JP2006237858A - Image processing apparatus, image processing method, program for allowing computer to execute the method, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus applicable to image data of both a natural image and an artificial image and capable of carrying out embedding of information wherein both the performance of immunity/image quality and the performance of density/image quality are high at the same time. <P>SOLUTION: An information embedding section 3 uses vector information of a pair of extrapolation line segments whose end points are respectively the same or close to each other and which are nearly in the same direction from the respective end points in vector information of image data converted from raster image data by a raster/vector conversion section 2 to detect embedded vectors of image data to be embedded. The information embedding section 3 minutely changes positional information of a pair of the detected vectors to embed information to be embedded so as to embed the embedded information as an electronic watermark. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus, an image processing method, a program for causing a computer to execute the method, and a recording medium, and more particularly to an image processing apparatus, an image processing method, and a method for embedding arbitrary information in image data. The present invention relates to a program to be executed and a recording medium.

  A technique for embedding information in image data is called a digital watermark technique, and has been actively studied in recent years. For example, copyright management can be performed by embedding attribute information of an image, or tampering detection or restoration can be performed by embedding information of the image itself. Many of the methods of the digital watermark technology are for so-called natural images taken with a digital camera or the like, and many are not suitable for so-called artificial images such as characters and graphs.

  On the other hand, a digital watermark technique for artificial images such as characters has been developed. This technique extracts character codes from image information by character recognition (Patent Document 1).

  On the other hand, the Mahalanobis distance between the feature amount space of the binary image and the reference vector is compared with the Mahalanobis distance between the feature amount space of the reference pattern and the reference vector, and the comparison result and access control information embedded in the binary image are used. Based on this, a technique has been devised in which a feature vector space of a binary image is translated to change the image. This technique is highly resistant because embedded information is assigned to a large number of vector groups instead of individual vectors. In addition, since all the vector groups are moved in parallel, image distortion is less likely to be detected, and image quality deterioration can be suppressed (Patent Document 2).

  By the way, the digital watermark technology can express the performance mainly by indexes such as tolerance, density, and image quality. Tolerance is the rate at which embedded information can be extracted correctly when a predetermined modification is made to an image. For example, when the embedded image is printed out, and the embedded information is extracted by scanning again, it is desirable that the embedded information can be extracted correctly even if it is inevitable that noise-like modification is added to the image.

  The density is a degree of how much information is filled per unit area of the image. For example, if the information to be embedded is attribute information (creator ID, creation date, etc.) of the entire image, that density is not required, but if it is information of the image itself such as a thumbnail image, a considerable density is required. It becomes. Originally, digital watermarks give changes to images as a price for embedding information, so it is inevitable that the quality of images, including the beauty, visibility, and meaning of images, will deteriorate due to the addition of digital watermarks. It was.

JP 2003-189084 A Japanese Patent Laid-Open No. 2001-223885

  Here, since the digital watermark technique targeted for the artificial image disclosed in Patent Document 1 is to extract and embed a character code from image information by character recognition, it cannot be applied to a natural image. When dealing with images, there is a disadvantage that it is necessary to use a technique different from that.

  Further, the technique of Patent Document 2 has a problem that the performance of density / image quality is low because only a 1-bit information can be filled with a large number of vector groups. In other words, the technique of Patent Document 2 has a problem that the tolerance / image quality performance is high, but the density / image quality performance is low.

  In this way, the greater the tolerance and density, the greater the change in the image and the lower the image quality. Since there is basically a trade-off relationship between tolerance and image quality and density and image quality, there has never been a technique that can maintain both tolerance / image quality performance and density / image quality performance at the same time.

  The present invention has been made in view of the above problems, and the object thereof is applicable to both natural images and artificial images, and images capable of embedding information with high tolerance / image quality performance and high density / image quality performance at the same time. It is to provide a processing device.

  In order to solve the above-described problems and achieve the object, the invention according to claim 1 is directed to a pair of vector information satisfying a predetermined condition in image data described by vector information in an image processing apparatus. Embedding means for embedding the predetermined embedding information in the image data by changing relative positional relationship information of the pair of vector information based on predetermined embedding information to be embedded in the image data It is characterized by that.

  According to a second aspect of the present invention, in the image processing apparatus according to the first aspect, the embedding unit defines a boundary line of a pixel group in which the pixel values of the pixels in the image data are the same or at least one of the vicinity. The outer peripheral line is divided into a plurality of line segments, and each of the divided line segments is changed by changing the parameters of the pair of vector information described by information via parameters in at least one of a straight line and a curved line. The embedding information is embedded.

  According to a third aspect of the present invention, in the image processing apparatus according to the second aspect, as the predetermined condition, the embedding unit extends the end point of the line segment from the end point of the first line segment to a predetermined distance. The end point of the second line segment exists on at least one of the extrapolated line and the vicinity of the extrapolated line, and the direction of the extrapolated line and the second line segment is substantially the same direction. The predetermined embedding information is embedded by changing relative positional relationship information of the end points of the first and second line segments.

  According to a fourth aspect of the present invention, in the image processing device according to any one of the first to third aspects, the embedding unit actually outputs a change amount of a relative positional relationship between the pair of vectors. When the image to be recorded is Ndpi (dot per inch), the relative positional relationship information is changed within a range of 3 / N inches or less, and the predetermined embedding information is embedded.

  According to a fifth aspect of the present invention, in the image processing apparatus, relative positional relationship information described by the pair of vector information is extracted from a pair of vector information satisfying a predetermined condition in the image data described by the vector information. It is characterized by having an extracting means.

