the representative color selection unit 22 determines the difference vector in the direction of the difference vector. The representative color closest to the straight line is selected. If the length of the difference vector is equal to or smaller than a predetermined threshold, a representative color closest to the color of the processing target pixel is selected in the color space.

  The replacement unit 23 replaces the color of the processing target pixel with the representative color selected by the representative color selection unit 22.

  The above configuration will be further described. The representative color acquisition unit 11 acquires a plurality of representative colors, but the method for acquiring the representative colors is arbitrary. When the user designates a representative color, for example, by displaying an input image and instructing several points, the color of the designated point may be acquired as the representative color. Alternatively, a representative color may be selected from a color palette, or a representative color may be designated by inputting a value.

  A representative color can also be extracted from the input image. An example is shown below. FIG. 2 is a block diagram showing an example of the representative color extraction unit, and FIG. 3 is an explanatory diagram of an example of the operation. In the figure, 31 is a color histogram calculation unit, 32 is a color value candidate selection unit, and 33 is a representative color determination unit.

  The color histogram calculation unit 31 sets a region of a predetermined size including a pixel to be processed as a target block, and calculates a color histogram of each pixel in the target block. In FIG. 3A, a portion surrounded by a thick line is taken as an example of the block of interest, and a histogram of the color of pixels within this range is calculated. The calculated histogram is a frequency value in, for example, a three-dimensional color space as shown in FIG.

  The color value candidate selection unit 32 selects a representative color candidate (color value candidate) that replaces the color of the processing target pixel. As a process for that purpose, first, a histogram in a certain partial color space is second-order differentiated from a position in the color space corresponding to the color of the pixel to be processed, and the color of the frequency convex portion (frequency becomes the local maximum value). Color). The color of the convex portion having the obtained frequency is set as a color value candidate.

  A black circle in FIG. 3B is set to a position corresponding to the color of the pixel to be processed, and a three-dimensional area (partial color space) having the black circle as a vertex is set as an object of secondary differentiation. In FIG. 3C, only the three-dimensional region that is the target of the secondary differentiation is extracted and shown, and the black circle indicates a color whose frequency becomes a convex portion by the secondary differentiation. This color is a color value candidate.

  The representative color determination unit 33 determines a representative color from the color value candidates selected by the color value candidate selection unit 32. Several methods can be considered as the determination method. For example, among the color value candidates, a color value candidate having a maximum frequency value, a color difference with a color of a pixel to be processed, a color value having high brightness, and the like can be selected. Of course, these may be combined or selected according to other conditions. Alternatively, the representative color can be determined by various methods, such as determining an intermediate color among a plurality of color value candidates as a representative color, or determining by weighting from the relationship with the color of the pixel to be processed.

  Note that the method of acquiring the representative color from the input image in the representative color acquisition unit 11 is not limited to the method illustrated in FIGS. 2 and 3, and it goes without saying that another method may be used.

  When the representative color is acquired by the representative color acquisition unit 11, the pixel value replacement unit 12 sequentially replaces each pixel of the input image as a processing target pixel, and replaces the color of the processing target pixel with one of the representative colors. By this processing, the color used in the image can be limited to the representative color.

  FIG. 4 is an explanatory diagram illustrating an example of the operation of the pixel value replacement unit according to the first embodiment of the present invention, and FIG. 5 is a flowchart illustrating an example of the operation. As a process for replacing the color of the processing target pixel with one of the representative colors, first, in the difference vector calculation unit 21, an average color of the peripheral area of the processing target pixel in the input image is obtained in S41, and the processing target is calculated from the average color A difference vector on the color space to the color of the pixel is calculated in S42. In FIG. 4A, a certain color space is shown, and an internal black circle indicates the representative color acquired by the representative color acquisition unit 11. Further, a point marked with “X” in the circle indicates the color of the processing target pixel, and a circle indicates the average color of the peripheral region on the input image of the processing target pixel. Then, a difference vector from the average color indicated by ◯ to the color of the processing target pixel is obtained. This vector is indicated by an arrow line.

  When the average color is close to the color of the processing target pixel, for example, it is considered that the color of the processing target pixel is similar to the surrounding color and the color is a flat region. Conversely, if the average color and the color of the pixel to be processed are separated, the color of the pixel to be processed is significantly different from the surrounding colors, and it is necessary to replace with a representative color that can be distinguished from the surrounding colors. is there. In addition, the difference vector indicates in which color direction the color of the pixel to be processed is different from the average color. In the direction of the difference vector, a color space area away from the average color is displayed on the document. It is possible that the original color exists.

