JP2006019957A - Image processor and image processing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processor and an image processing program for aiming at gaining both efficient image compression and the prevention of deterioration in image quality caused by the image compression. <P>SOLUTION: Inputted image data are separated into a character region and a non-character one by an image separator 164. A data substitution section 165 substitutes a portion in which pixel data belonging to the character region before the separation by the image separator 164 existed with pixel data except the pixel data belonging to the character region and are at the nearest position to the pixel data belonging to the character region. An image compression section 166 performs different image compressing processing for each region to the image data of the non-character region in which the data are substituted and those of the character region separated by the image separation section 164. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus and an image processing program, and more particularly to an image data compression technique for reducing the amount of image data.

Conventionally, when image data read by a scanner function is stored in an image forming apparatus or the like, the image data is compressed and stored in order to use the storage area of the storage device effectively. . As an image compression apparatus for efficiently performing this image compression process, for example, an apparatus disclosed in Patent Document 1 has been proposed. This image compression apparatus separates image data read by a scanner into a plurality of image areas, and compresses a character area or the like that is assumed to have severe image degradation due to compression, compared to other areas. The compression process is performed at a low compression rate.
JP 2001-186356 A

  However, when image compression processing is performed on areas other than character areas as described above, there are the following problems. That is, when image data is separated into character areas and other areas (hereinafter referred to as non-character areas), and image compression processing is performed after the pixel data of the character area portions are cut out from the non-character areas and removed. If the density difference between the part from which the pixel data of the character area has been removed and the other part is large, efficient image compression cannot be performed, and noise may be generated, reducing image quality. You may be invited.

  The present invention has been made to solve the above problems, and an object thereof is to provide an image processing apparatus and an image processing program capable of achieving both efficient image compression and prevention of image quality deterioration due to the image compression. To do.

The invention according to claim 1 of the present invention is an image separating means for separating input image data into a character region and a non-character region;
Of the pixel data constituting the image data of the non-character area separated by the image separation means, the portion where the pixel data belonging to the character area existed before the separation by the image separation means belongs to the character area Data replacement means for replacing the pixel data other than the pixel data with pixel data at a position closest to the pixel data belonging to the character area;
Image compression means for performing different image compression processing for each area on the image data of the character area separated by the image separation means and the image data of the non-character area subjected to data substitution by the data substitution means; Is an image processing apparatus.

The invention according to claim 5 is an image separation means for separating the input image data into a character area and a non-character area;
Of the pixel data constituting the image data of the non-character area separated by the image separation means, the portion where the pixel data belonging to the character area existed before the separation by the image separation means belongs to the character area Data replacement means for replacing the pixel data other than the pixel data with pixel data at a position closest to the pixel data belonging to the character area;
As image compression means for performing different image compression processing for each area on the image data of the character area separated by the image separation means and the image data of the non-character area subjected to data substitution by the data substitution means. ,
An image processing program for causing a computer to function.

  In these configurations, the input image data is separated into a character area and a non-character area by the image separation means, and among the image data of this non-character area, pixel data belonging to the character area before separation by the image separation means The data replacement means replaces the portion where the data has been replaced with the pixel data closest to the pixel data belonging to the character area other than the pixel data belonging to the character area. The image compression means performs different image compression processing for each area on the image data of the character area and the image data of the character area separated by the image separation means.

The invention according to claim 2 is the image processing apparatus according to claim 1, wherein the image identifying means for identifying the input image data into a halftone dot area and a non-halftone dot area;
A different smoothing process is applied to each halftone dot area and non-halftone dot area identified by the image identification means, and the halftone dot area is smoother than the non-halftone dot area. And smoothing processing means for performing the conversion processing.

  In this configuration, the input image data is discriminated into a halftone dot area and a non-halftone dot area by the image discriminating means, and the smoothing processing means smoothes the halftone dot area stronger than the non-halftone dot area. The processing is performed.

  The invention according to claim 3 is the image processing apparatus according to claim 1 or 2, wherein the image compression processing for the image data of the character area by the image compression means is a reversible method. is there.

  According to this configuration, since the image compression processing for the image data of the character area by the image compression means is a reversible method, the image quality can be maintained when the character area is compressed.

  According to a fourth aspect of the present invention, in the image processing apparatus according to any one of the first to third aspects, the image compression processing for the image data in the non-character area by the image compression means is irreversible. It is a method.

  According to this configuration, since the image compression processing for the image data of the non-character area by the image compression means is an irreversible method, the non-character area can be compressed with a relatively high compression rate, and the amount of image data is effectively reduced. Can be made.