  According to a sixth aspect of the present invention, in the image processing apparatus according to the fifth aspect, the extracting means defines a boundary line of a pixel group in which the pixel values of the pixels in the image data are the same or at least one of the vicinity. The peripheral position is divided into a plurality of line segments, and each of the divided line segments is described by the parameter of the pair of vector information described by the information via the parameter in at least one of a straight line and a curve. It is what is extracted.

  According to a seventh aspect of the present invention, in the image processing apparatus according to the sixth aspect, as the predetermined condition, the extraction unit extends an end point of the line segment from the end point of the first line segment to a predetermined distance. The end point of the second line segment is present on at least one of the extrapolation line and the vicinity of the extrapolation line, and the direction of the extrapolation line and the second line segment is substantially the same direction. On the condition, the relative positional relationship information of the end points of the first and second line segments is extracted.

  According to an eighth aspect of the present invention, in the image processing apparatus according to any one of the fifth to seventh aspects, the extraction unit changes the relative positional relationship information of the pair of vectors as the predetermined condition. However, when the actually output image is Ndpi (dot per inch), the relative positional relationship information is extracted within a range of 3 / N inches or less.

  According to a ninth aspect of the present invention, in the image processing method, a predetermined embedding to be embedded in the image data with respect to a pair of vector information satisfying a predetermined condition in the image data described by the vector information by the embedding means. An embedding step of embedding the predetermined embedding information in the image data by changing relative positional relationship information of the pair of vector information based on embedding information.

  According to a tenth aspect of the present invention, in the image processing method according to the ninth aspect, in the embedding step, the pixel value of the pixel in the image data is at least one of the same and the vicinity by the embedding unit. The parameter of the pair of vector information described by dividing an outer peripheral line defining a group boundary line into a plurality of line segments, and each divided line segment is described by information via a parameter in at least one of a straight line and a curve. The predetermined embedding information is embedded by changing.

  According to an eleventh aspect of the present invention, in the image processing method according to the tenth aspect, in the embedding step, an end point of the line segment is set as the first line segment as the predetermined condition by the embedding unit. The end point of the second line segment exists on at least one of the extrapolation line extending from the end point to a predetermined distance and the vicinity of the extrapolation line, and the extrapolation line and the direction of the second line segment The predetermined embedding information is embedded by changing the relative positional relationship information of the end points of the first and second line segments on the condition that the two are substantially in the same direction. .

  According to a twelfth aspect of the present invention, in the image processing method according to any one of the ninth to eleventh aspects, in the embedding step, the embedding unit changes the relative positional relationship between the pair of vectors. However, when the actually output image is Ndpi (dot per inch), the relative positional relationship information is changed within a range of 3 / N inches or less to embed the predetermined embedding information. It is characterized by.

  According to a thirteenth aspect of the present invention, in the image processing method, the relative position described by the pair of vector information from the pair of vector information satisfying a predetermined condition in the image data described by the vector information by the extracting unit. It includes an extraction process for extracting the relationship information.

  According to a fourteenth aspect of the present invention, in the image processing method according to the thirteenth aspect, in the extraction step, a pixel group in which the pixel value of the pixel in the image data is at least one of the same and the vicinity by the extraction means The peripheral line that defines the boundary line is divided into a plurality of line segments, and each of the divided line segments is described as the relative value from the parameters of the pair of vector information described by information via parameters in at least one of a straight line and a curve. It is characterized in that target positional relationship information is extracted.

  According to a fifteenth aspect of the present invention, in the image processing method according to the fourteenth aspect, in the extracting step, the end point of the line segment is determined from the end point of the first line segment as the predetermined condition by the extracting unit. The end point of the second line segment exists on at least one of the extrapolated line extending to a predetermined distance and the vicinity of the extrapolated line, and the direction of the extrapolated line and the second segment is approximately The relative positional relationship information of the end points of the first and second line segments is extracted on the condition that they are in the same direction.

  According to a sixteenth aspect of the present invention, in the image processing method according to any one of the thirteenth to fifteenth aspects, the extracting step includes the relative position of the pair of vectors as the predetermined condition by the extracting unit. The relative positional relationship information is extracted within a range of 3 / N inches or less when the amount of change in the relationship information is Ndpi (dot per inch). .

  The invention according to claim 17 is a program which causes a computer to execute the image processing method according to any one of claims 9 to 16.

  The invention according to claim 18 is characterized in that the program according to claim 17 is recorded in a computer-readable recording medium.

  According to the first aspect of the present invention, since the information embedding process is performed after the image information is converted into vector format information, it can be applied to both natural images such as photographs and artificial images such as characters. In addition, since the embedding process is performed by minutely changing vector information instead of individual pixels, the performance with respect to image quality is high. Further, since the image information can be embedded in all locations of vector pairs satisfying a predetermined condition, the density performance with respect to image quality is high. Therefore, when embedding information, the applicability of the image of the embedding destination is wide, and the resistance to image quality and the performance of density are high.

  According to the invention of claim 2, the embedding means divides the outer peripheral line that defines the boundary line of the pixel group into a plurality of line segments, and describes the parameter with a straight line or a curved line to change the parameter. Thus, by embedding predetermined embedding information, it is possible to embed embedding information by accurately describing the amount of change regardless of the type of image.

  According to the invention of claim 3, the embedding unit changes the relative positional relationship information at the two end points of the line segment and embeds the predetermined embedding information, so that it can be accurately performed regardless of the type of image. Embedding information can be embedded by describing the amount of change.

