JP2008092323A - Image processing equipment, and image reading apparatus and image forming apparatus equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a notable deterioration of images, and to achieve high-quality images as well as to suppress an increase in manufacturing cost, and to speed up processing, when pseudo half-tone images are reduced by an error diffusion method. <P>SOLUTION: The image processing equipment includes: a pseudo half-tone processing portion 33 for pseudo half-tone processing a multivalued image by the error diffusion method; an averaging portion 34 which calculates an average of pixel values of pixels within an observation window with an observed pixel as a reference with respect to the pseudo half-tone image obtained from the pseudo half-tone processing portion and sets the obtained average value as a pixel value of the observed pixel; and a reduction processing portion 35 which reduces the image obtained from the averaging portion according to a required reduction ratio. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image processing apparatus that performs a reduction process on an image that has been subjected to pseudo halftone processing using an error diffusion method, and an image reading apparatus and an image forming apparatus that include the image processing apparatus.

  Multi-valued original images are output in image reading devices (scanner devices, facsimile devices, multifunction devices, etc.) that read original images, and image forming devices (printers, facsimile devices, multifunction devices, etc.) that form images on recording paper An image processing apparatus that performs pseudo halftone processing by an error diffusion method is provided in order to convert an image having the number of gradations that conforms to the specifications of the previous apparatus.

In addition, in order to create a thumbnail image for confirming the contents of the image, or to create an image with a resolution suitable for the output destination device, a reduction process is performed to reduce the number of pixels from the original image. In such image reduction processing, a simple thinning technique is known in which pixels are uniformly thinned according to the cycle of the reduction rate (see Patent Document 1). In addition, a technique is known in which a binary image is converted into a multi-valued image and then converted to a predetermined resolution in order to suppress image degradation that occurs when the binary image is reduced by pixel thinning processing (Patent Literature). 2).
Japanese Patent Laying-Open No. 2004-241942 (FIG. 2) Japanese Patent Laying-Open No. 2005-348079 (FIG. 2)

  However, in the conventional technique for performing simple decimation for image reduction, in the case of a binary image subjected to pseudo halftone processing by the error diffusion method, it is diffused to pixels around the target pixel by pseudo halftone processing. Since the binarized density error information is lost by the simple thinning process, there is a problem that the image is significantly deteriorated.

  Further, in the conventional technique for converting the binary image into a multi-value image and then converting the binary image into a predetermined resolution, a special circuit for converting the binary image into the multi-value image is required. In addition, there is a problem that the speeding up of the processing is impaired because the conversion processing takes time and the conversion processing takes time.

  The present invention has been devised to solve such problems of the prior art, and the main purpose of the present invention is to significantly reduce the image degradation when the pseudo halftone image is reduced by the error diffusion method. To provide an image processing apparatus configured to avoid high-quality image while avoiding an increase in manufacturing cost and to increase processing speed, and an image reading apparatus and image forming apparatus including the image processing apparatus. It is in.

  The present invention relates to a pseudo halftone processing means for performing pseudo halftone processing on a multi-valued image by an error diffusion method, and an observation window based on a target pixel with respect to a pseudo halftone image obtained by the pseudo halftone processing means. An averaging processing unit that obtains an average value of pixel values for each of the pixels and sets the pixel value of the target pixel, and an image obtained by the averaging processing unit is reduced according to a required reduction ratio. And a reduction processing means.

  According to the present invention, density error information diffused to pixels around the target pixel by the error diffusion method is stored in the target pixel by averaging the pixel values of the pixels in the observation window based on the target pixel. Therefore, remarkable deterioration of the image due to the reduction process can be avoided, and a great effect can be obtained in improving the image quality of the reduced image of the pseudo halftone image by the error diffusion method. In addition, since there is no need to convert the pseudo halftone image into a multi-valued image, an increase in manufacturing cost can be suppressed and the processing speed can be increased.

