JP2011199404A - Image processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To certainly detect tint block patterns (unauthorized copy prohibition patterns) in an image processing apparatus, even when dot diameters of the printing tint block patterns vary by printer model and aging.SOLUTION: A tint block pattern detection processor 104 inputs original image data read by a reader 102 and corrects dots constituting the tint block patterns in the original image data to dot diameters which can be recognized as the dots of the tint block patterns. Then, the tint block patterns are detected by a pattern matching method using a standard tint block pattern as a mask pattern for the original image data with the corrected dot diameters.

Description

  The present invention relates to an image processing apparatus such as a digital copying machine, a facsimile apparatus, and a filing apparatus. More specifically, when a document having a specific pattern is read, the document image is printed on a recording sheet or other than the image data. The present invention relates to a technique for preventing transfer to a device.

  In recent years, safety of information security management has been regarded as important. Therefore, for the purpose of preventing the paper manuscript created by the user from being disclosed to an unspecified number of people, a specific pattern (background pattern) at the time of creating the manuscript is printed on the manuscript, the original is read, Various image processing apparatuses having a so-called unauthorized copy prevention function are known that, when detected, convert the document image data into other data so that it cannot be read (for example, paint the document image data). .

  In this case, it is necessary to reliably detect (detect) the tint block pattern added to the document image data in the image processing apparatus. When printing with a copy-forgery-inhibited pattern added to the original image, if the dot diameter of the dots forming the copy-forgery-inhibited pattern varies due to variations in the printing model or changes over time, the image processing device will display the copy-forgery-inhibited pattern superimposed on the original image data. In some cases, the document image cannot be recognized, and the document image may be directly printed on a recording sheet or transferred to another apparatus.

  Therefore, for the purpose of stabilizing the reproduction accuracy of the tint block pattern, a copy-forgery-inhibited pattern recognition process function has been provided on the device that adds the tint block pattern to the original image for printing, and the tint block pattern is superimposed on the original image data. After that, there is known a method in which a background pattern is recognized, and the dot diameter of the background pattern is adjusted so as to be printed out without variation (for example, Patent Document 1 and Patent Document 2).

  If the device that prints with the copy-forgery-inhibited pattern added to the original image, such as the A0 wide-width machine, uses a part with a shallow depth of focus such as an LED instead of LD as the writing means, irradiates the photosensitive drum with light. When the image is transferred, the image is blurred with a slight deviation, and the dot diameter of one dot becomes larger as a whole (generally, it becomes vertically long). For this reason, no matter how much the dot diameter of the tint block pattern is adjusted before printing, the dot size of the printed tint block pattern is not improved.

  The present invention stabilizes the accuracy of the dot diameter of the tint block pattern on the side of the image processing apparatus that reads and processes the original image even when the dot size of the printed tint block pattern varies depending on the printing model or the change over time. An object of the present invention is to improve the detection accuracy of a tint block pattern.

The present invention includes an image reading unit that reads a document image and an image data processing unit that processes document image data read by the image reading unit, and prints and stores the document image data processed by the image data processing unit. Or in an image processing device that transmits to another device,
Dot diameter correcting means for correcting dots forming a copy-forgery-inhibited pattern pattern in the original image data read by the image reading means to a dot diameter that can be recognized as dots of the copy-forgery-inhibited pattern pattern;
A tint block pattern detecting unit for detecting a tint block pattern based on the document image data corrected by the dot diameter correcting unit;
A discriminating unit for discriminating whether or not the original image data is prohibited from being printed or transferred to another device based on a result of the tint block pattern detection by the tint block pattern detecting unit;
Image conversion means for converting the document image data into unreadable image data when the document image data is prohibited from being printed or transferred to another device;
It is characterized by having.

  In one embodiment, the dot diameter correcting means has a main scanning direction so as to make the dot diameter capable of recognizing dots forming the copy-forgery-inhibited pattern pattern in the original image data read by the reading means, It has a scaling means for independently scaling in the sub-scanning direction, and dot correction is performed by the scaling means.

  The scaling unit measures a dot diameter of dots forming a tint block pattern in the document image data read by the reading unit, and calculates a scaling factor so that a recognizable dot diameter is obtained.

  The dot diameter correcting means further includes a mask scaling means for scaling a mask pattern for detecting a tint block pattern in accordance with scaling of the original image data read by the reading means.

