JP2009225308A - Image processing apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus capable of executing see-through reduction processing without causing scale-up of the apparatus and cost increase without impairing the color of a base A. <P>SOLUTION: The image processing apparatus has: an image data input section for inputting image data into the apparatus; an image data analyzing section 85 for determining the color of the base A in the input image data; and a color space changing section 86 for executing see-through reduction processing by mapping pixels in image data of a color in a predetermined range D in a color space to the determined base A from the color of the base A determined by the image data analyzing section 85. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image processing apparatus that processes input image data. The present invention also relates to an image forming apparatus that forms an image based on image data processed by the image processing apparatus.

  In recent years, in order to save paper and save resources, image formation (printing) is often performed on both sides of the paper. However, when a two-sided printed document is read by an image reading apparatus such as a copier or a scanner, there may be a show-through in which the image on the back side shows through not only the reading side but also the image data. That is, when the front image is read, the back image may be converted into data. In particular, show-through tends to occur when the paper is thin.

  Such show-through is unnecessary because it deteriorates the visibility of the reading surface (front surface) and reduces the fidelity of the image data to the document. That is, since the quality of the read image data is deteriorated, it is necessary to remove the show-through. Therefore, Patent Documents 1 and 2 describe inventions that remove show-through from image data. Specifically, Patent Document 1 discloses an image reading unit, an image forming unit, a density detecting unit, a peak detecting unit for detecting one or a plurality of frequency maximum positions from a density histogram, and an image density adjusting unit. And detecting three or more maximum positions in the histogram to detect the image peak position, the background peak position, and the show-through peak position, and the image density adjusting means detects the image peak position and the show-through with the highest density. An image forming apparatus that performs density adjustment processing using an intermediate position with respect to a peak position as a threshold is described (refer to Patent Document 1: Claims 1, 3 and 4).

Japanese Patent Application Laid-Open No. 2004-228561 is a copying apparatus that reads the first and second sides of an original, an image memory that individually stores image data of the first and second sides, and a first one in the first side. First comparison means for comparing image data for pixels with a first threshold value for density; image data for second pixels at positions opposite to the first pixels in the second surface; Or a comparison result of the first and second comparison means for comparing the image data relating to the color tone of both the second pixel and the first pixel. Based on this, there is a copying apparatus provided with image data processing means for performing processing that makes the image data of the first pixel unnecessary.
JP-A-10-257325 Japanese Patent Laid-Open No. 07-087295

  As a countermeasure against show-through generally performed, there is a method of skipping an image portion having a certain luminance or less and removing the show-through image with a constant background luminance. However, if the image is skipped uniformly, the original image on the original surface may be lost.

  Further, according to the invention described in Patent Document 1, it is considered that there is a case where the show-through can be erased. However, although the invention of Patent Document 1 determines the threshold value and performs density adjustment processing by binarization (see paragraph 0018 and the like), it targets monochrome images and cannot handle color images. For example, even if it corresponds to color, an image of the pixel portion below the threshold value is not formed, so if the calculated threshold density is high, most of the original image on the original surface may be lost. There is. Further, when the show-through erase process is performed on an image with relatively little show-through, the threshold value may be determined after the show-through peak position is erroneously detected, which is considered to be inferior in accuracy.

  Further, in both the countermeasures for show-through commonly performed and the invention described in Patent Document 1, if the background portion of the image data is not white but has some color, if the show-through elimination processing is performed, a colored background There is a problem that the color of the portion is lost and the print result of the image data may be completely different.

  Further, although it is considered possible to perform the show-through prevention processing even in the invention described in Patent Document 2, a configuration for simultaneously reading the front and back of the document is necessary only for preventing the show-through (see Patent Document 2: 0016, etc.). In addition, more members such as an image memory and comparison means are added to the copying apparatus. Therefore, there is a problem that the copying machine is inevitably increased in size and manufacturing cost. Further, the amount of image data to be handled is simply doubled, and the processing amount of the image data is also increased. Furthermore, it is necessary to accurately align the image data on the front and back sides of the document. Without this processing, the show-through cannot be erased appropriately.

  The present invention has been made in view of the above-described problems of the prior art, and in the image processing apparatus and the image forming apparatus, by adding a special configuration, the size of the apparatus is increased, and the cost is not increased. It is an object to perform a show-through reduction process without impairing the color of the image.

  The invention according to claim 1 is determined by an image data input unit for inputting image data to the apparatus, an image data analysis unit for determining a background color in the input image data, and the image data analysis unit. A color space changing unit that maps a pixel in image data having a color within a predetermined range in the color space from the background color to the determined background color and performs a show-through reduction process.

  According to this configuration, the image data analysis unit determines the color of the background of the input image data, and the color space change unit matches the pixels in the image data having a color within a predetermined range from the determined color of the background. Since the show-through reduction processing is performed by mapping to the color, the background color is not greatly impaired even if the show-through reduction processing is performed. In addition, the show-through reduction process can be realized without preparing an expensive image reading apparatus that can simultaneously read both sides of the document. Moreover, the color of the background is surely made uniform, and the visibility of the image is increased.

  According to a second aspect of the present invention, in the image processing apparatus according to the first aspect, the image data analysis unit is configured to perform the entire image data based on the value of each channel as the color information of each pixel of the input image data. Alternatively, for some pixels, a histogram generation unit that generates a histogram of each channel and a mode value determination unit that determines a mode value in each generated histogram, and a combination of the mode values determined It was decided to determine the color of the background.

