JP2000307857A - Pattern detecting method, image processing control method, image processor and recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prohibit an unauthorized copying in a copying machine, etc., without impairing the readability of an original document also while preventing document contents from being easily separated from a pattern by printing a special pattern on the rear face of the original by a method capable of printing the original document by normal monochrome printer or color printer. SOLUTION: A specific pattern detecting part 102 detects a specific pattern candidate printed on the rear face of a document from an acquired image, and decides whether the document is one on which the specific pattern was printed on the rear face of the document by checking arrangement relation about the pattern candidate, and an image outputting part 103 inhibits operations such as copying, when the specific pattern is printed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field 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, an image processing control method for controlling an image processing function according to the detection of the specific pattern, and image processing. The present invention relates to a device and a recording medium on which an image processing control program is recorded.

[0002]

2. Description of the Related Art Conventionally, as a method of preventing illegal copying, for example, a method using a special paper having a metallic luster that cannot be illegally copied (see Japanese Patent Application Laid-Open No. 6-155975) is used. (See Japanese Unexamined Patent Application Publication No. 6-259013), or a character / background that prints characters / background in two colors so that the reproduction density is almost the same when black-and-white copying is performed (Japanese Unexamined Patent Publication No. Japanese Unexamined Patent Application Publication No. 7-89215), a method in which a latent image appears after copying (see Japanese Utility Model Application Laid-Open No. 6-68051), a method devising a printing method, and the like have been proposed.

[0003]

However, in general, when creating a confidential document in an office or the like, a monochrome printer is often used, and it is functional and costly to use a special paper or a special printing method. Difficult. In addition, since the contents of a confidential document are a matter of concern, even if a sticker is attached to a part that prevents it from being reproduced clearly when copied, it will be copied in a readable state except where the sticker is attached. Therefore, the effect of deterring fraud is low.

There is also an apparatus for controlling an image processing process (copying) by identifying a target surface pattern (Japanese Patent Application Laid-Open No. 60-229572). However, this device is effective when the entire picture on the target surface is specified.However, the general pattern of the entire document surface cannot be specified in advance with a general confidential document, and the readability of the document is impaired. Even when a specific pattern is printed on a blank part or the like so as not to be hidden, it is easy to hide that part when reading an image, and it is not possible to prevent illegal copying.

SUMMARY OF THE INVENTION It is an object of the present invention to print a special pattern on the back side of a document in such a manner that it can be printed by a normal monochrome printer or color printer, without impairing the readability of the original document, and by comparing the document contents with the pattern. An object of the present invention is to provide a pattern detection method, an image processing control method, an image processing device, and a recording medium that can prevent unauthorized copying in a copying machine or the like while preventing easy separation.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a pixel having a density level within a predetermined range is extracted from an image obtained by scanning a document. A specific pattern printed on the back side of the scan surface is detected.

According to a second aspect of the present invention, a specific pattern printed on the back side of the scan surface is detected by detecting a change in density from an image obtained by scanning a document.

According to the third aspect of the present invention, it is possible to detect a specific pattern printed on the back side of the scan surface by extracting pixels of a predetermined range of colors from an image obtained by scanning a document. Features.

According to a fourth aspect of the present invention, there is provided a method for detecting, from an image obtained by scanning a document, a specific pattern printed in a grid pattern at a predetermined interval on the back surface of the scan surface. With one pattern candidate as the center, it is checked whether or not another pattern candidate exists on the circumference having the predetermined interval as a radius.If there is, a score is given, and the score for all detected pattern candidates is given. It is characterized in that a specific pattern is detected based on the accumulated value.

According to the fifth aspect of the present invention, when a plurality of other pattern candidates are detected on the circumference of the radius, the angle between the candidates with respect to the center of the circle is a specific angle or a predetermined angle. It is characterized by giving a high score in some cases.

In the invention according to claim 6, it is high when another candidate exists at a fixed magnification or an integral multiple of the radius on a line connecting the detected candidate on the circumference and the center point of the circle. It is characterized by giving points.

