JP5012696B2 - Copy machine - Google Patents

Description

  The present invention relates to a copying apparatus, and more particularly to an improvement of a copying apparatus that can add a copy-forgery-inhibited pattern image to a document image in which characters are arranged on a plain background.

  In recent years, as a technique for preventing information leakage due to printed matter by suppressing copying, a technique for embedding a character string indicating that take-out or the like is prohibited as a background pattern has been proposed (for example, Patent Document 1 and 2). For example, when document data is printed on paper, printing is performed by adding a copy-forgery-inhibited pattern image in which character strings such as a document name, a printer name, and copy prohibition are embedded as a latent image to a document image. Generally, a tint block image is formed by embedding a latent image showing characters or the like in a background image. A latent image is composed of a plurality of density points consisting of a plurality of pixels at the time of optical reading as a minimum unit, whereas a background image is composed of density points having a size equal to or smaller than the pixels at the time of optical reading as a minimum unit. The Usually, the density of the density points constituting the latent image and the background image is lower than the density of characters in the document image from the viewpoint of making it inconspicuous. When copying a printed matter to which such a copy-forgery-inhibited pattern image is added, a background image with a small density point size is removed at the time of copying, and thereby a latent image becomes apparent. Since the character string such as copy prohibition emerges when the latent image is exposed, copying of printed matter can be suppressed.

However, when a tint block image with a tint block image added to a document image is displayed by performing thumbnail processing, there is a problem that the contrast is lowered and it becomes difficult to see characters. In other words, in the thumbnail process, the image with a tint block pattern is divided into a plurality of blocks made up of a large number of pixels, the average density is obtained for each block, and a thumbnail image with a reduced image size is generated. At this time, when the pixel values for each block are averaged, the density of the background portion in the document image is higher than when the copy-forgery-inhibited pattern image is not added, so the contrast between the character and the background is reduced. There was a problem that it was difficult to see the characters.
JP 2004-274092 A JP 2005-136554 A

  The present invention has been made in view of the above circumstances, and when the copy-forgery-inhibited pattern image with the copy-forgery-inhibited pattern image added to the document image is reduced and displayed as a thumbnail image, the contrast is lowered and characters are difficult to see. An object of the present invention is to provide a copying apparatus capable of suppressing the above-described problem. In particular, when a document image with a copy-forgery-inhibited pattern in which a copy-forgery-inhibited pattern image is added to a document image in which characters are placed on a plain background is reduced and displayed as a thumbnail image, the contrast is reduced and the characters are difficult to see. An object of the present invention is to provide a copying apparatus capable of performing the above.

  A copying apparatus according to a first aspect of the present invention is a copying apparatus having a reading unit that generates a document image in which characters are arranged on a plain background by optical reading of the document, and a printing unit that prints the document image on paper. Thus, a background image in which a latent image formed with a first density point composed of a plurality of pixels at the time of optical reading as a minimum unit is configured with a second density point having a size equal to or smaller than the pixels at the time of optical reading as a minimum unit The present invention is applied to a copying apparatus that can print a copy-forgery-inhibited pattern image embedded in the original image. Specifically, the copy-forgery-inhibited pattern original image storage unit for holding the copy-forgery-inhibited pattern image to which the copy-forgery-inhibited pattern image having the density of the first density point and the second density point is lower than the density of characters in the document image; An image reduction unit that divides an original image with a tint block into two or more first blocks including a plurality of pixels, obtains an average density for each first block, and generates a reduced image with a reduced image size; and the reduced image Are divided into two or more second blocks composed of a large number of pixels, an average density is obtained for each second block, a second block having the average density equal to or lower than a predetermined threshold is extracted, and the second block is extracted. A tint block removing unit that generates a tint block-free image by removing the tint block image from the reduced image by converting the pixel value of each pixel to a constant value, and the tint block-free image is composed of a plurality of pixels. The image processing apparatus includes a thumbnail image generation unit that divides the image into third blocks, calculates an average density for each third block, generates a thumbnail image with a reduced image size, and a thumbnail image display unit that displays the thumbnail image. Is done.

