JP5067182B2 - Image processing apparatus and image processing program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus for improving data amount reduction effect caused by compression, and for reducing data amount of its drawing information at the case when an image is described by the drawing information. <P>SOLUTION: Representative pixel block deciding means of the image processing apparatus decides a pixel block which represents the pixel block from among similar pixel blocks within an image, then representative pixel block drawing information producing means produces the drawing information of the representative pixel block decided by the representative pixel block deciding means using a relative position. Individual pixel block drawing information producing means produces the drawing information of the individual pixel block by adding an absolute position in the image into the drawing information produced by the representative pixel block drawing information producing means, while reversible compressing means performs reversible compression about the drawing information produced by the individual pixel block drawing information producing means. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an image processing apparatus and an image processing program.

As a format of an electronic document, a portable document format (PDF: Portable Document Format (registered trademark)), an SVG (Scalable Vector Graphics) that represents a vector representation of an image, a postscript (registered trademark) that is a page description language, or various types There are document formats used in word processors.
In an electronic document described in these document formats, it is possible to express character shapes and graphic shapes using drawing commands such as straight lines and curves.
In a normal case, the user draws a straight line or a curve on the application software, and the application software converts it into a drawing command and converts it into the electronic document format.
Even when an input is an image, there is a technique for analyzing an input image and converting image information into a drawing command. That is, it is possible to convert the input image into a drawing command by rewriting the outline of the black pixel closed region of the input image with the drawing command and further performing a filling process (painting command) of the closed region.
By rewriting the drawing command in this way, an image with less jaggy can be obtained even when the image is enlarged.

As a technology related to this, for example, Patent Document 1 describes whether the data read from the RAM is straight line or curved line data for the purpose of converting to an outline font closer to the actual character outline. If it is determined by the CPU and is determined as curve data, the CPU determines whether or not an extremum exists in the curve formed by the curve data. If the determination is affirmative, the CPU determines that the curve is an extremum. And the data of the curve obtained by the division and the data of the straight line determined to be a straight line are stored in a RAM.
Japanese Patent Laid-Open No. 08-115419

By the way, drawing information in an electronic document is often written in, for example, a text code (ASCII code or the like). In that case, a plurality of text codes are required to express one straight line or curve.
The present invention provides an image processing apparatus and an image processing program that increase the data amount reduction effect by compression and reduce the data amount of the drawing information when the image is described by drawing information. It is aimed.

The gist of the present invention for achieving the object lies in the inventions of the following items.
According to the first aspect of the present invention, representative pixel block determining means for determining a pixel block representing the pixel block from similar pixel blocks in the image, and drawing information of the representative pixel block determined by the representative pixel block determining unit The representative pixel block drawing information generating unit for generating the pixel pixel using relative positions, and the drawing information generated by the representative pixel block drawing information generating unit by giving an absolute position in the image, An individual pixel block drawing information generation unit, and a reversible compression unit that reversibly compresses the drawing information generated by the individual pixel block drawing information generation unit, and the individual pixel block drawing information generation unit includes the representative pixel The image processing apparatus is characterized in that the drawing order of pixel blocks corresponding to the representative pixel block determined by the block determination unit is made closer .

According to the second aspect of the present invention, representative pixel block determining means for determining a pixel block representing the pixel block from similar pixel blocks in the image, and drawing information of the representative pixel block determined by the representative pixel block determining unit The representative pixel block drawing information generating unit for generating the pixel pixel using relative positions, and the drawing information generated by the representative pixel block drawing information generating unit by giving an absolute position in the image, An individual pixel block drawing information generation unit, and a reversible compression unit that reversibly compresses the drawing information generated by the individual pixel block drawing information generation unit, and the individual pixel block drawing information generation unit includes the representative pixel The image processing apparatus is characterized in that the drawing of pixel blocks corresponding to the representative pixel block determined by the block determination unit is made continuous .

The invention according to claim 3, wherein the individual pixel block drawing information generating means, based on the compression result of the lossless compression means any of claims 1-2, characterized in that to generate drawing information of an individual pixel block The image processing apparatus according to claim 1.

According to a fourth aspect of the present invention, the individual pixel block drawing information generating unit performs the drawing information generated by the representative pixel block drawing information generating unit and the affine transformation of a pixel block that is similar by affine transformation. including drawing information, an image processing apparatus according to any one of claims 1 to 3, characterized in that to generate drawing information of an individual pixel block.

