JP2006295624A - Image processor, method therefor, computer program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide image data for forming high-quality images by preventing the color taste and the density of a uniform colored or density portion from failing, character line drawing portions from getting out of shape, and a recording material from scattering. <P>SOLUTION: The image processor decides whether image data corresponding to an window area agree with a decision pattern (S909-S910) and outputs image data to an apparatus for forming images on a recording medium using a recording material, after the image data pass image processes (S911-S912) for changing values of pixels at specified positions of the window area agreeing with the decision pattern. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and method, a computer program, and a recording medium. For example, the present invention relates to image processing that outputs image data to an apparatus that forms an image on a recording medium using a recording material.

  In a printing apparatus that prints an image on a recording medium using a recording material such as ink or toner, control of the recording material is important. That is, it is important how to properly and stably arrange the recording material on the recording medium. Depending on the layout of the recording material, printing accuracy, print reproducibility, color stability, image smudges, show-through, etc. show various characteristics (sometimes causing problems) and may affect the quality of the printed results. It is no exaggeration to say.

  The loading amount of the recording material on the recording medium is the core of the above characteristics and problems. In particular, the applied amount of the solid image portion and the character / line image portion is relatively easy to cause a difference in applied amount although there is a difference in absolute amount depending on the printing apparatus. If the amount of the printed image is different from that of the character / line image, it is difficult to satisfy the conditions satisfying the two levels. If priority is given to the applied amount of the solid portion that strongly influences the image characteristics such as color and density, the character / line image portion may not be appropriately reproduced. As a result, it has been pointed out that the character line drawing portion is crushed or the recording material is scattered. On the contrary, if the loading amount is set so as to reduce the crushing of the character / line image portion and the scattering of the recording material, the color and density of the solid portion become insufficient.

  In the case of an electrophotographic printing apparatus, if the image forming conditions of the engine, such as the photosensitive member potential or the developing bias, are changed, it is possible to change both the loading amount of the solid portion and the character line drawing portion. However, there is originally a difference in the amount of loading between the solid part and the character line drawing part. Usually, the applied amount of the character / line image portion is large, and the applied amount ratio is about 1.5 to 2 times. In such a case, if the image forming conditions are changed, the applied amount of the solid portion and the character / line image portion respectively change with the applied amount ratio substantially maintained, so that either one becomes impossible. For example, if the solid part is given priority, a print image that is favorable in both color and density can be obtained, but the amount of application of the character line image part is larger than that in the solid part, so that the toner is scattered in the transfer unit and fixing unit of the printing apparatus. May occur or the character line drawing portion may be crushed. On the other hand, when the applied amount is reduced so as to suppress the scattering of the toner and the crushing of the character line drawing part, the color and density of the solid part are reproduced thinly.

  In general, the reproducibility of the color and density of the solid portion is often given priority over the toner scattering and crushing of the character / line image portion. This is because photographs and pictures are often judged by their quality. However, it is required to improve the reproducibility of image quality by suppressing toner scattering at the character drawing portion and the edge portion and crushing of the character drawing portion.

  Patent Document 1 discloses a method of detecting an edge portion of an image, calculating an optimum density of the edge portion, and converting the density of the edge portion in order to reduce toner scattering.

JP 9-65142 A

  However, in Patent Document 1, a large processing load is required for calculating the optimum density of the edge portion, which complicates the apparatus and increases the apparatus cost.

  An object of the present invention is to easily control the loading amount of a recording material.

  The present invention has the following configuration as one means for achieving the above object.

  The image processing according to the present invention determines whether or not the image data corresponding to the window area matches the determination pattern, and has undergone image processing that changes the value of the pixel at a predetermined position in the window area that matches the determination pattern. It is characterized by outputting data.

  Further, it is determined whether or not the image data corresponding to the window area matches the determination pattern, and the image data that has undergone image processing for changing the value of the pixel specified by the replacement pattern in the window area that matches the determination pattern is obtained. It is characterized by outputting.

  A determination step for determining whether or not there is an edge portion in the target region of the image data; and a step of thinning out a target pixel in the target region when the determination step determines that there is an edge portion in the target region. The target pixel is not an edge portion of the image data, but is located at a predetermined pixel away from the edge portion.

  A determination step for determining whether or not a target area of the image data matches a determination pattern; and a thinning-out step for thinning out a target pixel in the target area that matches the determination pattern, wherein the target pixel is the image It is not an edge portion of data but is located at a predetermined pixel away from the edge portion.

  According to the present invention, it is possible to easily control the loading amount of the recording material, for example, lack of solid color and density of the solid portion, crushing of the character line drawing portion, scattering of the recording material, and high quality image can be prevented. Can be used as image data.

  Hereinafter, image processing according to an embodiment of the present invention will be described in detail with reference to the drawings.

  As Example 1, image processing for thinning out one line inside with a fixed number of pixels will be described.

[Device configuration]
FIG. 1 is a block diagram illustrating a configuration example of a printing apparatus according to an embodiment.

  The printing device 15 is connected to the data processing device (host computer) 1 via a serial bus such as USB (Universal Serial Bus) or IEEE1394 or a network. The host computer 1 converts the data created by the application software or the like into print data that can be interpreted by the video controller 2 of the printing device 15 using a printer driver, and sends the print data to the printing device 15. When the printing device 15 receives the print data, the video controller 2 analyzes and processes the data.