  Based on such a viewpoint, the representative color selection unit 22 selects a representative color that should replace the color of the processing target pixel. In S43, it is determined whether or not the length of the difference vector is equal to or less than a predetermined threshold. If the length of the difference vector is longer than the predetermined threshold value, a representative color closest to the straight line passing through the difference vector is selected in the direction of the difference vector in S44. That is, the distance between the straight line passing through the difference vector and each representative color is obtained, and the representative color with the shortest distance is selected. FIG. 4B shows perpendicular lines from the representative color to the straight line for some representative colors close to the straight line passing through the difference vector, and the representative color having the shortest perpendicular length is selected. As a result, representative colors which are different from the representative colors to be replaced are selected to prevent disappearance, and the color change is minimized by selecting the representative color closest to the direction of the difference vector. .

  If the length of the difference vector is equal to or smaller than the predetermined threshold value, a representative color closest to the color of the processing target pixel is selected in S45. This state is shown in FIG. The surrounding pixels are also expected to have a short difference vector length, whereby a representative color similar to that of the surrounding pixels is selected in a portion where the color is flat.

  When the representative color is selected in S44 or S45, the color of the pixel to be processed is replaced with the selected representative color by the replacement unit 23 in S46. By executing the processes of S41 to S46 in order with each pixel of the input image as the processing target pixel, the color of each pixel of the input image is replaced with one of the representative colors, and the used color is represented. Can be limited to colors.

  In this example of operation, the representative color closest to the color of the processing target pixel is selected when the length of the difference vector is short. However, the processing of S44 is performed for all the processing target pixels without performing the determination of S43. The representative color may be selected by the above.

  Next, a second embodiment of the present invention will be described. The configuration of the second embodiment of the present invention is the same as that of the first embodiment shown in FIG. 1, and the operation of the representative color selection unit 22 of the pixel value replacement unit 12 is different. . Therefore, description of the same parts as those in the first embodiment will be omitted, and different parts will be mainly described.

  The representative color selection unit 22 in the second embodiment obtains the representative color closest to the straight line passing through the difference vector as the first representative color C1 in the direction of the difference vector calculated by the difference vector calculation unit 21. Further, the representative color closest to the color of the processing target pixel is obtained as the second representative color C2. Then, one of the first representative color C1 and the second representative color C2 is selected as a representative color that should replace the color of the processing target pixel. The method for selecting any one of the representative colors is arbitrary, but here the selection is made based on the length of the difference vector. As described above, when the length of the difference vector is long, the color of the processing target pixel is often a color different from the surroundings, and the disappearance can be prevented by selecting a representative color different from the surroundings. desired. When the length of the difference vector is short, it is assumed that the color is a flat region color, and it is desired to select a representative color similar to the surroundings. Therefore, based on the length of the difference vector, the first representative color C1 is selected when the length of the difference vector is long, and the second representative color when the length of the difference vector is short. What is necessary is just to comprise so that C2 may be selected.

As an example of selection, when the distance from the color of the processing target pixel to the first representative color C1 is D1, the distance from the color of the processing target pixel to the second representative color C2 is D2, and α is a constant, Formula α × D1 / (length of difference vector) ≦ D2
If this conditional expression is satisfied, the first representative color C1 can be selected. Otherwise, the second representative color C2 can be selected. Of course, the present invention is not limited to this conditional expression, and any one of various conditions can be selected. The distance D1 may be a distance between a straight line passing through the difference vector and the representative color C1.

  FIG. 6 is an explanatory diagram illustrating an example of the operation of the pixel value replacement unit according to the second embodiment of the present invention, and FIG. 7 is a flowchart illustrating an example of the operation. As a process for replacing the color of the processing target pixel with one of the representative colors by the pixel value replacement unit 12, first, the difference vector calculation unit 21 obtains the average color of the peripheral region of the processing target pixel in the input image in S51. A difference vector in the color space from the average color to the color of the processing target pixel is calculated in S52. In FIG. 6, as in FIG. 4, in a certain color space, a black circle indicates a representative color, a point marked with “X” indicates the color of the pixel to be processed, and “◯” indicates the periphery of the target pixel on the input image. The average color of the area is shown. Then, a difference vector from the average color indicated by ◯ to the color of the processing target pixel is obtained. This vector is indicated by an arrow line.

  In S53, the representative color closest to the straight line passing through the difference vector is selected in the direction of the difference vector. That is, the distance between the straight line passing through the difference vector and each representative color is obtained, and the representative color having the shortest distance is obtained as the first representative color C1. Further, a distance D1 between the color of the pixel to be processed and the first representative color C1 is obtained. In step S54, the representative color closest to the color of the processing target pixel is obtained as the second representative color C2. Further, the distance between the color of the pixel to be processed and the second representative color C2 is obtained as D2. Note that either the process for obtaining the first representative color C1 in S53 or the process for obtaining the second representative color C2 in S54 may be performed first or in parallel. The distance D1 may be a distance between a straight line passing through the difference vector and the representative color C1.

