KR100237851B1 - Image/text data processing method and device - Google Patents

Abstract

The disclosed image / text area data detecting method and the compression apparatus detect data of the image area and data of the text area when the data of the text area and the data of the image area coexist, and the data of the image area is lost according to the detection result. Algorithm compression, textual data is compressed using a lossless algorithm.

According to the present invention, data of a predetermined document sequentially scanned while being divided into a unit area having a predetermined number of pixels in the horizontal direction and the vertical direction is converted into gray scale data by a gray scale conversion unit, and converted into gray scale data values. The image / text data detector determines whether the data of the image area or the data of the text area, and according to the determination result, the data of the image area is compressed by the lossy algorithm in the lossy compression unit, and the data of the text area is the lossless algorithm in the lossless compression unit. By compressing the data in the image region, the data of the image region can be compressed at a high compression rate, and the data of the text region can be compressed without loss.

Description

Method for detecting image / text area data of document and compression device

The present invention provides an image / text of a document which detects data of an image region and data of a text region from data of one document, and efficiently compresses according to the detected data of the image region and data of a text region. A method for detecting area data and a compression apparatus.

In general, when transmitting or storing a predetermined document, if the data of the predetermined document is transmitted and stored as it is, the capacity of the data is very large, which requires a lot of transmission time, and requires a lot of storage capacity.

Therefore, the data of the predetermined document is compressed, transmitted and stored, and the compressed predetermined data is restored to the original data by using a predetermined restoration algorithm.

The compression of data is compressed using different compression algorithms depending on the type of data to be compressed.

For example, data is compressed by different compression algorithms according to data of a text area such as predetermined symbols and characters and data of an image area such as a picture and a picture.

Compression algorithms for compressing data include lossy algorithms such as Joint Photographic Experts Group (JPEG) and lossless algorithms such as Joint Bi-level Image Expert Group (JBIG).

The loss algorithm is used for compressing data in an image region, but it is generally used to compress data in an image region.

The lossless algorithm is capable of compressing and restoring data without losing data. However, since the compression rate is low for data in an image area, the lossless algorithm is used to compress data in a text area such as a document including predetermined characters and symbols.

Data of the text area is also applicable only to gray scale data having two levels (bi-level), which is very difficult to apply to data of color documents.

In general, a predetermined document is a mixture of text areas such as predetermined characters and symbols and image areas such as photographs and pictures.

If the above loss algorithm is used to compress the data of a document in which the text area and the image area are mixed, the data of the text area may be lost and the data of the original text area may not be restored. When compressing with a lossless algorithm, there is a problem that the data capacity becomes large due to the low compression rate of the data in the image region.

Accordingly, an object of the present invention is to provide a method for detecting image / text area data of a document for detecting data of an image area and data of a text area from data of a document.

Another object of the present invention is to provide an image / text area data compression device of a document which compresses data of the detected image area by a lossy algorithm and compresses data of the text area by a lossless algorithm.

1 is a view illustrating a process of scanning a predetermined document according to the present invention;

2 is a block diagram showing the configuration of a compression device of the present invention;

3 is a signal flow diagram illustrating an operation of determining data of an image area and data of a text area according to a detection method of the present invention;

4 is a diagram illustrating a procedure of determining a value by inputting a pixel of a unit area to an image / text data detector.

* Explanation of symbols for main parts of the drawings

10: gray scale conversion unit 20: image / text data detection unit

30: lossy compression unit 40: lossless compression unit

According to the method and the compression apparatus for image / text area data detection of a document of the present invention for achieving the above object, the color data scanned by dividing a predetermined document into a unit area is converted into gray scale data by a gray scale converter.

The number of colors is determined by determining the value of each gray scale data converted by the gray scale converter, and it is determined whether the data of the image area or the data area is the data by the determined number of colors.

When the type of data is determined, the data of the determined image region is compressed by the lossy algorithm by the lossy compression unit, and the data of the text region is compressed by the lossless algorithm by the lossless compressor.

Therefore, according to the present invention, the data of the image region can be compressed with a lossy algorithm and compressed at a high compression rate, and the data of the text region can be compressed without loss by compressing with a lossless algorithm.

Hereinafter, an image and text area data detection method and a compression apparatus of a document of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating an image scanning process of a general document.

As shown in the drawing, when a document is converted into data by scanning with a scanner or the like, scanning is performed while moving from the left to the right of the document, and also while moving from the top to the bottom.

In the present invention, the scanning is divided into unit areas having pixels of a predetermined size.

For example, the scanning is partitioned into unit areas having 8 x 8 pixels.

2 is a block diagram showing the configuration of the compression apparatus of the present invention.

As shown, the gray scale converter 10 converts the input data into gray scale data by dividing and scanning a predetermined document into a unit area having predetermined pixels, and the gray scale converter 10 outputs the gray scale data. An image / text data detector 20 detecting whether the unit region is data of the image region or data of the text region using the pixel value of the unit region, and the image / text data detector 20 detects the data of the image region. In this case, the lossy compression unit 30 compressing the input color data according to a loss algorithm, and the lossy algorithm of the input color data when the image / text data detector 20 detects data in a text area. It consists of a lossless compression unit 40 to compress according to.