  According to this configuration, the histogram generation unit generates a histogram of each channel, the mode value determination unit determines the mode value in each channel, and determines the combination of mode values as the background color. The color of the background such as colored paper can be determined appropriately. Therefore, the show-through reduction process can be reliably performed without impairing the background color.

  According to a third aspect of the present invention, in the image processing apparatus according to the first aspect, the image data analysis unit includes each pixel within a predetermined area from the edge of the image data corresponding to a blank portion of the input image data. An average value calculation unit that calculates an average value of each channel value as color information, and a combination of the average values calculated by the average value calculation unit is determined as a background color.

  According to this configuration, the average value calculation unit calculates the average value of each channel in the predetermined area from the edge of the image data, and determines the combination of the calculated average values as the background color. The color of can be determined appropriately. Therefore, the show-through reduction process can be reliably performed without impairing the background color.

  According to a fourth aspect of the present invention, in the image processing apparatus according to any one of the first to third aspects, with respect to each channel, the maximum value ± 0.5 that each channel can take, centered on the determined value of each channel of the background. The color space ranging from% to ± 5% is set to the predetermined range.

  According to this configuration, the color space up to a value different from the background color in the range of ± 0.5% to ± 5% at the maximum value in each channel of the image data having the predetermined range input is defined as the predetermined range. Therefore, mapping for reducing the number of colors can be appropriately performed. In other words, if the color is changed to a color exceeding ± 5%, it will be changed to a background color more than necessary. Therefore, by limiting the color to a range of ± 5% at the maximum, the show-through reduction processing and the document reproducibility Both can be achieved.

  According to a fifth aspect of the present invention, the image processing apparatus according to any one of the first to fourth aspects further comprises an operation input unit for performing operation and input of the apparatus, and the operation input unit changes the mode of the apparatus to the show-through. Transition to the show-through reduction mode, which is a mode for performing reduction processing, or accepting an input to cancel the show-through reduction mode, and only when the apparatus is in the show-through reduction mode, the image data analysis unit and the color space The change part was supposed to function.

  According to this configuration, the user can set whether or not to perform the show-through reduction process, and the convenience for the user can be improved.

  According to a sixth aspect of the present invention, in the image processing apparatus of the fifth aspect, the operation input unit accepts a plurality of levels of intensity setting of the show-through reduction processing, and the color space changing unit sets the intensity setting. Based on this, the range of the predetermined range is changed according to the stage.

  According to this configuration, since the user can set the strength of the show-through reduction processing, the show-through reduction processing can be set in consideration of the thinness of the read original sheet, the characteristics of the scanner that performs the reading, and the like. Therefore, user convenience can be improved.

  According to a seventh aspect of the present invention, in the image processing apparatus according to the first to sixth aspects, the image data input unit reads an image data of a document and generates image data, and / or The interface unit accepts transmission of image data from an external terminal.

  According to this configuration, the show-through reduction processing can be performed on, for example, image data generated based on a document by the image reading unit or image data transmitted from an external terminal.

  According to an eighth aspect of the present invention, in the image processing apparatus according to the first to seventh aspects, the image data input unit inputs RGB format image data to the apparatus.

  According to this configuration, since the image data input unit inputs RGB image data to the apparatus, it is possible to perform a show-through reduction process on frequently used RGB image data.

  According to a ninth aspect of the present invention, there is provided an image forming unit for forming an image based on image data, and the image processing apparatus according to any one of the first to eighth aspects, wherein the back side by the color space changing unit. The image forming unit forms an image on the recording medium based on the image data after the image reduction process.

  According to this configuration, the image forming apparatus forms an image on a recording medium such as paper on the basis of the image data after the show-through reduction process, so that it is possible to obtain a print result in which the show-through is eliminated.

  As described above, according to the present invention, as in the prior art, by providing a threshold value for density and brightness, and by uniformly invalidating pixels below or above the threshold value, the show-through effect is replaced with a color such as white. Since the reduction process is not performed, the background color is not impaired even when the show-through reduction process is performed on image data obtained by reading a colored paper or a document with a colored background. Therefore, conventionally, the show-through reduction processing has a problem with the fidelity to the original. However, according to the present invention, the fidelity to the original in the show-through reduction processing can be dramatically increased.

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. However, each element such as configuration and arrangement described in each embodiment does not limit the scope of the invention and is merely an illustrative example.

  First, an outline of the multifunction machine 1 (corresponding to an image forming apparatus) according to the first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic front cross-sectional view of a multifunction machine 1 according to a first embodiment of the present invention. FIG. 2 is a partially enlarged schematic cross-sectional view of the image forming unit 2 according to the first embodiment of the present invention.