  In this copying apparatus, when a copy-forgery-inhibited document image in which a copy-forgery-inhibited pattern image is added to a document image in which characters are arranged on a plain background is reduced and displayed as a thumbnail image, the average density is equal to or lower than a predetermined threshold value. Two blocks are extracted from the reduced image. Then, by converting the pixel value of each pixel in the second block into a constant value, a tint block-free image is generated by removing the tint block image from the reduced image. The thumbnail image for display is generated by reducing the background pattern image.

  According to such a configuration, since the copy-forgery-inhibited pattern image is removed by extracting the second block having a low average density from the reduced image, the copy-forgery-inhibited pattern image is removed directly from the original image with a copy-forgery-inhibited pattern having a large image size. Thus, the time required for image processing can be shortened. In addition, since the thumbnail image is generated by reducing the copy-forgery-inhibited pattern image from which the copy-forgery-inhibited pattern image is removed from the reduced image and the thumbnail image is displayed, it is possible to prevent the contrast from being lowered and the characters from becoming difficult to see. In other words, in a conventional copying apparatus, when a document image with a copy-forgery-inhibited pattern is reduced and displayed, the density difference between the copy-forgery-inhibited pattern image and the outline portion of the character in the document image is reduced when averaging pixel values for each block. This makes it difficult to see the characters. On the other hand, in the copying apparatus according to the present invention, a copy-forgery-inhibited pattern image constituted by the first density point and the second density point is used by utilizing the fact that the density of these density points is lower than the density of characters in the original image. Since the image is displayed after being removed, it is possible to prevent the characters from becoming difficult to see. Also, by removing the copy-forgery-inhibited pattern image by dividing the reduced image into second blocks made up of a plurality of pixels, it is possible to determine the density of a reduced image in a wider range than when performing copy-forgery-inhibited pattern for each pixel. Accuracy can be improved. Note that the threshold used when the tint block removal unit extracts the second block is determined as a value corresponding to the densities of the first density point and the second density point, for example.

  In the copying apparatus according to a second aspect of the present invention, in addition to the above-described configuration, the copy-forgery-inhibited pattern removal unit extracts a second block having the average density equal to or lower than the first threshold and equal to or higher than the second threshold. The background pattern-free image is generated by converting the pixel value of each pixel in the second block to a constant value smaller than the second threshold value. According to such a configuration, the copy-forgery-inhibited pattern image is removed by extracting the second block whose average density is equal to or lower than the first threshold value and equal to or higher than the second threshold value. Part of the background pattern can be prevented from being removed when the background pattern is removed.

  In addition to the above configuration, the copying apparatus according to a third aspect of the present invention includes a symbol adding unit that adds a symbol image indicating an image with a background pattern to the thumbnail image, and the thumbnail image display unit adds the symbol image. The thumbnail image is displayed. According to such a configuration, since the thumbnail image to which the symbol image indicating the image with the background pattern is added is displayed, the operator can recognize that the image is with the background pattern while suppressing the characters from being difficult to see. be able to.

  According to the copying apparatus of the present invention, since the copy-forgery-inhibited pattern image is removed by extracting the second block having a low average density from the reduced image, the copy-forgery-inhibited pattern image can be directly removed from the original image with the copy-forgery-inhibited pattern having a large image size. In comparison, the time required for image processing can be shortened. In addition, since the thumbnail image is generated by reducing the copy-forgery-inhibited pattern image from which the copy-forgery-inhibited pattern image is removed from the reduced image and the thumbnail image is displayed, it is possible to prevent the contrast from being lowered and the characters from becoming difficult to see. Therefore, when a document image with a copy-forgery-inhibited pattern in which a copy-forgery-inhibited pattern image is added to a document image in which characters are arranged on a plain background is reduced and displayed as a thumbnail image, it is possible to prevent the characters from being difficult to see due to a decrease in contrast. Can do.