According to a fifth aspect of the present invention, there is provided a computer comprising: a representative pixel block determining unit that determines a pixel block that represents the pixel block from similar pixel blocks in an image; and the representative pixel block determined by the representative pixel block determining unit. The representative pixel block drawing information generating unit that generates the drawing information using relative positions, and the drawing information generated by the representative pixel block drawing information generating unit is assigned an absolute position in the image to obtain individual pixel blocks. The individual pixel block drawing information generating unit for generating the drawing information of the first pixel block and the reversible compression unit for reversibly compressing the drawing information generated by the individual pixel block drawing information generating unit, An image processing program characterized in that the drawing order of pixel blocks corresponding to the representative pixel block determined by the representative pixel block determining means is brought close to each other .
According to a sixth aspect of the present invention, the computer comprises a representative pixel block determining means for determining a pixel block representing the pixel block from similar pixel blocks in the image, and the representative pixel block determined by the representative pixel block determining means. The representative pixel block drawing information generating unit that generates the drawing information using relative positions, and the drawing information generated by the representative pixel block drawing information generating unit is assigned an absolute position in the image to obtain individual pixel blocks. The individual pixel block drawing information generating unit for generating the drawing information of the first pixel block and the reversible compression unit for reversibly compressing the drawing information generated by the individual pixel block drawing information generating unit, The image processing program is characterized in that the drawing of pixel blocks corresponding to the representative pixel block determined by the representative pixel block determining means is made continuous.

According to the image processing apparatus of the first aspect, when the image is described by the drawing information, the data amount reduction effect by the compression can be increased, and the data amount of the drawing information can be reduced. The data amount reduction effect by compression can be further increased, and the data amount of the drawing information can be reduced.

According to the image processing apparatus of the second aspect, when an image is described with drawing information, the data amount reduction effect by compression can be increased, and the data amount of the drawing information can be reduced. The data amount reduction effect by compression can be further increased, and the data amount of the drawing information can be reduced.

According to the image processing device of the third aspect , it is possible to increase the speed of the generation processing and compression processing of the drawing information of the individual pixel block.

According to the image processing apparatus of the fourth aspect , it is possible to further increase the data amount reduction effect by the compression and to reduce the data amount of the drawing information.

According to the image processing program of the fifth aspect, when the image is described by the drawing information, the data amount reduction effect by the compression can be increased, and the data amount of the drawing information can be reduced. The data amount reduction effect by compression can be further increased, and the data amount of the drawing information can be reduced.
According to the image processing program of the sixth aspect, when the image is described by the drawing information, the data amount reduction effect by the compression can be increased, and the data amount of the drawing information can be reduced. The data amount reduction effect by compression can be further increased, and the data amount of the drawing information can be reduced.

First, an outline of the present embodiment will be described.
Note that the pixel block targeted by this embodiment includes at least a pixel region that is continuous in four or eight connections, and also includes a set of these pixel regions. The set of these pixel areas means that there are a plurality of continuous pixel areas such as 4-connected, and the plurality of pixel areas are in the vicinity. Here, what is in the vicinity is, for example, an image area in which the pixel areas are close to each other in distance, an image area that is projected vertically or horizontally so as to cut out one character at a time from a line as a sentence, and cut out at a blank spot Or an image region cut out at regular intervals.
In many cases, an image of one character is formed as one pixel block. However, it is not necessary that the pixel area is actually recognizable as a character by humans. There are a part of a character, a pixel region that does not form a character, and the like, and any pixel block may be used. For example, it may be a figure such as a circle or a line. Hereinafter, the term “character” or “character image” means “pixel block” unless otherwise specified.

This embodiment is intended for an image having a plurality of characters. In a normal document image, the same character may appear many times. In the present embodiment, the data size is reduced by giving the same drawing command to the same character.
However, simply arranging the description of the same rendering command does not reduce the data size.
In this embodiment, a drawing command is described, and the description is further losslessly compressed (for example, LZ compression (including a derivative version using an LZ compression algorithm)). For example, the LZ compression algorithm is a method that, when the same byte string sequence is found, is converted into a smaller code without reusing the byte sequence sequence, the file size can be reduced. Become. Hereinafter, LZ compression will be described as an example of lossless compression.

To create such a situation, it is necessary to find the same letter.
In the present embodiment, first, characters are cut out from the image, and the degree of difference between the characters is measured. For example, if the degree of difference is equal to or less than a predetermined threshold, it is determined that the characters are similar. The same drawing command is given to the similar characters. Of course, similar characters include the same characters.
There are various methods for creating drawing commands. For example, one character is selected from a plurality of characters determined as similar characters, and a drawing command is created using the character image as a representative image. Alternatively, a drawing command is created using an average image of a plurality of characters determined as the same character and using the average image as a representative image. Also, weighting may be performed when creating an average image. These methods will be described in detail later.
As described above, it is possible to reduce the file size by giving the same drawing command to similar characters and performing LZ compression.

Furthermore, in LZ compression, the buffer size for holding already compressed byte sequences may be limited.
In order to correspond to an encoder with such limited resources, the same characters may be compressed together.
For example, the character order is changed, and similar characters are described in order and then compressed. By changing the character order in this way, it becomes easy to hit the dictionary or the byte string in the buffer, and the compression rate can be increased (the file size can be reduced) even when the resources are limited.