  As shown in FIG. 1, the uppermost document transport device 3 of the multifunction machine 1 includes a document tray 31, a plurality of document transport roller pairs 32, a document transport path 33, and a document discharge tray 34. Documents are sent one by one to the document transport path 33. The fed document is automatically and continuously conveyed so as to be in contact with the feed reading contact glass 46 a on the upper surface of the image reading unit 4. Further, the document conveying device 3 can be lifted upward by a fulcrum (not shown) provided on the back side of the paper surface. For example, a document such as a book is placed on the placement reading contact glass 46 b on the upper surface of the image reading unit 4. You can also

  The image reading unit 4 is unitized as a scanner. The image reading unit 4 irradiates a document with light, reads the document based on the reflected light, and generates image data. Therefore, a moving frame 43 having an exposure lamp 41 and a plurality of mirrors 42, a lens 44, an image sensor 45 (for example, a CCD) having a light receiving element arranged in a line, and the like are provided to optically scan the document. When the original is read by the original conveying device 2, the moving frame 43 is fixed below the feed reading contact glass 46a. On the other hand, when the original on the placement reading contact glass 46b is read, the moving drum 43 Reading is performed by moving the moving frame 43 in the horizontal direction by winding the wire 48 by rotation driving (the moving frame 43 and the wire 48 are connected).

  In the generation of image data, the reflected light of the document is imaged by the lens 44, and the image sensor 45 outputs a current (voltage) for each pixel according to the intensity of the reflected light. The image sensor 45 of the multifunction machine 1 according to this embodiment is mounted with a color-compatible one. Then, the output current (voltage) of the image sensor 45 is amplified by the amplification unit 49a (see FIG. 3), and the A / D conversion unit 49b (see FIG. 3) performs quantization. For example, the A / D conversion unit 49b performs quantization to a total of 24 bits per pixel in the case of black and white image data and 8 bits per pixel in the case of color (Red = 8 bits, Green). = 8 bits, Blue = 8 bits, each taking a value of 0 to 255, 256 gradations). That is, the image reading unit 4 reads a document, generates RGB format image data, and inputs the image data to a control unit 7 and an image processing unit 8 described later.

  The image forming unit 2, the sheet supply unit 50, the sheet conveyance path 52, the intermediate transfer unit 60, and the fixing device 67 are provided below the image reading unit 4. The sheet supply unit 50 stores sheets such as paper of various sizes (A4, B4, etc.), and supplies the sheets at the time of image formation. The sheet conveyance path 52 conveys the supplied sheet to the discharge tray 53. Therefore, a guide plate 54 for guidance, a plurality of conveyance roller pairs 55, and the like are provided in the sheet conveyance path 52.

  The intermediate transfer unit 60 is provided below the image forming unit 2. The intermediate transfer belt 61 is stretched between a driving roller 62, a driven roller 63, and four primary transfer rollers 64 so that the upper outer peripheral surface and each photosensitive drum 21 are in contact with each other. Driving means (not shown) such as a motor and a gear is connected to the driving roller 62, and the intermediate transfer belt 61 rotates in the clockwise direction (arrow direction) in FIG. The primary transfer rollers 64 are rotatably arranged one by one so as to face the respective photosensitive drums 21, and a voltage of a predetermined magnitude is applied to the primary transfer rollers 64 at the appropriate timing so that each color is changed. The toner image is primarily transferred from each photosensitive drum 21 to the intermediate transfer belt 61. At the time of the primary transfer, the color toner images are superimposed to form a color toner image.

  The toner image on the intermediate transfer belt 61 is secondarily transferred to the sheet. Specifically, when the sheet and the toner image enter the nip between the secondary transfer roller 65 and the intermediate transfer belt 61 which are opposed to the driving roller 62 and abut against the intermediate transfer belt 61 and are rotatably supported, a predetermined amount is obtained. A voltage is applied to the secondary transfer roller 65, and the toner image is secondarily transferred to the sheet. The belt cleaning device 66 removes residual toner from the intermediate transfer belt 61 and cleans it. The fixing device 67 fixes the toner image transferred to the sheet. When the sheet passes through the fixing device 67, the toner is melted and heated, and the toner image is fixed on the sheet.

  Next, the image forming unit 2 will be described with reference to FIGS. The image forming unit 2 forms a toner image based on image data of an image to be formed. As shown in FIG. 1, the image forming unit 2 includes four image forming units 20K (forms a black toner image), 20C (forms a cyan toner image), 20M (forms a magenta toner image), 20Y (forms a yellow toner image) and an LSU 22 (Laser Scanning Unit) as an exposure device that performs exposure with light based on image data and forms an electrostatic latent image on each photosensitive drum 21. . Therefore, the multifunction device 1 of the present embodiment can form a color image. Each image forming unit 20 has a different toner color, but the basic configuration is the same. Therefore, in the following description, symbols K, Y, C, and M are omitted unless otherwise described.

  As shown in FIG. 2, each image forming unit 20 is supported rotatably in the direction of the arrow shown in FIG. 2, and extends in a direction perpendicular to the circumferential direction (= sheet conveying direction) of the intermediate transfer belt 61. It is rotationally driven in a predetermined direction by a motor (not shown) or the like. Around the photosensitive drum 21, a charging device 23 that uniformly charges the surface of the photosensitive drum 21 to a predetermined potential, and a developing device 24 that supplies toner to the electrostatic latent image and develops it (visualizes the image). A cleaning unit 25 for cleaning the surface of the photosensitive drum 21 is provided. With these configurations, a toner image is formed on the peripheral surface of the photosensitive drum 21.

  Next, the hardware configuration of the multifunction machine 1 will be described with reference to FIG. FIG. 3 is a block diagram illustrating an example of a hardware configuration of the multifunction machine 1 according to the first embodiment of the present invention.