  Depending on the data analysis function of the video controller 2, the print data output from the host computer 1 may have various forms such as command data written in a printer language and final form image data for generating a video signal. The present embodiment can be applied to any form of print data. Furthermore, the present embodiment is also applied to image data input from an image reading apparatus such as a scanner instead of the host computer 1 and image data (facsimile data, e-mail data, etc.) input from various devices via a network. Is possible.

  Hereinafter, a case where command data (print data) described in the printer language is input to the video controller 2 will be described. However, when image data is input, processing for interpreting a command described in the printer language is performed. A process for processing the image data may be executed by omitting it.

  The CPU 6 of the video controller 2 executes a control program stored in the program ROM 5 or the hard disk (HD) 12 using the RAM 7 as a work memory, and controls a configuration to be described later via the system bus 19.

  The CPU 6 stores print data received from the outside via the host interface (I / F) 4 in the RAM 7 or HD 12 via the system bus 19, and sequentially extracts the stored print data and analyzes the commands. Then, the print data is rendered into image data using data read from the data ROM 9 or the font ROM 8 as necessary. The CPU 6 stores the image data as a collection of pixels corresponding to each position of the spatial coordinates arranged two-dimensionally in the drawing memory 10 which is a storage area corresponding to a virtual plane space assuming a recording medium used for printing. Constitute.

  The range of the value of each pixel (corresponding to the number of gradations and density values that can be expressed) is determined by the number of bits of data assigned to each pixel. When 1 bit is assigned to one pixel, the range of pixel values that can be taken is either '0' or '1', and when converting image data to a video signal, '1' that generates a video signal, Will not be allowed or will be either '0'. In this case, the pixel is either not printed at all, or is printed with the complete pixel area or the darkest density.

  In addition, when 8 bits are allocated to one pixel, the pixel value can take any value between 0 and 255, and even when converting image data into a video signal, a 256 level signal can be generated. it can. That is, in this case, it is possible to express a level (density) between a level that is not printed at all and a level that is printed completely.

  The CPU 6 can further process the image for each pixel by the image data processing program stored in the program ROM 5 for the rendered image data.

  In general, various processing for image data is often realized by a hardware circuit having a dedicated I / O instead of software processing from the viewpoint of performance. In this case, image processing is executed using the image processing circuit 16 instead of the processing program called from the program ROM 5.

  The CPU 6 converts the image data in the final form by the above processing into a video signal by the engine I / F 11 and sends it to the printer engine 13.

  FIG. 2 is a diagram showing a schematic configuration of the printer engine 13 that prints an image on a recording medium based on a video signal output from the engine I / F 11. In FIG. 2, an electrophotographic printing apparatus is shown as an example of the printer engine 13, but an inkjet printing apparatus may be used, for example.

  The printer engine 13 includes a cylindrical photosensitive drum 102 as a photosensitive member at the center thereof. The photosensitive drum 102 is supported so as to be rotatable in the direction of the arrow R, and a static eliminator 103 for erasing the electric potential of the photosensitive drum 102 and a surface of the photosensitive drum 102 are uniformly disposed around the photosensitive drum 102 in order along the rotation direction. Primary charger 104 to be charged, exposure unit 105 for exposing the surface of the photosensitive drum 102 to form an electrostatic latent image, potential sensor 106 for measuring the potential of the photosensitive drum 102 after exposure, toner to be attached to the electrostatic latent image On the photosensitive drum 102, a developing charger 107 that transfers the toner image formed on the photosensitive drum 102, a transfer charger 108 that transfers the toner image to the recording medium P, a separation charger 109 that separates the recording medium P from the photosensitive drum 102, and the photosensitive drum 102. A cleaner 110 for removing residual toner is disposed.

  In the exposure unit 106, the laser beam emitted from the semiconductor laser element 130 in response to the video signal is scanned by the polygon mirror 131 and guided to the photosensitive drum 102 via the imaging lens 132 and the reflecting mirror 133, and the photosensitive drum. An electrostatic latent image is formed on 102.

  The recording medium P that is the transfer destination of the toner image is supplied from a paper feed deck 111 disposed below the photosensitive drum 102, that is, below the printer engine 13. The recording medium P in the paper feed deck 111 is supplied into the printer engine 113 by the paper feed roller 112, and is supplied between the photosensitive drum 102 and the transfer charger 108 via the transport roller 113 and the registration roller 115. Here, the toner image is transferred to the recording medium P, and the recording medium P is conveyed to the fixing device 117 by the conveying belt 116. The recording medium P on which the toner image is fixed by heat and pressure applied by the fixing device 117 is discharged onto the paper discharge tray 120 by the paper discharge roller 119.

  This completes the printing process for one page corresponding to the print data input from the outside.

[Image correction]
Next, a phenomenon that becomes a problem when image data is generated in the course of processing in the video controller 2 will be described.

  Fig. 3 shows (a) when image correction is not performed, (b) when first image correction is performed, and (c) second image correction is performed when a horizontal line (line) having a certain width is drawn. It is a figure explaining the case. It is an example of binary image data processing in which 1 bit is assigned to one pixel.

  3 (a), (b), and (c) are enlarged views of the region d of the print result shown in the right diagrams of FIGS. 3 (a), (b), and (c). In the black part, the video signal is turned on, and the white part is turned off.

  As described above, when setting the process so that the applied amount is appropriate in the solid part, if the width is narrow like the line shown in Fig. 3 (a), the applied amount of the line will exceed the appropriate amount. As shown on the right side of 3 (a), an unnecessary image due to toner scattering appears at the rear end of the line where no image data exists. In FIG. 3, the recording paper is conveyed upward, and the lower side of the drawing corresponds to the rear end.

