JP2006222940A - Image processing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus capable of preventing the fault in which the lines of characters disappear or the like when an image is shrunk. <P>SOLUTION: The image processing apparatus that makes a prescribed process to an input image data to output thereof comprises a separating means (S102) for separating the input image data into a specific region and a non-specific region, shrinking means (S103, S104) for shrinking the separated specific region and non-specific region by respectively different schemes, and a synthetically displaying means (S105) for synthetically displaying the shrunk specific region and non-specific region. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus that performs predetermined processing on input image data and outputs the image data, and more particularly to an image processing apparatus that can prevent problems such as disappearance of character lines when an image is reduced. It is.

Conventionally, when a registered document is displayed in a document management system or the like, an image compression method for reducing the image and displaying it as a thumbnail image has been used. To easily create a high-compression image This is realized by simply thinning out images in predetermined steps.
However, the method of simply thinning out this image in a predetermined step has a problem that thin lines such as characters disappear.
In order to solve this problem, for example, Patent Document 1 discloses an image processing apparatus that creates a reduced image that is high-speed, small-scale, and faithful to an original image by combining processing for reducing an image to an average color and a method for performing blink processing. It is disclosed.
Patent Document 2 discloses an image processing method capable of accurately extracting a character region from a color image including characters and images other than characters.
JP 2004-112346 A JP 2002-288589 A

However, even if the reduction process and the thinning process are combined as disclosed in Patent Document 1, the line of the character part may disappear.
Therefore, the present invention is to solve the above-described problems, and an object of the present invention is to provide an image processing apparatus capable of preventing a problem that a character line disappears when an image is reduced.

In order to achieve the above-described object, the invention according to claim 1 is an image processing apparatus that performs a predetermined process on the input image data and outputs the processed image data. Separation means for separating into non-specific areas, and reduction means for reducing the specific areas and non-specific areas separated by the separation means by different reduction methods, respectively.
According to a second aspect of the invention, there is provided composite display means for combining and displaying the reduced specific area and the non-specific area.
The invention according to claim 3 is characterized in that the different reduction methods by the reduction means are switched according to the characteristics of the non-specific region.
According to a fourth aspect of the present invention, there is provided compression means for compressing the separated specific area and non-specific area by different compression methods.

According to a fifth aspect of the present invention, the composition display unit synthesizes and displays the reduced image created by the reduction unit and the compressed image created by the compression unit.
According to a sixth aspect of the present invention, the separating means obtains a binary image from the multivalued image obtaining means for obtaining a multivalued image that is a processing target image, and the multivalued image obtained by the multivalued image obtaining means. A binary image acquisition unit to acquire, a specific attribute part extraction unit to extract a region having a specific attribute of the binary image, and a portion corresponding to a region that is not the specific attribute in the binary image as a white pixel White pixel replacement means for replacing; specific attribute portion erasure image generation means for generating an image in which pixels of the specific attribute portion of the multi-valued image are erased;
The image processing apparatus includes: a specific attribute color determining unit that determines a color constituting the specific attribute part; and a specific attribute pixel image generating unit that generates the specific attribute binary image including the determined colors.

The invention according to claim 7 is characterized in that the compression means compresses and encodes the specific attribute binary image composed of the non-characteristic multi-valued image and each determined color by a different method. .
In the invention according to claim 8, the reduced images of the specific area and the non-specific area created by the reduction means, and the compressed images of the specific area and the non-specific area created by the compression means are combined into one file as a plurality of layers. A storage means for combining and storing is provided.

The invention according to claim 9 is a composite reduced image obtained by synthesizing the reduced image of the specific area and the non-specific area created by the reducing means, and a compressed image of the specific area and the non-specific area created by the compression means. The composite compressed image can be transmitted.
The invention according to claim 10 is a composite reduced image obtained by synthesizing the reduced image of the specific area and the non-specific area created by the reduction means, and a compressed image of the specific area and the non-specific area created by the compression means. The composite compressed image can be printed.