  FIG. 1 is a block diagram showing an example of a schematic configuration of a copying apparatus according to an embodiment of the present invention. A multifunction machine 1 is shown as an example of the copying apparatus. The multifunction device 1 is an MFP (Multi-Function Peripheral) having a scanner function, a printer function, a facsimile function, and the like, and can selectively execute these functions.

  The MFP 1 includes a CPU 11, a ROM 12, a RAM 13, a display unit 14, an operation unit 15, a reading unit 16, a printing unit 17, a modem 18, an NCU 19, a network I / F 20, a storage 21, a tint block generation unit 22, and an image composition unit 23. And a thumbnail processing unit 24. The CPU 11, the ROM 12, the RAM 13, the display unit 14, the operation unit 15, the reading unit 16, the printing unit 17, the modem 18, the network I / F 20, the storage 21, the tint block generation unit 22, the image composition unit 23, and the thumbnail processing unit 24 are common. Connected to the bus 10.

  The NCU (Network Control Unit) 19 is a communication control device for communicating with other communication devices via a PSTN (Public Switched Telephone Networks), and is connected to the modem 18. The network I / F 20 is a communication control device for communicating with other terminal devices via a LAN.

  The reading unit 16 is a reading device that generates a document image by optical reading of a document. For example, a scanner device that scans light and reads an image is used. The reading unit 16 performs an operation of reading an image from a document on which characters or the like are printed on a sheet and generating a document image. Here, it is assumed that the document image is an image in which characters are arranged on a plain background, and each pixel value is either white (lower density limit) or black (density upper limit). .

  The printing unit 17 is a printing device that prints document data on a sheet. For example, an operation of printing a document image generated by the reading unit 16 on a sheet is performed.

  The storage 21 is a storage device for holding document data, and holds document images generated by the reading unit 16, document data transferred from other terminal devices, image data received by facsimile from other communication devices, and the like. Is done.

  The background pattern generation unit 22 performs an operation of generating a background pattern image to be added to the document image. This copy-forgery-inhibited pattern image is an image formed by embedding a latent image composed of a first density point as a minimum unit in a background image composed of a second density point smaller than the first density point as a minimum unit. . For example, an image representing a character string such as “copy prohibited” is embedded as a latent image.

  The first density point is a pixel at the time of optical reading, and is a constant density point composed of a plurality of adjacent pixels. On the other hand, the second density point is a constant density point having a size equal to or smaller than that of the pixel at the time of optical reading, and the density is lower than the first density point in terms of the pixel size.

  When the resolution (output resolution) when printing image data on paper is larger than the resolution (input resolution) when reading an image from a document, by using such a difference in resolution at the time of input / output, When a printed matter on which a copy-forgery-inhibited pattern image is printed is copied, the latent image embedded in the background image can be highlighted. In other words, when printing a copy-forgery-inhibited pattern image, a background image is printed together with a latent image, whereas when copying such a printed matter, a background image having a small density point and a low density is automatically read when reading the image. Therefore, the latent image is revealed in the copy.

  Here, in order to prevent the copy-forgery-inhibited pattern image from conspicuous when such a copy-forgery-inhibited pattern image is added to the document image, the density of the density points constituting the copy-forgery-inhibited pattern image, that is, the latent image and the background image, is the pixel size. As seen, it is lower than the character density in the original image.

  As the character string to be embedded as a latent image, identification information of the multifunction device 1, arbitrary registration information registered in advance in the multifunction device 1, printing information, and the like are conceivable. The print information is job information when printing document data. For example, the page number, the total number of pages, and the print date and time can be considered.

  The image synthesizing unit 23 performs an operation of synthesizing the manuscript image and the tint block image and generating a tint block original image at the time of printing the manuscript image held in the storage 21. The image composition unit 23 performs an operation of adding the copy-forgery-inhibited pattern image generated by the copy-forgery-inhibited pattern generation unit 22 to the document image generated by the reading unit 16 when reading the document. The storage 20 also stores such a document image with a background pattern.