  According to the first and fifth aspects of the present invention, the portion of the image data in the non-character area that includes the pixel data belonging to the character area before separation by the image separation means belongs to the character area. Since the image compression processing is performed after replacing the pixel data other than the pixel data with the pixel data closest to the pixel data belonging to the character area, the pixel data in the character area existed before separation by the image separation means And the density difference with other parts other than this becomes small. Therefore, efficient image compression can be performed, and noise and other factors are eliminated, and image quality does not deteriorate. Thereby, both efficient image compression processing and prevention of image quality deterioration due to the image compression processing are compatible.

  According to the second aspect of the present invention, since the smoothing process stronger than the non-halftone area is performed on the halftone area, the amount of image data in the halftone area can be effectively reduced. The image quality can be maintained by not performing a strong smoothing process on the point area.

  According to the third aspect of the present invention, since the image compression processing for the image data of the character area is a reversible method, the image quality can be maintained when the character area is compressed.

  According to the fourth aspect of the present invention, since the image compression processing for the image data in the non-character area is an irreversible method, the non-character area can be compressed with a relatively high compression rate, and the amount of image data can be effectively reduced. Can be reduced.

  Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 is a side view schematically showing an internal configuration of a multifunction machine including an image processing apparatus according to an embodiment of the present invention. The image processing apparatus according to the present invention is applied to a multifunction machine 1 having functions such as a copy function, a printer function, a scanner function, and a facsimile function. The multi-function device 1 includes a main body 2, a stack tray 3 disposed on the left side of the main body 2, a document reading unit 5 disposed on the top of the main body 2, and an upper side of the document reading unit 5. And a document feeding unit 6 disposed.

  An operation unit 47 is provided at the front part of the multifunction machine 1. The operation unit 47 displays a start key 471 for a user to input a print execution instruction, a ten key 472 for inputting the number of copies to be printed, operation guide information for various copying operations, and the like. A display unit 473 formed of a liquid crystal display or the like having a touch panel function, a reset key 474 for resetting setting contents set in the display unit 473, and a stop key for stopping a printing (image forming) operation being executed 475 and a function switching key 477 for switching between a copy function, a printer function, a scanner function, and a facsimile function.

  The document reading unit 5 includes a scanner unit 51 including a CCD (Charge Coupled Device) sensor and an exposure lamp, and a document table 52 and a document reading slit 53 made of a transparent member such as glass. The scanner unit 51 is configured to be movable by a drive unit (not shown). When reading a document placed on the document table 52, the scanner unit 51 is moved along the document surface at a position facing the document table 52, and the document image is scanned. The image data acquired while scanning is output to the control unit 100 (FIG. 2). Further, when reading a document fed by the document feeding unit 6, the document is moved to a position facing the document reading slit 53 and synchronized with the document feeding operation by the document feeding unit 6 via the document reading slit 53. The image of the original is acquired and the image data is output to the control unit 100.

  The document feeding unit 6 includes a document placing unit 61 for placing a document, a document discharge unit 62 for discharging a document whose image has been read, and a document placed on the document placing unit 61. A document transport mechanism 63 including a paper feed roller (not shown), a transport roller (not shown) and the like for feeding the paper one by one to a position facing the document reading slit 53 and discharging it to the document discharge section 62 is provided. The document conveyance mechanism 63 further includes a sheet reversing mechanism (not shown) that reverses the document and reversely conveys the document to a position facing the document reading slit 53, and scans both sides of the document through the document reading slit 53. 51 can be read.

  The document feeding unit 6 is provided so as to be rotatable with respect to the main body unit 2 so that the front side thereof can move upward. By moving the front side of the document feeder 6 upward to open the upper surface of the document table 52, the operator can place a read document, for example, a book in a spread state, on the upper surface of the document table 52. It has become.

  The main body 2 includes a plurality of paper feed cassettes 461, a paper feed roller 462 that feeds the recording paper from the paper feed cassette 461 one by one and transports it to the recording unit 40, and a recording paper transported from the paper feed cassette 461. And a recording unit 40 for forming an image.

  The recording unit 40 outputs an optical beam or the like based on the image data acquired by the scanner unit 51 to expose the photosensitive drum 43, and a developing unit 44 that forms a toner image on the photosensitive drum 43. A transfer unit 41 for transferring the toner image on the photosensitive drum 43 to the recording paper, a fixing unit 45 for fixing the toner image to the recording paper by heating the recording paper to which the toner image has been transferred, Conveying rollers 463 and 464 that are provided in the sheet conveying path and convey the recording sheet to the stack tray 3 or the discharge tray 48 are provided.