  In another embodiment, the dot diameter correcting means binarizes the original image data read by the reading means so that the dot diameter capable of recognizing dots forming a tint block pattern in the original image data is obtained. And binarizing means for performing dot correction by the binarizing means.

  The binarizing unit converts the document image data into 2 so that the dot diameter of dots forming the tint block pattern in the document image data read by the reading unit matches the dot detection condition of the tint block pattern detection mask pattern. The threshold value to be converted is calculated.

  In still another embodiment, the dot diameter correcting means performs main scanning so that the original image data read by the reading means has a dot diameter capable of recognizing dots forming a tint block pattern in the original image data. A scaling unit that scales independently in the direction and the sub-scanning direction, and a document image data read by the reading unit, so that a dot diameter that can recognize a dot that forms a tint block pattern in the document image data is set. According to the binarizing means for binarizing and the dot forming the copy-forgery-inhibited pattern in the original image data read by the reading means, either the scaling means or the binarizing means is selected. It is characterized by having correction processing discrimination means for performing correction.

  The correction process determining means selects the binarizing means when satisfying the minimum value of black pixels> the maximum value of white pixels, and selects the scaling means when not satisfying.

  In still another embodiment, the dot diameter correcting means has area specifying means for specifying the area of the document image data read by the reading means, and performs dot processing on the document image data in the specified area. carry out.

  According to the present invention, prior to the process of detecting the tint block pattern in the read document image data by the image processing apparatus that reads and processes the document image, the read document image data is processed in the document image data. By correcting the dots forming the tint block pattern so as to have a recognizable dot diameter, the dot diameter is stabilized and the detection accuracy of the tint block pattern is improved.

  Further actions and effects of the image processing apparatus of the present invention will be clarified in the description of the embodiment of the present invention.

1 is an overall configuration diagram of an embodiment of an image processing apparatus according to the present invention. FIG. 3 is a schematic flowchart of image data copying processing in the image processing apparatus. The figure which shows the schematic flowchart of the transmission process to the external device of the image data in this image processing apparatus. The detailed block diagram of the tint block detection processing part in FIG. The figure which shows the flow of a printing process of the image data which embedded the tint block pattern by the image forming apparatus side. The figure which shows an example of the dispersion | variation in the dot which forms a tint block pattern. The figure which shows the flowchart of Example 1 of the dot correction process in the dot diameter correction process part of FIG. FIG. 6 is a diagram for explaining a scaling factor calculation method according to the first embodiment. FIG. 10 is a diagram illustrating a specific example of binarized dots when there is no conventional scaling process and there is scaling in Example 1. The figure explaining scaling of the mask pattern for a tint block pattern detection. FIG. 5 is a diagram illustrating a flowchart of Example 2 of dot correction processing in the dot diameter correction processing unit of FIG. 4. The figure which shows the specific example of the mask pattern for a tint block pattern detection. The figure which shows the specific example of the pixel information of the read dot. FIG. 6 is a diagram illustrating a specific example of a binarized image with a conventional threshold and a binarized image with a correction threshold according to a second embodiment. FIG. 5 is a flowchart illustrating a dot correction process according to a third embodiment of the dot diameter correction processing unit illustrated in FIG. 4. The figure which shows the specific example of the pixel information of the mask pattern (dot detection condition) for the copy-forgery-inhibited pattern detection, and the read dot. FIG. 10 is a diagram for explaining correction processing determination in the third embodiment.

  Hereinafter, an embodiment of an image processing apparatus according to the present invention will be described with reference to the drawings.

  FIG. 1 shows an overall configuration diagram of an embodiment of an image processing apparatus according to the present invention. In FIG. 1, reference numeral 100 denotes an internal bus as an expansion bus, which is an operation display unit 101, a reading unit 102, a plotter unit 103, a tint block detection processing unit 104, an image data processing unit 105, a CPU 106, a memory 107, and a hard disk (HDD) 108. The external interface control unit (external I / F control unit) 109 and the like are connected. Furthermore, a NIC (Network Interface Card) 110 and a FAX transmission / reception unit 111 are connected to the external I / F control unit 109, and a personal computer (PC) 120 is connected to the NIC 110 via a network. Although omitted in FIG. 1, the FAX transmission / reception unit 111 is connected to the partner FAX apparatus via a communication line. That is, the image processing apparatus shown in FIG. 1 functions as a multifunction function copying machine.