  In order to avoid this phenomenon, a method of setting the process so that the applied amount is appropriate in the line part, the color (density) value specified for the line when processing the print data, and the applied amount of the line part There is a way to lower. In both cases, similar results are obtained. The example shown in FIG. 3B corresponds to the latter method (first image correction). Assuming that the original image data is represented by the diagram on the left side of FIG. 3 (a), generating image data with a reduced density value designated for the line results in the diagram on the left side of FIG. 3 (b).

  Since binary image data is assumed here, if the original image data with the maximum density specified is corrected to image data with a lower density value, pseudo halftone processing is performed by dithering or the like, and the line is processed. Corresponding image data is halftone data. When this halftone data is actually printed, it becomes as shown on the right side of FIG. As a result, an unnecessary image due to toner scattering does not appear at the rear end of the line, but the density of the entire line decreases, and a line that should be printed solidly is printed as a halftone image. In other words, the first image correction is not an optimal method because it causes degradation in the quality of the print result and is not a faithful reproduction of print data.

  Next, in the second image correction, line image data is generated with the density value specified in the print data, and a pixel at a specific position in the line portion is extracted from the image data, and a pixel at the specific position is extracted. Is subjected to processing such as thinning (the left side of FIG. 3 (c)). Thereby, the pixel at the specific position is converted from the original on state (black or color pixel) to the off state (white pixel) when the image data is converted into the video signal.

  If the second image correction is used, it is possible to operate only the pixels that can effectively suppress the scattering of the toner due to the excessive loading amount and to leave the other pixels unchanged. Therefore, as shown in the diagram on the right side of FIG. 3C, it is possible to suppress the appearance of an unnecessary image due to the scattering of toner while maintaining the density value of the line of the print image.

[Replace pixel]
FIG. 4 is a block diagram illustrating a configuration example of an image processing unit that performs the second image correction (pixel replacement) described above, and corresponds to a part of the image processing circuit 16 illustrated in FIG.

  First, of the input binary image data, the image data A that is not subject to the second image correction is sent directly to the pixel replacement unit 166 via the delay circuit 161. In this case, pixel replacement does not occur, and the pixel replacement unit 166 outputs output data E that matches the input data A.

  On the other hand, the image data to be processed for the second image correction is input to the pattern matching unit 163 via the delay circuit 161. The pattern matching unit 163 reads the determination pattern from the feature pattern memory 162, determines whether or not the input data matches the determination pattern, and determines that the input data matches the 3-bit signal B to the replacement pixel input unit 165. Is output. When the pattern matching unit 163 determines that the pattern does not match the determination pattern, the pattern matching unit 163 outputs the input data C to the pixel replacement unit 166. In this case, pixel replacement does not occur, and the pixel replacement unit 166 outputs output data E that matches the input data C.

  On the other hand, the replacement pixel input unit 165 that has received the signal B from the pattern matching unit 163 takes out the replacement data D from the replacement pixel memory 164 and outputs the replacement data D to the pixel replacement unit 166. In this case, the pixel replacement unit 166 outputs the input replacement data D as output data E. That is, pixel replacement occurs.

  The configuration shown in FIG. 4 may be realized by hardware, or may be realized by software having each configuration as a module.

  In the case of binary image data, the replacement pixel memory 164 and the replacement pixel input unit 165 are not necessary because only black pixels are replaced with white pixels. However, when processing image data other than binary data, It is desirable to replace image data that gives a density that is inconspicuous as a pixel. In this case, the data is stored in the replacement pixel memory 164 and read by the replacement pixel input unit 165.

  FIG. 5 is a diagram for explaining pixel replacement in detail.

  FIG. 5 is an enlarged view of the rear end of image data to be replaced with pixels. FIG. 5 (a) shows before correction, FIG. 5 (b) shows after correction, the black portion is a black or color pixel region (hereinafter referred to as “black pixel region”), and the white portion is a white pixel region. In FIG. 5A, the boundary between the black pixel region and the white pixel region is an edge that forms the rear end of the line.

  In order to prevent the toner on the rear end of the black pixel area from being scattered while preserving the edge shown in FIG. 5 (a), the black or color pixel (hereinafter referred to as “black pixel”) that is one pixel inside from the rear end The process is defined so that it is thinned out. Also, if all the black pixels in this portion are thinned out (converted to white pixels), a white line is generated inside the rear end of the line and image quality deterioration becomes obvious, so thinning is performed in a range that is not visually affected. As described above, which pixels on the scanning line corresponding to the part are to be thinned out. For example, it is defined that pixels on the scanning line are thinned out every other pixel. According to these regulations, the image data subjected to the second image correction is as shown in FIG. Here, thinning refers to a process of converting black pixels into white pixels, but in the case of non-binary image data, black pixels are converted into gray colors or white pixels with inconspicuous density. Processing is also thinned out.

  In the image data shown in FIG. 5 (b), white pixels are arranged every other pixel, so that the amount of applied scanning lines is reduced. The actual printing result is the same as the original print data except for the rear end of the line, and the thinned scanning line is in such a degree that white pixels cannot be visually recognized due to the influence of surrounding black pixels.

  FIG. 6 is a diagram illustrating an example of a determination pattern stored in the feature pattern memory 162 illustrated in FIG. 4 in order to perform the thinning process.