  When forming images on both sides of the recording paper, the recording unit 40 forms an image on one side of the recording paper, and then the recording paper is nipped by the conveyance roller 463 on the discharge tray 48 side. . In this state, the conveyance roller 463 is reversed to switch back the recording paper, and the recording paper is sent to the paper conveyance path L and conveyed again to the upstream area of the recording unit 40, and an image is formed on the other surface by the recording unit 40. Thereafter, the recording paper is discharged to the stack tray 3 or the discharge tray 48.

  FIG. 2 is a functional block diagram showing a schematic configuration of the multifunction machine 1. The multifunction machine 1 includes a control unit 100 that controls the operation of the entire apparatus. The control unit 100 includes a scanner unit 51 that can read an original image including an exposure lamp 511 and a CCD 512, and a recording unit 40 that includes a paper transport unit 131, an image forming unit 132, a transfer unit 41, a fixing unit 45, and the like. And are connected. Further, the control unit 100 includes an image memory 140 including a semiconductor storage device or the like in which document data read by the scanner unit 51 is temporarily stored, and a large capacity having a storage capacity capable of storing a large amount of document data. HDD (storage device) 150 is connected.

  The image processing unit 160 converts an analog image signal output from the scanner unit 51 into a digital image signal when image reading is performed by the scanner unit 51, performs image processing to improve image quality, and converts the image into a compressed image. is there. This compressed image is written into the image memory 140. In addition, under the control of the control unit 100, the compressed image written in the image memory 140 can be stored in the HDD 150 as file data to be managed by the document. At the time of printing out the stored document, the file data (compressed image) to be printed out is read from the HDD 150, and the image processing unit 160 decompresses the compressed file data and performs image processing according to the output state. For example, in the case of laser exposure, the laser signal is analog-modulated. The recording unit 40 (image forming unit 132) prints out based on the analog-modulated signal.

  The control unit 100 also functions as a scanner controller 101, a facsimile controller 102, a printer controller 103, a copy controller 104, and a network controller 105 that control each function that can be executed by the multifunction device 1.

  The scanner controller 101 performs operation control of each unit necessary for the operation of the scanner unit 51. The facsimile controller 102 controls the operation of each unit necessary for the facsimile operation, and controls the facsimile communication unit 170 that adjusts data necessary for facsimile communication. The facsimile communication unit 170 is provided with an NCU (Network Control Unit) that controls connection of a telephone line with a destination facsimile that is a data transmission / reception partner. The copy controller 104 controls the operation of each unit necessary for the copy operation.

  The printer controller 103 performs operation control of each unit necessary for printer operation. The printer controller 103 includes a parallel I / F unit 181 that is connected to an external device by parallel transmission that transmits several bits at a time using a plurality of signal lines, and one bit at a time using a single signal line. A serial I / F unit 182 connected to an external device by serial transmission for sending data is connected.

  The network controller 105 controls data transmission / reception performed with a computer on the network when the MFP 1 is connected to the computer on the network. The network controller 105 transmits / receives data to / from the outside via the network I / F unit 210.

  FIG. 3 is a block diagram illustrating a schematic configuration of the image processing unit 160 in the multifunction machine 1. As described above, the image processing unit (image processing apparatus) 160 performs predetermined image processing on the document image data received from the scanner unit 51, and outputs the image data after the image processing to the image memory 140. The image processing unit 160 includes an input image processing unit 161, an attribute determination unit 162, a smoothing processing unit 163, an image separation unit 164, a data replacement unit 165, and an image compression unit 166.

  The input image processing unit 161 performs image processing such as shading correction, CCD line correction, and color correction on the image data input from the scanner unit 51.

  An attribute determination unit (image identification unit) 162 is a region (hereinafter referred to as a halftone dot region) composed of image data when each part of the image data input from the scanner unit 51 reads a document image printed with halftone dots. And an area composed of image data when a document image that is not a halftone dot is read (hereinafter, referred to as a non-halftone dot area), and which attribute is determined.

  This determination is made based on whether the image reading signal value when an image of a certain region is read indicates a feature of a halftone dot region or a non-halftone dot region. For example, the determination is made based on the number of changes in the image signal from white to black in a predetermined section around the pixel of interest (the pixel to be processed among the read pixels). When a halftone dot print area on a document is read, among the R, G, and B signal values of the read image data, for example, the G signal value is composed of a white background and a halftone dot. Therefore, the G signal value representing the white background and the G signal value representing the halftone dot (black background) are repeated, and the characteristics of the white and black pixels are repeated frequently. Therefore, it is determined as a halftone dot region.

