JP2006166101A - Image processing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing system capable of forgery prevention determination of an PDL (Page Description Language) image with an inexpensive configuration. <P>SOLUTION: It is determined whether an image signal from a PC is RGB or CMYK. The RGB image is inputted into a determining circuit via a color correction matrix (3*3) and γ correction, and the CMYK image is inputted into the determining circuit via color spatial conversion, a color correction matrix (3*4), and γ correction. If a document is a bill or securities, output data are discarded. The forgery prevention system consists of the above configuration. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing system, and more particularly to an image processing system that suppresses counterfeiting of banknotes and securities.

  Conventionally, a so-called color document copying apparatus as shown in FIG. 10 is known as a system for digitally reading a color document image to generate a copy image.

  In FIG. 10, reference numeral 1001 denotes an image scanner unit which reads a document and performs digital signal processing. Reference numeral 1002 denotes a printer unit which prints out an image corresponding to the original image read by the image scanner 1001 on a sheet in full color.

  In the image scanner 1001, reference numeral 1000 denotes a specular pressure plate. A document 1004 on a platen glass (hereinafter referred to as a platen) 1003 is irradiated with a lamp 1005, guided to mirrors 1006, 1007, and 1008, and an individual of three lines by a lens 1009. An image is formed on an image sensor (CCD) 1010, and three image signals of red (R), green (G), and blue (B) as full color information are sent to the signal processing unit 1011.

  Note that 1005 and 1006 are the speed v, and 1007 and 1008 are the mechanical movement in the direction perpendicular to the electric scanning (main scanning) direction of the line sensor at a speed of 1/2 v, thereby scanning the entire surface of the document (sub scanning). ) Here, the document 1004 is read at a resolution of 400 dpi (dots / inch) for both main scanning and sub-scanning.

  The signal processing unit 1011 electrically processes the read image signal, decomposes it into magenta (M), cyan (C), yellow (Y), and black (Bk) components and sends them to the printer unit 1002. . In addition, one component of M, C, Y, and Bk is sent to the printer unit 1002 for one document scan in the image scanner 1001, and one printout is completed by a total of four document scans.

  M, C, Y, and Bk image signals sent from the image scanner unit 1001 are sent to the laser driver 1012. The laser driver 1012 modulates and drives the semiconductor laser 1013 in accordance with the sent image signal. The laser beam scans on the photosensitive drum 1017 via the polygon mirror 1014, the f-θ lens 1015, and the mirror 1016. Here, as with reading, both main scanning and sub-scanning are written at a resolution of 400 dpi (dots / inch).

  Reference numeral 1018 denotes a rotary developing unit, which includes a magenta developing unit 1019, a cyan developing unit 1020, a yellow developing unit 1021, and a black developing unit 1022, and four developing units are alternately in contact with the photosensitive drum 1017 and formed on the photosensitive drum. The electrostatic development is developed with toner.

  Reference numeral 1023 denotes a transfer drum which wraps a sheet supplied from a sheet cassette 1024 or 1025 around the transfer drum 1023 and transfers an image developed on the photosensitive drum onto the sheet.

  In this way, after the four colors M, C, Y, and Bk are sequentially transferred, the sheet passes through the fixing unit 1026 and is discharged after the toner is fixed on the sheet.

Such a color manuscript copying apparatus is equipped with forgery prevention processing from the viewpoint of preventing forgery of banknotes and securities. Even if a banknote is to be copied, if it is recognized as a banknote or securities, it is generally not output by a printer or painted in black (for example, see Patent Document 1).
Japanese Patent No. 2951964

  As described above, in the conventional example described above, forgery prevention processing of banknotes and securities is performed on the image via the scanner, but it does not function for the image via the LAN (Local Area Network). .

  The present invention has been made paying attention to the above points, and an object of the present invention is to provide an image processing system capable of determining forgery prevention for a PDL (Page Description Language) image with an inexpensive configuration. And

Therefore, in the present invention,
In an image processing system that electrically reads a document image, converts it into a digital signal for each pixel, and outputs a duplicate image of the document,
An image processing system for performing a forgery determination process on a signal input to an image processing apparatus via a network,
By performing forgery determination processing also on an image via a network, counterfeiting of banknotes and securities can be suppressed.

  Further, the first invention of the present invention will be described as follows.

  (1) In an image processing system that electrically reads a document image, converts it into a digital signal for each pixel, and outputs a copy image of the document, means for developing image data input via a network into bitmap data; An image having specific information extracting means for extracting specific information from the image data expanded into bitmap data, and performing color conversion before inputting the image data to the specific information extracting means; Processing system.

