JP5491458B2 - Image forming apparatus and control method thereof - Google Patents

Description

  Embodiments described herein relate generally to an image forming apparatus having a function of, for example, compression processing for image data, and a control method thereof.

  An image forming apparatus such as a multifunction copying machine (MFP) prints image data scanned from a document or image data input from a network-connected external device (so-called client terminal) on paper or compresses it to a small size. And save.

JP 2009-71832 A

  In the image forming apparatus as described above, it is desired that image data can be compressed with high image quality and smaller.

  An object of an embodiment of the present invention is to provide an image forming apparatus capable of compressing image data with high image quality and a control method thereof.

  An image forming apparatus according to an embodiment of the present invention includes a first median filter circuit that performs median filter processing on R, G, and B components of input image data, and an edge of a character image area in the image data that has passed through the first median filter circuit. A second median filter circuit that performs HSV conversion on the R, G, and B components of the input image data and performs median filter processing only on the V component, and image data that has passed through the second median filter circuit. An image capable of selectively generating a low-resolution conversion circuit for reducing the resolution and a third median filter circuit that performs HSV conversion on R, G, and B components of input background image data and median-filtering only the V component. A processor and the first median filter circuit are generated, and the first median filter circuit is generated. The edge extraction circuit is generated instead of the first median filter circuit after completion of the processing of the above, and the layout of the character region in the image data that has undergone the processing of the first median filter circuit is analyzed based on the extraction result of the edge extraction circuit. The second median filter circuit is generated instead of the edge extraction circuit after the end of the processing of the edge extraction circuit, and the low resolution conversion circuit is replaced with the second median filter circuit after the end of the processing of the second median filter circuit. The image data that has undergone the processing of the low-resolution conversion circuit is separated into character image data and background image data based on the analysis result and compressed, and the compressed background image data is input to the image processor. In addition, after the processing of the low resolution conversion circuit is completed, the low resolution conversion circuit is replaced. Generating said third median filter circuit comprises a controller for filing the background image data and character image data said compressed has been processed in this third median filter circuit.

The block diagram which shows the control circuit of one Embodiment. The block diagram which shows the specific structure of the 1st median filter circuit in one Embodiment. The block diagram which shows the concrete structure of the 2nd and 3rd median filter circuit in one Embodiment. The figure which shows the flow of a process of one Embodiment.

Hereinafter, an embodiment will be described with reference to the drawings.
In FIG. 1, reference numeral 1 denotes a composite image forming apparatus, a so-called MFP, which has a plurality of functions such as a copy function, a scan function, and a print function. The MFP 1 has a CPU 10 that functions as a controller. A bus 11 is connected to the CPU 10. The bus 11 includes a main memory 12 serving as storage means, an external interface 13, a hard disk drive (HDD) 14 serving as storage means, a local memory 15 serving as storage means, a scanner 16, a printer 17, a control panel 20, and an image processor. 30 is connected.

  The local memory 15 is for temporarily storing image data processed by the image processor 30. The scanner 16 optically reads an image of a document set on the MFP 1. The printer 17 prints image data on paper. The control panel 20 is used for setting operation conditions by the user, and includes a display unit 21 and an operation unit 22.

  A plurality of client terminals such as personal computers 61 are connected to the external interface 13 via a network cable 60. These personal computers 61 generate image data using various built-in application programs (word processor, spreadsheet, presentation, DTP software, etc.), and send the generated image data to the MFP 1.

  The image processor 30 is a dynamic reconfigurable processor, and has a DCPU 31 that functions as a control means. Under the control of the DCPU 31 based on an instruction from the CPU 10, a median filter circuit (first median processor) is provided. Filter circuit) 32, edge extraction circuit 33, median filter circuit (second median filter circuit) 34, low resolution conversion circuit 35, median filter circuit (third median filter circuit) 36, and median filter circuit The threshold values in 32, 34, and 36 are set.