Hereinafter, examples of various preferred embodiments for realizing the present invention will be described with reference to the drawings.
FIG. 1 is a conceptual module configuration diagram of a configuration example according to the first embodiment.
The module generally refers to components such as software (computer program) and hardware that can be logically separated. Therefore, the module in the present embodiment indicates not only a module in a computer program but also a module in a hardware configuration. Therefore, the present embodiment also serves as an explanation of a computer program, a system, and a method. However, for the sake of explanation, the words “store”, “store”, and equivalents thereof are used. However, when the embodiment is a computer program, these words are stored in a storage device or stored in memory. It is the control to be stored in the device. In addition, the modules correspond almost one-to-one with the functions. However, in mounting, one module may be composed of one program, or a plurality of modules may be composed of one program. A plurality of programs may be used. The plurality of modules may be executed by one computer, or one module may be executed by a plurality of computers in a distributed or parallel environment. Note that one module may include other modules. In the following, “connection” includes not only physical connection but also logical connection (data exchange, instruction, reference relationship between data, etc.).
In addition, the system or device is configured by connecting a plurality of computers, hardware, devices, and the like by communication means such as a network (including one-to-one correspondence communication connection), etc., and one computer, hardware, device. The case where it implement | achieves by etc. is also included. “Apparatus” and “system” are used as synonymous terms.

  In this embodiment, as shown in FIG. 1, a character segmentation processing module 110, a similar character search processing module 120, a representative character determination processing module 130, a representative character drawing command generation processing module 140, and an individual character drawing command generation processing module 150 The reversible compression processing module 160 is included.

In this embodiment, a binary image is received. When the received image is not a binary image, that is, a color image or a gray image is received, a character pixel extraction process (a process of extracting a character image in distinction from a photographic image or the like) is performed, and a character portion is set to 1, A binarization processing module that performs processing for generating a binary image in which the character portion is set to 0 may be added as preprocessing of the character segmentation processing module 110. By doing so, the operation of the present embodiment can be used as it is. Various methods can be used as the character pixel extraction process. For example, the methods disclosed in Japanese Patent Application Laid-Open Nos. 2005-39771, 2005-63445, 2005-175541, 2005-184402, 2005-184404, etc. Can be used.
Note that accepting an image means, for example, accepting an image input by a scanner or the like, receiving an image by fax, a hard disk (in addition to those incorporated in a computer, those connected via a network, etc. Etc.) and the like.

The character cutout processing module 110 is connected to the similar character search processing module 120, cuts out individual characters in the received binary image, and passes the cutout characters to the similar character search processing module 120.
Examples of character cutout processing performed by the character cutout processing module 110 include, for example, Japanese Patent Application Laid-Open No. 5-28301, Japanese Patent Application Laid-Open No. 5-120481, Japanese Patent Application Laid-Open No. 5-143776, Japanese Patent Application Laid-Open No. 5-174185, and Japanese Patent Application Laid-Open No. No. 44406, JP-A-6-187489, JP-A-6-348911, JP-A-7-13994, JP-A-7-160810, JP-A-8-161432, JP-A-8-297718. JP, 10-69524, JP 10-134145, JP 10-261047, JP 2000-57261, JP 2001-43314, JP 2004-78531, etc. Can be used.

  The character cutout processing module 110 receives a target image 300 as shown in FIG. 3, for example. When such a target image 300 is received, the character cutout processing module 110 cuts out characters. The result cut out for each character is shown in FIG. As a result of the cutout, a rectangle surrounding the character is displayed. This rectangle may be a circumscribed rectangle.

The similar character search processing module 120 is connected to the character cutout processing module 110 and the representative character determination processing module 130, receives characters cut out from the character cutout processing module 110, and searches for similar characters between the characters. To do. Then, the character is transferred to the representative character determination processing module 130.
For example, in the example shown in FIG. 4, there are 18 characters, and these 18 characters are received from the character cutout processing module 110. For each character, search for similar characters among the other 17 characters.
For example, there are 8 characters that are similar to the first character “A” appearing among the other 17 characters. In total, there are nine similar characters “A”. These nine “a” are registered as similar characters.

There are various ways to determine whether they are similar. Hereinafter, an example of a method for determining the difference or similarity of characters will be described.
The following is an example of a method for verifying the similarity of characters.
(A1) Two binary images that are clipped character images are input.
(A2) The centers of black pixels of the two input images are matched.
(A3) An XOR (eXclusive OR) operation is performed on two input images that have the same center of gravity.
(A4) Further, it is moved slightly (several pixels vertically and horizontally), and the number of pixels (different pixels) that become 1 as a result of the XOR operation is counted. As a result of various XOR operations after movement including non-movement, if the minimum value of the number of pixels that are 1 (different pixels) is equal to or less than a predetermined threshold, it is determined that the character images are similar. The predetermined threshold value may be a predetermined fixed numerical value or a numerical value proportional to the number of pixels of the character image.
(A5) The cut-out character images are calculated by using the above-described method for similarity to other character images, and character images that are similar to each other are grouped together (grouped).

In addition to the above, as a determination of whether or not the character images are similar, for example, the cut character image is treated as one vector data, clustered, and a character image similar to the character image is extracted. Also good. In this case, when the distance (for example, the Euclidean distance) between the vector data representing the character image and the vector data representing the character image to be determined is equal to or less than a predetermined value (that is, when the distance between the two vector data is short) The character image is determined to be similar to the character image to be determined.
Furthermore, an expanded image may be generated based on the result image of the logical operation of the two character image patterns, and it may be determined whether or not they are similar based on the ratio of overlapping with the expanded image. That is, the degree of difference may be determined based on the degree of expansion (expansion radius) when the two match.
In addition, "Managing Gigabytes" by JP-A-07-200755, IH Witten, A. Moffat, and TC Bell.
You may use the method described in Morgan Kaufmmann Publishers pp.320-332.