  A first invention made to solve the above problems is a pseudo halftone processing unit that performs pseudo halftone processing on a multi-value image by an error diffusion method, and a pseudo halftone image obtained by the pseudo halftone processing unit. On the other hand, an average processing unit that obtains an average value of pixel values for each pixel in the observation window based on the target pixel and sets the pixel value of the target pixel, and the average processing unit The image processing apparatus includes a reduction processing unit that reduces an image according to a required reduction rate.

  According to this, by averaging the pixel values of the pixels in the observation window based on the target pixel, density error information diffused to pixels around the target pixel by the error diffusion method is stored in the target pixel. Therefore, remarkable deterioration of the image due to the reduction process can be avoided. In addition, since there is no need to convert the pseudo halftone image into a multi-valued image, an increase in manufacturing cost can be suppressed and the processing speed can be increased.

  According to a second invention for solving the above-mentioned problems, in the first invention, the averaging processing means performs an averaging process of pixel values by simple averaging, and the reduction processing means includes a reduction ratio. The pixel is subjected to simple thinning processing according to the above.

  According to this, the processing procedure can be simplified and the processing speed can be increased.

  According to a third aspect of the present invention for solving the above problem, in the first aspect of the present invention, the averaging processing means performs an averaging process using the observation window having a size corresponding to a reduction ratio.

  According to this, since the invalid pixel value discarded in the thinning process performed by the reduction processing unit is reflected in the effective pixel in the averaging process, it is possible to suppress image degradation due to the thinning process.

  In this case, the observation window may be a rectangular area having a size that matches the thinning cycle in the simple thinning process performed by the reduction processing means. That is, the number of pixels in the main scanning direction is one effective pixel and the number of pixels in one cycle composed of a plurality of invalid pixels following in the main scanning direction. Similarly, the number of pixels in the sub-scanning direction is also one effective pixel. The number of pixels in one cycle composed of a plurality of invalid pixels following this in the sub-scanning direction may be used.

  Note that the pseudo halftone image obtained by the pseudo halftone process is not limited to binary (1 bit), but is usually 256 values (8 bit) such as 4 values (2 bits) and 8 values (3 bits). Any number of gradations may be used as long as the number of gradations is reduced from that of the multi-value image, and the number of gradations of the pseudo halftone image is set according to the capabilities of the image forming unit and the display unit of the output destination.

  According to a fourth aspect of the present invention, there is provided an image reading apparatus including the image processing apparatus according to any one of the first to third aspects.

  In this case, the image reading device is a scanner device, a facsimile machine, a multifunction peripheral, or the like that includes an image reading unit that reads an image of a document, and the multi-valued image obtained by the image reading unit is simulated by the pseudo halftone processing unit. Pseudo halftone images obtained by halftone processing and reduced images obtained through the averaging processing means and the reduction processing means are sent to another device via an appropriate communication medium such as a network, Alternatively, the image is displayed on a display unit provided in the own apparatus.

  According to a fifth aspect of the present invention, there is provided an image forming apparatus including the image processing apparatus according to any one of the first to third aspects.

  In this case, the image forming apparatus is a printer apparatus, a facsimile apparatus, a multi-function machine, or the like that includes an image forming unit that forms an image on a recording medium such as recording paper. Pseudo halftone images obtained through the pseudo halftone processing means obtained by other devices or the image reading means provided in the own apparatus through an appropriate communication medium, and through the averaging processing means and the reduction processing means The obtained reduced image is sent to and output from the image forming means, and is displayed on the screen on the display means provided in the apparatus.

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

  FIG. 1 is a block diagram showing a schematic configuration of a copying machine (image forming apparatus) to which the present invention is applied. This copying machine includes a document reading unit 1 that reads an image of a document by a line sensor in which an image pickup device such as a CCD is arranged, and a data processing unit 2 that performs necessary processing on image data obtained by reading here. And a printing unit 3 that prints an image of a document on a recording sheet by an electrophotographic method based on image data sent therefrom.