  The median filter circuit 32 performs median filter processing on the R, G, and B components of the input image. As shown in FIG. 2, the RGB decomposition processing unit 41, main processing unit 42, selection unit 43, and RGB A synthesis processing unit 44 is included.

  The RGB decomposition processing unit 41 performs RGB decomposition on input image data. The main processing unit 42 performs median filter processing on the R (red) component, G (green) component, and B (blue) component obtained by the RGB decomposition processing unit 41, respectively. This median filtering process arranges the values (density levels) of each pixel in the local area consisting of n × n pixels in the order of the size, and sets the value of the pixel existing in the center of the local area in the middle of the arrangement order. This is a well-known process for replacing a value existing in a position. By this processing, particulate noise on the image, so-called “roughness” is removed.

  The selection unit 43 has preset differences between the values of the R, G, and B components that have been processed by the main processing unit 42 and the values of the R, G, and B components obtained by the RGB decomposition processing unit 41. If the threshold value is greater than or equal to the threshold value, the R component, G component, and B component that have undergone the processing of the main processing unit 42 are selected. If the threshold value is less than the threshold value, the R component, G component, and B component obtained by the RGB decomposition processing unit 41 are selected. The RGB composition processing unit 44 performs RGB composition on the R component, G component, and B component selected by the selection unit 43 and finally outputs them. The selection using the threshold value prevents deterioration of thin line images and fine character images.

  The edge extraction circuit 33 extracts the edge of the character image area in the image data that has passed through the median filter circuit 32. The median filter circuit 34 performs HSV conversion on the R component, G component, and B component of the input image data and performs median filter processing only on the V component. As shown in FIG. 3, RGB-HSV conversion processing is performed. Section 51, main processing section 52, selection section 53, and HSV-RGB conversion processing section 54.

  The RGB-HSV conversion processing unit 51 performs HSV conversion on the R component, G component, and B component of the input image data. The main processing unit 52 performs median filter processing on only the V component among the H (hue) component, S (saturation) component, and V (luminance) component obtained by the RGB-HSV conversion processing unit 51. This median filter processing also arranges the values (density levels) of each pixel in the local area composed of n × n pixels in the order of the size, and sets the value of the pixel existing in the center of the local area in the middle of the arrangement order. This is a well-known process for replacing a value existing in a position. The median filter processing of only the V (luminance) component removes noise contained in the V (luminance) component while maintaining the H (hue) component and the S (saturation) component as they are. Since the hue and saturation are maintained as they are, it is possible to avoid the problem that the color of the image changes.

  The selection unit 53 sets in advance the difference between the H component, S component, and V component values that have undergone the processing of the main processing unit 52 and the H component, S component, and V component values obtained by the RGB-HSV conversion processing unit 51. If the threshold value is equal to or greater than the threshold value, the H component, S component, and V component that have been processed by the main processing unit 52 are selected. If the threshold value is less than the threshold value, the H component, S component, and V component obtained by the RGB-HSV conversion processing unit 51 are selected. Select. The HSV-RGB conversion processing unit 54 performs RGB conversion on the H component, S component, and V component selected by the selection unit 53 and finally outputs them. As described above, since the median filter processing is performed only on the V (luminance) component, the noise removal effect can be enhanced by setting the threshold as high as possible without adversely affecting the hue and saturation. As a result, the size of the file obtained by the filing process described later can be reduced.

  The low resolution conversion circuit 35 reduces the resolution of the image data that has passed through the median filter circuit 34. The median filter circuit 36 performs HSV conversion on the R, G, B components of the input background image data and performs median filter processing only on the V component, and has the same configuration as that of the median filter circuit 34 in FIG. Since the configuration is the same, the description thereof is omitted.