  The operation display unit 101 is an operation board that receives an input operation from the user and performs necessary display for the user. When the user operates a key group on the operation display unit 101, various operations (copy, FAX, data transfer, scaling, etc.) are executed under the control of the CPU.

  The reading unit 102 includes a sensor such as a CCD, an A / D converter, and a driving unit thereof. The reading unit 102 scans and reads a set original, and inputs it as digital image data including 8 bits per pixel, for example.

  Here, when it is desired to prohibit the printing of the original image data read by the reading unit 102 on a recording sheet or the transfer to another apparatus, a background pattern of a specific pattern is embedded in the original image in advance when the original image is created. deep. The specific pattern is generally embedded over almost the entire area of the original image.

  When the image processing apparatus operates as a copying machine, the plotter unit 103 prints the original image data read by the reading unit 102 on a recording sheet (printout). As will be described later, the original image data read by the reading unit 102 is subjected to necessary processing by the image data processing unit 105 and then printed on a recording sheet by the plotter 103.

  The plotter unit 103 is also used as a printer of the external personal computer 120 and an output device of the FAX unit 110, but details thereof are omitted.

  The copy-forgery-inhibited pattern detection processing unit 104 detects a copy-forgery-inhibited pattern pattern from the document image data read by the reading unit 102, and determines whether the document image is prohibited from being printed on a recording sheet or transferred to another apparatus. .

  The image data processing unit 105 performs necessary processing on the document image data read by the reading unit 102. Here, the necessary processing includes shading correction, γ correction, MTF correction, and the like. The image data processing unit 105 also cannot read the document image data when the copy-forgery-inhibited pattern detection processing unit 104 determines that the document image is prohibited from being printed on a recording sheet or transferred to another apparatus. Image conversion means for converting into possible image data is provided. For example, the image conversion means makes the original document image data unreadable by painting it.

  The CPU 106 controls the operation of the entire image processing apparatus in response to an operation input from the operation display unit 101. The memory 107 temporarily stores document image data read by the reading unit 102, document image data being processed or processed by the image data processing unit 105, input data from the external personal computer 120, received data from the counterpart FAX device, and the like. To remember. The HDD 107 is the original image data processed by the image data processing unit 105, the program for the CPU 106, the font data for the plotter unit 103, the standard background pattern (mask pattern) data for the background pattern detection processing unit 104, and the image data. LUTs (Look Up Tables) for the processing unit 105 are stored.

  The external I / F control unit 109 controls the operation of external devices such as the NIC 110 and the FAX unit 111. The NIC 110 communicates with an external personal computer 120 via a network. The FAX unit 111 transmits and receives FAX data to and from the partner FAX apparatus via a communication line.

  FIG. 2 shows a schematic flowchart of the copying process in the image processing apparatus of FIG. The reading unit 102 scans and reads a set original and outputs original image data (step 1001). The copy-forgery-inhibited pattern detection processing unit 104 inputs the document image data and performs a copy-forgery-inhibited pattern detection process (step 1002). When the copy-forgery-inhibited pattern detection processing unit 104 detects the copy-forgery-inhibited pattern pattern (YES in step 1003), the image data processing unit 105 paints the original image data read by the reading unit 102 to make the image unreadable. The data is converted and output (step 1004). On the other hand, when the copy-forgery-inhibited pattern detection processing unit 104 detects no copy-forgery-inhibited pattern (NO in step 1003), the image data processing unit 105 performs normal necessary image processing on the document image data read by the reading unit 102. Implement and output (step 1005). The plotter unit 103 inputs the document image data processed by the image data processing unit 105 and prints it on a recording sheet (step 1006). As a result, when the copy-forgery-inhibited pattern is included in the document set in the reading unit 102, the plotter unit 103 prints an unreadable image that is entirely filled or the like on a recording sheet.

  FIG. 4 shows a schematic flowchart of an external transmission process in the image forming apparatus of FIG. In FIG. 4, steps 2001 to 2005 are exactly the same as steps 1001 to 1005 of FIG. The document image data processed with the image data is temporarily stored in the memory 107 and then transmitted to the external personal computer 120 or the like via the external I / F control unit 109 and the NIC 110 (step 2006). Also in this case, when a copy-forgery-inhibited pattern is included in the document set in the reading unit 102. The unreadable image data that is entirely filled is transmitted to the external personal computer 120 or the like. The same applies to the case where data is transmitted to the partner FAX apparatus via the FAX unit 111.