  The first representative color C1 and the second representative color C2 obtained in S53 and S54 are also shown as C1 and C2 in FIG. In the following processing, one of the obtained first representative color C1 and second representative color C2 is selected, and the color of the processing target pixel is replaced.

  In S55, it is determined which of the first representative color C1 and the second representative color C2 is selected according to a predetermined condition based on the length of the difference vector. For example, it can be determined by whether or not the above conditional expression is satisfied. If the condition is satisfied, the first representative color C1 is selected in S56. If the condition is not satisfied, the second representative color C2 is selected in S57.

  When the representative color is selected in S56 or S57, the replacement unit 23 replaces the color of the processing target pixel with the selected representative color in S58. By executing the processes of S51 to S58 in order for each pixel of the input image as the processing target pixel, the color of each pixel of the input image is replaced with one of the representative colors, and the used color is represented. Can be limited to colors.

  In this way, the representative color to be replaced can be switched in accordance with the length of the difference vector. If the color of the pixel to be processed is different from the color of surrounding pixels, the difference is made as much as possible and on the document. Select a representative color that is close to the original color, and if the color of the pixel to be processed is the same color as the surrounding pixels, select the representative color so that it is the same as the surrounding pixels. Can be replaced.

  FIG. 8 is a block diagram showing a third embodiment of the present invention. In the figure, the same parts as those in FIG. Reference numeral 24 denotes a distance calculation unit. In the third embodiment, the representative color is determined based on the distance between the straight line passing through the background color and each representative color and the color of the processing target pixel without using the difference vector used in the above two embodiments. An example of selecting and replacing is shown.

  The pixel value replacement unit 12 in the third embodiment includes a distance calculation unit 24 and a replacement unit 23. The distance calculation unit 24 calculates the distance between the straight line passing through the background color and each representative color in the input image and the color of the processing target pixel. The background color in the input image can be obtained by various known methods. Alternatively, white may be used instead of the background color.

  The replacement unit 23 replaces the color of the processing target pixel with a representative color corresponding to the straight line having the smallest distance calculated by the distance calculation unit 24.

  FIG. 9 is an explanatory diagram illustrating an example of the operation of the pixel value replacement unit according to the third embodiment of the present invention. In FIG. 9, the background color of the input image is indicated by a white circle, each representative color acquired by the representative color acquisition unit 11 is indicated by a black circle, and the color of the pixel to be processed is indicated by ◯. As shown in FIG. 9, a straight line passing through each representative color and background color is considered, and a distance between the straight line and the color of the processing target pixel is obtained. This distance is the length of the perpendicular line from the color of the pixel to be processed to the straight line.

  The shorter the distance between the straight line passing through each representative color and the background color and the color of the processing target pixel, the more similar the color tendency between the representative color and the color of the processing target pixel. Therefore, in the third embodiment, the color of the processing target pixel is replaced with the representative color corresponding to the straight line having the shortest distance between the straight line passing through the background color and each representative color and the color of the processing target pixel. This prevents large discoloration. For example, when the representative color closest to the color of the pixel to be processed is selected, the representative color may be replaced with a representative color that differs greatly. However, in the third embodiment, the straight line indicates the direction of the color having a similar tendency, and by selecting a representative color close to the straight line, the color can be replaced with a color having a similar tendency.

  FIG. 10 is an explanatory diagram of an example of a computer program, a storage medium storing the computer program, and a computer when the functions of the image processing apparatus of the present invention are realized by a computer program. In the figure, 61 is a program, 62 is a computer, 71 is a magneto-optical disk, 72 is an optical disk, 73 is a magnetic disk, 74 is a memory, 81 is a CPU, 82 is an internal memory, 83 is a reading unit, 84 is a hard disk, 85, 86 is an interface, and 87 is a communication unit.

  Part or all of the functions of the respective units of the image processing apparatus of the present invention described in the above embodiments can be realized by a program 61 that can be executed by a computer. In that case, the program 61 and the data used by the program can be stored in a computer-readable storage medium. A storage medium causes a state of change in energy such as magnetism, light, electricity, etc. to the reading unit 83 provided in the hardware resource of a computer according to the description content of the program, and a signal corresponding thereto. In this format, the program description can be transmitted to the reading unit 83. For example, a magneto-optical disk 71, an optical disk 72 (including a CD and a DVD), a magnetic disk 73, a memory 74 (including an IC card and a memory card), and the like. Of course, these storage media are not limited to portable types.