  In the printing unit 17, for example, based on an instruction from the operation unit 15, an operation for printing a document image with a background pattern to which a background pattern image is added is performed.

  The thumbnail processing unit 24 performs an operation of generating a thumbnail image for display with a reduced image size, for example, when printing a document image held in the storage 20. In the thumbnail processing unit 24, when generating a thumbnail image from a copy-forgery-inhibited document image, an operation for removing the copy-forgery-inhibited pattern image based on the average density of blocks when the copy-forgery-inhibited document image is divided into a plurality of blocks composed of a large number of pixels. Is done. The thumbnail image from which the copy-forgery-inhibited pattern image is removed is output to the display unit 14 and displayed on the screen.

  FIG. 2 is a block diagram illustrating a configuration example relating to document reading of the multifunction machine 1 of FIG. In the reading unit 16, image data read from the original by the CCD image sensor 31 is processed in the read image processing unit 32. In the read image processing unit 32, for example, image processing such as shading correction and gamma correction is performed, and an operation of outputting the original image to the image composition unit 23 is performed.

  The image composition unit 23 synthesizes the document image from the read image processing unit 32 and the copy-forgery-inhibited pattern image from the copy-forgery-inhibited pattern generation unit 22 and writes the composite image as a copy-forgery-inhibited document image in the page memory 33 in the RAM 13. . In the encoding unit 34 in the CPU 11, an operation of reading and encoding a copy-forgery-inhibited document image in the page memory 33 and storing it in the storage 21 is performed.

  FIG. 3 is a block diagram illustrating a configuration example of a main part of the multifunction device 1 of FIG. 1, and illustrates an example of a functional configuration in the thumbnail processing unit 24. The thumbnail processing unit 24 includes a decoding unit 41, an image reduction unit 42, a background pattern removal unit 43, an image reduction unit 44, and a symbol addition unit 45.

  The decoding unit 41 performs an operation of reading and decoding a document image with a tint block in the storage 21 and outputting it to the image reduction unit 42.

  The image reduction unit 42 includes a blocking unit 51 and an average density calculation unit 52. The image reduction unit 42 divides a document image with a copy-forgery-inhibited pattern into a plurality of first blocks, obtains an average density for each first block, and reduces the image size. An operation to generate an image is performed.

  That is, the block forming unit 51 performs an operation of dividing the copy-forgery-inhibited pattern original image decoded by the decoding unit 41 into a plurality of first blocks including a large number of pixels. For example, a copy-forgery-inhibited document image is segmented using a square-shaped image region formed of 64 adjacent pixels in 8 rows and 8 columns as a first block.

  In the average density calculation unit 52, for each first block, an operation for obtaining an average density related to pixels in the first block is performed. By assigning the average density obtained from the first block to the first block as a pixel value, a reduced image with a reduced image size is generated.

  The copy-forgery-inhibited pattern removal unit 43 includes a blocking unit 61, an average density calculation unit 62, a threshold value storage unit 63, a comparison unit 64, and a pixel value conversion unit 65. The copy-forgery-inhibited pattern removal unit 43 generates an image without a copy-forgery-inhibited pattern from which a copy-forgery-inhibited pattern image is removed from the reduced image. Is going. The copy-forgery-inhibited pattern removal unit 43 divides the reduced image into a plurality of second blocks, extracts second blocks having an average density equal to or lower than a predetermined threshold, and sets the pixel value of each pixel in the second block to be constant. An operation for removing the copy-forgery-inhibited pattern image from the reduced image is performed by converting the value into a value.

  That is, the blocking unit 61 performs an operation of dividing the reduced image generated by the image reducing unit 42 into a plurality of second blocks including a large number of pixels. For example, the reduced image is segmented using a square-shaped image region constituted by 64 pixels of 8 rows and 8 columns as the second block.

  In the average density calculation unit 62, for each second block, an operation for obtaining an average density related to pixels in the second block is performed.