  Note that when a background pattern is detected by the background pattern detection processing unit 104, the CPU 106 may perform control so as to prohibit printing of the document image data on a recording sheet or transmission to the outside.

  The present invention relates to the background pattern detection processing unit 104 in FIG. FIG. 4 shows a configuration example of the tint block detection processing unit 104. Here, the tint block detection processing unit 104 includes a dot diameter correction unit 210, a tint block pattern detection unit 220, and an unauthorized copy determination unit 230.

  The dot diameter correction unit 210 inputs the document image data read by the reading unit 102 and corrects the dots forming the background pattern in the document image data to a dot diameter that can be recognized as the dots of the background pattern. . Specifically, a predetermined area in the original image is designated, and dot correction processing is performed on the original image data in the area. The feature of the present invention resides in that the dot diameter correction unit 210 is added before the background pattern detection unit 220. The dot correction processing in the dot diameter correction unit 210 will be described in detail later.

  The copy-forgery-inhibited pattern detection unit 220 detects a copy-forgery-inhibited pattern based on the document image data whose dot diameter has been corrected by the dot diameter correction unit 210. Specifically, with respect to the document image data in the designated area, the standard tint block pattern is scanned in pixel units as a mask pattern, and the tint block pattern is detected by the pattern matching method. Since the pattern matching method is conventionally known, detailed description thereof is omitted. Here, since the dot diameter of the dots forming the copy-forgery-inhibited pattern in the document image data is corrected to the dot diameter that can be recognized as the copy-forgery-inhibited pattern dot in the dot diameter correction unit 210, the copy-forgery-inhibited pattern detection accuracy is improved.

  The unauthorized copy determination unit 230 determines whether the document image data read by the reading unit 102 based on the result of the background pattern detection by the background pattern detection unit 220 is prohibited from being printed (copied) or transferred to another apparatus. To determine. That is, when a copy-forgery-inhibited pattern pattern is detected, it is determined that the document image data is prohibited from being printed or transferred to another apparatus.

  The determination result of the unauthorized copy determination unit 230 is notified to the image data processing unit 105 via the CPU 106 or directly. In response to this, the image data processing unit 105 cancels the necessary image processing, and the image conversion means in the image data processing unit 105 converts the document image data into unreadable image data by painting or the like, and outputs the image data. It will be.

  In the following, the dot correction processing in the dot diameter correction unit 210 of FIG. 4 will be described in detail, but before that, an outline of the operation for printing out a document in which a tint block pattern is embedded by the image forming apparatus will be described.

  FIG. 5 is a schematic flowchart of printing processing by the image forming apparatus. Desired image data is generated by an external device such as a personal computer (step 3001), and a specific background pattern is added to the image data (step 3002). Electronic data in which a tint block pattern is added to the image data is transferred to the image forming apparatus.

  The image forming apparatus inputs the electronic data with the copy-forgery-inhibited pattern added to the image data (step 3003), and prints it with the plotter unit (step 3004). As a result, a printed material of the document in which the background pattern is embedded in the image data is created.

  Here, the problem is that when the copy-forgery-inhibited pattern pattern is printed in the plotter unit, the dot diameter of the copy-forgery-inhibited pattern varies depending on the difference in model or change over time. On the other hand, a conventionally conceived method is to adjust the dot diameter for electronic data to which a tint block pattern is added in an image forming apparatus (for example, Patent Document 1 and Patent Document 2), but writing is performed. When a component with a shallow depth of focus such as an LED is used as a means, the focus is blurred with a slight deviation. Even if the dot diameter is adjusted in advance, the printed tint block pattern is not improved.

  FIG. 6 shows various dot variations. FIG. 6A shows a normal (standard) size dot that can be recognized. FIG. 6B shows elliptical dots that are longer in the horizontal or vertical direction (in the vertical direction in the example) than normal dots. Normally, the dots are rounded by adjusting the optical system as the photoconductor rotates, but when a component that cannot be adjusted is used, the dot becomes elliptical as shown in FIG. FIG. 6C shows a dot larger than the standard. A writing device using an LED as a light source has a shallow depth of focus and is easily out of focus, so that light hitting the photoreceptor is blurred and becomes large dots. FIG. 6D shows thin dots that are small and deformed by definition. When the photosensitive member is weakened due to the change with time and the adhesion of the toner becomes worse, the dots become smaller and smaller than specified.

