JP4014070B2 - Pattern detection method and image processing control method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pattern detection method for detecting a specific pattern in order to prevent unauthorized copying of a confidential document, and an image processing control method for controlling an image processing function in accordance with the detection of the specific pattern.
[0002]
[Prior art]
Conventionally, as a method for preventing unauthorized copying, for example, a special paper that has a metallic gloss and cannot be illegally copied is used (refer to Japanese Patent Laid-Open No. 6-155975), and a sticker for preventing unauthorized copying is printed on the printed matter. Attached (see Japanese Patent Laid-Open No. 6-259013) or a character / background printed in two colors so that the reproduction density is substantially the same when copying in black and white (Japanese Patent Laid-Open No. 7-89215) And a method in which a printing method is devised, such as a method in which a latent image appears after copying (see Japanese Utility Model Publication No. 6-68051).
[0003]
[Problems to be solved by the invention]
However, normally, when a confidential document is created in an office or the like, a monochrome printer is often used, and it is difficult in terms of function and cost to use special paper or a special printing method. In addition, since the content of confidential documents is a problem, even if a sticker is attached that prevents the document from being reproduced neatly when it is copied, it is copied in a readable state except where the sticker is attached. Therefore, the deterrence effect of fraud is low.
[0004]
There is also an apparatus for controlling an image processing process (copying) by identifying a target surface pattern (Japanese Patent Laid-Open No. 60-229572). However, this device is effective when the entire pattern on the target surface is specified, but in general confidential documents, the pattern on the entire document surface cannot be specified in advance, and the readability of the document is impaired. Even when a specific pattern is printed in a blank portion or the like, it is easy to conceal that portion when reading an image, and unauthorized copying cannot be prevented.
[0005]
It is an object of the present invention to print a special pattern on the back side of a document in such a way that it can be printed by a normal monochrome printer or color printer, without compromising the readability of the original document and easily separating the document contents and patterns. Another object of the present invention is to provide a pattern detection method and an image processing control method capable of prohibiting unauthorized copying in a copying machine or the like while preventing the above.
[0006]
[Means for Solving the Problems]
In order to achieve the object, according to the first aspect of the present invention, the step of inputting image data, the step of extracting pixels having a predetermined pixel value from the input image data, and the extracted pixels A step of detecting a specific pattern candidate existing in a grid pattern at a predetermined interval, and whether or not there is another pattern candidate on a circle centered on the detected one pattern candidate and having a radius of the predetermined interval And a step of detecting a specific pattern based on a value obtained by accumulating the scores for all the detected pattern candidates, and other pattern candidates on the circumference of the radius When a plurality of are detected, if the angle between the candidates with respect to the center of the circle is a specific angle or a predetermined angle, a high score is given .
[0007]
According to the second aspect of the present invention, there is provided an image processing control method for controlling an image processing operation of a document by reading the document, wherein a plurality of specific pattern arrangement relations and color arrangement relations printed on the back side of the document are determined. When it is detected by the method of claim 1 , the document copy prohibiting processing operation is controlled.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows the configuration of an embodiment of the present invention. In the figure, 101 is an image input unit such as a scanner unit, 102 is a specific pattern detection unit that is one of the features of the present invention, 103 is an image output unit that creates and prints an image obtained by scanning, 104 is a data storage unit for storing scanned image data and data being processed, 105 is an overall processing control unit, 106 is a data communication path, and 107 is communicated with an external device via a network or the like. Is an external notification means. FIG. 2 is a process flowchart of the present invention.
[0009]
The embodiment will be described below with reference to FIG. First, an image is acquired by optically scanning a document with the image input unit 101 (step 201). The image signal is assumed to be monochrome multi-value or RGB full color. Next, the specific pattern detection unit 102 detects specific pattern candidates from the acquired image (step 202).
[0010]
In the first embodiment, the specific pattern is printed in black on the back surface of a document (paper) to be scanned. FIG. 3 shows an example of the specific pattern. In the image signal obtained by scanning the document surface on which the specific pattern is printed on the back side of the document, the specific pattern on the back side appears as an intermediate density signal.
[0011]
For example, when the acquired image signal is a black and white multivalue of 0 (white) to 255 (black), an intermediate density signal of about level 50 is obtained (FIG. 4). FIG. 4 shows a state where the density is low. This level value depends on the paper quality and the characteristics of the image input unit 101, but if a “copy prohibited document” is intentionally printed, a certain level of paper quality can be selected even if it is plain paper. In addition, since the characteristics of the image input unit are known in advance, the expected level value can fall within a predetermined range.