According to a seventh aspect of the present invention, a specific pattern printed on at least one side is detected by scanning both sides of the document.

According to an eighth aspect of the present invention, there is provided an image processing control method for reading a document and controlling an image processing operation of the document, wherein the specific pattern printed on the back side of the document is provided. The method is characterized in that the image processing operation of the document is controlled when it is detected by the above method.

According to a ninth 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 the arrangement relation of a plurality of specific patterns and the color When the arrangement relation is detected by the method according to the fourth, fifth or sixth aspect, the image processing operation of the document is controlled.

According to a tenth aspect of the present invention, there is provided a means for extracting pixels having a density level within a predetermined range from an image obtained by scanning a document, and a specific pattern on the back surface of the scan surface based on the extraction result. Means for detecting whether or not is printed.

According to the eleventh aspect, whether one pattern candidate detected from an image obtained by scanning a document is located at the center and another pattern candidate exists on a circumference having a predetermined interval as a radius is determined. Means for judging whether or not, a specific pattern printed in a grid pattern at predetermined intervals on the back surface of the scan surface based on a value obtained by accumulating scores for all detected pattern candidates based on the accumulated score for all detected pattern candidates. It is characterized by having a detecting means.

According to a twelfth aspect of the present invention, there is provided an image processing apparatus for reading a document and controlling an image output operation of the document, comprising: means for detecting a specific pattern printed on the back side of the document; Means for prohibiting or permitting the image output operation of the document when the is detected.

According to a thirteenth aspect of the present invention, a computer has a function of detecting a specific pattern printed on the back of a document and a function of prohibiting or permitting image output of the document in response to detection of the specific pattern. The present invention is characterized in that it is a computer-readable recording medium on which a program for realizing the above is recorded.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be specifically described below 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 which is one of the features of the present invention, 103 is an image output unit that forms and prints an image obtained by scanning, Reference numeral 104 denotes a data storage unit for storing image data obtained by scanning, data being processed, and the like; 105, an overall processing control unit; 106, a data communication path; 107, communication with external devices via a network; External notification means for performing FIG. 2 is a processing flowchart of the present invention.

An embodiment will be described below with reference to FIG. First, a document is optically scanned by the image input unit 101 to obtain an image (step 201). It is assumed that the image signal is black and white multi-valued or RGB full color. next,
The specific pattern detection unit 102 detects a specific pattern candidate from the acquired image (Step 202).

In the first embodiment, a 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 front surface of the document having the specific pattern printed on the back surface of the document, the specific pattern on the back surface appears as a signal of intermediate density.

For example, if the acquired image signal is 0 (white) to 2
In the case of 55 (black) multi-valued black and white, an intermediate density signal having a level of about 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 image input unit 101.
Depending on the characteristics of the paper, if the "copy prohibited document" is intentionally printed, the paper quality can be selected to a certain degree even if it is plain paper, and the characteristics of the image input section are known in advance. Therefore, the expected level value can be within a predetermined range.

Accordingly, the pixels having the above-mentioned 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 preferable that the specific pattern has as little directionality as possible, and if the rotation invariant is used as a feature amount, pattern matching can be performed without being influenced by a certain rotation. As the rotation invariant feature, a known method such as a Fourier descriptor or a moment method is used.

The specific pattern may be detected not by the absolute value of the density value but by the relative difference from the ground (usually white) level value.

When the document image obtained by scanning as described above is full color, the template image may be simply converted into a luminance component and then subjected to the template matching process as described above. (For example, whether there is a predetermined range of color pixels)
May be performed.

Further, in the above example, the front side (one side) of the document is scanned. However, by scanning both sides of the document, a specific pattern printed on at least one side may be detected. Good.

Next, the specific pattern detection unit 102 makes a determination based on the relative position of the specific pattern candidate (step 2).
03). Characters are printed on the front side of the document regardless of the position of the pattern on the back side. Therefore, it is expected that the characters (features) on the front side and the pattern on the back side overlap as shown in FIG. If the overlapping portion 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.