As described above, according to the image processing apparatus of the present invention, the separation unit separates the image data into the specific region and the non-specific region, and the separated specific region and the non-specific region are reduced by the reduction unit using different methods. After that, the specific area and the non-specific area are synthesized by the synthesis display unit, so that it is possible to prevent the problem that the character line disappears when the image is reduced.
Further, if the image reduction processing of the present invention is performed simultaneously with the compressed image creation processing, the separation processing for separating the specific area and the non-specific area can be shared, so that the processing is simplified and the processing speed is increased accordingly. Can be achieved.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a configuration diagram of an embodiment of an image processing apparatus according to the present invention.
The image processing apparatus of the present embodiment shown in FIG. 1 is a configuration example when implemented by software. The CPU 11, the memory 12, the hard disk 13, the input device 14 such as a mouse, the disk drive 15, the display 16, and the like are internal buses 10. It is comprised by the general purpose image processing apparatus connected by these.
A program for realizing the processing functions and processing procedures of the present invention is recorded on a recording medium 17 such as a CD or DVD-ROM loaded into the disk drive 15 and read out.
The original image to be processed is stored, for example, in the hard disk 13 or the like. The CPU 11 reads out and executes a program for realizing the processing functions and procedures described above from the recording medium 17. Then, the image processing result is stored in the hard disk 13 and output to the display 16 as necessary.

Next, a first embodiment of the image processing apparatus according to the present invention will be described.
FIG. 2 is a diagram illustrating an operation performed by the image processing apparatus as the first embodiment. When image data is input to the image processing apparatus according to the present embodiment as illustrated in FIG. 2 (S101), The input image is separated into a character part (specific area) and another area (non-specific area) (S102).
Next, a process of reducing the separated character part (specific area) and the other background area (non-specific area) by different reduction methods is executed (S103, S104).
When two reduced images obtained by reducing the specific area and the non-specific area by different reduction methods as described above are displayed, the two reduced images are combined (S105) and then displayed or saved. (S106).

Here, the reduction method in the present embodiment will be described.
There are two methods for reducing the image file size: the reduction method and the compression method. The compression method is a method for reducing the file size while maintaining the number of pixels of the file, whereas the reduction method is the number of pixels of the file. This is a method of reducing the size by reducing the resolution.
Up to now, many proposals have been made to reduce the file size by using different compression methods for specific areas and non-specific areas. However, in the present invention, the file size is reduced by using different reduction methods for specific areas and non-specific areas. It is what you do.

  FIG. 3 is a diagram showing the concept of reduction by the reduction method. An input image as shown in FIG. 3A is converted into a small area (m × n pixel size) on a mesh as shown in FIG. 3B. Dividing and determining one pixel (= representative value) P as shown in FIG. 3C from the pixels in the small area. Then, as shown in FIG. 6D, a reduced image of 1 / (n × m) of the original file is created with the representative value P. Note that n = m may be used.

Area (m × n pixel size),
As a method of determining the representative value P,
(1) A specific pixel (for example, the left corner) of n × m pixels is a representative value. (2) An average color of n × m pixels is a representative value. (3) The darkest color of n × m pixels is a representative value. (4) The lightest color of n × m pixels is used as a representative value. (5) A random pixel among n × m pixels is used as a representative value. (6) The most frequently used pixel among n × m pixels. Can be considered as a representative value.

As an average color calculation method (2), an average value (Rm, Gm, Bm) of R, G, B values of pixels in an m × n pixel area is obtained.
Rm = (ΣR) / N
Gm = (ΣG) / N
Bm = (ΣB) / N
However, N = m × n
As the darkest color calculation method (3), the lightness (= (R + G + B) / 3) is obtained from the R, G, and B values of the pixels in the m × n pixel area, and the m × n pixels The value with the smallest brightness is used as the representative value.
As the calculation method of the brightest color in (4), the brightness is obtained in the same manner as in (3) above, and the value with the highest brightness is used as the representative value.
As a random pixel calculation method of (5), pixels in m × n are generated by a value generated by random number generating means that can randomly generate values 1 to N (N = m × n). Determine the value. Specifically, the value of the left corner (0, 0) shown in FIG. 4 is set to 2, and the pixel value of (0, 1) is set to 2. FIG. 4 shows an example of m × n = 4 × 2.
In addition, as a method of calculating a pixel value with high frequency (6), a frequency histogram of R, G, and B values is created, and the most frequently used value is used.

As a reduction method effective for the character part, it is preferable to determine the representative value P from the above (2), (3), and (4). However, the method of determining the representative value P according to the above (3) and (4) is better switched according to the characteristics of the image. Specifically, in the case of black characters on the white ground, the representative value P may be determined by the determination method of (3) above, and in the case of white characters on the black ground, the representative value P may be determined by the determination method of (4) above.
As a reduction method effective for the non-character portion, the representative value P may be determined from the above (1), (2), (5), and (6).

  In this embodiment, as a reduction method, for example, one is a thinning process in which image data is thinned and reduced with a specific pixel (for example, the left corner) as a representative value, and the other is an average in which the average color of the pixel area is the representative color. As a colorization process, an average colorization process is performed on the character portion (specific area), and a thinning process is performed on the background area (non-specific area). In other words, in this embodiment, when the original image is reduced to create a reduced image (thumbnail image), if a thinning process is performed on the character portion, a character line disappears. For example, when a reduced image having a size of 1 / n is created, a thumbnail image is created using an average color of n × n pixel areas as a representative color. As a result, it is possible to eliminate the problem that the character lines disappear when the image is reduced.