Note that the similarity is the amount that is maximized when two images are congruent and decreases according to the degree of difference.
Instead of similarity, an amount that is minimized when two images are congruent and increases according to the degree of difference may be used. In this case, it is called “distance” or “degree of difference”. The distance is an image represented by a vector (such as a pixel value itself as a vector or an image feature amount as a vector). This is the distance (distance) between the images. For example, there are Euclidean distance, Manhattan distance, Hausdorff distance, Mahalanobis distance, angles between vectors θ, cos θ, and the square of cos θ.
That is, in order to search for similar characters, “distance” or “difference” may be used in addition to the similarity.

  In the above-described similar character search process, the degree of similarity of one character with all other characters is measured. However, in order to increase the speed, the size of the character rectangle is somewhat the same. Only for the above, similarity calculation with a large amount of calculation may be performed.

FIG. 5 is an explanatory diagram illustrating an example in which similar characters are grouped.
As a result of similar character search by the similar character search processing module 120, similar characters are grouped (grouped) as in the example shown in FIG. That is, it is divided into five groups. FIG. 5A shows the first group (9 character images similar to the character image “A”), and FIG. 5B shows the second group (“ FIG. 5C shows a third group (two character images similar to the character image “U”), and FIG. ) Is the fourth group (three character images similar to the character image “e”), and FIG. 5E is the fifth group (one character image “o”).

The representative character determination processing module 130 is connected to the similar character search processing module 120 and the representative character drawing command generation processing module 140, receives a similar character search result from the similar character search processing module 120, and for each group, A representative character representing the character image is determined. The representative character is transferred to the representative character drawing command generation processing module 140.
Various types of representative character determination processing can be used. For example, the character that appears first may be selected as the representative character. Alternatively, after moving all similar characters to a position where the above-mentioned XOR operation result is minimized, the average value is obtained, and further binarization is performed to create a representative character. Good.

Alternatively, the following representative character determination process may be used.
First, enlarge all similar characters. After enlarging, a position where an error between all characters (a square error or an absolute value error) is minimized is extracted. At that position, an average value of each pixel of the character image may be acquired, and binarization may be performed to create a representative character. This enlargement process will be described in more detail.

An example of processing by the character cutout processing module 110, the similar character search processing module 120, the representative character determination processing module 130, and the representative character drawing command generation processing module 140 will be described with reference to FIG. The representative character determination processing module 130 performs enlargement processing.
The character cutout processing module 110 uses the character image 611, the character image 612, and the character image 613 in the input image 610 on which a plurality of characters “2” are described as target images. Then, each character image is cut out with the resolution of the character image 611. Alternatively, the character size / character position data 650 of each character image may be extracted and passed to the representative character drawing command generation processing module 140.
The similar character search processing module 120 searches for similar character images and generates a plurality of character image groups “2”.
Then, the representative character determination processing module 130 obtains the emphasis (intersection of the center of gravity line 611A, etc.) of the character image 611, the character image 612, and the character image 613, and moves the phase so that the emphasis coincides with each other. 620 is generated. Further, the representative character determination processing module 130 may assign, for example, character code data 640 of a character image “2”. The character code assignment processing may be performed by character recognition processing.
The representative character drawing command generation processing module 140 generates, for example, font data 630 that is outline information from the high resolution character image 620 received from the representative character determination processing module 130.

A representative character image generation by the representative character determination processing module 130, that is, an enlargement processing example for generating a high-resolution character image will be described with reference to FIG.
FIG. 7A shows a sampling grid (first sampling grid 701, first sampling grid 702, first sampling grid 703, first resolution) at the resolution of the input image 610 (first resolution). The sampling grid 704) and the gravity center positions (centroid 701A, centroid 702A, centroid 703A, centroid 704A) of the character image are shown.
First, as shown in FIG. 7B, the representative character determination processing module 130 moves the phases of the four sampling grids based on the center of gravity of the character image.

FIGS. 7C and 7D are diagrams illustrating an example of a technique for setting a sampling grid having a second resolution higher than the first resolution. The circled numbers (1, 2, 3, 4) illustrated in FIG. 7C exemplify the value of the character image at the first resolution. Here, the character image is plotted so that the circled numbers are represented on the grid points of the sampling grid at the first resolution.
In FIG. 7D, a second sampling grid 706 is a sampling grid for high-resolution images.
When the phases of the four sampling grids at the first resolution are moved, the representative character determination processing module 130 sets the sampling grid at the second resolution as shown in FIG. As shown in (D), the phase of the sampling grid at the second resolution is moved so that the centroids of the character images coincide.