  The present invention solves the problem that the dot diameter varies as described above, in the image processing apparatus that reads and processes the document image, the dot diameter of the dot that forms the background pattern is detected before the background pattern detection is performed on the read document image data. The problem is solved by correcting and stabilizing the dot diameter so that it can be recognized. Hereinafter, the dot correction processing in the dot diameter correction unit 210 in FIG. 4 will be described in detail.

  FIG. 7 shows a flowchart of an example (referred to as Example 1) of dot correction processing in the dot diameter correction unit 210 of FIG. Here, step 4001 functions as a region specifying means. Steps 4002 and 4003 function as a scaling unit, and step 4005 functions as a mask scaling unit.

<Step 4001>
An area is specified for the document image data read by the reading unit 102, and only the document image data in the area is cut out. Specifically, the image data is cut out by specifying the image area (area with good dot conditions) to be cut out by counting the number of pixels. Thereafter, dot correction processing and tint block pattern detection processing are performed on the cut-out document image data.

  In a model that handles a wide-area image such as the A0 width, even if the entire A0 width is read, a part of the image data is sufficient for detecting the copy-forgery-inhibited pattern (usually, the copy-forgery-inhibited pattern is the entire pattern of the document). Embedded in the area). It is not meaningful to load all the original image data because of the processing load.

  By specifying the area and cutting out and capturing only the original image data in that area, even when handling a wide area image, it is necessary only for the good part of the dot condition of the stable part of the reading device and writing device. Therefore, it is possible to cut out an image of only a small portion and eliminate waste such as dot correction processing and tint block pattern detection processing.

<Step 4002>
A scaling factor for optimizing the dot diameter is set so that the dot diameter of the dot forming the copy-forgery-inhibited pattern in the original image data cut out in step 4001 becomes a recognizable dot diameter. The variable magnification is set independently in the main scanning direction and the sub-scanning direction.

Specifically, when creating document image data in which a background pattern is embedded, a dot having a dot diameter (for example, one dot) for forming the background pattern is added to a certain portion. As a result, the dots are printed together with the original image data in which the tint block pattern is embedded, and are read by the reading unit 102 of the image processing apparatus. When an area is designated in step 4001, the dot is included in the area. Then, the dot diameter of the dot in the cut-out document image data is measured (this represents the dot diameter of the dot forming the tint block pattern read by the reading unit 102), and the following recognizable dot diameter is used. Calculate the scaling factor using the formula
(Recognizable dot diameter) / (measured dot diameter) × 100
Here, since variation in the size of dots is assumed in the horizontal direction and the vertical direction, it is necessary to calculate a scaling factor in each of the main scanning direction and the sub-scanning direction. Here, an example will be described in which the dot diameter of the dots forming the tint block pattern read by the reading unit 102 is smaller than the standard (case in FIG. 6D).

Now, the recognizable dot diameter and the measured dot diameter are assumed to be the values shown in FIG. In this case, the scaling factor in the main scanning direction and the sub-scanning direction is calculated as follows.
Main scan: 160 ÷ 90 = 170%
Sub-scan: 160 ÷ 100 = 160%
In the case of FIGS. 6B and 6C, the scaling factors in the main scanning direction and the sub-scanning direction can be calculated in the same manner.

<Step 4003>
The document image data cut out in step 4001 is scaled independently in the main scanning direction and the sub-scanning direction at the scaling factor calculated in step 4002. As a result, the dot diameter of the dots forming the tint block pattern read by the reading unit 102 can be set to a recognizable dot diameter.

  For example, when the dot diameter of the dots forming the copy-forgery-inhibited pattern pattern read by the reading unit 102 is thin and vertically long, it is recognized by independently changing the magnification in the main scanning direction and the sub-scanning direction at the above magnification. The dot diameter assumed to be used can be set.

<Step 4004>
The document image data scaled in step 4003 (document image data in a predetermined area) is binarized. In the case of binarization without scaling, for example, in the case of FIG. 6D, the black pixel portion is insufficient, but by scaling, the dots become the prescribed size. It can be detected.