  On the other hand, the CPU 10 generates the median filter circuit 32 when inputting image data from the scanner 16 or the personal computer 61, and after the processing of the median filter circuit 32 is completed, the edge extraction circuit 33 is replaced with the median filter circuit 32. The layout of the character region in the image data generated and processed by the median filter circuit 32 is analyzed based on the extraction result of the edge extraction circuit 33, and the edge extraction circuit 33 is replaced with the edge extraction circuit 33 after the processing of the edge extraction circuit 33 is completed. The median filter circuit 34 is generated. After the processing of the median filter circuit 34 is completed, the low resolution conversion circuit 35 is generated instead of the median filter circuit 34, and the image data subjected to the processing of the low resolution conversion circuit 35 is analyzed. Sentence based on results The image data and the background image data are separated and compressed, respectively, and the compressed background image data is input to the image processor 30, and after the processing of the low resolution conversion circuit 35 is finished, the median is substituted for the low resolution conversion circuit 35. A filter circuit 36 is generated, and the background image data and the compressed character image data that have undergone the processing of the median filter circuit 36 are filed. The DRP control means 10a, the layout analysis processing means 10b, the character / background compression processing means 10c, and file processing means 10d.

  That is, the DRP control means 10a selectively generates the Dian filter circuit 32, the edge extraction circuit 33, the median filter circuit 34, the low resolution conversion circuit 35, and the median filter circuit 36 in the image processor 30 by the DCPU 31 of the image processor 30. And instructing the DCPU 31 of the image processor 30 to set a threshold value to be used in the generated median filter circuits 32, 34, and 36. The layout analysis processing means 10 b analyzes the layout of the character area in the image data that has undergone the processing of the median filter circuit 32 based on the extraction result of the edge extraction circuit 33. The character / background compression processing means 10c separates and compresses the image data that has undergone the processing of the low resolution conversion circuit 35 into character image data and background image data based on the analysis result of the layout analysis processing means 10b. The file processing unit 10d converts the background image data processed by the median filter circuit 36 and the character image data compressed by the character / background compression processing unit 10c into a PDF file.

Next, the operation will be described with reference to FIG.
When inputting image data from the scanner 16 or the personal computer 61, the CPU 10 generates a median filter circuit 32 and sets a threshold value of the median filter circuit 32 in the image processor 30. The generated median filter circuit 32 performs median filter processing on the R, G, and B components of the input image.

  After the processing of the median filter circuit 32 is completed, the CPU 10 generates an edge extraction circuit 33 instead of the median filter circuit 32. The generated edge extraction circuit 33 extracts the edge of the character image area in the image data that has passed through the median filter circuit 32.

  The CPU 10 analyzes the layout of the character area in the image data that has undergone the processing of the median filter circuit 32 based on the extraction result of the edge extraction circuit 33.

  After the processing of the edge extraction circuit 33 is completed, the CPU 10 generates a median filter circuit 34 instead of the edge extraction circuit 33. The generated median filter circuit 34 performs HSV conversion on the R component, G component, and B component of the input image data, and median-filters only the V (luminance) component.

  After the processing of the median filter circuit 34 is completed, the CPU 10 generates a low resolution conversion circuit 35 instead of the median filter circuit 34. The generated low resolution conversion circuit 35 reduces the resolution of the image data that has passed through the median filter circuit 34.

  The CPU 10 separates and compresses the image data that has been processed by the low resolution conversion circuit 35 into character image data and background image data based on the analysis result.

  The CPU 10 inputs the compressed background image data to the image processor 30 and generates a median filter circuit 36 instead of the low resolution conversion circuit 35 after the processing of the low resolution conversion circuit 35 is completed. The generated median filter circuit 36 performs HSV conversion on the R component, G component, and B component of the input background image data, and median-filters only the V (luminance) component.

  The CPU 10 files the background image data that has undergone the processing of the median filter circuit 36 and the compressed character image data into one PDF file. The PDF file is stored in the main memory 12 and then stored in, for example, the hard disk drive 14.

  In this way, the median filter circuit 32 is generated in the image processor 30 and the R, G, B components of the input image data are subjected to median filter processing, thereby removing particulate noise on the image, so-called “roughness”. can do.

  The median filter circuit 34 is generated in the image processor 30, and the R, G, and B components of the input image data are subjected to HSV conversion, and only the V (luminance) component is subjected to median filter processing. The noise contained in the luminance component is removed while maintaining the hue and saturation as they are. Since the hue and saturation are maintained as they are, it is possible to avoid the problem that the color of the image changes.