FIG. 7E is a diagram for explaining an example of a technique for calculating the value of the character image at the second resolution. The circle numbers at the center of the second sampling grid 706A, the second sampling grid 706B, the second sampling grid 706C, and the second sampling grid 706D indicate the value of the character image at the second resolution. This is just an example. Here, the character image in the second resolution is shown such that the circled numbers at the center are represented on the grid points of the sampling grid in the second resolution.
Then, the representative character determination processing module 130 interpolates the pixel value of the character image at the second resolution from the pixel value of each character image based on the phase of each character image at the first resolution. In this example, the representative character determination processing module 130 applies the nearest neighbor interpolation method to interpolate the pixel values of the character image at the second resolution. That is, the representative character determination processing module 130 samples the character image at the second resolution among the four values of the character image at the first resolution (circle numbers 1, 2, 3, and 4 in FIG. 7E). The value closest to the grid point is selected as the character image value at the second resolution. Specifically, in the second sampling grid 706A, the value closest to the center is “1”, and “1” is adopted (the circled number is 1). The interpolation method is not limited to this method, and other methods (for example, linear interpolation method) may be applied.
The processing of the representative character determination processing module 130 is not limited to the processing described above, and linear interpolation, cubic convolution, or the like may be used.

The representative character drawing command generation processing module 140 is connected to the representative character determination processing module 130 and the individual character drawing command generation processing module 150 and includes drawing commands for representative character images determined by the representative character determination processing module 130. Drawing information is generated using relative positions. The drawing information is passed to the individual character drawing command generation processing module 150.
The drawing command in the drawing information is an instruction for drawing a straight line, a curve or the like. The drawing command generation process is a process of approximating the outline of a character image. It should be noted that it is not necessarily approximate, and the character image may be traced faithfully. Furthermore, a process for filling the inside of the outline may be included. There are various methods for generating a drawing command, and these methods may be used. For example, there are techniques described in JP-A-5-35862, JP-A-6-223176, JP-A-8-115419, and the like. Alternatively, a drawing command for drawing a straight line such that one pixel is regarded as a square and the sides of the square are traced may be generated. Note that the drawing command generation process may be referred to as outlining or vectorization.

  The drawing command generation processing by the representative character drawing command generation processing module 140 is to generate a drawing command using a relative position. That is, instead of using the absolute position in the original target image, a relative position based on a certain position (drawing start position, center of the image, etc.) in the representative character image is used.

  The individual character drawing command generation processing module 150 is connected to the representative character drawing command generation processing module 140 and the lossless compression processing module 160, and the drawing information generated by the representative character drawing command generation processing module 140 includes the absolute information in the target image. A position is given and drawing information of an individual character image is generated. That is, the representative character image drawing command is converted into an individual character image drawing command.

  The drawing commands generated by the representative character drawing command generation processing module 140 and the individual character drawing command generation processing module 150 will be described below using the examples shown in FIGS. In FIG. 8, there are two triangular images (drawing target triangles 801 and 802) having the same shape. Since this triangle is the same shape, it can be drawn as one representative character.

The drawing command used here has the following properties.
(B1) Designate the drawing start position. If the drawing start position is not specified, the end point of the previous drawing may be set as the drawing start position.
(B2) The end point, control point, etc. are designated by the relative position from the drawing start position. The control points are necessary for drawing a curve.
Using such a drawing command, a drawing command for a representative character is formed. In this representative character drawing command, only the relative position (B2) is described. That is, there is no designation (B1) of the first drawing start position. The designation may be made but is ignored by the individual character drawing command generation processing module 150.

When the representative character is as in the example shown in FIG. 9 (triangle having vertices A, B, and C), as a result of the generation processing by the representative character drawing command generation processing module 140 of the representative character drawing command, A drawing command composed of (C1) to (C3) is created.
(C1) A straight line is drawn from A to B with the drawing start position A as the origin.
(C2) A straight line is drawn from B to C.
(C3) A straight line is drawn from C to A. Alternatively, a command for returning to the origin by a straight line may be used.
In this drawing command, since the drawing start position A is the origin, the representative character drawing command is described using only the relative positional relationship.

Next, in the individual character drawing command generated by the individual character drawing command generation processing module 150, the relative position described in the generation processing of the representative character drawing command is converted into an absolute position.
That is, the coordinates of the drawing start positions (D and E) of each triangle in FIG. 8 are used. That is, the absolute position in the electronic document 800. Note that the position of the character extracted by the character cutout processing module 110 may be used as the drawing start position.
(D1) Draw the first triangle (drawing target triangle 801).
A representative character drawing command (drawing command including (C1) to (C3)) is copied and described here.
(D2) Drawing of the second triangle (drawing target triangle 802) Let E be the drawing start position.
A representative character drawing command (drawing command including (C1) to (C3)) is copied and described here.
As shown in (D1) and (D2), the drawing start position is designated by an absolute position, and thereafter, a drawing command for the representative character designated by the relative coordinates is described, whereby two triangles (drawing target triangle 801) are written. , 802).