  FIG. 9A is an example of a binarized dot without scaling (filled portion). In this case, since the dot is smaller than the standard (the dot read by the reading portion is small), the original black pixel B portion Do not detect dots without enough. On the other hand, FIG. 9B shows an example of a dot that has been scaled and binarized. In this case, the dot becomes large due to zooming, and the state becomes detectable.

<Step 4005>
By performing the scaling process in step 4003, the arrangement of dots of the background pattern included in the original image data read by the reading unit 102 may be lost, and the background pattern pattern detection unit 220 may not be able to detect the background pattern. Arise. Therefore, the mask pattern (standard pattern data) for detecting the tint block pattern is also scaled in advance. The scaling factor is the value calculated in step 4002.

  The copy-forgery-inhibited pattern detection unit 220 performs copy-forgery-inhibited pattern detection processing on image data obtained by scaling and binarizing document image data in a predetermined area based on the scaled mask pattern. As a result, the tint block pattern can be reliably detected.

  A specific example is shown in FIG. FIG. 10A is a diagram showing the relationship between the ground pattern without scaling and the mask pattern for detecting the ground pattern. Here, the filled portions are dots of the tint block pattern, and B is a black pixel of the mask pattern. This is no problem.

  FIG. 10B shows the relationship between the tint block pattern and the mask pattern when the original image data is scaled. In this way, when zooming is performed, the black pixels B of the mask pattern and the actual dots (filled portions) of the tint block pattern are shifted, and there is a possibility that the tint block pattern cannot be detected.

  FIG. 10C is a diagram showing the relationship between the tint block pattern and the mask pattern when the original image data is scaled and the mask pattern is scaled similarly. As described above, since the position of the black pixel of the mask pattern is changed in accordance with the magnification change according to the scaled copy-forgery-inhibited pattern pattern, it can be matched with the copy-forgery-inhibited pattern pattern. Note that the scaled mask pattern may be stored in the memory 107 or the HDD 108.

  According to this embodiment, the original image data read by the reading unit 102 is subjected to scaling processing independently in each of the main scanning direction and the sub-scanning direction, and the dispersed dot diameter can be recognized as the dots of the tint block pattern. By correcting to the dot diameter, the dots forming the tint block pattern can be reliably detected, and the detection accuracy of the tint block pattern is improved. Furthermore, by changing the size of the mask pattern for detecting a tint block pattern, the detection accuracy of the tint block pattern is further improved. Further, only a predetermined area of the document image data read by the reading unit is cut out and used for dot correction processing and tint block pattern detection processing, so that waste of processing can be saved even when a wide area image is handled.

  FIG. 11 shows a flowchart of another embodiment (embodiment 2) of the dot correction processing in the dot diameter correcting section 210 of FIG. Here, step 5001 functions as an area designating means as in step 4001 of FIG. Alternatively, steps 5002 and 5003 function as binarization means.

  In this embodiment, the original image data read by the reading unit 102 is directly subjected to the binarization pattern with the dot diameter dispersed in the binarization process without performing the scaling process as in the first embodiment. The dot diameter is corrected to a recognizable dot diameter.

<Step 5001>
The processing here is the same as in step 4001 of FIG. That is, an area is specified for the document image data read by the reading unit 102, and only the document image data in the area is cut out. Specifically, the image data is cut out by specifying the image area (area with good dot conditions) to be cut out by counting the number of pixels. Thereafter, dot correction processing and pattern detection processing are performed on the cut document image data.

<Step 5002>
When the document image data cut out in step 5001 is binarized, a binarization threshold value is calculated so that the dot diameter of dots forming the copy-forgery-inhibited pattern in the document image data falls within a recognizable dot diameter range.

  Specifically, as in the first embodiment, when creating original image data in which a background pattern is embedded, a dot (for example, one dot) for forming the background pattern is added to a certain portion. As a result, the dots are printed together with the original image data in which the tint block pattern is embedded, and read by the reading unit 102 of the image processing apparatus. When an area is designated in step 5001, the dot is included in the area. Then, an optimum binarization threshold value is calculated from the state of the dot in the cut document image data and the state of the dot of the mask pattern for detecting the tint block pattern. A specific example will be described below.