  The data processing unit 2 performs necessary processing on image data in accordance with a user instruction from a read image correction unit 11 that performs necessary processing on the image data according to the characteristics of the document reading unit 1 and an operation panel (not shown). A read image processing unit (image processing apparatus) 12, a page memory 13 that stores image data for one page, a system memory 14 that stores image data of all pages of a document, and image data to and from the system memory 14 A compression / decompression unit 15 that sometimes performs compression / decompression processing of image data, a recording image processing unit 16 that performs necessary processing such as gamma correction processing so that an appropriate print image can be obtained by the printing unit 3, and a portion between these units A direct memory access (DMA) control unit 17 that controls the data transfer of the printer, and an engine interface unit 18 that drives the printing unit 3.

  FIG. 2 is a block diagram showing a schematic configuration of the read image correction unit 11 shown in FIG. The read image correction unit 11 includes a shading correction unit 21, a gamma correction unit 22, and a lower color correction unit 23, and performs shading correction and gamma correction according to the sensitivity characteristics of the image sensor of the document reading unit 1. In addition, undercolor correction is performed in which the gray component of the three primary colors of YMC is replaced with a K (black) component.

  Pixel data for each pixel is sequentially input to the read image correction unit 11 by repeating the reading of one line in the main scanning direction for each line in the sub-scanning direction in the document reading unit 1 according to the pixel arrangement order. After necessary processing is performed in each unit, pixel data for each pixel is sequentially output.

  FIG. 3 is a block diagram showing a schematic configuration of the read image processing unit 12 shown in FIG. The read image processing unit 12 includes a spatial filter 31 that performs image processing such as edge enhancement, an enlargement / reduction processing unit 32 that converts an image to a resolution suitable for the printing unit 3, and a printing unit 3 that converts a multi-valued image using an error diffusion method. And a pseudo halftone processing unit (pseudo halftone processing means) 33 for converting into a pseudo halftone image having the number of gradations suitable for the above.

  Pixel data for each pixel is sequentially input from the read image correction unit 11 to the spatial filter 31 according to the pixel arrangement order, and the spatial filter 31, the enlargement / reduction processing unit 32, and the pseudo halftone processing unit 33 obtain the required data. After the processing is performed, pseudo-halftone pixel data is sequentially output and stored in the page memory 13 via the DMA control unit 17, and further compressed by the compression / decompression unit 15 and stored in the system memory 14. . When the pseudo halftone processing is not performed, the multivalued pixel data output from the enlargement / reduction processing unit 32 does not pass through the pseudo halftone processing unit 33, but passes through the page control memory via the DMA control unit 17. 13 and further compressed by the compression / decompression unit 15 and stored in the system memory 14.

  Further, the read image processing unit 12 obtains an average value of pixel values for each pixel in the observation window based on the target pixel with respect to the pseudo halftone image obtained by the pseudo halftone processing unit 33. An averaging processing unit (averaging processing unit) 34 that uses the pixel value of the target pixel, and a reduction processing unit (reducing processing unit) that performs a reduction process on the image obtained by the averaging processing unit 34 in accordance with a required reduction ratio. 35).

  When a user instruction from the operation panel or the like requires a reduced image, the pseudo halftone pixel data stored in the page memory 13 is averaged via the DMA control unit 17 in order to create a reduced image. The pixel data of the reduced image that is sequentially input to the conversion processing unit 34 and is generated by performing the required processing in the averaging processing unit 34 and the reduction processing unit 35 is accumulated in the page memory 13 via the DMA control unit 17, Further, the data is compressed by the compression / decompression unit 15 and stored in the system memory 14.

  The reduced image data stored in the system memory 14 is decompressed by the compression / decompression unit 15 and then sent to the printing unit 3 via the recording image processing unit 16 and the engine interface unit 18 to obtain a plurality of thumbnail images. A list image in which is arranged is printed. In addition, the thumbnail image is sent to a display control unit and an output control unit (not shown), and a thumbnail image is preview-displayed on the display unit of the operation panel of the own apparatus or the display of a PC connected to the network.