In the above-described example, the absolute coordinate is used as the start position of the drawing command. However, the method of giving the absolute coordinate is not limited to this. For example, as shown in FIG. 4, the coordinates of the circumscribed rectangle vertex (for example, the upper left vertex) of the character “A” may be designated as absolute coordinates. In the case of a representative character, the movement to the drawing start position may be shown as a relative position.
In addition, the drawing start position (the position of D or E) may be indicated by an absolute position, or the drawing start position may be expressed by a relative position from the previous drawing end point. As a result, it is only necessary that the drawing start position can be specified on the electronic document.
In addition, a character code may be included in the drawing command.

The lossless compression processing module 160 is connected to the individual character drawing command generation processing module 150, receives a drawing command from the individual character drawing command generation processing module 150, and reversibly compresses it. That is, the final electronic document is generated by reversibly compressing the text string describing the drawing command. As this lossless compression, LZ compression is excellent. For example, there is one described in JP-A-8-237138. There are various other versions of LZ compression, and any of them may be used.
In LZ compression, when the same byte string appears in a byte string that has appeared in the past, the byte string that appears in the second and subsequent times is not encoded as it is, and the same byte string in the past is referred to. Since the code amount at the time of reference is smaller than the code amount in the case of encoding as it is, the byte string can be compressed.
In the present embodiment, the representative character drawing command is copied and described a plurality of times. Since the representative character drawing command is the same command (the same byte sequence), it is possible to refer to the same byte sequence in the past as described above, and a high compression rate can be obtained.

FIG. 2 is a flowchart illustrating a processing example according to the first exemplary embodiment.
In step S202, the character cutout processing module 110 receives a target image.
In step S204, the character cutout processing module 110 cuts out characters in the target image received in step S202. Moreover, you may extract the character size, character position, etc. of each character.
In step S206, the similar character search processing module 120 searches for and groups similar characters from the characters extracted in step S204.
In step S208, the representative character determination processing module 130 determines a representative character using the similar characters grouped in step S206. A character code may be assigned to the representative character.
In step S210, the representative character drawing command generation processing module 140 generates a drawing command based on the relative position for the representative character determined in step S208.
In step S212, the individual character drawing command generation processing module 150 generates an individual character drawing command using the absolute position using the drawing command generated in step S210.
In step S214, the lossless compression processing module 160 performs lossless compression on the drawing command generated in step S212.
In step S216, the lossless compression processing module 160 generates an electronic document using the drawing command and the like compressed in step S214. This electronic document reproduces the image received in step S202.

Next, a second embodiment will be described. The configuration example of the second embodiment is the same as that of the first embodiment. However, the individual character drawing command generation processing module 150 performs the following processing. In other words, the present invention relates to processing for writing individual character drawing commands.
Normally, since the characters are arranged as shown in the example of FIG. 4, the characters are arranged in this order (that is, “A”, “I”, “U”, “A”, “E”, “O”). A drawing command will be described.
However, if the drawing commands are described in this order, the compression rate of LZ compression may decrease. In other words, in LZ compression, it is necessary to store past byte sequences, and the buffer size for storing the past byte sequences is limited. When the buffer overflows, old byte sequences are deleted. Will be. The buffer may be a buffer that simply stores byte sequences in order, or may be a memory area that registers byte sequences as a dictionary.
Furthermore, if the buffer size is reduced, there is an advantage that the speed at the time of compression and decompression is improved.
As described above, when an old byte string is erased, the byte string cannot be referred to, and thus the compression rate cannot be increased.
Therefore, in the second embodiment, the compression rate can be increased even when the buffer size is small.

In the first embodiment, the description order of each character is not specified in the processing by the individual character drawing command generation processing module 150, but in the second embodiment, the order is specified.
Assume that there is a search result of similar characters as in the example shown in FIG. In the second embodiment, similar characters are described consecutively. For example, the characters corresponding to the representative character image are arranged according to the similar character search result by the similar character search processing module 120. The drawing commands for individual characters are described in the order of arrangement.
As a result, the same byte string, that is, a representative character drawing command is present nearby, so that the hit ratio of the byte string can be improved even when the LZ compression buffer size is small.
In the above-described example, similar characters are described continuously, but it is not always necessary to continue them. The effect of improving the compression ratio of LZ compression can be obtained simply by changing the order so that similar characters are closer to each other than the order in which they appear in the image.

Next, a third embodiment will be described. The configuration example of the third embodiment is the same as that of the first embodiment. However, the individual character drawing command generation processing module 150 performs the following processing. In other words, the present invention relates to processing for writing individual character drawing commands. The individual character drawing command generation processing module 150 generates an individual character drawing command based on the compression result by the lossless compression processing module 160.
In the first and second embodiments described above, LZ compression is performed after a text string of a rendering command is once formed. However, this order is not necessarily required.
In LZ compression, a search process for searching for the same byte string from past byte strings is required.
However, in the third embodiment, since it is known in advance that the drawing command for the representative character is the same byte string, there is no need to perform a search by LZ compression, and the byte string is referred to. It becomes possible to do.
That is, the individual character drawing command generation processing module 150 of the third embodiment uses the reference information for LZ compression for the second and subsequent representative character drawing commands without describing the text string that is the drawing command. Output. The first drawing command of the representative character is processed in the order of the individual character drawing command generation processing module 150 and the lossless compression processing module 160, and the second and subsequent drawing commands are again processed by the individual character drawing command generation processing module 150. Then, the process (description of reference information for LZ compression) is performed and the process is passed to the lossless compression processing module 160.