  As shown in FIG. 3, the multifunction machine 1 according to the present embodiment includes a control unit 7 inside. The control unit 7 controls the overall operation of the multifunction machine 1 and includes, for example, a CPU 71, a storage unit 72, and the like.

  The CPU 71 is a central processing unit, and controls and calculates each unit of the multifunction machine 1 based on a control program stored in the storage unit 72 and developed. The storage unit 72 includes a storage device such as a ROM, a RAM, an HDD, or a flash ROM. The storage unit 72 stores a control program, control data, setting data, image data scanned by the image reading unit 4, and the like of the multifunction machine 1.

  Then, the control unit 7 includes the document conveyance device 3, the image reading unit 4, the sheet supply unit 50, the sheet conveyance path 52, the intermediate transfer unit 60, the image forming unit 2, the fixing device 67, and the image processing unit that constitute the multifunction device 1. 8 (details will be described later), an operation panel 9 (corresponding to an operation input unit, details will be described later) and the like, and based on the control program and data in the storage unit 72, the operation of each unit is performed so that image formation is performed appropriately. Control.

  Further, the multi-function device 1 can connect the user terminal 100 as an external computer via the interface unit 73 via a network or the like. For example, the multifunction device 1 can transmit image data read by the image reading unit 4 to the user terminal 100 (scanner function), and can perform image formation by receiving, for example, transmission of RGB format image data from the user terminal 100 (printer). function). Accordingly, the interface unit 73 has a function of inputting image data to the multi-function peripheral 1 and the image processing unit 8 and the like, like the image reading unit 4.

  Next, the image processing unit 8 will be described with reference to FIG. FIG. 4 is a block diagram for explaining the image processing unit 8 according to the first embodiment of the present invention.

  The image processing unit 8 according to the present embodiment performs image processing by performing operations related to image data, and performs a CPU 81 for performing various operations, a work RAM 82 as a work area for image data, and shifts image data as necessary. The circuit includes a shift memory 83 and a flash ROM 84, and other electronic components such as an ASIC (Application Specific Integrated Circuit), LSI, and various ICs as dedicated circuits for image processing. Note that the image processing unit 8 can be realized by software by storing an image processing program in the CPU 71 or the storage unit 72 of the control unit 7.

  With such a configuration of the image processing unit 8, for example, an image data analysis unit 85, a color space changing unit 86, an image data output unit 87, and the like are functionally realized. Note that image processing that can be executed by the image processing unit 8 includes various image processing such as γ correction processing and density conversion processing. In the present embodiment, the show-through reduction processing is mainly described, and other images are processed. As processing, a known technique is applied, and detailed description of other image processing is omitted.

  The image data analysis unit 85 determines the color of the background A in the input image data, and includes, for example, a histogram generation unit 85a and a mode value determination unit 85b. For example, the histogram generation unit 85a generates a histogram of each channel from the values of Red, Green, and Blue as the color information of each pixel, for example, for all pixels or a partial area of RGB format image data. To do. That is, the histogram generation unit 85a generates a histogram of each channel for the entire image data or a part of the pixels based on the value of each channel as the color information of each pixel of the input image data. The mode value determination unit 85b determines the most frequent value (mode value) in each generated histogram. Then, the combination of the determined mode values is determined as the color of the background A.

  The color space changing unit 86 can change the color space of the image data in the RGB format, for example, to a color space in the L * a * b format or an XYZ format as necessary. In the present invention, the color space changing unit 86 can perform mapping (color matching) by reducing the number of colors (compressing the color gamut) for a certain area in the color space. The image data output unit 87 performs processing when outputting the image data to the LSU 22, such as when outputting the image-processed data to the LSU 22 of the image forming unit 2 after converting the format of the image data to the CMYK format. I do. When the multifunction device 1 is used as a scanner, for example, image data after image processing is output to the control unit 7, the user terminal 100, or the like instead of the LSU 22. Further, in the present invention, the color space changing unit 86 performs pixel reduction in the image data of the color within the predetermined range D in the color space from the color of the background A determined by the image data analysis unit 85 as the show-through reduction processing. Mapping is performed on the determined color of the background A.

  Here, the image processing unit 8 or the like performs the show-through reduction processing on the image data input by the image reading unit 4 or the interface unit 73 as an image data input unit for inputting image data to the apparatus. Therefore, it can be said that the image reading unit 4, the interface unit 73, the image processing unit 8 and the like constitute the image processing apparatus according to the present invention. In other words, the multifunction machine 1 includes an image processing apparatus.

  Next, the show-through reduction processing of the multifunction machine 1 according to the first embodiment of the present invention will be described with reference to FIGS. 5A and 5B are explanatory diagrams for explaining the show-through reduction processing according to the first embodiment of the present invention. FIG. 5A shows an example of the outline of the processing, and FIG. 5B shows an example of the histogram. FIG. 6 is an explanatory diagram showing an example of color space change in the show-through reduction process according to the first embodiment of the present invention. In the following, the show-through reduction process such as the generation of a histogram will be described. However, in the MFP 1 and the image processing unit 8 of the present embodiment, the image process for reducing the show-through is performed on image data in RGB format. This will be described below. For example, when image data other than the RGB format is transmitted from the user terminal 100, the image data can be changed to the RGB format by the color space changing unit 86 or the like.