  According to the invention of claim 4, the embedding means has a change amount of the relative positional relationship between the pair of vectors of 3 / N inches or less when the actually output image is Ndpi (dot per inch). By embedding predetermined embedding information by changing the relative positional relationship information within the range, it is possible to embed the embedding information while suppressing image deterioration.

  According to the invention of claim 5, since the embedded information is extracted after converting the image information into vector format information, it can be applied to both natural images such as photographs and artificial images such as characters. In addition, since the extraction process is performed not from individual pixels but from minute fluctuations in vector information, extraction with high resistance to image quality is achieved. In addition, since image information can be extracted from all locations of vector pairs that satisfy a predetermined condition, extraction with high density performance with respect to image quality is achieved. Therefore, it is possible to extract relative positional relationship information from an image having wide applicability of information embedding and having high image quality tolerance and density performance.

  According to the invention of claim 6, the extracting means divides the outer peripheral line defining the boundary line of the pixel group into a plurality of line segments, and a pair of vector information described by information via parameters with straight lines or curves. By extracting the relative positional relationship information from the parameters, it is possible to accurately extract the relative positional relationship information from the amount of change regardless of the type of image.

  According to the invention of claim 7, the extracting means extracts the relative positional relationship information accurately from the amount of change regardless of the type of image by extracting the relative positional relationship information at the two end points of the line segment. I can do it.

  According to the eighth aspect of the present invention, the extracting means has a change amount of the relative positional relationship information of the pair of vectors of 3 / N inches or less when the actually output image is Ndpi (dot per inch). The relative positional relationship information can be accurately extracted from the amount of change regardless of the type of image by extracting the relative positional relationship information within the range of.

  According to the ninth aspect of the present invention, since the information embedding process is performed after the image information is converted into vector format information, it can be applied to both natural images such as photographs and artificial images such as characters. In addition, since the embedding process is performed by minutely changing vector information instead of individual pixels, the performance with respect to image quality is high. Further, since the image information can be embedded in all locations of vector pairs satisfying a predetermined condition, the density performance with respect to image quality is high. Therefore, when embedding information, the applicability of the image of the embedding destination is wide, and the resistance to image quality and the performance of density are high.

  According to the tenth aspect of the present invention, the embedding means divides the outer peripheral line defining the boundary line of the pixel group into a plurality of line segments, and describes the parameter with a straight line or a curve to change the parameter. Thus, by embedding predetermined embedding information, it is possible to embed embedding information by accurately describing the amount of change regardless of the type of image.

  According to the invention of claim 11, the embedding means changes the relative positional relationship information at the two end points of the line segment and embeds the predetermined embedding information, so that it can be accurately performed regardless of the type of image. Embedding information can be embedded by describing the amount of change.

  According to the twelfth aspect of the present invention, the embedding means has an amount of change in the relative positional relationship between the pair of vectors of 3 / N inches or less when the actually output image is Ndpi (dot per inch). By embedding predetermined embedding information by changing the relative positional relationship information within the range, it is possible to embed the embedding information while suppressing image deterioration.

  According to the invention of claim 13, since the embedded information is extracted after converting the image information into the vector format information, it can be applied to both natural images such as photographs and artificial images such as characters. In addition, since the extraction process is performed not from individual pixels but from minute fluctuations in vector information, extraction with high resistance to image quality is achieved. In addition, since image information can be extracted from all locations of vector pairs that satisfy a predetermined condition, extraction with high density performance with respect to image quality is achieved. Therefore, it is possible to extract relative positional relationship information from an image having wide applicability of information embedding and having high image quality tolerance and density performance.

  According to the fourteenth aspect of the present invention, the extracting means divides the outer peripheral line defining the boundary line of the pixel group into a plurality of line segments, and includes a pair of vector information described by information via parameters with straight lines or curves. By extracting the relative positional relationship information from the parameters, it is possible to accurately extract the relative positional relationship information from the amount of change regardless of the type of image.

  According to the fifteenth aspect of the present invention, the extracting means extracts the relative positional relationship information accurately from the amount of change regardless of the type of image by extracting the relative positional relationship information at the two end points of the line segment. I can do it.

  According to the sixteenth aspect of the present invention, the extraction means has a change amount of the relative positional relationship information of the pair of vectors of 3 / N inches or less when the actually output image is Ndpi (dot per inch). The relative positional relationship information can be accurately extracted from the amount of change regardless of the type of image by extracting the relative positional relationship information within the range of.

  According to the seventeenth aspect of the present invention, it is possible to cause a computer to execute the image processing method according to any one of the ninth to sixteenth aspects.

  According to the invention of claim 18, the program described in claim 17 can be read by a computer.

  Exemplary embodiments of an image processing apparatus, an image processing method, a program for causing a computer to execute the method, and a recording medium according to the present invention will be explained below in detail with reference to the accompanying drawings.

(1. Embodiment 1)
The image processing apparatus according to the first embodiment of the present invention converts any image information into a vector format, and then embeds an arbitrary image to be embedded as a digital watermark by minutely changing the vector, so that either a natural image or an artificial image can be obtained. It is possible to embed information in images. That is, the image processing apparatus according to the first embodiment generates a digital watermark in which predetermined information is embedded in a character or a natural image.

  Here, since embedding is performed not in individual pixels but in vector format information, it is possible to improve the durability / image quality performance in digital watermarking.

  Also, density / image quality performance can be improved by embedding information in all vector pairs of images that satisfy a predetermined condition.