Next, a fourth embodiment will be described. The configuration example of the fourth embodiment is the same as that of the first embodiment. However, the similar character search processing module 120 and the individual character drawing command generation processing module 150 perform the following processing. In other words, the present invention relates to processing for writing individual character drawing commands. The individual character drawing command generation processing module 150 also includes individual drawing commands generated by the representative character drawing command generation processing module 140 and affine transformation drawing commands for characters that are similar by affine transformation. Generate a character drawing command.
In the first to third embodiments described above, it is assumed that the sizes of the representative character and the individual character are the same.
However, it need not be the same. In other words, the similar character search processing module 120 also makes a similar character a similar character by performing affine transformation (enlargement and reduction).
Then, the individual character drawing command generation processing module 150 copies the representative character drawing command even for characters that are similar by affine transformation, and further adds an affine transformation command as a drawing command to obtain individual characters. Generate a drawing command.

  With reference to FIG. 10, a hardware configuration example of the first to fourth embodiments will be described. The configuration illustrated in FIG. 10 is configured by, for example, a personal computer (PC), and illustrates a hardware configuration example including a data reading unit 1017 such as a scanner and a data output unit 1018 such as a printer.

  A CPU (Central Processing Unit) 1001 includes various modules described in the above-described embodiments, that is, a character segmentation processing module 110, a similar character search processing module 120, a representative character determination processing module 130, and a representative character drawing command generation processing module. 140, a control unit that executes processing according to a computer program describing an execution sequence of each module such as the individual character drawing command generation processing module 150 and the lossless compression processing module 160.

  A ROM (Read Only Memory) 1002 stores programs used by the CPU 1001, calculation parameters, and the like. A RAM (Random Access Memory) 1003 stores programs used in the execution of the CPU 1001, parameters that change as appropriate in the execution, and the like. These are connected to each other by a host bus 1004 including a CPU bus.

  The host bus 1004 is connected to an external bus 1006 such as a PCI (Peripheral Component Interconnect / Interface) bus via a bridge 1005.

  A keyboard 1008 and a pointing device 1009 such as a mouse are input devices operated by an operator. The display 1010 includes a liquid crystal display device or a CRT (Cathode Ray Tube), and displays various types of information as text and image information.

  An HDD (Hard Disk Drive) 1011 includes a hard disk, drives the hard disk, and records or reproduces a program executed by the CPU 1001 and information. The hard disk stores received images, drawing commands, and the like. Further, various computer programs such as various other data processing programs are stored.

  The drive 1012 reads data or a program recorded on a removable recording medium 1013 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory, and the data or program is read out to the interface 1007 and the external bus 1006. , The bridge 1005, and the RAM 1003 connected via the host bus 1004. The removable recording medium 1013 can also be used as a data recording area similar to a hard disk.

  The connection port 1014 is a port for connecting the external connection device 1015 and has a connection unit such as USB and IEEE1394. The connection port 1014 is connected to the CPU 1001 and the like via the interface 1007, the external bus 1006, the bridge 1005, the host bus 1004, and the like. A communication unit 1016 is connected to a network and executes data communication processing with the outside. The data reading unit 1017 is a scanner, for example, and executes document reading processing. The data output unit 1018 is a printer, for example, and executes document data output processing.

  Note that the hardware configuration shown in FIG. 10 shows one configuration example, and the embodiment is not limited to the configuration shown in FIG. 10, and is a configuration that can execute the modules described in the embodiment. I just need it. For example, some modules may be configured with dedicated hardware (for example, Application Specific Integrated Circuit (ASIC), etc.), and some modules are in an external system and connected via a communication line In addition, a plurality of systems shown in FIG. 10 may be connected to each other via communication lines so as to cooperate with each other. Further, it may be incorporated in a copying machine, a fax machine, a scanner, a printer, a multifunction machine (an image processing apparatus having any two or more functions of a scanner, a printer, a copying machine, a fax machine, etc.).

In the above embodiment, LZ compression is exemplified as the lossless compression. However, other compression algorithms may be adopted as long as the compression rate is high when the same information sequence is present.
Further, the individual character drawing command generation processing module 150 of the first to fourth embodiments may be combined.