  First, the outline and effect of the show-through reduction process will be described with reference to FIG. Here, in the following description, a case where the background A (background) of the image data subjected to the show-through reduction process is a color will be described. In FIG. 5A, the background A in the image data is shaded to indicate that the background A is a color.

  In the state before the show-through reduction process in FIG. 5A, there is a show-through portion B (in FIG. 5A, the show-through portion B is indicated by an oval-shaped shade different from the background A). . The show-through portion B is, for example, an image on the back side that has been read as image data through the reading surface when a double-side printed document is read by the image reading unit 4. Due to this show-through, unnecessary information appears in the image. Therefore, the MFP 1 of the present embodiment performs a show-through reduction process on the image data, and performs a process of eliminating show-through as shown on the right side of FIG. Moreover, according to the show-through reduction processing by the multifunction device 1 of the present embodiment, the color of the background A is not impaired as in the conventional case.

  Accordingly, determination of the color of the background A necessary for the show-through reduction processing of the present embodiment will be described with reference to FIG. As shown in FIG. 5 (b), the histogram generation unit 85a of the image processing unit 8 displays the histogram of each channel of Red, Green, and Blue for all pixels in the image data or pixels in one region. Generate.

  Explaining each histogram, the horizontal direction in FIG. 5B indicates the value in each channel in the pixel, and it is assumed that 8 bits are used per channel. Therefore, the minimum value in the horizontal direction of the histogram is 0, and the maximum value is 255. And the up-down direction in FIG.5 (b) represents the frequency. For example, if the R value of one pixel of the image data is 100, the frequency of the 100 portion of the Red histogram value is incremented by one. This operation is repeated, and all or some of the pixels in the image data are reflected in the histogram to obtain the distribution. Note that if a histogram is generated for all pixels in the image data, the accuracy in determining the color of the background A can be increased. On the other hand, if, for example, pixels in an area of about 1/4 to 1/2 of the image data are targeted, it is possible to increase the processing speed by reducing the amount of calculation while maintaining a certain accuracy.

  Then, after generating the histogram, the mode value determining unit 85b determines the mode value in each channel (illustrated by a broken line in FIG. 5B). In the processing, a portion with the highest frequency in the histogram is specified, and its value is specified. For example, in the histogram shown in FIG. 5B, the mode value of the Red component is 230, the mode value of the Green component is 205, and the mode value of the Blue component is 55. A color combining R = 230, G = 205, and B = 55 is determined as the color of the background A in the image data.

  Next, based on FIG. 6, the color space changing process in the multifunction machine 1 of the present embodiment will be described. First. In FIG. 6, the upper part of each channel of Red, Green, and Blue shows before the show-through reduction process, and the lower stage shows after the show-through reduction process, and each shows a value range from 0 to 255. The shaded portion indicates a predetermined range D in which processing for reducing the number of colors is performed.

  The reason for performing the process of reducing the number of colors is the result that the back surface of the reading surface appears in the show-through portion B. Therefore, the image data on the back surface is not displayed unless a transparent or translucent sheet is read. It does not appear as it is on the reading surface. That is, when comparing the reading surface of an original with an image with show-through, the density of the show-through portion B often appears light. In short, it tends to appear slightly as a color is added to the background A of the reading surface. Therefore, the show-through can be eliminated by subtracting the number of colors within the predetermined range D from the determined color of the background A and compressing the color gamut to the same color as the background A.

  The predetermined range D can be a range having a width of about 10% of the maximum value of the channel in each channel. For example, the width of 10% is assigned to the determined value of each channel of the background A at a ratio of ± 5% at the maximum. That is, in each channel, a color space having a value different from ± 0.5% to ± 5% of the maximum value that each channel can take is set as the predetermined range D with the value of each channel of the determined background A as the center. Specifically, in the image data of this embodiment, since the maximum value of each channel is 255, 255 × 5% ≈ ± 12. Therefore, if applied to the example shown in FIG. 6, the predetermined range D is in the range of 218 to 242 with a value of 230 for the Red channel, and 193 to 217 of the value for the Green channel with 205 as the center. In the Blue channel, the value is in the range of 43 to 67 with 55 as the center.

  The color space changing unit 86 performs a process of reducing the number of colors (color gamut compression) in which the pixels in the image data within the predetermined range D are centered on the color of the background A and the color of the background A. Using FIG. 6 as an example, the value of Red is a value within the range of 218 to 242, the value of Green is a value within the range of 193 to 217, and the value of Blue is a value within the range of 43 to 67. Mapping is performed in which the pixels in the image data in the color space are replaced with R = 230, G = 205, and B = 55 determined as the background A color. The image data after processing by the color space changing unit 86 is as shown in FIG.

  By the processing of the color space changing unit 86, the show-through portion B that has appeared on the background A can be erased. In addition, the color of the background A is not impaired even if the show-through reduction processing is performed on image data obtained by reading a document using colored paper or a document with a colored background.

  Next, a method for setting the strength of the show-through reduction process according to the first embodiment of the present invention will be described with reference to FIG. FIG. 7 is a plan view showing an example of the operation panel 9 according to the first embodiment of the present invention.