  According to the present invention, by performing color space conversion, color correction, and gradation correction, it is possible to use a forgery determination circuit that has been possessed in the past, so it is possible to determine forgery prevention for PDL images with an inexpensive configuration. It becomes.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples.

[First embodiment]
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a block diagram showing an example of a configuration for carrying out the present invention.

[Reading section]
A document to be copied is placed on a document placing table glass (not shown) of the scanner unit 101 and read. As in FIG. 10, the scanner unit digitally reads an original image pixel by pixel with a color 3-line CCD and transfers a color image signal to the first input image processing unit 102. The input image processing unit 102 performs known image processing such as shading correction, CCD line correction, and color correction on the RGB color image signal sent from the scanner unit.

  Reference numeral 103 denotes a block that performs image area separation processing on the color image signal that has been processed by the input image output from 102, and detects image features such as a photo area, a character area, and a dot area for each pixel of the input image. Thus, the image area separation processing unit generates flag data representing an attribute for each image area.

[Image area separation processing]
Here, the image area separation processing unit will be described.

  The image area separation process is for extracting a feature of an original image and generating a signal indicating an image area attribute (hereinafter referred to as flag data) in order to perform optimum image processing according to the feature of the image included in the original image. To be done. For example, in a document, various image areas such as a continuous tone full-color photographic area, a black-colored character area, or a halftone dot printing area such as newspaper printing are usually mixed.

  If these are uniformly processed by the same image processing procedure and output, the output image generally does not often have a desirable image quality.

  Therefore, in the present invention, the attribute of the image data included in the document image is detected using the color image signal input from 102, and flag data for identifying the attribute is generated. A specific procedure is shown in FIG.

  FIG. 2 shows an example of an original image, and shows a state in which a silver halide photograph area 202, a black character area 203, a halftone dot print area 204, and a color graphic area 205 are mixed in one page 201. .

  Here, the scanner unit scans the original image with a color CCD sensor and reads it as a color digital signal (R, G, B) for each pixel. The read RGB signal has a characteristic determined by an attribute for each region of the image. FIG. 3 shows, for example, a plot of the G signal among the signal values (R, G, B) read by the CCD sensor in each region in the CCD arrangement direction.

  3, 302, 303, 304, and 305 are examples of characteristics that appear characteristically when the areas 202 to 205 in FIG. 2 are read. The horizontal axis represents the pixel position in the CCD and the vertical direction, and the vertical axis represents the read. This indicates that the pixel value is closer to white (brighter) as it goes upward in the signal value.

  The characteristics of each region will be described. Since 202 is a photographic region, the change 302 depending on the position of the image signal to be read is relatively gentle, and the difference 312 between the pixel values in the short distance is a small value.

  Reference numeral 303 denotes a characteristic of the black character region 203. Since black characters are written on a white background, the signal value plot has such a characteristic that the read signal value changes rapidly from the white background portion 313 to the character portion 323.

  Reference numeral 304 denotes a characteristic of the halftone dot area 204. The halftone dot area is a repetition of the white background 314 and the halftone dot 324 printed thereon, so that the signal values plotted are white and black as shown in the figure. It becomes a characteristic that repeats frequently.

  305 is a plot diagram of the graph area. In the graphic edge portion 315, the signal value is abruptly decreased, and the internal colored portion 325 has a characteristic that a certain intermediate level continues.

  In order to determine these attributes, the characteristics for each region as described above may be detected and determined from the read signal value. For this purpose, the amount of change in the image data in the vicinity of the target pixel, or the integrated value of the amount of change within a certain interval, the luminance value of the surrounding pixels (whether white or colored background), the white of the image data within the certain interval A feature extraction method using a known method such as the number of changes to black can be used, and a known attribute discrimination method based on the feature extraction method can be used.

  FIG. 4 shows an example of the attribute flag generated for the document image shown in FIG. Here, three types of flags, a character flag, a graphic flag, and a halftone dot flag, are generated as attribute flags (flag data), but of course the invention is not limited thereto. FIG. 4A shows a character flag. Pixels represented by black in the drawing are pixels having character attributes, and character flag = 1 is generated. Otherwise, character flag = 0 (white portion in the figure). Yes. (B) is a graphic flag which is 1 in the graphic area and 0 otherwise. (C) is a halftone dot flag which represents an area which is 1 in the halftone area and 0 otherwise. Yes.

  Since the photographic area does not correspond to any of these, all the flags are 0, and they do not appear in FIG.