  The smoothing processing unit (smoothing processing means) 163 includes a smoothing filter 1631 and a Gaussian filter 1632. The smoothing processing unit 163 performs a smoothing process on the image data input from the scanner unit 51 to give a density average of pixels in a certain region centered on the pixel instead of the density of a certain pixel. . The Gaussian filter 1632 performs spatial filter processing having a smoothing effect stronger than that of the smoothing filter 1631 on the image data input from the scanner unit 51.

  The image separation unit (image separation unit) 164 reads the image data input from the scanner unit 51 from an area composed of image data obtained by reading a character print portion (hereinafter referred to as a character region) and a print portion other than characters. A process of separating the area into image data areas (hereinafter, non-character areas) is performed.

  The image separation unit 164 determines whether the region is a character region or a non-character region based on whether the image reading signal value when the image of a certain region is read indicates a character region or a non-character region. Determine if there is a separation. For example, when an area in which black characters are printed on a white background is read, a plot of the G signal value related to the character area among the R, G, and B signal values of the read image data extends from the white background portion to the character portion. The characteristics change rapidly. In addition, the white pixel and the black pixel do not repeat as frequently as when the halftone dot area is read. A character area is determined when such a signal value characteristic is detected, and the image data is separated into a character area and a non-character area.

  The data replacement unit (data replacement unit) 165 has pixel data belonging to the character region (that is, data of pixels constituting the character) for the non-character region image data separated by the image separation unit 164. The portion other than the pixel data belonging to the character area is replaced with the pixel data at the position closest to the pixel data belonging to the character area. This pixel data replacement processing is performed by, for example, (1) replacing the part of the image data in the non-character area where the pixel data belonging to the character area has existed in the main scanning direction of the scanner unit 51 immediately before the other part or Replace with the pixel data immediately after (that is, replace the data of all the pixels that had previously constituted the character with the data of other pixels that do not constitute the character), (2) in the image data of the non-character area (3) In the image data of the non-character region, the portion where the pixel data belonging to the character region has existed is replaced with the pixel data immediately before or after the portion other than the portion in the sub-scanning direction of the scanner unit 51. Replace the part that previously had pixel data belonging to the character area with the pixel data immediately before or after the part other than the part arranged obliquely with respect to this part. , It is carried out as an equal.

  The image compression unit (image compression unit) 166 performs compression processing on the image data input from the scanner unit 51, and includes a lossless compression unit 1661 and an irreversible compression unit 1662. The reversible compression unit 1661 performs image compression in such a manner that the data is completely restored when the compressed data is expanded. The irreversible compression unit 1662 performs image compression in such a manner that when the compressed data is expanded, it is not completely restored. When performing image compression processing, when priority is given to image quality over compression rate, compression processing by the lossless compression unit 1661 is performed, and when priority is given to compression rate over image quality, compression processing by the lossy compression unit 1662 is performed. .

  An example of image processing by the image processing unit 160 when a document image is read by the scanner unit 51 will be described with reference to FIGS. 4 and 5 in addition to FIG. FIG. 4 is a diagram showing an example of a document on which a character image, a photographic image and a halftone dot image are printed. FIG. 5 is a diagram virtually showing a state in which a character image portion image is cut out from a non-character region image. .

  When the image on the original is read by the scanner unit 51, first, the image data is sent to the input image processing unit 161, and the input image processing unit 161 performs shading correction and CCD line-line correction on the entire image data. Image processing such as color correction is performed. Each part of the image data that has undergone image processing in the input image processing unit 161 is identified by the attribute determination unit 162 as a halftone dot region or a non-halftone dot region, and it is determined which attribute it will have. For example, as shown in FIG. 4, when the image of the document 300 is composed of a character area 301, a silver halide photograph area 302, a halftone dot area 303, and a background area 304, only the halftone dot area 303 is determined as a halftone dot area. The other character area 301, silver halide photograph area 302, and background area 304 are all determined to be non-halftone areas.

  Then, the smoothing processing unit 163 performs a smoothing process on the region determined by the attribute determination unit 162 as a non-halftone dot region by the smoothing filter 1631. Further, the area determined to be a halftone dot area is subjected to smoothing processing stronger than the smoothing filter 1631 by the Gaussian filter 1632. This smoothing process is performed for the purpose of reducing the amount of image data in addition to the purpose of noise removal.

  After the smoothing process, the image data is separated into a character region or a non-character region by the image separation unit 164. For example, in the original 300 shown in FIG. 4, only the character region 301 is a character region, and the other silver halide photograph region 302, halftone dot region 303, and background region 304 are all non-character regions. Here, the image data of the character area is compressed by the lossless compression unit 1661 of the image compression unit 166 with an emphasis on the image quality rather than the compression rate for the purpose of accurately reproducing the outline of the character image. .