  In the multifunction device 1 of the present embodiment, an operation panel 9 as shown in FIG. A user or the like inputs settings and operation instructions of the multifunction device 1 from the operation panel 9. The operation panel 9 is provided with a start key 91, a numeric keypad 92, a function setting key 93 and the like for operating instructions and settings of the multifunction device 1, and a liquid crystal display unit 94 for displaying various information of the multifunction device 1. Can be provided. The liquid crystal display unit 94 is of a touch panel type, and the user can select a menu or the like displayed on the liquid crystal display unit 94 to perform operation instructions and settings of the multifunction device 1.

  When performing the above-described show-through reduction process, for example, the user operates a menu (not shown) that appears on the liquid crystal display unit 94 of the operation panel 9 to shift the mode of the multifunction device 1 to the show-through reduction mode. Let In this mode, for example, the user uses the image reading unit 4 to copy a document that has been printed on both sides. Note that the show-through reduction mode can also be canceled using the operation panel 9.

  In the show-through reduction mode, a setting screen for setting the strength of the show-through reduction process can be displayed on the liquid crystal display unit 94. Since the liquid crystal display unit 94 is a touch panel type, if the strong button 95 is pressed, the degree of the show-through reduction process can be increased, and if the weak button 96 is pressed, the degree of the show-through reduction process can be reduced. For example, as shown in FIG. 7, the strength can be set in five stages. The auto button 97 is a button for automatically setting the strength of the show-through reduction processing.

  Here, the degree (intensity) of the show-through reduction processing can be realized, for example, by changing the predetermined range D in the color space in which the color space changing unit 86 changes the color of the background A. For example, if 5 is the strongest among the 5 levels, the width is 10% of the maximum value of each channel (for example, ± 5% width centered on the color of the background A), and if the weakest 1 is , 2% width with respect to the maximum value (for example, the width is ± 1% centered on the color of the background A) In this way, by changing the predetermined range D according to the user's setting, the user can control the strength of the show-through reduction processing, which is highly convenient. In addition, the auto setting is, for example, based on an experiment repeated in the development stage of the multifunction device 1, based on elements such as the color of the background A as a reference, a predetermined range D that is recognized from a rule of thumb when the show-through reduction processing can be appropriately performed. It can be automatically selected from a data table or the like.

  Here, with respect to the color of the background A, the predetermined range D is defined as a color space having a different range up to ± 5% of the maximum value of each channel. If the predetermined range D includes a range exceeding ± 5%, the image data This is because the influence of the show-through reduction process on the image becomes stronger. For example, if a range exceeding ± 5% is included in the predetermined range D, a portion that is not show-through will be mapped to the color of the background A more than necessary. On the other hand, for example, even if a different range up to about ± 0.5% (1% width) of the maximum value of each channel is determined as the predetermined range D, the effect of the show-through reduction processing appears unless it is zero. Therefore, for example, in each channel, a color space different from ± 0.5% to 5% of the maximum value of each channel around the determined color of the background A can be defined as the predetermined range D.

  When the multifunction device 1 is used as a printer, the mode of the multifunction device 1 is changed to a show-through reduction mode by a printer driver program installed in the user terminal 100, and the liquid crystal display shown in FIG. The intensity of the show-through reduction process may be set by performing the same display as that of the unit 94 or the like. In this case, it can be said that the interface unit 73 is an operation input unit. As a result, the show-through reduction process can be performed even when image formation of show-through image data is performed using the multifunction device 1 as a printer.

  In summary, the multi-function device 1 has an operation panel 9 and an interface unit 73 for operating and inputting the device, and the operation input unit is a show-through reduction mode that is a mode for performing the show-through reduction process. The image data analyzing unit 85 and the color space changing unit 86 function only when an input for canceling the show-through reduction mode is received and the apparatus is in the show-through reduction mode. Furthermore, the operation panel 9 or the like accepts a plurality of levels of intensity setting for the show-through reduction processing, and the color space changing unit 86 changes the range of the predetermined range D according to the level based on the intensity setting.

  Next, a control flow of the show-through reduction process according to the first embodiment of the present invention will be described with reference to FIG. FIG. 8 is a flowchart illustrating an example of the control of the show-through reduction process according to the first embodiment of the present invention. In this description, a case where one image is formed will be described.

  First, when the user operates the operation panel 9 or inputs an instruction to shift to the show-through reduction mode from the user terminal 100, the mode of the multifunction device 1 shifts to the show-through reduction mode (step # 1). . Next, RGB image data is input to the image processing unit 8 by the image reading unit 4 or the interface unit 73 as an image data input unit (step # 2). Next, the image processing unit 8 generates a histogram of each channel of Red, Green, and Blue by the histogram generation unit 85a (step # 3). For example, if the image data transmitted from the user terminal 100 is not in the RGB format, the image processing unit 8 may change the format to the RGB format.

  Next, the mode value determining unit 85b determines the mode value from the histogram of each channel (step # 4). Then, the color of the background A in the image data is determined from the mode value (step # 5). Next, the color space changing unit 86 changes the color of the pixels within the predetermined range D to the color of the background A around the color of the background A, and performs a process of reducing the number of colors (step # 6). ). When the multifunction device 1 is used as a scanner, the image data may be stored in the storage unit 72 of the control unit 7 or transmitted to the user terminal 100 after this processing.