  When the image attributes are detected for each pixel by the above image area separation processing, the second input image processing unit 104 performs image processing according to the image attributes.

  Here, for example, the high frequency component of the image is emphasized for the character area to enhance the sharpness of the character, and the so-called low-pass filter processing is performed for the dot area to remove the moire component peculiar to the digital image. Can be performed. These processes can be switched in units of pixels according to the attribute flag data generated in 103.

[Storage of image data]
The image data read by the scanner and subjected to various input image processing and the attribute flag data generated by the above procedure are temporarily stored in the image memory 1 105 and the flag memory 1 106. At this time, the image data and the attribute flag data are stored as a partial image of the entire original page or a predetermined size of one page.

  The temporarily stored image data and attribute flag data are compressed by the data compression unit 109 and stored in the storage device 110. 110 is preferably a high-speed storage means such as a semiconductor memory device. The data compression unit performs different data compression processes on the image data and the flag data. In other words, image data is irreversible like JPEG compression, but high-efficiency compression processing is applied so that image degradation is inconspicuous in consideration of human visual characteristics. Therefore, it is desirable to use a reversible compression method such as JBIG compression because no attribute flag information is lost or changed.

  In this way, the image data and the flag data subjected to different compression processes are stored in the original 110 in units of one page. The stored data may also be written to 111 auxiliary storage devices. The auxiliary storage device is preferably a medium such as a hard disk that can store a large amount of data although the recording speed is slightly slow. By doing so, it is possible to efficiently store and accumulate a large number of pages of document images.

[Reading image data]
The image data and attribute flag data stored in 110 or 111 are read out for output from the print unit, and the compressed data is decompressed by 112 data decompression units, respectively. It is written to the flag memory 2.

  At this time, the pixel density conversion unit 113 may convert the pixel density of the stored image data. This is used, for example, when it is desired to print out the enlarged image data by enlarging or reducing the accumulated image data, or when it is desired to combine and output a plurality of accumulated pages on one print output sheet.

  For example, the composite output of a plurality of pages is as shown in FIG. That is, it is assumed that two document images 501 and 502 are stored in the storage device in advance. This is a case where a print output such as 503 is obtained by combining two sheets on output paper of the same size as the original.

  For this purpose, first, the stored image data 501 is read from the storage means, and the compressed data is decompressed, reduced at a predetermined magnification by the pixel density conversion unit 113, and rotated 90 degrees to the left by a rotation processing unit (not shown). It is written in a predetermined area of the image memory 2 (area corresponding to 504 in FIG. 5).

  Next, the image data 502 is read out, similarly decompressed, converted in resolution, and rotated, and written in an area corresponding to 505 in the image memory 2.

  At this time, the flag data corresponding to the originals A and B are similarly decompressed, resolution-converted and rotated, and written in the corresponding area of the flag memory 2.

  Here, it is desirable to apply different methods to the resolution conversion of image data and the resolution conversion of flag data. For example, a known method such as a linear interpolation method or a bicubic spline interpolation method can be applied to image data. For the resolution conversion of flag data, it is desirable to use a resolution conversion method suitable for binary data such as nearest neighbor processing.

[Output image data]
The image data and flag data temporarily stored in the image memory 2 and the flag memory 2 are transferred to the output image processing unit 116 when reaching a predetermined size.

  The output image processing unit 116 performs well-known image processing for printing out RGB image data, that is, luminance density conversion, RGB → CMYK conversion, gamma correction, binarization processing, and the like, and transfers them to the printer unit 117. To do.

  The printer unit 117 is laser-driven by the transferred CMYK image signal, and forms and outputs a visible image on the transfer paper in the same procedure as in FIG.

  Here, the flag data stored in the flag memory 2 is used for switching the processing of the output image processing unit 116. That is, the image quality of the output image can be improved by making the coefficient of RGB → CMYK conversion different between the photo area and the character area. For example, for a pixel having a character region, ie, a character flag = 1, a conversion coefficient such that a black character can be reproduced only with black toner (that is, a coefficient such that C, M, Y = 0 when the image data is achromatic) In other cases, C, M, and Y do not become 0 even if the color is achromatic, and a coefficient that can reproduce deep black can be used.

  In the binarization process, the C, M, Y, and K signals are converted into a binary signal of 0 or 1 using a known error diffusion process or dither process. At this time, an output image is output in the character area or the graph area. Since the sharpness of the image is given priority, the error diffusion process is applied, and the dithering process is applied because the gradation is emphasized in the photograph and the halftone area. The image quality of the output image can be improved by switching according to.