[0012]
Accordingly, the pixels having the density level values are extracted from the entire document image, matched with the template of the specific pattern, and when they match, it is detected that the specific pattern is printed on the back side of the document. In order to increase the matching accuracy, it is better to make the specific pattern as non-directional as possible. If the rotation invariant is used as the feature amount, the pattern can be collated without being influenced by some rotation. As the rotation-invariant feature quantity, for example, a known method such as a Fourier descriptor or a moment method is used.
[0013]
Further, the detection of the specific pattern described above may use a relative difference from the level value of the ground (usually white) instead of the absolute value of the density value.
[0014]
In addition, when the document image obtained by scanning as described above is full color, the template matching process may be performed in the same manner as described above after simply converting into a luminance component, and in addition to this, the color information (For example, whether or not there is a color pixel in a predetermined range) may be performed.
[0015]
Furthermore, although the above example is a case where the surface (one side) of the document is scanned, a specific pattern printed on at least one side may be detected by scanning both sides of the document.
[0016]
Next, the specific pattern detection unit 102 performs determination based on the relative position of the specific pattern candidate (step 203). Characters are printed on the front side of the document regardless of the position of the pattern on the back side. Therefore, as shown in FIG. 5, it is expected that the character (special) on the front surface and the pattern on the back surface overlap. If the overlapping part is large, matching may not be achieved. Further, if there is a portion printed in halftone on the surface of the document, there is a possibility that the portion is erroneously detected as a specific pattern.
[0017]
Therefore, it is next determined whether or not the document is a specific pattern print document based on the relative positional relationship between the detected plurality of specific pattern candidates. For example, it is assumed that the specific pattern is printed at the distance d as shown in FIG. 6, and the detection result (pattern candidate) of the pattern is as shown in FIG.
[0018]
Here, as shown in FIG. 8, it is locally checked whether another candidate exists at the position of the radius d of a certain pattern candidate. If one candidate exists, point = 1 is set to the pattern candidate. give. Also, if there are two candidates and they are in a 180 degree symmetrical position, or if they are at a 90 degree angle, give point = 3 to the pattern candidate and calculate the point To go. Alternatively, a high point may be given when another candidate exists on a line connecting the center of the circle and the detected candidate at a constant magnification or an integer multiple of d.
[0019]
These point calculation processes are performed for all detected candidates, and finally the total number of points exceeds a threshold value (absolute value) or the total number of points is normalized by the number of detection pattern candidates. When the threshold value is exceeded, the document is determined to have a specific pattern printed on the back side. Note that, as the normalized value, a value obtained by normalizing the total number of points by the document size (original size such as A4, B5, or a postcard) may be used.
[0020]
In the case of performing an operation such as printing the above-described specific pattern on the back side of the copy-prohibited document, when it is determined in step 203 that the document is a specific pattern print document, the image output unit 103 performs image printing (copying). Control is performed so as not to be performed (step 204). In addition to simply not copying and printing the document, the subsequent operation as a copier may be stopped until some processing is performed again. You may make it notify to another apparatus etc. via this.
[0021]
On the contrary, in the case of performing an operation such as printing the above-described specific pattern on the back side of the copy-permitted document, the image output unit 103 prints an image only when the specific pattern is successfully detected in step 203 ( The image output is controlled so as to be copied (step 204).
[0022]
In FIG. 1, the image obtained by scanning is stored once in the data storage unit 104. However, this may store the entire image of the document or every time a part of the image is captured and stored. A method may be employed in which the pattern candidate is extracted by the specific pattern detection unit 102 and the overall arrangement relationship is checked later.
[0023]
In the second embodiment, the specific pattern is printed in color on the back side of the document. Each individual pattern candidate is printed by printing each specific pattern in one color other than black or several predetermined colors and using not only the density value or density difference as in the previous embodiment, but also the color information. (Whether or not a pixel of a specific color has been detected) is detected. Further, when examining the overall arrangement relationship, not only the arrangement of pattern candidates but also the arrangement of pattern candidate colors (for example, patterns of specific colors are arranged in a specific direction as shown in FIG. 9) have regularity. Whether such a color pattern exists on the back side of the document is determined.
[0024]
The above embodiment is an example applied to a copying machine that controls the copying operation by detecting the presence or absence of a specific pattern printed on the back side of a document, but the present invention is not limited to this, It can also be applied to a scanner. In other words, the image output unit does not print, but transfers the image to the outside. By detecting the presence or absence of a specific pattern printed on the back side of the document, the image reading operation or image transfer operation is performed. This is an embodiment of a scanner for controlling the above.