  For image data in a non-character area, the data replacement unit 165 includes the above-described data replacement process (the pixel data belonging to the character area (that is, the data of the pixels constituting the character). Is replaced with pixel data other than the pixel data belonging to the character area and closest to the pixel data belonging to the character area. For example, when the above-described process (1) is performed, as shown in FIG. 5, pixel data corresponding to the part a of the character image “A” is converted into pixel data corresponding to the part b immediately before in the scanning direction by the scanner unit 51, or Immediately thereafter, the pixel data corresponding to the portion c is replaced. That is, out of the pixel data constituting the image data of the non-character area, the pixel data corresponding to the portion a of the character image “A” is cut out and removed, and the pixel data corresponding to the portion b immediately before the cut-out portion a, or Immediately thereafter, the pixel data corresponding to the portion c is embedded.

  The non-character region image data subjected to the data replacement process by the data replacement unit 165 does not require as accurate reproducibility as a character image. Compression processing is performed by the compression unit 1662. The image data of the character area and the non-character area after being compressed by the image compression unit 166 is stored in the image memory 140.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the above-described embodiment, an embodiment in which the image processing apparatus according to the present invention is applied to the multifunction machine 1 is shown. However, the image processing apparatus can also be applied to a single machine such as a facsimile machine or a copying machine.

  The present invention also provides a recording medium that records a software program that implements the functions of the above-described embodiments, and a computer (such as a CPU) reads the programs recorded on the recording medium and executes the functions of the above-described embodiments. May be achieved by doing so. In addition, the program read by the computer is not limited to the case where the functions of the above-described embodiments are realized, and an operating system or the like operating on the computer based on the program may be a part of the actual processing or This includes all cases where the functions of the above-described embodiments are realized.

  In the above embodiment, the configuration and processing of the image processing apparatus according to the present invention and the multi-function device 1 to which the image processing device is applied have been described with reference to FIGS. 1 to 5. However, these configurations and processing are merely examples. However, the present invention is not limited to the above.

1 is a side view schematically showing an internal configuration of a multifunction machine including an image processing apparatus according to an embodiment of the present invention. FIG. 2 is a functional block diagram illustrating a schematic configuration of the multifunction machine illustrated in FIG. 1. FIG. 2 is a block diagram illustrating a schematic configuration of an image processing unit in a multifunction peripheral. FIG. 4 is a diagram illustrating an example of a document on which a character image, a photographic image, and a halftone dot image are printed. It is a figure which shows virtually the state where the image of the character image part was cut out from the image of a non-character area | region.

Explanation of symbols

1 MFP 51 Scanner Unit 160 Image Processing Unit 161 Input Image Processing Unit 162 Attribute Determination Unit 163 Smoothing Processing Unit 1631 Smoothing Filter 1632 Gaussian Filter 164 Image Separation Unit 165 Data Replacement Unit 166 Image Compression Unit 1661 Lossless Compression Unit 1661 Non-Reversible Compression unit 300 Document 301 Character area 302 Silver salt photograph area 303 Halftone area 304 Base area

Claims (5)

Image separation means for separating input image data into a character area and a non-character area;
Of the pixel data constituting the image data of the non-character area separated by the image separation means, the portion where the pixel data belonging to the character area existed before the separation by the image separation means belongs to the character area Data replacement means for replacing the pixel data other than the pixel data with pixel data at a position closest to the pixel data belonging to the character area;
Image compression means for performing different image compression processing for each area on the image data of the character area separated by the image separation means and the image data of the non-character area subjected to data substitution by the data substitution means; An image processing apparatus. Image identifying means for identifying input image data into a halftone dot region and a non-halftone dot region;
A different smoothing process is applied to each halftone dot area and non-halftone dot area identified by the image identification means, and the halftone dot area is smoother than the non-halftone dot area. The image processing apparatus according to claim 1, further comprising a smoothing processing unit that performs a conversion process.   The image processing apparatus according to claim 1, wherein the image compression processing on the image data of the character area by the image compression unit is a reversible method.   The image processing apparatus according to claim 1, wherein the image compression processing on the image data in the non-character area by the image compression unit is an irreversible method. Image separation means for separating input image data into a character area and a non-character area;
Of the pixel data constituting the image data of the non-character area separated by the image separation means, a portion where the pixel data belonging to the character area existed before separation by the image separation means belongs to the character area Data replacement means for replacing the pixel data other than the pixel data with pixel data at a position closest to the pixel data belonging to the character area;
As image compression means for performing different image compression processing for each area on the image data of the character area separated by the image separation means and the image data of the non-character area subjected to data substitution by the data substitution means. ,
An image processing program that causes a computer to function.

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