  FIG. 4 is a block diagram showing a schematic configuration of the pseudo halftone processing unit 33 shown in FIG. The pseudo halftone processing unit 33 generates a pseudo halftone (for example, 1 bit, binary) output image by performing pseudo halftone processing on an input image having multiple values (for example, 8 bits, 256 values) by an error diffusion method. , An adder 41, a comparator 42, a 0/1 forcible processing unit 43, a subtractor 44, a distribution value calculation unit 45, a random number generator 46, and an error memory 47.

  In the following, an example of converting multi-value pixel data into 256 gradations of 8 bits and 0 to 255 and converting this to binary (1 bit) pixel data is shown. In a color image, gradation value processing is performed for each primary color.

  First, the adder 41 receives a gradation value (density value) for each pixel, and adds a diffusion error value stored in the error memory 47 to the gradation value to generate a corrected gradation value. The comparator 42 compares the corrected gradation value from the adder 41 with the binarization threshold value. If the correction gradation value is larger than the binarization threshold value, the output value is set to the maximum value (255), and the correction gradation value is If it is smaller than the binarization threshold, the process of setting the output value to the minimum value (0) is performed. In the 0/1 forcible processing unit 43, processing for converting the output value from the comparator 42 into binary (1 bit) is performed, and an output image of pseudo halftone (1 bit, binary) is obtained.

  The subtractor 44 calculates an error value that is a difference between the output value from the comparator 42 and the corrected gradation value from the adder 41. The distribution value calculation unit 45 calculates a diffusion error value for each peripheral pixel from the error value obtained by the subtractor 44 based on a weighting coefficient (error diffusion coefficient) indicating a ratio of distributing the error value to the peripheral pixels. And stored in the error memory 47. As the weighting coefficient of the distribution value calculation unit 45, the weighting coefficient pattern is selected by the selector based on the random number generated by the random number generator 46, and the weighting coefficient pattern is switched at random.

  Here, an example is shown in which multi-value pixel data is binarized with one threshold value and converted to binary (1 bit) pixel data. However, the number of gradations of this pseudo halftone image is binary (1 bit). However, the pixel data can be converted into pixel data such as four values (2 bits) or eight values (3 bits) using a plurality of threshold values.

  FIG. 5 and FIG. 6 are schematic diagrams showing an outline of processing performed by the averaging processing unit 34 and the reduction processing unit 35 shown in FIG. FIG. 5 shows a case where an input image having a resolution of 600 dpi is reduced to 300 dpi, and FIG. 6 shows a case where an input image having a resolution of 600 dpi is reduced to 150 dpi.

  In the averaging processing unit 34, the average value of the gradation value (density value) of each pixel is obtained for each pixel in the observation window with the target pixel as a reference, and the average value is used as the gradation value of the target pixel. The averaging process is performed by a simple average obtained by dividing the sum of the gradation values of each pixel by the number of pixels. In a color image, gradation value averaging processing is performed for each primary color.

  The observation window is a rectangular area starting from the target pixel (upper left upper end), that is, a predetermined number of peripheral pixels following the target pixel in the main scanning direction, and the target pixel and the peripheral pixels in the sub-scanning direction. This is a rectangular area composed of a predetermined number of surrounding pixels. The size of the observation window (number of pixels) is set according to the reduction ratio, and when the reduction ratio is 1 / n, the size of the observation window is n × n pixels.