As another reduction method, for example, it is conceivable that one of the processes uses the darkest color as a representative color and the other uses the brightest color as a representative color. In this case, a thumbnail image is created using the darkest pixel value or the brightest pixel value in the n × n region as a representative color.
At this time, as described above, when selecting the darkest pixel in the character part, for example, in the case of a black character on a white background, on the contrary, in the case of a white character in black, a bright pixel is selected. Can be prevented from disappearing. The same effect can be obtained even if the character image is binarized and ORed. Further, the selection method for selecting the representative color may be switched by selecting whether the background is white or black according to the color of the non-specific region (background).
The background color can be determined by calculating an average color in the n × n region and comparing it with a predetermined threshold (th).
For example, if the pixel value of the average color is smaller than the threshold value (th), it is determined as a black background, otherwise it is determined as a white background.

  It should be noted that average colorization processing, thinning processing, processing with the darkest color as the representative color, and processing with the brightest color as the representative color may be combined according to the situation (characteristics of the non-specific area) as follows. it can. As a reduced image display method, a combined reduced image obtained by combining reduced images of a specific area and a non-specific area may be stored, or each reduced image may be stored separately and displayed on the display 17. You may synthesize and display it.

FIG. 5 is a diagram showing the image transition by the processing operation shown in FIG. 2, where the image Io is the original original color image, and the images If and Ib are the character part (specific area) and the other area (non-display area). The images separated into the specific region) and the images Ift and Ibt are reduced images reduced by different reduction methods. The image It is a composite image obtained by combining these two reduced images Ift and Ibt, and the composite image It is displayed or stored.
As described above, according to the first embodiment of the image processing apparatus of the present invention, the inputted input image is separated into the specific area and the non-specific area, and the specific area and the non-specific area are reduced to different reduction methods. This makes it possible to create an optimal reduced image.
Further, if two reduced images are combined into a file format capable of having a plurality of layers and saved as one file, it can be handled easily.

Next, a second embodiment of the image processing apparatus of the present invention will be described with reference to FIG.
FIG. 6 is a diagram showing operations executed by the image processing apparatus as the second embodiment.
In the image processing apparatus shown in FIG. 6, when creating a high-compression PDF in a document format creation unit (compression unit) that creates a high-compression PDF (high-compression portable document format) that is a kind of document format, Since the image is separated into non-specific areas, image reduction processing is simultaneously performed using the separated data.
In this case, when image data is input (S201), the image processing apparatus separates the input image into a character part (specific area) and other areas (non-specific areas) (S202). Such image data separation processing is executed in a document format creation processing unit for creating a high-compression PDF described later.
In this embodiment, the character format (specific region) separated by the document format creation processing unit and the other background region (non-specific region) are used to perform reduction processing using different reduction methods. (S203, S204).

As a reduction method in this case, as described above, for example, one is a thinning process for thinning and reducing the image data, and the other is an average colorization process using the average color of the pixel area as its representative color, and the character portion (specific area) Is subjected to average colorization processing, and a background image (non-specific region) is thinned out to create a thumbnail image. For example, one of the processing uses the darkest color as a representative color, and the other uses the lightest color as a representative color. Process to create a thumbnail image.
In addition, the character part (specific area) and the other background area (non-specific area) separated in the document format creation unit are compressed by the high compression PDF creation process described below (S205, S206).
The compressed image of the specific area and the compressed image of the non-specific area created as described above, and the reduced image of the specific area and the reduced image of the non-specific area are combined (S207), and the generated compressed image of the specific area and non-specific The compressed image of the area, the reduced image of the specific area, and the reduced image of the non-specific area are combined into a single file and stored as a plurality of layers (S208). At this time, the original image may be stored in the same file.

FIG. 7 is a diagram showing image transition by the processing operation shown in FIG.
An image Io is an input original color image, an image Ia is an image obtained by binarizing the original color image Io, and images If and Ib are character portions (specific areas) using the information of the binarized image Ia and others Images Ifc and Ibc are compressed images compressed by different compression methods, and Ift and Ibt are reduced images reduced by different reduction methods. As examples of different compression methods, for example, Jpeg2000 is used for the compressed image Ifc and Jpeg is used for the compressed image Ibc.
Although the image size of the image If and the compressed image Ifc shown in FIG. 7 seems to be different, the resolution (number of pixels) does not change because compression processing is performed here. Similarly, the resolution (number of pixels) of the image Ib and the compressed image Ibc does not change.
Further, the relationship between the resolution (number of pixels) between the compressed image Ifc and the reduced image Ift is larger in the compressed image Ifc than in the reduced image Ift. The relationship between the compressed image Ibc and the reduced image Ibt is the same. That is, the relationship of the resolution of each image with respect to the input image is input image ≧ compressed image> reduced image.