  FIG. 1 is a configuration diagram of an image processing apparatus according to the first embodiment. The image processing apparatus 100 includes a CPU 101, a storage unit 102 that is a ROM or HDD that stores programs and data of the CPU, a RAM 103 that is a working memory for developing image data and execution programs to be processed, a paper document scanned by a scanner, or a digital An image input unit 104 that inputs a photographed image by a camera, an image output unit 105 that prints and outputs image information on recording paper, an operation unit 106 that includes switches and buttons and receives an operation from an operator, an LCD (Liquid Crystal Display), a liquid crystal display ), A line unit 108 for connecting an Ethernet, a telephone line, a radio, and the like, and a storage unit 109 such as a detachable IC card, CD, or DVD.

  The operation unit 106 and the display unit 107 accept exchange of information related to operations between the operator and the image processing apparatus 10. The storage unit 109 exchanges information between the image processing apparatus 10 and the outside.

  FIG. 2 is a functional block diagram of the image processing apparatus according to the first embodiment. The image processing apparatus 100 includes a bitmap information generation unit 1, a raster / vector conversion unit 2, an information embedding unit 3, a vector / raster conversion unit 4, an image input unit 104, and an image output unit 105.

  The bitmap image generation unit 1 generates bitmap image information from image information input via the image input unit 104 such as a scanner.

  The bitmap information generation unit 1 also rasterizes page description language data such as PostScript using the CPU 101 to create a bitmap image. The bitmap information generation unit 1 can also capture a bitmap image created outside the apparatus via a telecommunication line or a removable storage unit 109.

  The raster / vector conversion unit 2 converts a bitmap (raster) format image into a vector format image.

  The information embedding unit 3 changes the image data in the vector format based on the embedding information to be embedded as a digital watermark.

  The vector / raster converter 4 converts a vector format image into a bitmap (raster) format image.

  The image output unit 105 embeds the embedded information by the information embedding unit and prints out the image information raster-converted by the vector / raster conversion unit 4 or outputs it to the line unit 108 or the removable storage unit 109. .

  Next, the vector / raster converter 2 will be described. The vector / raster conversion unit 2 performs a process of drawing a virtual outer circumference line in a coordinate space having a resolution to be obtained and painting the enclosed pixels with a predetermined value using vector format data.

  FIG. 3 is a functional block diagram of the raster / vector conversion unit. The raster / vector conversion unit 2 includes a color reduction processing unit 21, a peripheral line division processing unit 22, and a fitting processing unit 23.

  The color reduction processing unit 21 performs color reduction processing to reduce the number of types of pixel values in one image. A pixel has a maximum of 16,777,216 types in the case of a color image of 24 bits / pixel, and can take a maximum of 256 types of values even in the case of a grayscale image of 8 bits / pixel. Therefore, processing that replaces the same value in the adjacent pixel group is performed. In this digital watermark, color information is not so important, and color reduction processing is performed for speeding up and simplifying the processing.

  FIG. 4 is a diagram for explaining a color reduction process for an image. Here, the image 401 subjected to the color reduction processing is an example of a gray scale image, and actually has about 200 kinds of pixel values. When the color reduction process is performed on the image 401, as shown in the image 402, it is possible to reduce the color to 8 types. As described above, it is effective to perform color reduction processing on an image having a large number of types of pixel values. However, color reduction processing is unnecessary for an image with a small number of types from the beginning, for example, a binary image 1 bit / pixel such as a character image.

  The peripheral line division processing unit 22 performs a process of dividing the peripheral line of the pixel group having the same value in the image into a plurality of line segments. The peripheral line division processing unit 22 tracks the peripheral line in the image and determines the division at a point where the curvature of the peripheral line changes rapidly. For tracking the outer circumference line, any route may be employed topologically, for example, a counterclockwise direction or a clockwise direction may be employed as long as information on a point at which the curvature changes rapidly can be acquired.

  FIG. 5 is a diagram for explaining that the peripheral line dividing process is performed on the image shown in FIG. In this case, an image 501 in which the entire peripheral line drawing is drawn is obtained by tracking the peripheral line drawing of the natural image 402 obtained by photographing the apple with a digital camera and reducing the color. An image 502 is obtained by enlarging a part of the entire outer peripheral line image 501.

  In addition, when the unevenness | corrugation of an outer periphery line is severe, after performing a smoothing process, it is desirable to produce | generate a dividing line segment.

  FIG. 6 is a diagram for explaining that the peripheral line dividing process is performed on the population image. An image 602 obtained by dividing the image 601 of characters A and B shown in FIG. 6 by the outer peripheral line is obtained, and an image obtained by enlarging a part 602a thereof is a partial enlarged image 603.

  The fitting processing unit 23 approximates each line segment in the image generated by the peripheral line dividing process with a predetermined straight line or curve. For example, from a straight line, a quadratic Bezier curve, a cubic Bezier curve, or the like, it is determined what line should be used to represent the line segment of the target image, and those parameters are optimized.

  If it can be regarded as a straight line, the coordinates of both end points of the line segment, the coordinates of both end points and one control point in the case of a quadratic Bezier curve, and the coordinates of both end points and two control points in the case of a cubic Bezier curve Then, express the target line. The example shown in FIGS. 5 and 6 is an example in which the outer peripheral lines are all approximated by straight lines.

  As described above, the raster / vector conversion processing performed by the color reduction processing unit 21, the peripheral line division processing unit 22, and the fitting processing unit 23 causes the image data to be converted into pixel values within the peripheral line, some coordinates on the peripheral line, and a line. Can be converted into an expression format based on the “direction” information. Here, since “direction” information is used, this is called a vector format.