  For example, as shown in FIG. 5A, in the case of 1/2 reduction in which the resolution 600 dpi is reduced to 300 dpi, the observation window is a rectangular area composed of 2 × 2 = 4 pixels starting from the target pixel, The tone value P1 of the pixel of interest = (A1 + A2 + B1 + B2) ÷ 4. Further, as shown in FIG. 6A, in the case of 1/4 reduction in which the resolution 600 dpi is reduced to 150 dpi, the observation window is a rectangular area composed of 4 × 4 = 16 pixels starting from the target pixel, The tone value P1 of the target pixel is (A1 + A2 + A3 + A4 + B2 + B2 + B3 + B4 + C1 + C2 + C3 + C4 + D1 + D2 + D3 + D4) ÷ 16.

  In the reduction processing unit 35, simple thinning-out processing is performed in which pixels are thinned out at a constant rate with respect to an image in which the gradation value for each pixel is replaced with an average value by the averaging processing unit 34. The thinning ratio is set according to the reduction ratio, and when reducing to 1 / n, only one of the n pixels is valid and the remaining n-1 pixels are discarded.

  For example, as shown in FIG. 5B, in the case of 1/2 reduction in which the resolution is reduced to 600 dpi to 300 dpi, the thinning threshold is 1, and only one of the two pixels is valid, and the remaining one pixel is discarded. Is done. As shown in FIG. 6B, in the case of 1/4 reduction in which the resolution of 600 dpi is reduced to 150 dpi, the thinning threshold is 3, and only one of the four pixels is valid, and the remaining three pixels are discarded. Is done.

  The reduction ratio, that is, the size of the reduced image is displayed, for example, when a list image in which a plurality of thumbnail images are arranged is printed, or the thumbnail image is displayed as a preview on the display unit of the operation panel of the own apparatus or the display of a network-connected PC. In this case, the setting is appropriately set according to the use of the reduced image according to the user's instruction.

  Although the reduction ratios in the main scanning direction and the sub-scanning direction are the same here, the reduction ratios in the main scanning direction and the sub-scanning direction may be different. In this case, assuming that the reduction ratio 1 / M in the main scanning direction and the reduction ratio 1 / N in the sub scanning direction, the size of the observation window is M × N pixels, the thinning threshold in the main scanning direction is M−1, and the sub scanning direction. The thinning threshold is N-1.

  FIG. 7 is a block diagram showing a schematic configuration of the averaging processing unit 34 shown in FIG. The averaging processing unit 34 stores a line memory 71 in which pixel data of a required number of lines corresponding to the size of the observation window is accumulated, and a pixel selection unit that extracts pixel data of each pixel included in the observation window from the line memory 71 72 and a simple average calculator 73 that simply averages the gradation values for each pixel in the observation window sent from the pixel selector 72 to obtain an average value.

  The averaging processing unit 34 receives pseudo-halftone (for example, 1 bit, binary) pixel data stored in the page memory 13, and the pixel data is sent to the line memory 71, and the line memory 71 receives the required data. When the pixel data of several lines is accumulated, the averaging process is executed. When the averaging process for one line is completed, the pixel data for one line in the line memory 71 is replaced and the averaging process for the next line is performed. Is executed.

  The simple average computing unit 73 includes an adder 74 that adds gradation values for each pixel in the observation window, and a bit shift unit 75 that divides the addition value acquired by the adder 74 by the number of pixels in the observation window; have.

  In the adder 74, after the gradation values for each pixel included in the observation window are added in binary, division by the bit shift method is performed in the bit shift unit 75, for example, as in the example of FIG. When the number of pixels in the observation window is 4, it is shifted by 2 bits. When the number of pixels in the observation window is 16 as in the example of FIG. 6, the number of bits is shifted by 4 bits and is the same as the original pixel data. A simple average value (for example, 1 bit, binary) is output.

  The pixel selection unit 72 receives a window size setting signal that specifies the size of the observation window, and sets the size of the observation window accordingly. In the bit shift unit 75, a divisor at the time of division, that is, a shift number setting signal for designating a shift number corresponding to the number of pixels in the observation window is input, and the shift number is set accordingly.