FIG. 8 is a diagram showing another example of image transition by the processing operation shown in FIG. It should be noted that the same image as in FIG.
FIG. 8 differs from FIG. 7 in that the image If is divided into _two different images If ₁ and If ₂ . In this case, as a compression method for the image If, in the case of a compression method for binary images, for example, the MRR method used in Fax or the like, a plurality of images If ₁ are used for each color of characters constituting the image If. , If ₂ is created and compressed. Also, the character color for each of the various compressed images If _1c and If _2c is also held. Note that the compression method of the compressed images If _1c and If _2c at this time may generally be the same.

As described above, in the second embodiment of the image processing apparatus of the present invention, the input image that has been input is separated into a specific area and a non-specific area, and the specific area and the non-specific area are compressed by different compression methods and input. A compressed image having the same resolution as that of the image or a reduced resolution is created, and a specific area and a non-specific area are reduced by different reduction methods to generate a reduced image having a resolution lower than that of the compressed image. . When two images having different resolutions, ie, a compressed image and a reduced image, are created in this way, various display modes can be realized.
For example, in document management software or the like, when displaying a list of a plurality of files as thumbnail images, it is possible to display a reduced image and to display a compressed image when confirming details of the contents.
Also, when displaying an image in an environment with a small communication band such as a cellular phone, it is possible to first display a reduced image and display a compressed image if the details of the content are to be confirmed.

Hereinafter, a method for creating a highly compressed PDF image will be described with reference to FIGS.
9 is a functional block diagram of a document format creation unit that creates a high-compression PDF, FIG. 10 is a diagram showing processing of the document format creation unit shown in FIG. 9, and FIG. 11 is a conceptual diagram of the processing shown in FIG. It is.
The document format creation unit shown in FIG. 9 includes a multi-valued image acquisition unit 21, a binary image acquisition unit 22, a specific attribute portion erased image generation unit 23, a specific attribute portion extraction unit 24, and a white pixel replacement unit 25 that constitute a separating unit. , A specific attribute portion color determination unit 26, a specific attribute pixel image generation unit 27, an image encoding unit 28 constituting a compression unit, and a summary file creation unit 29.
The document format creation unit configured as described above acquires a document image of an original image (multi-value) Io as shown in FIG. 11 using a multi-value image acquisition unit 21 such as an image scanner (S301). The multi-valued image acquired by the multi-valued image acquiring unit 21 is binarized by the binary image acquiring unit 22 to acquire a binary image Ia as shown in FIG. 11 (S302). Next, the position of a part having a specific attribute, for example, a character part is specified and extracted from the binary image by the specific attribute part extraction unit 24 (S303).

Here, the following description will be made on the assumption that a specific area is acquired from a binary image. However, it is of course possible to extract a character area from multiple values (including color).
A technique for directly acquiring from a multi-valued image is disclosed in Patent Document 2 and the like. A technique for generating a binary image from a multi-valued image and acquiring it from the binary image may be a character area extraction technique disclosed in, for example, Japanese Patent Laid-Open No. 6-20092.
Next, as shown in FIG. 11, the white pixel replacement unit 25 replaces white pixels other than the characters of the binary image Ia to form an image If that leaves only the characters (S304). Note that the position of the character can be known in units of pixels by such processing.

Next, the specific attribute portion erased image generation unit 23 creates an image Ib from which the specific attribute portion (character region) as shown in FIG. 11 is erased (S305). In the color image, an image in which the pixels in the character portion are replaced with surrounding colors may be created.
Next, the color of the specific attribute portion is determined by the specific attribute portion color determination unit 26 (S306). That is, all the pixel colors of the color image at the positions of the black pixels constituting the character are obtained, and several frequently used colors are selected from this data as representative colors. Then, it is determined for each pixel or for each connected component which representative color the pixel constituting the character is closest to.
Next, as shown in FIG. 11, the specific attribute pixel image generation unit 27 generates images If ₁ and If ₂ having colors determined for each pixel or each connected component, using pixels having specific attributes (S307). . Although the following description will be made assuming that one binary image is provided for each color, a multi-value image having only a limited color may be used, or one binary image may be provided for each color.