  An example of a block diagram of the configuration at this time is shown in FIG.

  The image memory 2 114, the flag memory 2 115, and the printer unit 117 are the same as those in FIG. The RGB color image data read from the image memory 2 is input to two RGB → CMYK conversion circuits 601 and 602 in parallel, and converted into CMYK image signals, respectively. One of the outputs 601 and 602 is selected by the selector 1 603 in accordance with the flag signal of the flag memory. When the conversion coefficient for the character area is set in 601 and the coefficient in other cases is set in 602, the output of 601 is selected when the character flag in the flag memory = 1, and the character flag = When 0, the output of 602 is selected.

  The output of the selector 1 is also separated into two systems in parallel, one of which passes through the gamma correction circuit 1 of 604 and the error diffusion binarization processing unit of 606 and is input to the selector 2 of 608 as a binary CMYK signal. .

  The other is passed through the gamma correction circuit 2 of 605 and the dither processing binarization circuit of 607 and is also inputted to the selector 2 of 608 as a binary CMYK signal.

  The selector 2 selects either the output 606 or 607 and transfers it to the printer unit. Here, since error diffusion processing is selected in the character area and the graph area, the selector when the character flag = 1 or the graphic flag = 1 is selected. 2 may select the output of 606, otherwise the output of 607 may be selected.

[Print image]
Typical image data input from the external communication path 119 through the communication interface 118 is image data described in a so-called PDL (Page Description Language).

  The PDL data input from the communication interface 118 is converted into an intermediate language format called a display list by the interpreter 108. This display list is sent to a RIP (Raster Image Processor) 107 and developed into bitmap data. The developed image data is stored in the image memory 1 105. At this time, the RIP 107 generates attribute information of the developed image data as flag data and stores it in the flag memory 1 106.

  The flag data refers to the attribute information (such as a photograph or text or graphic) held in each part of the PDL data input to the RIP, and the flag data of the corresponding pixel of the developed image is obtained. It may be generated. That is, when a PDL command for generating a character part is input to the RIP, the RIP generates a bitmap image of the character data, and at the same time, generates a character flag = 1 as flag data corresponding to the area where the character is generated. .

[Forgery determination processing]
There are several methods for forgery determination processing such as banknotes performed in the forgery determination processing 120, but a typical method is pattern matching. Features such as the shape and color of banknotes or features embedded intentionally are extracted, and the degree of coincidence with those stored in advance is determined for determination. An example is shown in FIG.

  An image signal RGB for determination is input to the determination circuit 700. The RGB signal is binarized by the binarization unit 701. The threshold for binarization is variable and is stored in the memory 702. The binarized signal is input to the feature point extraction unit 703, and when it corresponds to the feature stored in the memory 704, the part is cut out. The features stored in the memory 704 are a shape, a color, a specific mark, and the like representing the features of the banknote. It also includes intentionally embedded features.

  The cut out signal is input to the pattern matching unit 705, and when it matches the pattern corresponding to the memory 706, the determination result is transmitted to the control CPU 707. The control CPU 707 that has received the result of forgery prevents the forgery by painting an image to be output by the printer unit.

  The above is an example of the forgery determination process performed by the copying machine, but is not limited thereto.

  An image signal input via the external communication path 119 and the communication interface 118 is developed into bitmap data by the RIP 107. The expanded bitmap data is held in the normal image memory 105, but is also transmitted to the forgery determination processing unit 120 at the same time.

  In the forgery determination processing unit 120, the bitmap data is input to the color conversion circuit 800 shown in FIG. 8 before being input to the determination circuit 700 for normal copying. The color conversion circuit 800 can perform color conversion on any of RGB and CMYK input signals.

  When the input signal is an RGB signal, the color correction matrix unit 802 performs color correction by, for example, 3 × 3 matrix calculation. Further, in the gamma conversion unit 803, gradation correction processing is performed and then input to the determination circuit 700 for forgery determination processing.

  When the input signal is a CMYK signal, the CMYK → RGB conversion unit 801 converts the signal into an RGB signal by, for example, a 3 × 4 matrix operation. The input signal converted from the CMYK signal to the RGB signal is color-corrected by the color correction matrix unit 802 and tone-corrected by the gamma conversion unit 803 and input to the determination circuit 700 for forgery determination processing.

  Although a system for performing gamma conversion after color correction has been described here, it may be reversed.

  As described above, even for an image signal input from the outside through a communication interface, by using a forgery determination processing circuit that has been conventionally possessed by performing color correction and gradation correction on bitmap-expanded data, It is possible to prevent counterfeiting at low cost. Even if the input image signal is a CMYK signal, it can be determined by converting it to an RGB signal by color space conversion processing.