  The comparison unit 64 compares the average density calculated by the average density calculation unit 62 with the threshold value in the threshold value storage unit 63, and extracts a second block whose average density is equal to or less than the threshold value based on the comparison result. Is done. Alternatively, an operation of extracting a second block having an average density equal to or lower than the first threshold and equal to or higher than the second threshold smaller than the first threshold is performed. The threshold value storage unit 63 holds a first threshold value and a second threshold value as predetermined threshold values.

  Then, the pixel value conversion unit 65 performs an operation of generating a tint block-free image by converting the pixel value of each pixel in the second block extracted by the comparison unit 64 into a constant value. More specifically, by converting the pixel value to a constant value smaller than the second threshold value for each pixel in the second block, a tint block-free image is generated by removing the tint block image from the reduced image.

  The image reduction unit 44 divides the copy-forgery-inhibited pattern image into a plurality of third blocks including a plurality of pixels, obtains an average density for each third block, and generates a thumbnail image with a reduced image size. It has become.

  The symbol adding unit 45 performs an operation of adding a symbol image indicating that the image has a copy-forgery-inhibited pattern to the thumbnail image generated by the image reducing unit 44. As the symbol image to be added to the thumbnail image, characters, symbols, figures, and the like are conceivable. For example, the symbol “x” is added as the symbol image.

  Here, it is assumed that the density of the symbol image added to the thumbnail image is determined based on the density of the density points constituting the latent image and the background image. For example, the average value of the density of the first density point constituting the latent image and the density of the second density point constituting the background image is determined as the density of the symbol image. Alternatively, the density of the symbol image is determined in accordance with the density of the first density point constituting the latent image.

  In the display unit 14, for example, based on an instruction from the operation unit 15, an operation of displaying a thumbnail image to which a symbol image is added by the symbol addition unit 45 is performed.

  FIG. 4 is a diagram showing an example of an operation at the time of document reading in the multifunction machine 1 of FIG. 1, and shows a document image A1 with a background pattern to which a background pattern image is added. The copy-forgery-inhibited document image A1 is image data obtained by adding a copy-forgery-inhibited pattern image to the image read from the document by the reading unit 16 by the image combining unit 23, and the character A2 is arranged on a rectangular solid background.

  The copy-forgery-inhibited pattern image is formed by a background image composed of a large number of second density points B2 having a size equal to or smaller than the pixel at the time of optical reading, and a latent image embedded in the background image. The latent image is constituted by a large number of first density points B1 composed of a plurality of pixels at the time of optical reading. That is, the density point B2 has a smaller area than the density point B1.

  The density of density points B1 and B2 is lighter than the density of character A2, and the density of density point B2 is lighter than the density of density point B1 in terms of the pixel size. Further, the density point B2 is arranged at a higher density than the density point B1, and if an area of a predetermined size including the plurality of density points B1 or B2 is viewed, the density point in the area at an arbitrary position on the document image A1. The average density due to is constant.

  When such a copy-forgery-inhibited original image is printed on a sheet, the latent image is difficult to recognize because there is no difference in density between the latent image and the background image in a predetermined size area. However, when the printed matter on which the copy-forgery-inhibited pattern original image A1 is printed is copied, the background image having a small density point and a low density is automatically removed, so that the latent image becomes obvious and the latent image As a result, a character string such as “copy” embedded in the background image is easily recognized.

  In the present embodiment, when such a copy-forgery-inhibited document image is reduced and displayed as a thumbnail image, a copy-forgery-inhibited pattern image from which the copy-forgery-inhibited pattern image is removed is generated.

  5 and 6 are diagrams illustrating an example of an operation when displaying a thumbnail image in the multi-function device 1 of FIG. FIG. 5 shows a processing unit when the original image A1 with copy-forgery-inhibited pattern is reduced to generate a reduced image.

  When generating a reduced image by reducing the original image A1 with the copy-forgery-inhibited pattern, the original image A1 is divided into a plurality of blocks (first blocks) made up of 8 × 8 adjacent pixels, and the reduction is performed using this block as a processing unit. Processing is executed. In other words, an image region composed of 8 pixels in the row direction and 8 pixels in the column direction is set as the first block, and the reduction process is performed using the first block as a processing unit.