  The image data (area) subject to the application amount limitation represented by the line, and the reference (decimation amount) of how much black pixels are to be thinned out at various positions in the target image data vary depending on the process conditions of the printer engine 13. is there. The target image data and the thinning amount are defined from the characteristics of the printer engine 13, and the determination pattern to be actually used is also created based on the above.

  FIG. 6 shows that there are five or more black pixels that are continuous in the conveyance direction of the recording paper (sub-scanning direction, the direction from the top to the bottom of the figure), and three or more black pixels that are continuous in the main scanning direction. A pattern for extracting an image in which at least one pixel of a white pixel region exists adjacent to the rear end of the region is shown. A pixel surrounded by a thick frame in the third row from the bottom and the second column from the left of the extracted image is the target pixel to be replaced.

  When the determination pattern shown in FIG. 6 is used, the black or color horizontal line with a width of four pixels or less is not replaced, and the black or color horizontal line with a width of five pixels or more replaces the target pixel. Of course, the image to which the pixel replacement is applied is not limited to a line, but has a black pixel area of 5 pixels or more in the sub-scanning direction and 3 pixels or more in the main scanning direction, and is adjacent to the rear end of the black pixel area. Thus, in the image in which at least one pixel is present in the white pixel area, the target pixel is replaced. That is, the thinning-out process also functions on the outlines of characters and general graphics.

[Thinning processing]
FIG. 7 is a flowchart for explaining the above-described thinning-out algorithm, which is a process executed by the image processing circuit 16.

  First, designation of the number M of determination target lines corresponding to the height of image data when performing pattern matching is accepted (S901). The number M of determination target lines corresponds to the height of the determination window, and M = 6 in the determination pattern shown in FIG. Subsequently, designation of the position of the target pixel to be replaced is accepted (S902). The position of the target pixel is specified by the coordinates (m, n) of the determination window area. If the origin is at the upper left, the determination pattern shown in FIG. 6 is (m, n) = (2, 4). The number of lines to be determined and the position of the target pixel may be input by the user operating the panel unit 14, or the CPU 6 inputs the number of lines to be determined and the position of the target pixel recorded on HD 12 or the like. Also good.

  Next, the determination pattern is read from the feature pattern memory 162 (S903), the determination target line number M is set to the variable L for determining the number of lines read from the drawing memory 10 (S904), and the correction flag F is set. It is initialized to '0' (S905). In this embodiment, instead of replacing all target pixels whose image in the window area matches the determination pattern, replacement is performed every other pixel for pixels on the same scanning line, so the previous target pixel is replaced. A correction flag indicating whether or not has been obtained is required. When the correction flag is “0”, the window area including the target pixel is compared with the determination pattern, and if they match, the target pixel is replaced and the correction flag is inverted. When the correction flag is “1”, the correction flag is inverted without replacing the target pixel even in the case of an image that matches the determination pattern.

  Next, the image data stored in the drawing memory 10 is read into the two line memories by the designated number M of determination target lines (S906). The line memory is allocated to the RAM 7 or a storage area in the image processing circuit 16. Pattern matching is started by matching the origin of the image (upper left) with the origin of the judgment window (upper left) for the image data of height M read into the line memory for judgment. Move the area to perform pattern matching. Accordingly, the left end of the window area is set to the left end of the image data in the line memory (S907).

  Subsequently, it is determined whether or not the correction flag F is '0' (S908). If F = '1', the correction flag F is inverted (S913), and the process proceeds to step S914. If F = '0', the determination pattern is compared with the window area image (S909), and it is determined whether or not they match (S910). If they do not match, the process proceeds to step S914. If they match, the replacement data is read from the replacement pixel memory 164 (S911), the pixel of the replacement line memory corresponding to the target pixel is replaced (S912), the correction flag F is inverted (S913), and the processing is performed. Advances to step S914.

  In step S914, it is determined whether or not the next pixel of interest exists in the image data read into the line memory (S914) .If it exists, the window area is moved by one pixel in the main scanning direction (S915), The process returns to step S908.

  If the next pixel of interest does not exist (that is, the right end of the window area has reached the right end of the image data in the line memory), the variable L is compared with the number Y of lines of image data stored in the drawing memory 10. (S916), if L <Y, the image data in the line memory is shifted by one line, and the image data for one line is read from the drawing memory 10 to the lowermost line (the first line in the sub-scanning direction) ( S917). If L = Y, similarly, the line is shifted by one line, and since there is no unread line, white pixel data is written in the lowermost line (S918). This is a countermeasure when there is a black pixel region at the bottom of the image data. Further, image data for one line discharged from the uppermost line (rear end line in the sub-scanning direction) of the replacement line memory by the line shift is, for example, the image data of the image processing circuit 16 as the image data after the thinning process is completed. Store in memory etc. Thereafter, the variable L is incremented (S919), and the process returns to step S908.

  If L> Y, data excluding the lowermost line of the replacement line memory is stored in, for example, the memory of the image processing circuit 16 and the process is terminated.

  By the above processing, an area having a pixel arrangement matching the determination pattern, a black pixel area having a height of 5 pixels or more and a width of 3 pixels or more in the case of the determination pattern in FIG. A thinning process can be performed in which a black pixel corresponding to one pixel is left from the boundary portion of the area having a boundary, and the black pixels inside thereof are replaced with white pixels every other pixel in the main scanning direction.

  Note that the position of the pixel of interest to be replaced is not limited to the above description or FIG. 6, but any position can be set by changing the determination pattern or the setting of the correction flag F. Is possible. For example, if the correction flag F is set to a plurality of bits, it is possible to count the number of pixels that are not replaced, and for example, to thin out one pixel every two pixels or every three pixels.