  As described above, forgery determination processing is performed on PDL image data input from the external communication path 119 via the communication interface 118 after the PDL image data is expanded into bitmap data. At that time, by performing color space conversion, color correction, and gradation correction on the PDL image, it becomes possible to use forgery determination processing mounted in the color document copying apparatus.

[Second Embodiment]
In the first embodiment, an example in which color conversion is performed in the forgery determination process 120 has been described. However, the function of the input image process 102 may be used instead.

[Third embodiment]
If the image signal input from the external communication path 119 via the communication interface 118 is image data that has already been expanded into bitmap data, the data is compressed at 109 and stored in 110 as shown in FIG. Thereafter, the data is decompressed at 112 and stored in the image memory 114.

  Thereafter, the image is sent to the output image processing unit 116 to output an image, but at the same time, the image is sent to the forgery determination processing unit 120 to perform forgery determination processing. If it is determined to be a forgery action, a control CPU (not shown) controls the printer to forcibly stop the output or to paint the image with black or the like.

  As described above, forgery determination processing is performed on bitmap image data input from the external communication path 119 via the communication interface 118. At that time, by performing color space conversion, color correction, and gradation correction on the bitmap image data, it becomes possible to use forgery determination processing mounted in the color document copying apparatus.

[Fourth embodiment]
When outputting highly confidential data from a host computer not shown in FIGS. 1 and 9, an image signal input via the external communication path 119 and the communication interface 118 is stored in the auxiliary storage device 111. At this time, a password such as a password is set. The data sender goes to a place where the output device is located after data transmission, inputs a password from an operation unit (not shown in FIGS. 1 and 9), and outputs the data stored in the auxiliary storage device 111.

  Data is input from the auxiliary storage device 111 to the storage device 110, decompressed, held in the image memory 114, subjected to predetermined output image processing 116, and output from the printer 117. At that time, image data is sent from the image memory 114 to the forgery determination process 120, and the forgery determination process is performed. If it is determined to be a forgery action, a control CPU (not shown) controls the printer to forcibly stop the output or to paint the image with black or the like.

  As described above, forgery determination processing is performed on image data even when image data input from the external communication path 119 via the communication interface 118 is temporarily stored in the auxiliary storage device 111. At that time, by performing color space conversion, color correction, and gradation correction on the bitmap image data, it becomes possible to use forgery determination processing mounted in the color document copying apparatus.

The block diagram which shows an example of the structure which implements this invention The figure which shows an example of the original image applied to this invention The figure explaining the image area separation processing of this invention The figure explaining the flag data by this invention The figure explaining the layout synthetic output by this invention The block diagram which shows an example of the output image processing structure of this invention The figure which shows an example of the forgery determination process applied to this invention The figure explaining the color conversion process applied to this invention The block diagram which shows an example of the structure which implements this invention The figure explaining the conventional color image copying apparatus

Explanation of symbols

101 Scanner 102 Input Image Processing 1
103 Image area separation processing 104 Input image processing 2
105 Image memory 1
106 Flag memory 1
107 RIP
108 Interpreter 109 Data compression 110 Storage device 111 Auxiliary storage device 112 Data decompression 113 Pixel density conversion 114 Image memory 2
115 Flag memory 2
116 Output Image Processing 117 Printer 118 Communication I / F
119 External communication channel 120 Forgery determination processing

Claims (8)

In an image processing system that electrically reads a document image, converts it into a digital signal for each pixel, and outputs a duplicate image of the document,
Means for developing image data input via a network into bitmap data;
Specific information extraction means for extracting specific information from the image data expanded into bitmap data,
An image processing system for performing color conversion before inputting the image data to the specific information extracting means.   The image processing system according to claim 1, wherein the color conversion includes color space conversion.   The image processing system according to claim 1, wherein the color conversion includes color correction.   The image processing system according to claim 1, wherein the color conversion includes gradation correction. In an image processing system that electrically reads a document image, converts it into a digital signal for each pixel, and outputs a duplicate image of the document,
Having storage means for storing image data input via a network;
Specific information extraction means for extracting specific information from the image data stored in the storage means,
An image processing system for performing color conversion before inputting the image data to the specific information extracting means.   The image processing system according to claim 5, wherein the color conversion includes color space conversion.   The image processing system according to claim 5, wherein the color conversion includes color correction.   The image processing system according to claim 5, wherein the color conversion includes gradation correction.