  FIG. 6 shows a state in which the image size is reduced by assigning the average density calculated for the pixels in the first block to the first block as a pixel value. The reduced image is generated for each first block in the document image A1 by assigning the average density calculated from the first block to the first block as a pixel value.

  That is, the image size is reduced by assigning the average density calculated from the pixel values of the 8 × 8 pixels in the first block as a pixel value to a new pixel corresponding to the first block. .

  Steps S101 to S106 in FIG. 7 are flowcharts showing an example of an operation at the time of document reading in the multi function device 1 in FIG. First, the read image processing unit 32 performs image processing on the read image read from the original by the CCD image sensor 31 (step S101).

  Next, the background pattern generation unit 22 refers to the background pattern setting preset by the operator, and generates a background pattern image based on the set value (steps S102 and S103). The image composition unit 23 synthesizes the document image from the read image processing unit 32 and the copy-forgery-inhibited pattern image from the copy-forgery-inhibited pattern generation unit 22, and writes the composite image into the page memory 33 as a document image with a copy-forgery-inhibited pattern (step S104).

  Next, the encoding unit 34 reads and encodes the copy-forgery-inhibited document image in the page memory 33 and stores it in the storage 21 (steps S105 and S106).

  Steps S201 to S212 in FIG. 8 are flowcharts showing an example of the operation at the time of displaying thumbnail images in the multi function device 1 in FIG. First, the decoding unit 41 acquires a document image with a background pattern from the storage 21 based on an instruction from the operation unit 15, and performs a decoding process (steps S201 and S202).

  Next, the image reduction unit 42 divides the decoded document image with copy-forgery-inhibited pattern into a plurality of first blocks, and calculates an average density for each first block (steps S203 and S204).

  Then, the image reduction unit 42 generates a reduced image by assigning the average density calculated from the first block to the first block as a pixel value (step S205).

  Next, the background pattern removing unit 43 divides the reduced image into a plurality of second blocks, and calculates an average density for each second block (steps S206 and S207).

  Then, the tint block removing unit 43 extracts a second block having an average density equal to or less than a certain density, and converts the pixel value of each pixel in the second block into a certain value (steps S208 and S209). As a result, a tint block-free image is generated by removing the tint block image from the reduced image.

  Next, the image reduction unit 44 divides the copy-forgery-inhibited pattern image into a plurality of third blocks including a plurality of pixels, obtains an average density for each of the third blocks, and generates a thumbnail image with a reduced image size ( Step S210).

  The symbol adding unit 45 adds a symbol image indicating that the image has a background pattern to the thumbnail image generated by the background pattern removing unit 43 (step S211). The display unit 14 displays the thumbnail image to which the symbol image is added by the symbol adding unit 45 (step S212).

  According to the present embodiment, the second block having a low average density is extracted from the reduced image and the copy-forgery-inhibited pattern image is removed, so that the copy-forgery-inhibited pattern image can be directly removed from the original image A1 with the copy-forgery-inhibited pattern having a large image size. In comparison, the time required for image processing can be shortened. In addition, since the thumbnail image is generated by reducing the copy-forgery-inhibited pattern image from which the copy-forgery-inhibited pattern image is removed from the reduced image and the thumbnail image is displayed, it is possible to prevent the contrast from being lowered and the characters from becoming difficult to see. In addition, since the thumbnail image to which the symbol image indicating the image with the background pattern is added is displayed, it is possible to make the operator recognize that the image has the background pattern while suppressing the characters from being difficult to see.

  In the present embodiment, an example in which the copy-forgery-inhibited pattern image is removed from the reduced image obtained by reducing the image size by obtaining the average density for each first block has been described. However, the present invention is not limited to this. is not. For example, the copy-forgery-inhibited pattern image may be removed after repeating the process of obtaining the average density and reducing the image size.