  In this way, the vector / raster converter 4 uses the data in the vector format to convert the pixels surrounded by the virtual outer peripheral line obtained as described above into a predetermined coordinate space in the resolution space to be obtained. Paint by value.

  These vector / raster conversion programs are already on the market, and for example, by using AutoTrace (R) or PoTrace (R), which is a freeware program that can be obtained free of charge on the Web, an embodiment is provided. 1 can be applied to the image processing apparatus. Alternatively, commercially available programs such as KIP Image Processor Pro (R) (manufactured by KIP Corporation) may be applied.

  Incidentally, if the image is generated from page description language data such as PostScript, the vector conversion process in which characters are originally described in the vector format is not necessary.

  Next, a description will be given of how the information embedding unit 3 performs information embedding processing on the image information converted into the vector format by the raster / vector converting unit 2.

  The information embedding unit 3 includes a pair of vectors (two line segments) satisfying a predetermined condition in the converted vector format image information within a range satisfying the predetermined condition. A process for changing the relative positional relationship is performed. First, the predetermined conditions will be described.

  FIG. 7 is a diagram for explaining processing for changing the positional relationship between vector pairs. An image 701 shown in FIG. 7 is divided by the outer peripheral line, and an image 702 is obtained by changing the positional relationship between vector pairs in the image 701.

  The vertical and horizontal grids of the images 701 and 702 represent digital coordinates at a predetermined resolution. If the resolution is 600 dpi (dot per inch), the coordinate interval is 1/600 inch. The point a in the image 701 is set as the end point of the line segment currently focused on. Consider extending the extrapolation line of the line segment a from the end point a to a predetermined distance. An extrapolation line is a line connecting points. In this example, since the line of interest is in the vertical direction, the extrapolated line is also extended in the vertical direction.

  Here, 5/600 inch is a predetermined distance, and the first condition is that it is within the range of 4/600 inch on both sides of the extrapolation line from the target point. That is, the line segment ab connecting the point a and the point b with the predetermined distance 5/600 inch is an extrapolated line.

  On this extrapolated line, there are five coordinate points, and further, there are end points of other line segments in the vicinity of the left / right 4/600 inch (gray section in the figure). The end points of the point c and the point d in the image 701 do not satisfy this condition, but the end points of the point e and the point f satisfy this condition.

  Furthermore, the second condition is that the directions of the two line segments are substantially the same. Since the line segment having the end point of the point e in the image 701 is in an oblique direction, this condition is not satisfied. However, since the line segment having the point f of the image 701 as the end point is in the same vertical direction as the target line segment, this condition is satisfied, and it can be said that both line segments substantially overlap. The information embedding unit 2 detects two line segments satisfying the above “predetermined condition”, in this case, the line segment a and the line segment f, as portions where information can be embedded.

  Here, a process in which the information embedding unit 3 embeds arbitrary information 1 bit will be described with reference to an image 702 in FIG. The corresponding end points (points a and f of the image 702) of the two line segments are detected, and one of the points f is moved to g if the embedding information is 0 and to h if the embedding information is 1. That is, the relative positional relationship such as the extrapolated line of the attention line segment and the strength of the overlapping degree of the other line segment is changed according to the embedded information. That is, in this case, the case where the degree of overlap is strong is 0, and the case where it is weak is 1.

  Incidentally, if the embedded information is 0 and the end points of the two line segments are a and g from the beginning, there is no need to move them. Similarly, when the embedded information is 1 and a and h, it is not necessary to move the information. In this case, 0 and 1 are determined depending on the pattern of the image to be embedded, and the pattern based on 0 and 1 thus determined becomes a digital watermark.

  Next, an image processing procedure according to the first embodiment will be described. FIG. 8 is a flowchart for explaining an image processing procedure according to the first embodiment. The image input unit 104 determines whether the received image information is bitmap information (step S101). If the image information is not bitmap information (No in step S101), the image input unit 104 transmits to the bitmap information generation unit 1 for conversion. Then, bitmap information is generated (step S102). A technique for generating bitmap information is already known.

  If it is bitmap information (Yes in step S101) or if bitmap information is generated in step S102, the raster / vector conversion unit 2 converts the bitmap information into vector information (step S103), and information The embedding unit 3 embeds information according to predetermined information (step S104). Note that step S104, which is the information embedding step, will be further described with reference to the following flowchart.

  The vector / raster conversion unit 4 converts the vector format information in which predetermined information is embedded by the information embedding unit 3 to raster information again, and outputs an image from the image processing unit 105. Here, the vector / raster conversion unit 4 can apply, for example, PoTrace (R), which is a freeware program that can be acquired free of charge on the Web. Alternatively, a commercially available program such as Vector to Rster (R) (manufactured by KIP Corporation) can be applied (step S105).

  Next, an information embedding procedure according to the first embodiment will be described. FIG. 9 is a flowchart illustrating a procedure for embedding information by the information embedding unit of the image processing apparatus according to the embodiment. FIG. 10 is a diagram for explaining an image embedded by the information embedding unit 3 and its outer peripheral line.

  The information embedding unit 3 detects a portion where information can be embedded in a predetermined range in the lattice coordinates in the image information in the vector format as an embedding target. Explaining with reference to FIG. 6, the outer peripheral line shown in the image 602 is obtained from the image 601. As shown in the partial enlarged image 603 of the image 602, it is determined whether or not the line segments 603a and b represented by two thick lines satisfy the above-described predetermined condition (step S201). As shown in the partially enlarged image 603 of 602, the line segments 603a and b represented by two thick lines satisfy the above-described predetermined condition, that is, the end points are close to each other, and the line segment is Since the overlapping degree is close, the vector information satisfying the condition is detected (Yes in step S201).