  Also, the judgment pattern and the window area image are compared, and the replacement target area is determined according to whether or not they match. However, the edge area judgment processing is performed on the window area without using the judgment pattern. The target area may be determined. As edge determination processing, for example, the pixel value at the center of the window area is compared with the average value of the remaining pixels (other than the center pixel) in the window area. Is determined to be an edge.

  The image processing according to the second embodiment of the present invention will be described below. Note that the same reference numerals in the second embodiment denote the same parts as in the first embodiment, and a detailed description thereof will be omitted.

  In the image correction described in the first embodiment, the position of a pixel to be replaced within one scan line is controlled. In the second embodiment, the position of a pixel to be replaced is controlled over a plurality of scan lines using the configuration of the first embodiment.

  In the first embodiment, the scan line inside one pixel portion from the boundary between the black pixel region and the white pixel region is the target line of the thinning process, but in order to further reduce the applied amount, the number of pixels to be thinned on one scan line is set to Will increase. However, if the number of pixels to be thinned out on one scan line is increased, white pixels may become visible, leading to degradation of image quality. Therefore, in the second embodiment, by controlling the position of the pixel to be replaced with a plurality of scan lines as the thinning process target lines, the effect of reducing the applied amount is improved while suppressing a reduction in image quality.

[Replace pixel]
FIG. 8 is a diagram for explaining in detail the pixel replacement in Example 2, in which the rear end of the image data to be replaced is enlarged, FIG. 8 (a) shows the state before correction, and FIG. 8 (b) (c ) Indicates after correction.

  For the image data shown in FIG. 8 (a), FIG. 8 (b) replaces black pixels on the scan line Yn-1 on the inner side from the scan line Yn at the boundary with white pixels every other pixel, Further, an example is shown in which the black pixel at the X coordinate position that has not been replaced with Yn-1 is replaced with the white pixel on the scan line Yn-2 on the inner side of the other pixel. Furthermore, Fig. 8 (c) shows an example of replacing the black pixel at the X coordinate position that was replaced with Yn-1 and not replaced with Yn-2 with a white pixel in the scan line Yn-3 inside another pixel. ing. By performing such replacement, the reduction amount of the loading amount can be increased.

  To achieve this replacement, if the coordinates of the pixel of interest are (Xm, Yn-1), and the X coordinate Xm is an even number, the black pixel (that is, the pixel of interest) one pixel from the boundary and the black inside the three pixels It is specified that the pixel (coordinate (Xm, Yn-3)) is replaced, and that the black pixel (coordinate (Xm, Yn-2)) inside the two pixels from the boundary is replaced when Xm is an odd number.

  For example, if the window area of a certain pixel of interest D (Xm, Yn-1) matches the determination pattern shown in FIG. 6 and Xm is an odd number, the inside of the two lines of the edge portion shown on the left side of FIG. 9 is controlled. The pattern replaces the pixels (Xm, Yn-2) surrounded by a thick frame as shown on the right side of FIG. If Xm is an even number, the pattern shown on the left side of FIG. 10 controls the inside of the three lines of the edge portion, and the pixels (Xm, Yn-3) surrounded by a thick frame are shown on the right side of FIG. replace. As described above, the thinning process for each scan line can be controlled by replacing one window area with a plurality of patterns.

According to this method, the following processing can be executed for one window area.
When Xm of the target pixel D (Xm, Yn-1) is an even number
1. Control one line inside edge (see Fig. 6)
2. Control inside 3 lines of edge (see Fig. 10)
When Xm of the target pixel D (Xm, Yn-1) is odd
3. Control inside 2 edges of edge (see Fig. 9)

  That is, the thinning process shown in FIG. 8C can be performed by switching the pixel replacement pattern to be applied according to the position of the target pixel in the main scanning direction.

[Thinning processing]
FIG. 11 is a flowchart for explaining an algorithm for thinning-out processing according to the second embodiment. This processing is executed by the image processing circuit 16. The same processes as those in FIG. 7 are denoted by the same reference numerals, and detailed description thereof is omitted.

  First, after receiving the designation of the number M of determination target lines (S901) and the designation of the position of the target pixel (S902), the designation of the number of replacement patterns is accepted (S931), the pattern for determination from the feature pattern memory 162, and The specified number of replacement patterns is read (S932). The number of replacement patterns may be input by the user operating the panel unit 14 or the CPU 6 may input the number of replacement patterns recorded on the HD 12 or the like. For example, “1”, “2”, and “3” can be specified as the number of replacement patterns. For example, when “1” is specified, the pattern shown in FIG. When “3” is designated for the patterns shown in 6 and 9, the patterns shown in FIGS. 6, 9, and 10 are read.

  Next, the judgment target line number M is set in the variable L (S904), and the image data stored in the drawing memory 10 is read into two line memories by the designated judgment target line number M (S906). Is set to the left end of the image data in the line memory (S907).

  Subsequently, the determination pattern and the window area image are compared (S909) to determine whether or not they match (S910). If they do not match, the process proceeds to step S914. If they match, the position Xm of the target pixel in the main scanning direction is determined (S933). If it is odd, the pixel in the replacement line memory is replaced according to the replacement pattern for odd positions (for example, FIG. 9) ( If it is an even number, the pixel in the line memory for replacement is replaced according to the replacement pattern for the even position (for example, FIG. 6 or FIGS. 6 and 10) (S935), and the process proceeds to step S914. If “1” is designated as the number of replacement patterns and Xm is an odd number, pixel replacement is not performed.