  Now, the dots of the mask pattern for detecting the tint block pattern are shown in FIG. On the other hand, the above-described dots in the cut-out document image data (the dots forming the copy-forgery-inhibited pattern read by the reading unit 102 are the same) are in the state shown in FIG. Here, it is assumed that the pixel value takes a level from 0 (pure white) to 255 (pure black). FIG. 13 (b) shows that the dots correspond to FIG. 6 (c).

12 and 13, when the maximum value of the black pixel W region is 130 and the minimum value of the black pixel B region is 210, the binarization threshold is 130 <threshold <210.
In the range, the read background pattern is white in an area that must be white and black in an area that must be black.

<Step 5003>
The document image data cut out in step 5001 is binarized with the threshold value calculated in step 5002. Thus, the tint block pattern detection unit 220 can reliably detect dots forming the tint block pattern in the document image data when pattern matching with the mask pattern is performed, and the tint block pattern detection accuracy is improved.

  For example, in the case of the example of FIG. 13A, when binarization is performed using the above-mentioned range 209 as a threshold, the binarized image is as shown in FIG. 14A. This applies to the dot detection conditions of the mask pattern shown in FIG. 12, so that dots larger than the standard of the tint block pattern read by the reading unit 102 (for example, the case of FIG. 13B) can be detected reliably. Become.

  On the other hand, the conventional method for determining the threshold value is generally (maximum value of image + minimum value of image) / 2. In this case, in the example of FIG. 13A, the threshold value is 115. When binarization is performed with this threshold value, the binarized image is as shown in FIG. 14B. Since this does not apply to the mask pattern condition shown in FIG. 12, the dots of the tint block pattern cannot be detected.

  In the present embodiment, in the process of binarizing the clipped document image data, the dot diameter correction unit 210 performs correction so that the dots forming the tint block pattern in the document image data match the detection conditions of the mask pattern. The dot correction process is simplified compared to the first embodiment. In addition, the tint block pattern detection unit 220 can reliably detect the tint block pattern in the clipped original image data using the original mask pattern.

  As in the first embodiment, only a predetermined area of the document image data read by the reading unit is cut out and used for dot correction processing and tint block pattern detection processing. Can be omitted.

  FIG. 15 shows a flowchart of still another embodiment of the dot diameter correction processing in the dot diameter correction unit 210 of FIG. In the present embodiment, the first and second embodiments described so far are selectively used depending on the state of the dots forming the tint block pattern.

  15, step 6001 corresponds to steps 4001 and 5001 in FIGS. 7 and 11, and steps 6003 and 6004 surrounded by a frame 6100 correspond to steps 5002 and 5003 in FIG. 11, and steps surrounded by a frame 6200. Since 6005 to 6008 correspond to 4002 to 4005 in FIG. 7, detailed description thereof will be omitted. Hereinafter, step 6002 will be described. Here, step 6002 functions as a correction process determination unit.

  The threshold value correction process according to the second embodiment is simple, but there is a concern that the black area necessary for dot detection may disappear when the dot diameter becomes too small. In that case, the zoom correction process of the first embodiment is selected, and the dot is enlarged to cope with it. The conditional expression is such that the minimum value of the black pixel (B)> the minimum value of the white pixel (W). If the conditional expression is satisfied, the processing (6100) of the second embodiment is selected. The process (6200) is selected.

  Now, the dots of the mask pattern for detecting the tint block pattern are shown in FIG. 16A (dot detection conditions). On the other hand, the state of the dots forming the tint block pattern read by the reading unit 102 is shown in FIG. 16B (case in FIG. 6D). When Example 2 is applied, the maximum value of the white pixel (W) is 10 and the minimum value of the black pixel is also 10. Therefore, it is necessary to binarize with a threshold value of 11. However, if binarization is performed with a threshold value of 11, one required dot is lost (does not satisfy the dot detection condition), and dot detection cannot be performed. FIG. 17A shows a case where binarization is performed with the threshold 11. That is, if the dot is too small, the second embodiment cannot cope with it. Therefore, the first embodiment is applied to enlarge the dots. In this case, the dots are as shown in FIG. 17B and satisfy the dot detection conditions.