  The program 61 is stored in these storage media, and the program 61 is read from the computer and stored in the internal memory 82 or the hard disk 84 by, for example, mounting these storage media on the reading unit 83 or the interface 85 of the computer 62. By executing the program 61 by the CPU 81, the function of the image processing apparatus of the present invention can be realized. Alternatively, the program 61 is transferred to the computer 62 via a network or the like, and the computer 62 receives the program 61 by the communication unit 87 and stores it in the internal memory 82 or the hard disk 84. You may implement | achieve the function of the image processing apparatus of invention. In addition, the computer 62 can be connected to various devices via the interface 86. For example, a display device for displaying information and an input device for inputting information by the user are also connected.

  Of course, some functions may be configured by hardware, or all may be configured by hardware. Alternatively, it can be configured as a program including the present invention together with other configurations. For example, an apparatus including an image reading apparatus such as a copying machine or an image forming apparatus may be configured as a single program together with a control program, and may be configured to perform limited color processing on an image read by the image reading apparatus. it can. Of course, in the case of application to other purposes, integration with a program for that purpose is also possible. Needless to say, the computer 62 may have one or both of the image reading apparatus and the image forming apparatus, or another structure.

It is a block diagram which shows the 1st Embodiment of this invention. It is a block diagram which shows an example of a representative color extraction part. It is explanatory drawing of an example of operation | movement in an example of a representative color extraction part. It is explanatory drawing of an example of operation | movement of the pixel value replacement part in the 1st Embodiment of this invention. It is a flowchart which shows an example of operation | movement of the pixel value replacement part in the 1st Embodiment of this invention. It is explanatory drawing of an example of operation | movement of the pixel value replacement part in the 2nd Embodiment of this invention. It is a flowchart which shows an example of operation | movement of the pixel value replacement part in the 2nd Embodiment of this invention. It is a block diagram which shows the 3rd Embodiment of this invention. It is explanatory drawing of an example of operation | movement of the pixel value replacement part in the 3rd Embodiment of this invention. FIG. 11 is an explanatory diagram of an example of a computer program, a storage medium storing the computer program, and a computer when the functions of the image processing apparatus of the present invention are realized by a computer program.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Representative color acquisition part, 12 ... Pixel value substitution part, 21 ... Difference vector calculation part, 22 ... Representative color selection part, 23 ... Replacement part, 24 ... Distance calculation part, 31 ... Color histogram calculation part, 32 ... Color value Candidate selection unit 33 ... representative color determination unit 61 ... program 62 ... computer 71 ... magneto-optical disc 72 ... optical disc 73 ... magnetic disc 74 ... memory 81 ... CPU 82 ... internal memory 83 ... read 84, hard disk, 85, 86 ... interface, 87 ... communication unit.

Claims (7)

  Representative color acquisition means for acquiring a plurality of representative colors, and selecting one of the representative colors acquired by the representative color acquisition means for each pixel color of the input image and replacing the pixel color with the selected representative color Pixel value replacement means, and the pixel value replacement means calculates a difference vector from the average color of the peripheral area of the pixel to be processed in the input image to the color of the pixel to be processed; Representative color selection means for selecting a representative color closest to a straight line passing through the difference vector in the direction of the difference vector, and replacement means for replacing the color of the pixel to be processed with the representative color selected by the representative color selection means. An image processing apparatus comprising:   The said representative color selection means selects the representative color closest to the color of the pixel to be processed when the length of the difference vector is not more than a predetermined threshold value. Image processing device.   Representative color acquisition means for acquiring a plurality of representative colors, and selecting one of the representative colors acquired by the representative color acquisition means for each pixel color of the input image and replacing the pixel color with the selected representative color Pixel value replacement means, and the pixel value replacement means calculates a difference vector from the average color of the peripheral area of the pixel to be processed in the input image to the color of the pixel to be processed; One of the first representative color closest to the straight line passing through the difference vector in the direction of the difference vector and the second representative color closest to the color of the pixel to be processed is used as a representative color to be replaced. An image processing apparatus comprising: a representative color selecting unit that selects based on a length; and a replacement unit that replaces the pixel to be processed with a representative color to be replaced selected by the representative color selecting unit.   Representative color acquisition means for acquiring a plurality of representative colors, and selecting one of the representative colors acquired by the representative color acquisition means for each pixel color of the input image and replacing the pixel color with the selected representative color A pixel value replacing unit, the pixel value replacing unit calculating a distance between a line passing through a background color and each representative color in the input image and a color of the pixel to be processed; An image processing apparatus comprising: replacement means for replacing the color of a target pixel with a representative color corresponding to a straight line having the smallest distance calculated by the distance calculation means.   The image processing apparatus according to claim 1, wherein the representative color acquisition unit extracts the representative color from the input image.   The image processing apparatus according to claim 1, wherein the representative color acquisition unit acquires a color designated by a user as the representative color. An image processing program for causing a computer to execute the function of the image processing apparatus according to any one of claims 1 to 6.

Images