  The information embedding unit 3 detects the overlapping degree of the extrapolation line end points, and embeds information according to the detected overlapping degree. Here, 0 is set when the degree of overlap is high, and 1 is set when the degree of overlap is low. Here, when the information “1” is embedded, since the degree of overlap is low, a process of shifting the vertical line 603b to the right with respect to the vertical line 603a is performed. A bitmap image obtained from the vector image processed in this manner is an image 601 'shown in FIG. The image 602'a is a schematic diagram of the outer periphery of the hit map image 601 'after information embedding. Here, a partially enlarged image 602′a is an image 603 ′, and the vertical line 603′a in the upper part is set at a position shifted from the vertical line 603′b in the lower part. (Step S202). It is determined whether or not all the predetermined image information has been embedded (step S203). If not, the process returns to step S202. If all the predetermined image information has been processed, the process ends.

  In this case, the simple case of the characters A and B has been described. However, in a vector display format image, a predetermined condition is imposed on the end point and its line segment, and the relative positional relationship is 0 and 1. The predetermined information to be embedded is expressed as 0 and 1 with respect to the described information of 0 and 1, and the information of 0 and 1 described at the corresponding position is changed. Since the change is embedded as a minute relative position change, digital watermark information can be embedded.

  In addition, not only an artificial image but also a natural image shown in FIGS. 4 and 6, for example, if a pair of line segments in the same direction having end points is detected under a certain condition in a vector expression format, You can embed information.

  Next, it is examined whether an image in which information thus obtained is embedded is resistant to noise. FIG. 11 is a diagram for explaining an image obtained by printing and scanning the image shown in FIG. 10 embedded with information. In the figure, an image 601 ″ is a printed image obtained by printing out the image shown in FIG. 10. An image 602 ″ is an image of a peripheral line obtained from an image obtained by reading the printed image 601 ″ with a scanner. Is a partially enlarged view 603 ″ in which a portion 602 ″ a of the peripheral line image 602 ″ is enlarged. Here, as shown in the image 603 ″, the image is modified with noise 604 by printing and scanning. "A and 604" b are added, but as seen in the partial enlargement 603 ", the two line segments 603" a and 603 "b in which the information is embedded still satisfy the predetermined condition described above. It can be seen that the embedded information can be extracted correctly.

Here, the performance as a digital watermark technique will be described.
(A) Resistance The processing for modifying an image includes a processing for artificially adding embedded information so that it cannot be extracted correctly, and a processing for not. A general digital watermark including the present invention cannot obtain sufficient resistance to the former processing.

  The latter processing includes irreversible compression & decompression, printing & scanning, etc. These modifications are (a) sudden noise in pixel units, (b) dot thickening and (c) the entire image. Geometric distortion, etc.

  The method of the present invention has high resistance to the modification (a) because sudden noise can be eliminated in the process of color reduction processing or peripheral line division processing during extraction. Further, the relative positional relationship between two adjacent vectors is hardly affected by the modification of (b) and (c). Therefore, it can be said that the method of the present invention has high tolerance.

(B) Density There are many vector pairs that satisfy the predetermined conditions of the present invention, that is, places where embedding is possible. If it is a character image, it is always present at the intersection of lines. There are especially many kanji with many strokes. Even if it is a natural image, there are not a few places where it can be embedded, as shown in the partial enlargement of FIG. Thus, it can be said that the method of the present invention has a high density.

(C) Image Quality Since the method of the present invention changes the image in a vector state, it is less likely to cause unnaturalness than the conventional method in which the image is changed in units of pixels. Although beauty such as the uniformity of the line width is impaired, it is generally difficult for the smoothness of the outer shape to be significantly impaired. Also, the amount of change is small. In the example shown in FIG. 7, since the end point is moved only by a maximum of 3/600 inch = 1/200 inch, this change does not appear even if it is observed at the same magnification on a normal personal computer display (about 100 ppi). Thus, it can be said that the image quality degradation is small in the method of the present invention.

  Thus, the image processing apparatus according to the first embodiment embeds information by changing vector information to image information converted into a vector format, whether it is a natural image or an artificial image. In the digital watermark method in which predetermined information is embedded in the image information, the application range of the image is wider than that in the conventional method, and the density and the image quality are good while suppressing the deterioration of the image quality.

(2. Embodiment 2)
The image processing apparatus 200 according to the second embodiment is different from the first embodiment in that the information embedding unit 3 is not provided, but an information extracting unit 5 is provided instead. Is converted into a vector format, and information on the degree of overlap in the paired vector information is extracted from the image information in the converted vector format. By extracting information on the degree of overlap in the paired vector information, it is possible to extract the included information. In this way, the image processing apparatus 200 can extract information including an embedded digital watermark. Hereinafter, differences from the first embodiment will be mainly described in detail.

  FIG. 12 is a functional block diagram of the image processing apparatus according to the second embodiment. FIG. 13 is a flowchart for explaining an image processing procedure according to the second embodiment. The image processing apparatus 200 includes a bitmap image input unit 1, a raster / vector conversion unit 2, an information extraction unit 5, a vector / raster conversion unit 4, an image input unit 104, and an image output unit 105.

  The raster / vector conversion unit 2 performs raster vector conversion processing in the same manner as in the first embodiment, and can transmit and receive images and embedded information even with a vector-format electronic image immediately after the embedding processing. In this case, the images are exchanged in a standard image format such as SVG (Scalable Vector Graphics).