  The median filter circuit 36 is generated in the image processor 30, and the R, G, B components of the compressed background image data are subjected to HSV conversion, and only the V (luminance) component is subjected to median filter processing. In the image, the noise contained in the luminance component is removed while maintaining the hue and saturation as they are. Since the hue and saturation are maintained as they are, it is possible to avoid the problem that the color of the background image changes.

  Since the median filter circuits 34 and 36 perform median filter processing only on the V (luminance) component, the threshold values of the median filter circuits 34 and 36 are set as high as possible without adversely affecting the hue and saturation, thereby providing a noise removal effect. Can be increased. As a result, the size of the filed PDF file obtained by the file processing described later can be reduced.

  As described above, it is possible to compress image data with higher image quality and smaller size.

  Since a plurality of circuits are sequentially generated one by one on one image processor 30, the configuration is simplified and the cost is reduced as compared with the case where fixed hardware such as an ASIC in which a plurality of circuits are individually provided is used. Reduction can be achieved.

  The above embodiment is presented as an example, and is not intended to limit the scope of the invention. The novel embodiment can be implemented in various other forms, and various omissions, rewrites, and changes can be made without departing from the spirit of the invention. In these embodiments and modifications, the scope of the invention is included in the gist, and is included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... MFP, 10 ... CPU (controller), 10a ... DRP control means, 10b ... Layout analysis processing means, 10c ... Character / background compression processing means, 10d ... File conversion processing means, 30 ... Image processing processor (DRP), 32 ... Median filter circuit (first median filter circuit), 33 ... Edge extraction circuit, 34 ... Median filter circuit (second median filter circuit), 35 ... Low resolution conversion circuit, 36 ... Median filter circuit (third median filter circuit)

Claims (6)