  After the process of reducing the number of colors, the image data output unit 87 transmits image data to the LSU 22 (step # 7). In response to the transmission of the image data, the image forming unit 2 forms an image (step # 8). In this way, image formation without show-through is performed.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 9 is an explanatory diagram for explaining the show-through reduction processing according to the second embodiment of the present invention, where (a) shows an example of the outline of the processing, and (b) shows the image data before processing. It is the elements on larger scale of an upper edge part. FIG. 10 is a block diagram for explaining an image processing unit 8 according to the second embodiment of the present invention. FIG. 11 is a flowchart illustrating an example of the control of the show-through reduction process according to the second embodiment of the present invention. In the description of the second embodiment, only the parts different from the first embodiment described above will be described, and the parts common to the first embodiment can be applied to the first embodiment, and the description thereof will be omitted. .

  First, as shown in FIG. 9A, as in the first embodiment, the show-through reduction processing of this embodiment does not impair the color of the background A, and only the show-through portion B is obtained from the image data. Erased. Therefore, an outline of the show-through reduction process in the second embodiment will be described with reference to FIG. In the show-through reduction processing of the present embodiment, as indicated by hatched hatching in FIG. 9B, image data corresponding to a blank portion in the image data (the front end portion in FIG. 9B) is predetermined from the image data. For each pixel in the region E, an average value of values of each channel is obtained. Then, the obtained combination of average values is handled as the color of the background A in the image data.

  Here, the predetermined area E from the edge of the image data is an area corresponding to a margin in the print image. In general, margins in image data are provided with a constant width W at the upper end, lower end, left end, and right end of the image data. Therefore, as shown in FIG. 9B, an average value of pixels in the area of the band-shaped constant width W from the tip portion may be calculated from the image data, or the band-shaped predetermined area E is imaged. An average value may be calculated for the rear end portion, left end portion, and right end portion of the data. Alternatively, the predetermined value E may be set so as to border the periphery of the image data, and the average value may be calculated.

  And the width W of the predetermined area | region E shown in FIG.9 (b) can be defined arbitrarily. For example, a predetermined width such as 1 cm from the edge of the image data may be set as the predetermined area E, or if the image data includes margin information, a portion corresponding to the margin may be set as the predetermined area E. Alternatively, the average value may be obtained for one line of pixels at a certain distance from the edge of the image data (for example, 5 mm from the edge of the printed image). Further, the width W and size of the predetermined area E may be changed by, for example, input to the operation panel 9. Then, the setting of the predetermined area E is stored in, for example, the storage unit 72 of the control unit 7 or the flash ROM 84 of the image processing unit 8, and the setting of the predetermined area E is read to perform the show-through reduction process.

  Next, the configuration of the image processing unit 8 of the second embodiment will be described with reference to FIG. In the present embodiment, the image data handled by the image processing unit 8 will be described as being in RGB format. In the second embodiment, instead of the histogram generation unit 85a and the mode value determination unit 85b in the first embodiment, a predetermined region E from the end of the image data corresponding to the blank portion of the input image data. An average value calculation unit 85c is provided that calculates the average value of each channel as color information of each pixel. For example, the average value calculation unit 85c calculates an average value of each channel of Red, Green, and Blue of each pixel in the predetermined area E. Then, the combination of the average values calculated in each channel is determined as the density of the background A. Note that the color space changing unit 86 reduces the number of colors around the determined background A color, and the function of the image data output unit 87 is the same as in the first embodiment. Thus, the show-through reduction processing can be performed even if the average value of each channel of the predetermined region E in the image data is obtained.

  As shown in FIG. 11, the flow of control of the show-through reduction process in the second embodiment is basically the same as that in the first embodiment, and among the steps in FIG. 1 and 2 correspond to steps # 11 and # 12 in FIG. 11, and steps # 6 to 8 in FIG. 8 correspond to steps # 15 to 17 in FIG. 11, so that the description in FIG. Description of steps # 11-12 and steps # 15-17 in FIG. 11 is omitted.

  In the second embodiment, after step # 12, the image processing unit 8 uses the average value calculation unit 85c to calculate the average value of the Red, Green, and Blue channels of each pixel in the predetermined area E. Calculate (step # 13). Next, the color of the background A is determined by combining the calculated average values of the respective channels (step # 14). Even in this case, image formation without show-through is performed.

  In this manner, according to the first and second embodiments of the present invention, the image data analysis unit 85 (histogram generation unit 85a, mode value determination unit 85b, average value calculation unit 85c, etc.) The color of the background A is determined, and the color space changing unit 86 performs a show-through reduction process by mapping pixels in the image data of a color within the predetermined range D from the determined color of the background A to the same color. Therefore, even if the show-through reduction process is performed, the color of the background A is not greatly impaired. In addition, the show-through reduction process can be realized without preparing an expensive image reading apparatus (scanner) that can simultaneously read both sides of the document. In the first embodiment, the histogram generation unit 85a generates a histogram for each channel, the mode value determination unit 85b determines the mode value for each channel, and the combination of mode values is determined for the background A. In the second embodiment, the average value calculation unit 85c calculates the average value of each channel in the predetermined area E from the end of the image data, and uses the combination of the calculated average values as the color of the background A. Therefore, the color of the background A can be appropriately determined. Therefore, the show-through reduction process can be reliably performed without impairing the color of the background A. Furthermore, the color of the background is surely made uniform, and the visibility of the image is increased.