Then, based on the relative positional relationship between the plurality of detected specific pattern candidates, it is determined whether or not the document is a specific pattern print document. For example, suppose that a specific pattern is printed at an interval of a distance d as shown in FIG. 6, and the detection result (pattern candidate) of the pattern is as shown in FIG.

Here, as shown in FIG. 8, it is locally examined whether or not another candidate exists at the position of the radius d of a certain pattern candidate. = 1. When two candidates exist and are located at 180-degree symmetrical positions or at positions forming an angle of 90 degrees, point = 3 is given to the pattern candidate, and the points are calculated. To go.
In addition, a high point may be given on a line connecting the center of the circle and the detected candidate when another candidate exists at a fixed magnification of d or an integer multiple of d.

These point calculation processes are performed on 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 detected pattern candidates. If the value exceeds a threshold value, it is determined that the document has a specific pattern printed on the back side. In addition, as the normalized value described above,
A value obtained by normalizing the total number of points by the document size (original size such as A4, B5, or postcard) may be used.

In the case where the above-described specific pattern is printed on the back side of the copy-inhibited document, if it is determined in step 203 that the document is a specific pattern print document, the image output unit 103 prints the image ( (Copy) is controlled (step 204). In addition to not simply performing the copy printing of the document, the subsequent operation as the copying machine may be stopped until some processing is performed again.
7 may notify other devices via a network or the like.

On the contrary, in the case where the above-described specific pattern is printed on the back side of the copy-permitted document, the image output unit 103 outputs the image only when the specific pattern is successfully detected in step 203. Print (copy)
Image output is controlled (step 204).

In FIG. 1, an image obtained by scanning is once stored in the data storage unit 104. This may be performed by storing an image of the entire document or by storing a part of the image. Every time the specific pattern detection unit 102 extracts a pattern candidate, and later examines the entire arrangement relationship.

The second embodiment is an embodiment in which a specific pattern is printed in color on the back of a document. Each specific pattern is printed in one color other than black or a predetermined number of colors, and not only the density value or density difference as in the previous embodiment but also color information is used to enable individual pattern candidates. (Whether or not a pixel of a specific color is detected). Further, when examining the overall arrangement relationship, not only the arrangement of the pattern candidates but also the arrangement of the colors of the pattern candidates (for example, patterns of specific colors are arranged in a specific direction as shown in FIG. 9) have regularity. Then, it is determined whether such a color pattern exists on the back side of the document.

The above embodiment is an example in which the present invention is applied to a copying machine which controls a copying operation by detecting the presence or absence of a specific pattern printed on the back side of a document. However, the present invention is not limited to this. However, the present invention can be applied to a scanner. In other words, the image output unit does not perform printing, 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 the image transfer operation is performed. Is an embodiment of a scanner for controlling the scanner.

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 printer is connected to a host personal computer (hereinafter, PC), and the PC sends a confidential document command together with document data to the printer. The printer uses a two-sided printing mechanism to print a specific pattern on one side in response to a confidential document printing instruction.
The original document data is printed on the other side.

FIG. 11 shows a configuration in the case where the processing in FIG. 10 is executed by driver software of a printer. P 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 created by the driver software of C, and sent to the printer.

FIG. 12 shows a configuration in a case where the present invention is applied to a printer having no duplex printing mechanism. If there is no duplex 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 a command from a PC or a designation from the operation panel of the printer.

In this specific mode, the paper on which the specific pattern has been printed on one side is set in one of the paper feed trays, turned upside down, and set again in the printer. To do. After that, when the document is printed by the confidential document print 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 by a copying machine or the like.

It should be noted that the present invention is not limited to a specific hardware configuration, and the specific pattern detection unit which is the subject of the present invention can be realized by a program. FIG. 13 shows a configuration example in a case where image processing control by detecting a specific pattern is executed by a program.

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 are installed in the system from a CD-ROM drive, or the programs are downloaded from a network. When a specific pattern is detected from a document image input by the image input device, control is performed such that image output by the image output device is prohibited or permitted. Note that, in the configuration example shown in FIG. 13, when the input image is not temporarily stored, an external storage device such as an HD may not be provided. 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.