A first median filter circuit that performs median filter processing on R, G, and B components of input image data, an edge extraction circuit that extracts an edge of a character image region in image data that has passed through the first median filter circuit, A second median filter circuit that performs HSV conversion on R, G, and B components of image data and performs median filter processing only on the V component, and a low resolution conversion circuit that lowers the resolution of image data that has passed through the second median filter circuit. An image processor capable of selectively generating a third median filter circuit that performs HSV conversion on R, G, B components of the background image data and median filter processing only the V component;
When the image data is input, the first median filter circuit is generated, and after the processing of the first median filter circuit is completed, the edge extraction circuit is generated instead of the first median filter circuit, and the first median filter circuit Analyzing the layout of the character image area in the processed image data based on the extraction result of the edge extraction circuit, and generating the second median filter circuit instead of the edge extraction circuit after the processing of the edge extraction circuit is completed, After the processing of the second median filter circuit is completed, the low resolution conversion circuit is generated instead of the second median filter circuit, and the image data subjected to the processing of the low resolution conversion circuit is converted into character image data and background based on the analysis result. The image data is separated and compressed, and the compressed background image data Input to the image processing processor, and after the processing of the low resolution conversion circuit is completed, the third median filter circuit is generated instead of the low resolution conversion circuit, and the background image data subjected to the processing of the third median filter circuit and A controller for converting the compressed character image data into a file;
An image forming apparatus comprising: The image processor is a dynamic reconfigurable processor,
2. The image forming apparatus according to claim 1, wherein: The first median filter circuit includes an RGB decomposition processing unit that performs RGB decomposition on the input image data, and a main processing unit that performs median filter processing on R, G, and B components obtained by the RGB decomposition processing unit, respectively. If the difference between the R component, G component, and B component values that have undergone the processing of the main processing unit and the R component, G component, and B component values obtained by the RGB decomposition processing unit is greater than or equal to a threshold value, the main processing is performed. R component, G component, and B component that have undergone part processing are selected, and if it is less than the threshold value, a selection unit that selects the R component, G component, and B component obtained by the RGB decomposition processing unit, and a selection unit that selects An R, G, and B components that are RGB-combined and finally output,
The second median filter circuit includes an RGB-HSV conversion processing unit that performs HSV conversion on the R component, G component, and B component of the input image data, and an H component, S obtained by the RGB-HSV conversion processing unit. A main processing unit that performs median filtering on only the V component of the components and V components, an H component that has undergone processing of the main processing unit, a value of the S component, a V component, and an H component obtained by the RGB-HSV conversion processing unit, When the difference between the S component and the V component is greater than or equal to the threshold value, the H component, S component, and V component that have been processed by the main processing unit are selected, and when the difference is less than the threshold value, the RGB-HSV conversion processing unit obtains the difference. A selection unit that selects an H component, an S component, and a V component, and an HSV-RGB conversion processing unit that performs RGB conversion on the H component, the S component, and the V component selected by the selection unit, and finally outputs the RGB component,
The third median filter circuit includes an RGB-HSV conversion processing unit that performs HSV conversion on R component, G component, and B component of the input background image data, and an H component obtained by the RGB-HSV conversion processing unit, A main processing unit that performs median filtering on only the V component of the S component and V component, and the H component, S component, and V component values that have undergone the processing of the main processing unit, and the H component obtained by the RGB-HSV conversion processing unit If the difference between the values of S, S, and V is greater than or equal to the threshold, the H, S, and V components that have undergone the processing of the main processing unit are selected. If the difference is less than the threshold, the RGB-HSV conversion processing unit A selection unit that selects the H component, the S component, and the V component, and an HSV-RGB conversion processing unit that performs RGB conversion on the H component, the S component, and the V component selected by the selection unit, and finally outputs them.
2. The image forming apparatus according to claim 1, wherein: The controller instructs the selective generation of the first median filter circuit, the edge extraction circuit, the second median filter circuit, the low resolution conversion circuit, and the third median filter circuit in the image processor, Setting a threshold value of the first median filter circuit, a threshold value of the second median filter circuit, and a threshold value of the third median filter circuit;
The image forming apparatus according to claim 3. The image processor is configured to selectively generate the first median filter circuit, the edge extraction circuit, the second median filter circuit, the low resolution conversion circuit, and the third median filter circuit according to an instruction from the controller. Control means for controlling
The controller controls the selective generation of the first median filter circuit, the edge extraction circuit, the second median filter circuit, the low resolution conversion circuit, and the third median filter circuit in the image processor. Layout analysis processing means for analyzing a layout of a character image area in the image data processed by the first median filter circuit based on an extraction result of the edge extraction circuit; and image data processed by the low resolution conversion circuit Character / background compression processing means for separating and compressing character image data and background image data based on the analysis result of the layout analysis processing means, and the background image data and the characters that have undergone the processing of the third median filter circuit / Character image data compressed by background compression processing means Includes a file processing unit that Airu of the,
2. The image forming apparatus according to claim 1, wherein: In an image forming apparatus having an image processor capable of selectively generating a plurality of circuits,
A first median filter circuit that performs median filter processing on R, G, and B components of input image data, an edge extraction circuit that extracts an edge of a character image region in image data that has passed through the first median filter circuit, A second median filter circuit that performs HSV conversion on R, G, and B components of image data and performs median filter processing only on the V component, and a low resolution conversion circuit that lowers the resolution of image data that has passed through the second median filter circuit. Generating a third median filter circuit that sequentially performs RV, G, and B components of the background image data to be subjected to HSV conversion and median filtering only the V component on the image processor;
A procedure for analyzing a layout of a character image area in image data that has undergone processing of the first median filter circuit based on an extraction result of the edge extraction circuit;
A procedure for separating the image data that has undergone the processing of the low resolution conversion circuit into character image data and background image data based on the analysis result;
A procedure for compressing the separated character image data and background image data, respectively;
Inputting the compressed background image data into the image processor;
A procedure for creating a file of the background image data and the compressed character image data that have been processed by the third median filter circuit;
An image forming apparatus control method comprising:

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