  The information extraction unit 5 extracts information from the relative positional relationship between a pair of vectors composed of two line segments that satisfy a predetermined condition. The predetermined condition is as already described. By comparing the information consisting of 0 and 1 obtained from a pair of vectors with the information consisting of predetermined 0 and 1, it can be determined whether or not the image is actually an image with a watermark.

  In the first embodiment, the information embedding unit 3 determines 0 and 1 based on the positional relationship between the pair of line segments having end points, and displaces the relative position of the pair corresponding to the information to be included. In contrast, the information extraction unit 5 according to the second embodiment extracts information consisting of 0 and 1 from the read vector format image information according to the positional relationship between the pair of line segments having end points. Since it can be extracted, when it is applied to an apparatus that actually detects a digital watermark, the presence or absence of the digital watermark can be determined by determining whether or not the extracted information includes a watermark information pattern to be included. .

  FIG. 13 is a flowchart illustrating an image processing procedure performed by the image processing apparatus according to the second embodiment. Steps S301 to S303 are the same as steps S101 to S103 described in FIG.

  The information extraction unit 5 extracts watermark information for image information in vector format. That is, for example, if the other line segment having the end point f with respect to one line segment having the end point a shown in FIG. 7 is within the dark gray region 703, the information when the information is embedded is 0. If the information is embedded in the light gray area, it is determined that the information is 1 (step S304). In this way, the information extraction unit 5 can determine whether or not a digital watermark is included.

  FIG. 14 is a diagram illustrating another example of vector displacement for information embedding. The present invention is not limited to the above embodiment. For example, in the example shown in FIG. 7, not only the end points are translated by the information embedding, but the entire line segment is translated, but only the end points may be moved as shown in FIG. With such a displacement, the embedding process can be performed independently at each lattice point.

  The extrapolated line is not limited to the tangential direction at the end point of the line segment, but may be a curve 1402b extending in a direction along the curvature of the line segment 1402a as shown in an image 1402 in FIG. This increases the number of places that satisfy the predetermined condition.

  In addition, even if the other end point with respect to the end point a in FIG. 7 is at a position such as f or h, an image that is changed to the position of g after the extraction processing may be created. As a result, the image may be returned to the state before embedding. This is because there is a high possibility that the two end points were at positions a and g before embedding.

  In this way, the image processing apparatus 200 can extract the embedded information, and when the digital watermark is embedded, the digital processing can be determined by comparing the extracted information with the embedded information. .

  Since the image processing apparatus of the present invention converts any image such as an artificial image such as a character or a natural image such as a landscape photograph into a vector format, it performs an information embedding process and an extraction process. Incorporation of information into both natural images and artificial images and extraction can be performed.

  In addition, since the information is embedded in the vector, not the individual pixels, but the vector is minutely changed, so that the deterioration of the image quality is suppressed and the performance of the tolerance / image quality is high and the vector pair satisfying the predetermined condition is embedded in all places. Therefore, it is possible to embed information with high density / image quality performance.

(3. Hardware configuration etc.)
A hardware configuration of the image processing apparatus according to the embodiment will be described with reference to FIG. 1. The CPU 101 performs overall control of image processing control of the image processing apparatus. The ROM and the HDD 102 are read-only memories that are used as memory for storing programs and data, and the RAM 103 is a writable and readable memory that is used as a memory for developing programs and data, an image drawing memory at the time of image processing, and the like. .

  The image processing program executed by the image processing apparatus of the present embodiment is a file in an installable or executable format, such as a CD-ROM, a flexible disk (FD), a CD-R, a DVD (Digital Versatile Disk), or the like. You may comprise so that it may record and provide on a computer-readable recording medium.

  Furthermore, the image processing program executed by the image processing apparatus of the present embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Alternatively, it may be configured to be provided or distributed via a network such as the Internet.

  The image processing program executed by the image processing apparatus according to the present embodiment includes the above-described units (bitmap information generation unit, raster / vector conversion unit, information embedding unit, vector / raster conversion unit, information extraction unit, etc.). As the actual hardware, the CPU (processor) reads the image processing program from the ROM and executes it to load each unit on the main storage device, and the bitmap information generation unit, A raster / vector conversion unit, an information embedding unit, a vector / raster conversion unit, an information extraction unit, and the like are generated on the main memory.

  As described above, the image processing apparatus, the image processing method, the program for causing the computer to execute the method, and the recording medium according to the present invention are useful for the image processing technology. It is useful as an image processing technique for embedding as a watermark and extracting a digital watermark.

1 is a configuration diagram of an image processing apparatus according to Embodiment 1. FIG. 1 is a functional block diagram of an image processing apparatus according to Embodiment 1. FIG. It is a functional block diagram of a raster / vector conversion unit. It is a figure explaining the color reduction process with respect to an image. It is a figure explaining performing an outer periphery line division | segmentation process with respect to the image shown by FIG. It is a figure explaining performing a perimeter line division processing to a population image It is a figure explaining the process which changes the positional relationship of a vector pair. 5 is a flowchart for explaining an image processing procedure according to the first embodiment. It is a flowchart explaining the procedure of embedding information by the information embedding part of the image processing apparatus by embodiment. It is a figure explaining the image embedded by the information embedding part 3, and its outer periphery. It is a figure explaining the image obtained by printing and scanning the image which was shown by FIG. 10 and embedded information. 6 is a functional block diagram of an image processing apparatus according to Embodiment 2. FIG. 10 is a flowchart illustrating an image processing procedure according to the second embodiment. It is a figure explaining the other example of the vector displacement for information embedding.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bitmap information generation part 2 Raster / vector conversion part 3 Information embedding part 4 Vector / raster conversion part 5 Information extraction part 21 Color reduction process part 22 Peripheral line division | segmentation process part 23 Fitting process part 104 Image input part 105 Image output part 100 200 Image processing device