The program described above may be provided by being stored in a recording medium, or the program may be provided by communication means. In that case, for example, the above-described program may be regarded as an invention of a “computer-readable recording medium recording the program”.
The “computer-readable recording medium on which a program is recorded” refers to a computer-readable recording medium on which a program is recorded, which is used for program installation, execution, program distribution, and the like.
The recording medium is, for example, a digital versatile disc (DVD), which is a standard established by the DVD Forum, such as “DVD-R, DVD-RW, DVD-RAM,” and DVD + RW. Standards such as “DVD + R, DVD + RW, etc.”, compact discs (CDs), read-only memory (CD-ROM), CD recordable (CD-R), CD rewritable (CD-RW), etc. MO), flexible disk (FD), magnetic tape, hard disk, read only memory (ROM), electrically erasable and rewritable read only memory (EEPROM), flash memory, random access memory (RAM), etc. It is.
The program or a part of the program may be recorded on the recording medium for storage or distribution. Also, by communication, for example, a local area network (LAN), a metropolitan area network (MAN), a wide area network (WAN), a wired network used for the Internet, an intranet, an extranet, etc., or wireless communication It may be transmitted using a transmission medium such as a network or a combination of these, or may be carried on a carrier wave.
Furthermore, the program may be a part of another program, or may be recorded on a recording medium together with a separate program. Moreover, it may be divided and recorded on a plurality of recording media. Further, it may be recorded in any manner as long as it can be restored, such as compression or encryption.

It is a notional module block diagram about the structural example of 1st-4th embodiment. It is a flowchart which shows the process example by 1st Embodiment. It is explanatory drawing which shows the example of the image made into object. It is explanatory drawing which shows the example which cut out the character from the target image. It is explanatory drawing which shows the example which grouped the similar character. It is explanatory drawing which shows the process example by 1st Embodiment. It is explanatory drawing which shows the example of a production | generation process of the high resolution character image data by a representative character determination processing module. It is explanatory drawing which shows the example which draws a representative character. It is explanatory drawing for showing the example of a drawing command. It is a block diagram which shows the hardware structural example of the computer which implement | achieves 1st-4th embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 110 ... Character cut-out processing module 120 ... Similar character search processing module 130 ... Representative character determination processing module 140 ... Representative character drawing command generation processing module 150 ... Individual character drawing command generation processing module 160 ... Lossless compression processing module

Claims (6)

Representative pixel block determining means for determining a pixel block representing the pixel block from similar pixel blocks in the image;
Representative pixel block drawing information generating unit for generating drawing information of the representative pixel block determined by the representative pixel block determining unit using a relative position;
Individual pixel block drawing information generating unit for generating drawing information of individual pixel blocks by giving an absolute position in the image to the drawing information generated by the representative pixel block drawing information generating unit;
Reversible compression means for reversibly compressing the drawing information generated by the individual pixel block drawing information generating means ,
The individual pixel block drawing information generating means includes:
An image processing apparatus, wherein the drawing order of pixel blocks corresponding to the representative pixel block determined by the representative pixel block determining means is made closer . Representative pixel block determining means for determining a pixel block representing the pixel block from similar pixel blocks in the image;
Representative pixel block drawing information generating unit for generating drawing information of the representative pixel block determined by the representative pixel block determining unit using a relative position;
Individual pixel block drawing information generating unit for generating drawing information of individual pixel blocks by giving an absolute position in the image to the drawing information generated by the representative pixel block drawing information generating unit;
Reversible compression means for reversibly compressing the drawing information generated by the individual pixel block drawing information generating means ,
The individual pixel block drawing information generating means includes:
An image processing apparatus, wherein a pixel block corresponding to the representative pixel block determined by the representative pixel block determining unit is continuously drawn . The individual pixel block drawing information generating means includes:
Based on the compression result of the reversible compressing unit, an image processing apparatus according to any one of claims 1-2, characterized in that to generate drawing information of an individual pixel block. The individual pixel block drawing information generation unit includes individual drawing blocks generated by the representative pixel block drawing information generation unit and drawing information of the affine conversion for pixel blocks that are similar by affine transformation. the image processing apparatus according to any one of claims 1 to 3, characterized in that to generate drawing information of the pixel block. Computer
Representative pixel block determining means for determining a pixel block representing the pixel block from similar pixel blocks in the image;
Representative pixel block drawing information generating unit for generating drawing information of the representative pixel block determined by the representative pixel block determining unit using a relative position;
Individual pixel block drawing information generating unit for generating drawing information of individual pixel blocks by giving an absolute position in the image to the drawing information generated by the representative pixel block drawing information generating unit;
Functioning as reversible compression means for reversibly compressing the drawing information generated by the individual pixel block drawing information generating means ,
The individual pixel block drawing information generating means includes:
An image processing program for causing a drawing order of pixel blocks corresponding to a representative pixel block determined by the representative pixel block determining means to approach each other .   Computer
  Representative pixel block determining means for determining a pixel block representing the pixel block from similar pixel blocks in the image;
  Representative pixel block drawing information generating unit for generating drawing information of the representative pixel block determined by the representative pixel block determining unit using a relative position;
  Individual pixel block drawing information generating unit for generating drawing information of individual pixel blocks by giving an absolute position in the image to the drawing information generated by the representative pixel block drawing information generating unit;
  Reversible compression means for reversibly compressing the drawing information generated by the individual pixel block drawing information generating means
  Function as
  The individual pixel block drawing information generating means includes:
  Drawing of pixel blocks corresponding to the representative pixel block determined by the representative pixel block determining means is made continuous.
  An image processing program characterized by that.

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