  The processing after step S914 is almost the same as the processing described in FIG. However, the difference is that after the window area is moved by one pixel in the main scanning direction in step S915, the process returns to step S909.

  Hereinafter, image processing according to the third embodiment of the present invention will be described. Note that the same reference numerals in the third embodiment denote the same parts as in the first embodiment, and a detailed description thereof will be omitted.

  FIG. 12 is a diagram for explaining the replacement method of the I pixel in Example 3, in which the rear end of the image data to be replaced is enlarged, FIG. 12 (a) is before correction, and FIG. 12 (b) is correction. Shows the back.

  For the image data shown in FIG. 12 (a), FIG. 12 (b) shows four black pixels (Xm) on the scan lines Yn-1 and Yn-2 one and two pixels inside from the scan line Yn at the boundary. And Xm + 1) are replaced with white pixels every two pixels. This replacement pattern is particularly effective for high-resolution image data when the above-described replacement in units of one pixel cannot provide a substantial effect. In other words, it is effective when it is desired to obtain the same effect as when the thinning process described in the first embodiment is performed on 300 dpi image data with 600 dpi image data.

  In order to realize this replacement, the target pixel is set to four pixels (Xm, Yn-1) (Xm, Yn-2) (Xm + 1, Yn-1) (Xm + 1, Yn-2) in FIG. The determination pattern shown on the left side is prepared, and when the image data in the window area matches the determination pattern, the four pixels (target pixel) surrounded by a thick frame are replaced as shown on the right side of FIG.

  In order to perform the thinning process using the determination pattern shown in FIG. 13, the window area may be moved by two pixels in the main scanning direction in step S915 shown in FIG. The correction flag F indicates whether or not the previous four pixels have been replaced.

  Hereinafter, image processing according to the fourth embodiment of the present invention will be described. Note that the same reference numerals in the fourth embodiment denote the same parts as in the first to third embodiments, and a detailed description thereof will be omitted.

  In the fourth embodiment, a user interface for the user to set whether or not to perform the correction of the loading amount described in the first to third embodiments and what kind of correction to perform when performing the correction will be described. .

  FIG. 14 is a diagram showing an example of a user interface (UI) for setting the correction of the applied amount (image correction). The user interface (UI) is displayed on the panel unit 14 by the CPU 6 or is virtually displayed on the monitor by the printer driver of the host computer 1. Displayed as a panel.

  When the user desires image correction, the user presses the “use” button at the top of the panel, and further sets the correction level from the correction level pull-down menu. Note that image correction settings and correction level settings are not limited to the combinations of buttons and pull-down menus shown in FIG. 14, and various user interfaces (such as check boxes and slide bars shown in FIG. 15) can be used. .

  FIG. 15 is a diagram for explaining processing for setting image correction using a user interface.

For example, when three types of documents indicated by reference numeral 720 are transmitted from the host computer 1 to the printing apparatus 15, the following settings are made using the printer driver operating on the host computer 1 or the panel unit 14 of the printing apparatus 15. Do.
Document 1: Amendment / Level 1 (Settings indicated by reference numerals 723 and 724)
Document 2: Amendment / Level 2 (Settings indicated by reference numerals 723 and 725)
Document 3: No correction (setting indicated by reference numeral 726)

  The setting information and ID list 727 are notified to the CPU 6 via the host I / F 4 or panel I / F 3 of the video controller 2 and stored in the RAM 7 or the like. The CPU 1 generates the image data 729 of the document 1 by applying the processing described in the first embodiment to the document 1 for which correction execution / level 1 is set. Further, the processing described in the second embodiment is performed on the document 2 in which the correction execution / level 2 is set, and the image data 729 of the document 2 is generated. Also, the image 3 of the document 3 that is faithful to the original print data is generated for the document 3 for which no correction is set, without performing image correction. As described above, the thinning-out width can be changed by adjusting the correction level using the user interfaces 723 and 724 in FIG.

  FIG. 16 is a flowchart illustrating a procedure for controlling image correction for print data input by the CPU 1.

  First, it is determined whether or not image correction is set (S1101). If it is not set, the image processing circuit 16 is set not to perform image correction (S1105). In this case, the image processing circuit 16 performs normal processing without performing image correction.

  If image correction is set, the set correction level is determined (S1102, S1103). When the correction level 1 is set, the image processing circuit 16 is set so as to execute the image correction described in the first embodiment (S1106), and when the correction level 2 is set, the processing described in the second embodiment is performed. The image processing circuit 16 is set so as to execute image correction (number of replacement patterns 2) (S1107). If not (that is, the correction level 3 is set), the image correction (replacement) described in the second embodiment is performed. The image processing circuit 16 is set to execute the number of patterns 3) (S1108).

  The relationship between the image correction level and the image correction level and the print data can be held for each document by linking the document ID in the document ID list 727 and the job information table 728 as shown in FIG. is there.

  Hereinafter, image processing according to the fourth embodiment of the present invention will be described. Note that the same reference numerals in the fifth embodiment denote the same parts as in the first to fourth embodiments, and a detailed description thereof will be omitted.

  As described in the fourth embodiment, the correction of the applied amount can be performed by a method set by the user or by the CPU 1 according to the status of the printing apparatus 15. In the fifth embodiment, a method will be described in which the CPU 1 sets whether or not to perform the correction of the loading amount, and the correction level when the correction is performed according to the state of the printing apparatus 15 (for example, process conditions) and the printing environment. .