1 is a block diagram showing an example of a schematic configuration of a copying apparatus according to an embodiment of the present invention, in which a multifunction machine 1 is shown as an example of the copying apparatus. FIG. 2 is a block diagram illustrating a configuration example relating to document reading of the multifunction machine 1 of FIG. 1. FIG. 2 is a block diagram illustrating a configuration example of a main part of the multifunction peripheral 1 in FIG. 1, in which an example of a functional configuration in a thumbnail processing unit 24 is illustrated. FIG. 2 is a diagram illustrating an example of an operation at the time of document reading in the multifunction machine 1 of FIG. FIG. 7 is a diagram illustrating an example of an operation at the time of displaying a thumbnail image in the multifunction machine 1 in FIG. FIG. 7 is a diagram illustrating an example of an operation at the time of displaying a thumbnail image in the MFP 1 of FIG. 1, and illustrates a state in which the image size is reduced by assigning an average density. 3 is a flowchart illustrating an example of an operation at the time of reading a document in the multifunction machine 1 of FIG. 1. 3 is a flowchart illustrating an example of an operation when displaying a thumbnail image in the multifunction machine 1 of FIG. 1.

Explanation of symbols

1 MFP 10 Bus 11 CPU
12 ROM
13 RAM
14 Display unit 15 Operation unit 16 Reading unit 17 Printing unit 18 Modem 19 NCU
20 Network I / F
21 Storage 22 Background pattern generation unit 23 Image composition unit 24 Thumbnail processing unit 31 CCD image sensor 32 Read image processing unit 33 Page memory 34 Encoding unit 41 Decoding unit 42 Image reduction unit 43 Background pattern removal unit 44 Image reduction unit 45 Symbol addition unit 51 Blocking unit 52 Average density calculating unit 61 Blocking unit 62 Average density calculating unit 63 Threshold storage unit 64 Comparison unit 65 Pixel value conversion unit A1 Original image with background pattern A2 Character B1 First density point B2 Second density point

Claims (3)

A copying apparatus having a reading unit that generates a document image in which characters are arranged on a plain background by optical reading of the document, and a printing unit that prints the document image on paper,
A latent image composed of a first density point composed of a plurality of pixels at the time of optical reading as a minimum unit is included in a background image composed of a second density point having a size equal to or smaller than the pixels at the time of optical reading as a minimum unit. In a copying apparatus capable of printing an embedded copy-forgery-inhibited pattern image added to the original image,
A copy-forgery-inhibited pattern image storage unit that holds a copy-forgery-inhibited pattern original image to which the copy-forgery-inhibited pattern image having the density of the first density point and the second density point is lower than the density of characters in the document image;
An image reduction unit that divides the original image with a tint block into two or more first blocks including a plurality of pixels, obtains an average density for each first block, and generates a reduced image with a reduced image size;
The reduced image is divided into two or more second blocks including a plurality of pixels, an average density is obtained for each second block, a second block having the average density equal to or lower than a predetermined threshold is extracted, and the second block is extracted. A tint block removal unit that generates a tint block-free image by removing the tint block image from the reduced image by converting the pixel value of each pixel in two blocks to a constant value;
A thumbnail image generation unit that divides the copy-forgery-inhibited pattern image into two or more third blocks including a plurality of pixels, obtains an average density for each third block, and generates a thumbnail image with a reduced image size;
A copying apparatus comprising a thumbnail image display unit for displaying the thumbnail image.   The copy-forgery-inhibited pattern removing unit extracts a second block having the average density equal to or lower than the first threshold and equal to or higher than the second threshold and lower than the first threshold, and sets a second pixel value for each pixel in the second block. 2. The copying apparatus according to claim 1, wherein the copy-forgery-inhibited pattern image is generated by converting to a constant value smaller than a threshold value. A symbol adding unit for adding a symbol image indicating that the image has a background pattern to the thumbnail image;
The copying apparatus according to claim 1, wherein the thumbnail image display unit displays the thumbnail image to which the symbol image is added.

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