  In addition, since the predetermined range D is the maximum value in each channel of the input image data, the color space up to a value different from the color of the background A in the range of 0.1 to ± 5% is set as the predetermined range D. Mapping that reduces the number of colors can be performed appropriately. In other words, if the color is changed to a color exceeding ± 5%, it will be changed to the background A color more than necessary. Can be achieved. In addition, the user can set whether or not to perform the show-through reduction process by the operation input unit (operation panel 9 and interface unit 73), and the convenience for the user can be improved. Furthermore, since the user can set the strength of the show-through reduction process using the operation panel 9 or the like, the show-through reduction process can be set in consideration of the thinness of the read original paper, the characteristics of the scanner that performs the reading, and the like. it can. Therefore, user convenience can be improved.

  Further, for example, in the image processing apparatus of the present invention, the show-through reduction process can be performed on image data generated based on a document by the image reading unit 4 or image data transmitted from an external terminal. Further, since the image data input unit inputs RGB image data to the apparatus, it is possible to perform a show-through reduction process on frequently used RGB image data. Furthermore, since the image forming apparatus forms an image on a recording medium such as paper based on the image data after the show-through reduction processing, a print result in which the show-through is eliminated can be obtained.

  Although the embodiments of the present invention have been described above, the scope of the present invention is not limited to these embodiments, and various modifications can be made without departing from the spirit of the invention.

  The present invention can be used in an image processing apparatus including an image reading unit such as a scanner, an interface unit, an image processing unit, and an operation panel, and an image forming apparatus including the image processing apparatus.

1 is a schematic front sectional view of a multifunction machine according to a first embodiment. FIG. 2 is a partially enlarged schematic cross-sectional view of an image forming unit according to the first embodiment. FIG. 2 is a block diagram illustrating an example of a hardware configuration of the multifunction peripheral according to the first embodiment. It is a block diagram for demonstrating the image process part which concerns on 1st Embodiment. It is explanatory drawing for demonstrating the show-through reduction process which concerns on 1st Embodiment, (a) shows an example of the outline | summary of a process, (b) shows an example of a histogram. It is explanatory drawing which shows an example of the color space change of the show-through reduction process which concerns on 1st Embodiment. It is a top view which shows an example of the operation panel which concerns on 1st Embodiment. It is a flowchart which shows an example of the control of the show-through reduction process which concerns on 1st Embodiment. It is explanatory drawing for demonstrating the show-through reduction process which concerns on 2nd Embodiment, (a) shows an example of the outline | summary of a process, (b) is the elements on larger scale of the upper edge part of the image data before a process. is there. It is a block diagram for demonstrating the image process part which concerns on 2nd Embodiment. It is a flowchart which shows an example of the show-through reduction process control which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Multifunction machine (image forming apparatus) 2 Image forming part 4 Image reading part (Image data input part, a part of image processing apparatus)
73 Interface unit (image data input unit, operation input unit, part of image processing device)
85 Image data analysis unit 85a Histogram generation unit (image data analysis unit 85, part of image processing apparatus)
85b Mode value determination unit (image data analysis unit 85, part of image processing apparatus)
86 Color space changing unit 85c Average value calculating unit (image data analyzing unit 85)
9 Operation panel (operation input unit, part of image processing device)
A background B show-through part D predetermined range E predetermined region

Claims (9)

An image data input unit for inputting image data to the apparatus;
An image data analysis unit that determines the color of the background in the input image data;
A color space changing unit that performs a show-through reduction process by mapping pixels in image data having a color within a predetermined range in the color space from the background color determined by the image data analysis unit to the determined background color When,
An image processing apparatus comprising:   The image data analysis unit generates a histogram of each channel for the entire image data or a part of the pixels based on the value of each channel as color information of each pixel of the input image data, The image processing apparatus according to claim 1, further comprising: a mode determining unit that determines a mode value in each of the histograms, wherein the mode value combination is determined as a background color.   The image data analysis unit calculates an average value of values of each channel as color information of each pixel in a predetermined area from an end of the image data corresponding to a blank portion in the input image data The image processing apparatus according to claim 1, wherein a combination of average values calculated by the average value calculation unit is determined as a background color.   In each channel, a color space ranging from ± 0.5% to ± 5% different from the maximum value that each channel can take, with the value of each channel of the determined background as the center, is set as the predetermined range. The image processing apparatus according to any one of claims 1 to 3. It has an operation input unit for operating and inputting devices.
The operation input unit shifts the mode of the apparatus to a show-through reduction mode, which is a mode for performing the show-through reduction process, or accepts an input to cancel the show-through reduction mode,
The image processing apparatus according to claim 1, wherein the image data analysis unit and the color space changing unit function only when the apparatus is in the show-through reduction mode. The operation input unit accepts intensity settings of a plurality of stages of the show-through reduction processing,
The image processing apparatus according to claim 5, wherein the color space changing unit changes the range of the predetermined range according to a step based on the intensity setting.   2. The image data input unit is an image reading unit that reads image data of a document and generates image data, and / or an interface unit that receives transmission of image data from an external terminal. 7. The image processing device according to any one of items 1 to 6.   The image processing apparatus according to claim 1, wherein the image data input unit inputs RGB format image data to the apparatus. An image forming unit that forms an image based on the image data;
The image processing apparatus according to claim 1,
An image forming apparatus, wherein the image forming unit forms an image on a recording medium based on image data after the show-through reduction processing by the color space changing unit.

Images