  FIG. 17 is a diagram for explaining processing for setting the correction of the applied amount by predicting toner scattering from the type of the selected recording medium.

For example, when three types of documents indicated by reference numeral 720 are transmitted from the host computer 1 to the printing apparatus 15, the following designation is made using the printer driver operating on the host computer 1 or the panel unit 14 of the printing apparatus 15. Do.
Document 1: Printed on cardboard (reference numeral 803)
Document 2: Printed on coated paper (reference numeral 804)
Document 3: Print on plain paper (reference numeral 805)

  The designation information and ID list 727 are notified to the CPU 6 via the host I / F 4 or panel I / F 3 of the video controller 2 and stored in the RAM 7 or the like.

For the above three types of recording media, the amount of toner scattered at the rear end of the line under the standard process conditions of the printing apparatus 15 is as follows based on plain paper. This information is stored in the data ROM 9 or HD 12.
Plain paper: Normal (standard)
Cardboard: Slightly bad (a little scattered)
Coated paper: Poor (large amount of scattering)

  The CPU 1 reads information indicating the toner scattering amount corresponding to the set recording medium from the data ROM 9 or the like, and sets image correction of the image processing circuit 16 when generating image data according to the information. Example 3 that can set correction level 2 image correction when thick paper with a slightly larger scattering amount is specified, and can suppress the loading amount from correction level 2 when coated paper with a large amount of scattering is specified The four-pixel image correction described in (4) is set (correction level 4). When plain paper is designated, the image correction is not performed.

  Note that the relationship between the image correction level and the image correction level and the print data can be held for each document by linking the document ID in the document ID list 727 and the job information table 728 as shown in FIG. is there.

  FIG. 18 is a flowchart illustrating a procedure for controlling image correction for print data input by the CPU 1.

  First, information indicating the amount of scattering with respect to the recording medium is acquired (S1201), the designated recording medium is determined (S1202-S1203), and image correction of the image processing circuit 16 is performed based on the determined information indicating the recording medium and the amount of scattering. Set. The image processing circuit 16 is set so that image correction is not performed when plain paper is specified (S1204), and correction level 2 image correction (number of replacement patterns 2) is executed when thick paper is specified. The image processing circuit 16 is set to perform (S1205), and if not (that is, coated paper is designated), the image processing circuit 16 is set to execute the correction level 4 (four pixel replacement) (S1206). ).

  Further, the relationship between the printing environment and the amount of scattering may be stored in the data ROM 9 or HD 15. For example, if you want to estimate the amount of splashing from process conditions that are affected by dynamic changes in the printing environment, such as the durability of the fixing unit 17 (use time, number of outputs, etc.) and the installation environment (temperature, humidity, etc.), CPU 1 Receives this information from the printer engine 13 information via the engine I / F 11, predicts how much the amount of scattering is larger than the standard based on the received information, and does not correct the image and the correction level Can be determined sequentially.

  Of course, if the image is not corrected according to a plurality of elements (user instructions, recording medium type, printing environment, etc.) and a table indicating the correction level to be set is stored in the data ROM 9 or HD 15 The CPU 1 can set the image processing circuit 16 according to the user instruction, the type of the recording medium, the printing environment, and the like with reference to the table.

  As described above, based on the information indicating the relationship between the recording medium and the amount of scattering, and the information indicating the relationship between the printing environment and the amount of scattering, it is possible to appropriately select whether or not to perform image correction and the correction level.

  According to each of the above-described embodiments, it is possible to selectively and locally control the loading amount of an image having a characteristic shape such as a character line image with respect to the optimum value of the loading amount on the solid portion. As a result, it is possible to control the loading amount without degrading the image quality, and to prevent the character line drawing portion from being crushed and the recording material from being scattered.

[Other embodiments]
Note that the present invention can be applied to a system including a plurality of devices (for example, a host computer, an interface device, a reader, and a printer), and a device (for example, a copying machine and a facsimile device) including a single device. You may apply to.

  Also, an object of the present invention is to supply a storage medium (or recording medium) on which a program code of software that realizes the functions of the above-described embodiments is recorded to a system or apparatus, and the computer (or CPU or Needless to say, this can also be achieved by the MPU) reading and executing the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention. Further, by executing the program code read by the computer, not only the functions of the above-described embodiments are realized, but also an operating system (OS) running on the computer based on the instruction of the program code. It goes without saying that a case where the function of the above-described embodiment is realized by performing part or all of the actual processing and the processing is included.

  Furthermore, after the program code read from the storage medium is written into a memory provided in a function expansion card inserted into the computer or a function expansion unit connected to the computer, the function is determined based on the instruction of the program code. Needless to say, the CPU of the expansion card or the function expansion unit performs part or all of the actual processing and the functions of the above-described embodiments are realized by the processing.

  When the present invention is applied to the storage medium, the storage medium stores program codes corresponding to the flowcharts described above.