[0025]
The present invention can also be applied to a printing machine that prints a specific pattern for determining whether copying is prohibited or permitted on the back side of a document printing surface. FIG. 10 shows a configuration example when the present invention is applied to a printer. A personal computer (hereinafter referred to as a PC) serving as a host is connected to a printer, and a confidential document command is sent from the PC to the printer together with document data. The printer uses a duplex printing mechanism to print a specific pattern on one side and the original document data on the other side in response to a confidential document print command.
[0026]
FIG. 11 shows a configuration when the process of FIG. 10 is executed by printer driver software. Using a PC driver software (not shown), a print command (data) in which document data is arranged on the front and a specific pattern is arranged on the back is generated and sent to the printer.
[0027]
FIG. 12 shows a configuration when the present invention is applied to a printer having no double-sided printing mechanism. When there is no double-sided printing mechanism, a specific mode for printing a specific pattern is provided in advance, and the specific pattern is printed on one side. This specific mode may be an instruction from the PC or designation from the operation panel of the printer.
[0028]
In this specific mode, paper with a specific pattern printed on one side is turned upside down on one side of the paper feed tray, reversed and set in the printer, and paper is fed from this paper cassette in response to confidential document printing instructions. To do. Thereafter, when the document is printed by the confidential document printing command from the PC, the specific pattern is printed out on the back side. This makes it possible to print a confidential document that can prevent unauthorized copying with a copying machine or the like.
[0029]
The present invention is not limited to a specific hardware configuration, and the specific pattern detection unit that is the subject of the present invention can also be realized by a program. FIG. 13 shows a configuration example when image processing control by specific pattern detection is executed by a program.
[0030]
For example, the specific pattern detection program and the image output control program are stored in a recording medium such as a CD-ROM and installed in the system from a CD-ROM drive, or the program is downloaded from a network. Control is performed to prohibit or permit image output in the image output device in response to detection of a specific pattern from the document image input by the image input device. In the configuration example shown in FIG. 13, when the input image is not temporarily held, an external storage device such as an HD may not be provided. Further, when the input image is not output on paper, the image output device may not be provided. Further, when the image processing control result is not communicated to the outside, it is not necessary to provide an external communication device.
[0031]
【The invention's effect】
As described above, according to the present invention, it is possible to accurately detect a specific pattern printed on the back side of a document by a normal printing method without impairing the readability of the document. In addition, when such a specific pattern is printed in advance on the reverse side of a document that is prohibited from being copied and printing of a copy-prohibited document is executed using a copying machine or a scanner, the specific pattern is detected. Accordingly, unauthorized copying can be prevented.
[Brief description of the drawings]
FIG. 1 shows a configuration of an embodiment of the present invention.
FIG. 2 is a processing flowchart of an embodiment of the present invention.
FIG. 3 shows an example of a specific pattern.
FIG. 4 shows how an acquired image appears.
FIG. 5 shows how an acquired image appears when a character and a specific pattern overlap.
FIG. 6 shows a first example of pattern arrangement.
FIG. 7 shows an example of a pattern candidate detection result.
FIG. 8 is a diagram for explaining relative position detection of pattern candidates.
FIG. 9 shows a second example of pattern arrangement.
FIG. 10 shows a configuration example when the present invention is applied to a printer.
FIG. 11 shows a configuration when the process of FIG. 10 is executed by printer driver software.
FIG. 12 shows a configuration when the present invention is applied to a printer having no double-sided printing mechanism.
FIG. 13 shows a configuration example when image processing control by specific pattern detection is executed by a program.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 Image input part 102 Specific pattern detection part 103 Image output part 104 Data storage part 105 Control part 106 Data communication path 107 External notification part

Claims (2)

A step of inputting image data; a step of extracting pixels having a predetermined pixel value from the input image data; and a step of detecting specific pattern candidates existing in a grid pattern at predetermined intervals from the extracted pixels; Investigate whether there is another pattern candidate on the circumference centered on the detected one pattern candidate and having a radius of the predetermined interval, and if there is, give a score, and detect all the detected patterns A step of detecting a specific pattern based on a value obtained by accumulating scores for the candidates, and when a plurality of other pattern candidates are detected on the circumference of the radius, the candidates are compared with each other with respect to the center of the circle. A pattern detection method characterized in that a high score is given when the angle formed by is a specific angle or a predetermined angle . An image processing control method for reading a document and controlling an image processing operation of the document, wherein the arrangement relationship of a plurality of specific patterns and the arrangement relationship of colors printed on the back side of the document are detected by the method according to claim 1. An image processing control method, comprising: controlling a document copy prohibiting processing operation.

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