  Conversely, if the dots forming the copy-forgery-inhibited pattern pattern read by the reading unit 102 are too large (for example, the case of FIG. 6C), the reduction rate is increased in the first embodiment, and the dots are changed by scaling. There is a concern that it is difficult to detect the tint block pattern even if the space between the dots becomes too narrow and the mask pattern is scaled. This case may be dealt with in the second embodiment.

  If the minimum value of the black pixel (B) in the matrix (for example, FIG. 16A) constituting the dot detection mask pattern exceeds the maximum value of the white pixel (W), the pixel becomes true black and there are no dots. The second embodiment can be applied. Therefore, the minimum value of B and the minimum value of W of the dots (for example, FIG. 13 and FIG. 16B) forming the tint block pattern added to a certain part of the document image data read by the reading unit 102 are obtained. In comparison, if the minimum value of B> the maximum value of W is satisfied, the second embodiment is selected, and if not, the first embodiment is selected (step 6002). Thereby, for example, dot detection can be performed for all the dots shown in FIGS. For example, even if the large dot diameter becomes smaller over time and cannot be handled in the second embodiment, the first embodiment can handle it.

DESCRIPTION OF SYMBOLS 101 Operation display part 102 Reading part 103 Plotter part 104 Background pattern detection processing part 105 Image data processing part 210 Dot diameter correction part 220 Background pattern detection part 230 Unauthorized copy discrimination | determination part

JP 2008-035376 A JP 2008-042746 A

Claims (9)

An image reading means for reading an original image and an image data processing means for processing the original image data read by the image reading means, and the original image data processed by the image data processing means is printed, stored, or sent to another apparatus In the image processing apparatus to transmit,
Dot diameter correcting means for correcting dots forming a copy-forgery-inhibited pattern pattern in the original image data read by the image reading means to a dot diameter that can be recognized as dots of the copy-forgery-inhibited pattern pattern;
A tint block pattern detecting unit for detecting a tint block pattern based on the document image data corrected by the dot diameter correcting unit;
A discriminating unit for discriminating whether or not the original image data is prohibited from being printed or transferred to another device based on a result of the tint block pattern detection by the tint block pattern detecting unit;
Image conversion means for converting the document image data into unreadable image data when the document image data is prohibited from being printed or transferred to another device;
An image processing apparatus comprising:   The dot diameter correction means is independent of the main scanning direction and the sub-scanning direction so that the original image data read by the reading means has a dot diameter capable of recognizing dots forming a tint block pattern in the original image data. The image processing apparatus according to claim 1, further comprising a scaling unit that performs scaling, and dot correction is performed by the scaling unit.   The scaling unit measures a dot diameter of dots forming a tint block pattern in the document image data read by the reading unit, and calculates a scaling factor so that a recognizable dot diameter is obtained. The image processing apparatus according to claim 2.   3. The dot diameter correcting means further comprises a mask scaling means for scaling a mask pattern for detecting a tint block pattern in accordance with scaling of original image data read by the reading means. Or the image processing apparatus of 3.   The dot diameter correcting unit binarizes the document image data read by the reading unit so as to binarize so that dots forming a tint block pattern in the document image data can be recognized. The image processing apparatus according to claim 1, wherein the dot correction is performed by the binarization unit.   The binarizing unit converts the document image data into 2 so that the dot diameter of dots forming the tint block pattern in the document image data read by the reading unit matches the dot detection condition of the tint block pattern detection mask pattern. The image processing apparatus according to claim 5, wherein a threshold value to be converted is calculated. The dot diameter correcting means is
A scaling unit that independently scales the original image data read by the reading unit in the main scanning direction and the sub-scanning direction so that the dots forming the tint block pattern in the original image data can be recognized. When,
Binarization means for binarizing the original image data read by the reading means so that the dots forming the copy-forgery-inhibited pattern pattern in the original image data have a recognizable dot diameter;
A correction processing discriminating unit for performing dot correction by selecting either the scaling unit or the binarizing unit according to the state of dots forming a tint block pattern in the document image data read by the reading unit;
The image processing apparatus according to claim 1, further comprising:   The correction processing determining means selects the binarizing means when satisfying the minimum value of black pixels> the maximum value of white pixels, and selects the scaling means when not satisfying. The image processing apparatus according to claim 7.   The dot diameter correcting means includes area designating means for designating an area of document image data read by the reading means, and performs dot processing on the document image data in the designated area. The image processing apparatus according to claim 1.

Images