  In addition to the simple averaging, the averaging process may be performed by a weighted average in which a weighting coefficient is set for each pixel in the observation window.

  FIG. 8 is a block diagram showing a schematic configuration of the reduction processing unit 35 shown in FIG. FIG. 9 is a timing chart of the thinning process in the main scanning direction performed by the reduction processing unit 35 shown in FIG. FIG. 10 is a timing chart of the thinning process in the sub-scanning direction performed by the reduction processing unit 35 shown in FIG.

  The reduction processing unit 35 performs simple thinning processing in the main scanning direction in which pixels are thinned out from pixels in one line at a fixed rate, and simple thinning processing in the sub-scanning direction in which lines are thinned out at a fixed rate. In simple thinning processing in the main scanning direction, the number of pixels is counted to distinguish between valid pixels and invalid pixels. In simple thinning processing in the sub-scanning direction, the number of lines is counted to distinguish between valid lines and invalid lines. Only the effective pixels of the effective line are output.

  The example of FIGS. 9 and 10 is a case of 1/4 reduction in which an input image with a resolution of 600 dpi is reduced to 150 dpi, the thinning threshold is 3, and one pixel in four pixels is effective as in the example of FIG. One of the four lines becomes a valid line, and the valid pixels P1, P5, P9, and P13 of the valid line L1 are output, and the valid pixels of the valid lines L5, L9, L13, and L16 are output.

  First, the main scanning pixel counter 81 receives the pixel clock signal S1, the main scanning image valid signal S2, and the pixel counter clear signal S5 from the comparator 82, and generates a pixel counter signal S4 based on the pixel clock signal S1. The comparator 82 receives the thinning threshold and the pixel counter signal S4 from the main scanning pixel counter 81, and generates a pixel counter clear signal S5 by comparing these.

  The comparator 83 receives the pixel counter signal S4 from the main scanning pixel counter 81, and generates a signal indicating the timing of the effective pixel by comparing it with 0. The AND circuit 84 receives the main scanning image effective signal S2 and the signal indicating the effective pixel timing from the comparator 83, and generates the main scanning gate signal S6 for selectively extracting the image signal of the effective pixel. In the AND circuit 85, the image input signal S3 and the main scanning gate signal S6 from the AND circuit 84 are input, and the effective pixel signal S7 of only the image signal of the effective pixel is generated.

  The rear end detection unit 88 receives the main scanning image valid signal S2 and generates a rear end detection signal. The AND circuit 89 receives the sub-scanned image valid signal S8 and the rear end detection signal from the rear end detection unit 88, and generates a signal indicating the timing of the rear end of one line. The sub-scanning line counter 90 receives the pixel clock signal S1, the signal indicating the timing of the rear end of one line from the AND circuit 89, and the line counter clear signal S10 from the comparator 91, and generates a line counter signal S9. . The comparator 91 receives the thinning threshold and the line counter signal S9 from the sub-scanning line counter 90, and generates a line counter clear signal S10.

  The comparator 92 receives the line counter signal S9 from the sub-scanning line counter 90, and generates a signal indicating the effective line timing by comparing it with 0. In the AND circuit 93, the main scanning image effective signal S2, the sub scanning image effective signal S8, and a signal indicating the timing of the effective line from the comparator 92 are input, and the sub scanning for selectively extracting the image signal of the effective line. A gate signal S11 is generated. In the AND circuit 94, the effective pixel signal S7 from the AND circuit 85 and the sub-scanning gate signal S11 from the AND circuit 93 are input, and an image output signal S13 of only the image signal of the effective pixels in the effective line is generated.

  In SEL95, the main scanning image effective signal S2, the sub-scanning image effective signal S8, and the main scanning gate signal S6 from the AND circuit 84 are input, and the main scanning image effective signal S12 is generated.