Next, the image encoding unit 28 generates a compressed image from an image in which the generated specific attribute pixel is deleted and an image including only the specific attribute pixel (S308). That is, the file size is effectively reduced when JPEG compression is performed in the former and MMR compression is performed in the latter.
Next, the summary file creation unit 29 synthesizes an image composed of only the specific attribute pixels with an image from which the specific attribute unit has been deleted in a form that can be displayed in an overlapping manner (S309). If these are superposed, characters are pasted on the background, and a highly compressed PDF that can be viewed in the same manner as the original image is obtained.
With the above processing, the document format creation unit that creates a high-compression PDF can create a high-compression PDF image that can greatly compress the file size of the multi-value document image without reducing the visibility of characters. .

  Further, in the present embodiment, the composite reduced image and the composite compressed image file created as described above are transmitted through communication means represented by the Internet, an image display device such as a display, a printer, etc. Of course, it is also possible to output to an external output device for printing.

1 is a configuration diagram of an embodiment of an image processing apparatus according to the present invention. 3 is an operation flowchart of the first embodiment of the image processing apparatus according to the present invention. The figure which showed the concept of reduction by a reduction method. The figure which showed an example of the area | region of an mxn pixel. The figure which showed the image transition by the processing operation of 1st Embodiment. The operation | movement flowchart of 2nd Embodiment of the image processing apparatus by this invention. The figure which showed the image transition by the processing operation of 2nd Embodiment. The figure which showed the other example of the image transition by the processing operation of 2nd Embodiment. The functional block diagram of embodiment of the image processing apparatus in the case of performing highly compressed PDF. 10 is an operation flowchart of the image processing apparatus illustrated in FIG. 9. FIG. 11 is a conceptual diagram of the operation process shown in FIG. 10.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Internal bus, 11 CPU, 12 Memory, 13 Hard disk, 14 Input device, 15 ROM drive, 16 Display 16 Recording medium 21 Multi-value image acquisition part, 22 Binary image acquisition part, 23 Specific attribute part deletion image generation part, 24 Specific attribute part extraction part, 25 White pixel replacement part, 26 Specific attribute part color determination part, 27 Specific attribute pixel image generation part, 28 Image encoding part, 29 Summary file creation part

Claims (10)

An image processing apparatus that performs predetermined processing on output image data and outputs the processed image data,
Separating means for separating the input image data into a specific area and a non-specific area;
Reduction means for reducing the specific area and the non-specific area separated by the separation means by different reduction methods;
An image processing apparatus comprising:   The image processing apparatus according to claim 1, further comprising: a composite display unit that combines and displays the reduced specific area and the non-specific area.   The image processing apparatus according to claim 1, wherein different reduction methods by the reduction unit are switched according to characteristics of the non-specific region.   4. The image processing apparatus according to claim 1, further comprising a compression unit configured to compress the separated specific area and the non-specific area using different compression methods. 5.   The image processing apparatus according to claim 2, wherein the composite display unit combines and displays the reduced image created by the reduction unit and the compressed image created by the compression unit. The separation unit includes a multi-value image acquisition unit that acquires a multi-value image that is a processing target image;
Binary image acquisition means for acquiring a binary image from the multi-value image acquired by the multi-value image acquisition means;
Specific attribute part extraction means for extracting a region having a specific attribute of the binary image;
White pixel replacement means for replacing a portion corresponding to a region that is not the specific attribute in the binary image with a white pixel;
Specific attribute portion erasure image generation means for generating an image in which pixels of the specific attribute portion of the multi-valued image are erased;
Specific attribute color determining means for determining a color constituting the specific attribute part;
Specific attribute pixel image generation means for generating the specific attribute binary image composed of the determined colors;
The image processing apparatus according to claim 1, further comprising:   7. The image processing apparatus according to claim 6, wherein the compression means compresses and encodes the specific attribute binary image including the non-characteristic multi-value image and each determined color by a different method. .   A storage unit configured to combine and save a reduced image of the specific area and the non-specific area created by the reduction unit and a compressed image of the specific area and the non-specific area created by the compression unit into a single file as a plurality of layers; The image processing apparatus according to claim 4, wherein:   The composite reduced image obtained by combining the reduced image of the specific area and the non-specific area created by the reduction means, and the composite compressed image obtained by combining the compressed image of the specific area and the non-specific area created by the compression means can be transmitted. The image processing apparatus according to claim 8.   The composite reduced image obtained by synthesizing the reduced image of the specific area and the non-specific area created by the reduction means, and the synthesized compressed image obtained by synthesizing the compressed image of the specific area and the non-specific area created by the compression means can be printed. The image processing apparatus according to claim 8.

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