A block diagram showing a configuration example of a printing apparatus of an embodiment, The figure which shows schematic structure of the printer engine which prints an image on a recording medium based on the video signal which engine I / F outputs, The figure explaining the case where the image correction is not performed when the horizontal line (line) having a certain width is drawn, when the first image correction is performed, and when the second image correction is performed. A block diagram showing a configuration example of an image processing unit for performing second image correction (replacement of pixels); A diagram explaining pixel replacement in detail, The figure which shows the example of the pattern for determination for performing a thinning process, A flowchart for explaining an algorithm of thinning processing; The figure explaining in detail the replacement of the pixel of Example 2, The figure which shows the example of the pattern for substitution, The figure which shows the example of the pattern for substitution, Flowchart for explaining the algorithm of the thinning process of the second embodiment, The figure explaining the replacement method of I pixel of Example 3, The figure which shows the example of the pattern for judgment, The figure which shows an example of the user interface for setting the correction (image correction) of the amount of loading of Example 4. The figure explaining the process which sets image correction using a user interface, A flowchart illustrating a procedure for controlling image correction for print data; The figure explaining the process which estimates the scattering of a toner from the kind of selected recording medium, and sets correction | amendment of a loading amount, 6 is a flowchart illustrating a procedure for controlling image correction for print data.

Claims (20)

Determination means for determining whether or not the image data corresponding to the window area matches the determination pattern;
Changing means for changing a value of a pixel at a predetermined position in the window area matching the determination pattern;
An image processing apparatus comprising: output means for outputting image data that has undergone image processing by the determining and changing means.   2. The image processing apparatus according to claim 1, wherein the determination pattern includes a white pixel area at a lower end of the window area, and a black pixel area other than the white pixel area.   The change means is characterized in that the pixels on the line entering the black pixel region for one pixel or a plurality of pixels from the boundary with the white pixel region are changed to white pixels at a predetermined interval. The image processing apparatus described in 1. Determination means for determining whether or not the image data corresponding to the window area matches the determination pattern;
Changing means for changing the value of the pixel specified by the replacement pattern in the window area matching the determination pattern;
An image processing apparatus comprising: output means for outputting image data that has undergone image processing by the determining and changing means.   5. The image processing apparatus according to claim 4, wherein the determination pattern has a white pixel area at a lower end of the window area, and is a black pixel area other than the white pixel area.   6. The image processing apparatus according to claim 5, wherein the replacement pattern designates pixels on a line that has entered the black pixel region for one pixel or a plurality of pixels from a boundary with the white pixel region. .   7. The image processing apparatus according to claim 6, wherein the changing unit changes the designated pixel to a white pixel at a predetermined interval.   The replacement pattern includes a first pattern for designating pixels on a line entering the black pixel region for one pixel from the boundary with the white pixel region, and two pixels from the boundary for the black pixel region. 6. The image processing apparatus according to claim 5, wherein there is a second pattern for designating pixels on a line that has entered, and the changing unit uses the first and second patterns alternately. .   The replacement pattern includes a first pattern for designating a plurality of pixels on a line entering the black pixel region for one and three pixels from the boundary with the white pixel region, and two pixels from the boundary, 6. The method according to claim 5, wherein there is a second pattern that specifies pixels on a line that has entered the black pixel region, and the changing unit uses the first and second patterns alternately. Image processing device. In the replacement pattern, one pixel from the boundary with the white pixel region, a first pattern designating pixels on a line that has entered the black pixel region, two pixels from the first pattern and the boundary, A second pattern combining a pattern for designating pixels on the line that has entered the black pixel area, pixels on the line that has entered the black pixel area for three pixels from the first and second patterns and the boundary And a fourth pattern that specifies a plurality of pixels on a line that has entered the black pixel region for one and two pixels from the boundary,
The image forming apparatus further comprises setting means for selectively setting the first to fourth patterns in the changing means according to at least one of a user instruction, a type of recording medium, and an image forming environment. Item 6. The image processing device according to Item 5. A determination step of determining whether image data corresponding to the window area matches a determination pattern;
A change step of changing a value of a pixel at a predetermined position in the window area that matches the determination pattern;
An image processing method comprising: an output step of outputting image data that has undergone image processing in the determination and change steps. A determination step of determining whether image data corresponding to the window area matches a determination pattern;
A change step of changing a value of a pixel specified by a replacement pattern in a window area matching the determination pattern;
An image processing method comprising: an output step of outputting image data that has undergone image processing in the determination and change steps. Determining means for determining whether there is an edge in the target area of the image data;
When it is determined by the determination means that there is an edge portion in the target area, the thinning means for thinning the target pixel of the target area;
The image processing apparatus according to claim 1, wherein the pixel of interest is not an edge portion of the image data, but is located at a predetermined pixel away from the edge portion. Determination means for determining whether the target area of the image data matches the determination pattern;
Thinning means for thinning out the target pixel of the target area that matches the determination pattern;
The image processing apparatus according to claim 1, wherein the pixel of interest is not an edge portion of the image data, but is located at a predetermined pixel away from the edge portion.   15. The image processing apparatus according to claim 13, wherein the thinning width is instructed by an operation unit.   15. The image processing apparatus according to claim 13, wherein the thinning width is set according to a type of a recording medium on which the image data is formed. A determination step of determining whether there is an edge portion in the target area of the image data;
When it is determined by the determination step that there is an edge portion in the target area, a thinning step for thinning the target pixel of the target area is included.
The image processing method according to claim 1, wherein the target pixel is not an edge portion of the image data but is located at a predetermined pixel away from the edge portion. A determination step of determining whether or not the target area of the image data matches the determination pattern;
A thinning-out step of thinning out the target pixel of the target area that matches the determination pattern,
The image processing method according to claim 1, wherein the target pixel is not an edge portion of the image data but is located at a predetermined pixel away from the edge portion.   A program that controls an image processing device to realize the image processing according to any one of claims 11, 12, 17, and 18.   20. A recording medium on which the program according to claim 19 is recorded.

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