  FIG. 11 is a block diagram showing a schematic configuration of a scanner device (image reading device) to which the present invention is applied. As in the copier shown in FIG. 1, the scanner device includes a document reading unit 1, a read image correction unit 11, a read image processing unit 12, a page memory 13, a system memory 14, and a compression / decompression unit 15. And the DMA controller 17, and the reduced image data generated by the read image processor 12 as described above is transferred to an external device such as a PC via the output controller 101 and the interface unit 102. Is done.

  FIG. 12 is a block diagram showing a schematic configuration of a printer apparatus (image forming apparatus) to which the present invention is applied. In the same manner as the copying machine shown in FIG. 1, the printer apparatus includes a printing unit 3, a system memory 14, a compression / decompression unit 15, a recorded image processing unit 16, a DMA control unit 17, and an engine interface unit 18. The image data is transferred from an external device such as a PC via the interface unit 111 and the input control unit 112, and the image processing unit 113 is similar to the read image processing unit 12 described above. A process for converting the input image into a resolution and number of gradations suitable for the printing unit 3 is performed and a reduced image is created. The printing unit 3 performs normal printing of the input image and printing of the reduced image.

  An image processing apparatus according to the present invention, and an image reading apparatus and an image forming apparatus provided with the image processing apparatus, when reducing a pseudo halftone image by an error diffusion method, achieve high image quality while avoiding remarkable deterioration of the image. , An image processing apparatus for reducing an image subjected to pseudo halftone processing by an error diffusion method, and an image processing apparatus having the effect of suppressing an increase in manufacturing cost and speeding up the processing It is useful as a reading device and an image forming device, for example, a scanner device, a printer device, a facsimile device, a multifunction device, and the like.

1 is a block diagram showing a schematic configuration of a copying machine (image forming apparatus) to which the present invention is applied. The block diagram which shows schematic structure of the read image correction | amendment part shown in FIG. 1 is a block diagram showing a schematic configuration of a read image processing unit shown in FIG. The block diagram which shows schematic structure of the pseudo halftone processing part shown in FIG. The schematic diagram which shows the outline | summary of the process performed by the averaging process part and reduction process part shown in FIG. The schematic diagram which shows the outline | summary of the process performed by the averaging process part and reduction process part shown in FIG. The block diagram which shows schematic structure of the averaging process part shown in FIG. The block diagram which shows schematic structure of the reduction process part shown in FIG. Timing chart of thinning processing in the main scanning direction performed by the reduction processing unit shown in FIG. FIG. 8 is a timing chart of thinning processing in the sub-scanning direction performed by the reduction processing unit shown in FIG. 1 is a block diagram showing a schematic configuration of a scanner device (image reading device) to which the present invention is applied. 1 is a block diagram showing a schematic configuration of a printer apparatus (image forming apparatus) to which the present invention is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Document reading part 2 Data processing part 3 Printing part 12 Reading image processing part (image processing apparatus)
13 page memory 17 DMA control unit 33 pseudo halftone processing unit (pseudo halftone processing means)
34 Averaging processing unit (averaging processing means)
35 Reduction processing unit (reduction processing means)

Claims (5)

  A pseudo halftone processing unit that performs pseudo halftone processing on a multi-valued image by an error diffusion method, and each pixel in the observation window based on the target pixel with respect to the pseudo halftone image obtained by the pseudo halftone processing unit An averaging processing unit that obtains an average value of pixel values for the target pixel and sets the pixel value of the target pixel, and a reduction processing unit that reduces the image obtained by the averaging processing unit according to a required reduction ratio An image processing apparatus comprising:   2. The image processing according to claim 1, wherein the averaging processing unit performs pixel value averaging processing by simple averaging, and the reduction processing unit performs simple pixel thinning processing according to a reduction ratio. apparatus.   The image processing apparatus according to claim 1, wherein the averaging processing unit performs an averaging process with the observation window having a size corresponding to a reduction ratio.   An image reading apparatus comprising the image processing apparatus according to claim 1.   An image forming apparatus comprising the image processing apparatus according to claim 1.

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