[0042]

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, such a specific pattern is printed in advance on the back side of a document or the like where copying is prohibited, and when printing of a copy-prohibited document is attempted using a copying machine or a scanner, the detection of the specific pattern is not possible. Accordingly, illegal 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 a pattern arrangement.

FIG. 7 shows an example of a pattern candidate detection result.

FIG. 8 is a diagram illustrating relative position detection of pattern candidates.

FIG. 9 shows a second example of a pattern arrangement.

FIG. 10 shows a configuration example when the present invention is applied to a printer.

FIG. 11 shows a configuration in a case where the processing in FIG. 10 is executed by driver software of a printer.

FIG. 12 shows a configuration when the present invention is applied to a printer without a double-sided printing mechanism.

FIG. 13 shows a configuration example in a case where image processing control by detecting a specific pattern is executed by a program.

[Explanation of symbols]

 Reference Signs List 101 image input unit 102 specific pattern detection unit 103 image output unit 104 data storage unit 105 control unit 106 data communication path 107 external notification unit

Claims (13)

[Claims] 1. By extracting pixels having a density level within a predetermined range from an image obtained by scanning a document,
A pattern detection method comprising: detecting a specific pattern printed on the back side of the scan surface. 2. A method according to claim 1, wherein a specific pattern printed on the back side of said scan surface is detected by detecting a change in density from an image obtained by scanning a document. 3. A pattern detecting method, wherein a specific pattern printed on the back side of the scan surface is detected by extracting pixels of a predetermined range of colors from an image obtained by scanning a document. . 4. A method for detecting, from an image obtained by scanning a document, a specific pattern printed in a grid pattern at predetermined intervals on the back surface of the scan surface, wherein one detected pattern candidate is centered. It is checked whether there is another pattern candidate on the circumference having the predetermined interval as a radius,
A pattern detection method comprising: providing a score when present, and detecting a specific pattern based on a value obtained by accumulating scores for all detected pattern candidates. 5. When a plurality of other pattern candidates are detected on the circumference of the radius, a high score is obtained when an angle formed by the candidates with respect to the center of the circle is a specific angle or a predetermined angle. The pattern detection method according to claim 4, wherein the pattern detection is performed. 6. A high score is given on a line connecting the detected candidate on the circumference and the center point of the circle when another candidate exists at a constant magnification or an integral multiple of the radius. The pattern detection method according to claim 4, wherein 7. Scanning both sides of the document,
5. The pattern detection method according to claim 1, wherein a specific pattern printed on at least one surface is detected. 8. An image processing control method for reading a document and controlling an image processing operation of the document, wherein a specific pattern printed on the back side of the document is detected by the method according to claim 1, 2, or 3. And an image processing control method for controlling an image processing operation of a document. 9. An image processing control method for reading a document and controlling an image processing operation of the document, wherein an arrangement relation of a plurality of specific patterns and an arrangement relation of colors printed on the back side of the document are provided. 7. An image processing control method comprising: controlling an image processing operation of a document when detected by the method according to 5 or 6. 10. A means for extracting pixels having a density level within a predetermined range from an image obtained by scanning a document, and whether or not a specific pattern is printed on the back surface of the scan surface based on the extraction result. An image processing device comprising: 11. A means for judging whether or not another pattern candidate exists on a circle having a predetermined interval as a radius centered on one pattern candidate detected from an image obtained by scanning a document. And means for giving a score when present, and detecting a specific pattern printed in a grid pattern at a predetermined interval on the back surface of the scan surface based on a value obtained by accumulating scores for all detected pattern candidates. An image processing apparatus characterized by the above-mentioned. 12. An image processing apparatus for reading a document and controlling an image output operation of the document, comprising: means for detecting a specific pattern printed on the back side of the document; An image processing apparatus comprising means for prohibiting or permitting an image output operation of the document. 13. A program for causing a computer to implement a function of detecting a specific pattern printed on the back side of a document and a function of prohibiting or permitting image output of the document in response to detection of the specific pattern. A computer-readable recording medium on which is recorded.