Claims (18)

  Based on predetermined embedding information to be embedded in the image data for a pair of vector information satisfying a predetermined condition in the image data described by the vector information, the relative positional relationship information of the pair of vector information is An image processing apparatus comprising an embedding unit that embeds the predetermined embedding information in the image data by changing.   The embedding unit divides an outer peripheral line that defines a boundary line of a pixel group in which the pixel value of the pixel in the image data is the same and / or the vicinity thereof into a plurality of line segments, and each divided line segment is divided 2. The predetermined embedding information is embedded by changing the parameters of the pair of vector information described by information via parameters in at least one of a straight line and a curve. Image processing apparatus. The embedding means has a second condition that the end point of the line segment is at least one of an extrapolation line extending from the end point of the first line segment to a predetermined distance and the vicinity of the extrapolation line as the predetermined condition. On condition that an end point of the line segment exists, and that the extrapolated line and the direction of the second line segment are substantially the same direction,
The image processing apparatus according to claim 2, wherein the predetermined embedding information is embedded by changing relative positional relationship information of end points of the first and second line segments.   The embedding means has the relative positional relationship within a range of 3 / N inch or less when the change amount of the relative positional relationship between the pair of vectors is Ndpi (dot per inch). The image processing apparatus according to claim 1, wherein the predetermined embedding information is embedded by changing information.   Image processing comprising: extraction means for extracting relative positional relationship information described by a pair of vector information from a pair of vector information satisfying a predetermined condition in image data described by the vector information apparatus.   The extraction unit divides an outer peripheral line that defines a boundary line of a pixel group in which the pixel values of the pixels in the image data are at least one of the same and nearby, into a plurality of line segments, and each of the divided line segments is a straight line 6. The image processing apparatus according to claim 5, wherein the relative positional relationship information is extracted from the parameters of the pair of vector information described by information via parameters in at least one of a curve and a curve. . The extraction means may include a second line on the extrapolation line extending from the end point of the first line segment to a predetermined distance and in the vicinity of the extrapolation line as the predetermined condition. On the condition that there is an end point of the minute, and that the extrapolated line and the direction of the second line segment are substantially the same direction,
The image processing apparatus according to claim 6, wherein relative position relationship information of end points of the first and second line segments is extracted.   The extraction means has, as the predetermined condition, a change amount of relative positional relationship information of the pair of vectors in a range of 3 / N inches or less when an actually output image is Ndpi (dot per inch). The image processing apparatus according to claim 5, wherein the relative positional relationship information is extracted.   Relative to the pair of vector information based on the predetermined embedding information to be embedded in the image data with respect to the pair of vector information satisfying a predetermined condition in the image data described by the vector information by the embedding means An image processing method comprising an embedding step of embedding the predetermined embedding information in the image data by changing target positional relationship information.   In the embedding step, the embedding unit divides an outer peripheral line that defines a boundary line of a pixel group in which the pixel value of the pixel in the image data is the same and / or the vicinity thereof into a plurality of line segments, Each of the divided line segments is embedded in the predetermined embedding information by changing the parameter of the pair of vector information described by information via the parameter in at least one of a straight line and a curve. The image processing method according to claim 9. In the embedding step, as the predetermined condition, the embedding unit includes at least an extrapolation line extending from the end point of the first line segment to a predetermined distance and in the vicinity of the extrapolation line as the predetermined condition. On the condition that the end point of the second line segment exists in any one of the above, and that the direction of the extrapolated line and the second line segment are substantially the same direction,
The image processing method according to claim 10, wherein the predetermined embedding information is embedded by changing relative positional relationship information of end points of the first and second line segments.   In the embedding step, the amount of change in the relative positional relationship between the pair of vectors by the embedding unit is within a range of 3 / N inches or less when an actually output image is Ndpi (dot per inch). 12. The image processing method according to claim 9, wherein the predetermined embedded information is embedded by changing the relative positional relationship information.   Including an extraction step of extracting relative positional relationship information described by the pair of vector information from a pair of vector information satisfying a predetermined condition in the image data described by the vector information by an extraction unit. Image processing method.   In the extraction step, the extraction unit divides an outer peripheral line defining a boundary line of a pixel group in which the pixel value of the pixel in the image data is the same and / or the vicinity thereof into a plurality of line segments. 14. The relative positional relationship information is extracted from the parameters of the pair of vector information in which each line segment is described by information via parameters in at least one of a straight line and a curve. The image processing method as described. In the extraction step, as the predetermined condition, at least one of the end point of the line segment extending from the end point of the first line segment to a predetermined distance and the vicinity of the extrapolation line is performed by the extracting unit. On the condition that the end point of the second line segment exists, and that the extrapolated line and the direction of the second line segment are substantially the same direction,
The image processing method according to claim 14, wherein the relative positional relationship information of the end points of the first and second line segments is extracted.   In the extraction step, the amount of change in the relative positional relationship information of the pair of vectors is Ndpi (dot per inch) as the predetermined condition by the extraction unit. 16. The image processing method according to claim 13, wherein the relative positional relationship information is extracted within a range of N inches or less.   A program causing a computer to execute the image processing method according to any one of claims 9 to 16.   A computer-readable recording medium on which the program according to claim 17 is recorded.