In the compression apparatus of the present invention configured as described above, color data scanned by dividing a predetermined document into a unit area having predetermined pixels is scanned by a gray scale converter 10, a lossy compression unit 30, and a lossless compression unit 40. Is entered.

The gray scale converter 10 converts the input color data into gray scale data and outputs the gray color data.

In general, the NTSC color video signal satisfies Equation 1 to implement accurate colors.

[Equation 1]

Luminance signal = 0.30 × R + 0.59 × G + 0.11 × B

Where R is the red signal,

G is the green signal,

B is a blue signal.

However, when the color data is converted into the gray scale data in accordance with Equation 1, the circuit configuration becomes very complicated.

In the present invention, it is not necessary to implement accurate colors, and only the number of colors of pixels constituting the unit area needs to be determined.

Therefore, in the present invention, the number of colors is determined by converting the color data into the gray scale data so as to satisfy the equation (2), and the circuit configuration of the gray scale converter 10 is simplified.

[Equation 2]

Luminance signal = R + G + B

The gray scale data output from the gray scale converter 10 is input to the image / text data detector 20, and the image / text data detector 20 converts the number of colors into values of the respective gray scale data. It is determined whether the data of the image area or the data area is data based on the determined number of colors.

That is, the image / text data detector 20 determines values of 64 pixels constituting the unit area, counts types of pixels having different determination results, and determines the type of data based on the counted values.

In general, in the case of a text document, the number of colors of a unit area having 8 × 8 pixels is two or less.

However, in case of image data such as photograph, it has continuous-tone due to the characteristics of the image, and it may have the same color to the human eye. .

Therefore, in the present invention, data of the text area and data of the image area are distinguished by the number of colors of the 64 pixels constituting the unit area.

The image / text data detector 20 outputs a predetermined control signal according to a result of determining the data of the text area and the data of the image area by the number of colors, and according to the output control signal, the lossy compression unit 30 and lossless compression The unit 40 selectively operates to compress the input color data.

For example, when the image / text data detector 20 determines the data of the unit area as the data of the image area, the loss compression unit 30 operates according to a control signal output from the image / text data detector 20. The compressed color data is compressed according to a loss algorithm.

When the image / text data detector 20 determines the data of the unit area as the data of the text area, the lossless compression unit 40 is operated according to the control signal output from the image / text data detector 20. The resulting color data is compressed according to a lossless algorithm.

3 is a signal flowchart illustrating an operation of determining, by the image / text data detector 20, data of an image region and a text region according to the detection method of the present invention.

As shown therein, the image / text data detector 20 initializes the value of the pixel variable i to '0' in step S1 and resets the value of the count variable CNT to '0' in step S2. After initialization to step S3, one pixel is input.

For example, as illustrated in FIG. 4, pixels in the unit area are sequentially input one by one.

In the next step S4, it is determined whether the value of the currently input pixel is the same by comparing the value of the previously input pixel.

If there is no pixel having the same pixel value as a result of the comparison, in step S5, '1' is added to the value of the count variable CNT, and in step S6, the value of the count variable CNT is set in advance (N). ) To determine if it is abnormal.

If the value of the count variable CNT is not equal to or greater than the preset value N in step S6, 1 is added to the pixel variable i in step S7, and the pixel variable i in step S8. ) Is a value of '64'.

When the value of the pixel variable i is not 64 in the step S8, the process returns to the step S3, inputs one pixel, and continuously repeats the operation of determining the value of the input pixel.

If the pixel value is the same as the result of the comparison in the step S4, 1 is added to the pixel variable i in the step S7, and the value of the pixel variable i is 64 in the step S8. When the value of the pixel variable i is not '64', the process returns to step S3 to input one pixel, and the operation of determining the value of the input pixel is repeated.

In this state, if the value of the count variable CNT is greater than or equal to the preset value N in step S6, the color is determined as the image data in step S9, and the loss compression unit 30 is operated. The data is compressed according to the loss algorithm.

If the value of the count variable CNT does not become equal to or greater than the preset value N until the value of the pixel variable i becomes '64' in step S8, the process determines the text data in step S10. The lossless compression unit 40 is operated to compress the input color data according to a lossless algorithm.

In the above description, the unit area having 8 × 8 pixels has been described as an example.

In the present invention, the present invention is not limited thereto, and the size of the unit region may be arbitrarily changed.

The number of colors separating the data of the text area and the data of the image area is preferably set to 2. However, since a slight error may occur when determining the pixel value, the color is set to be slightly larger than 2.

As described above, according to the present invention, the number of colors may be determined by dividing the data of a predetermined document into unit areas, and the type of data may be accurately determined by determining the data of the text area and the data of the image area based on the determined number of colors. .

In addition, since the present invention compresses by a lossy algorithm or a lossless algorithm according to the type of the determined data, the data of the image region can be compressed at a high compression rate, and the data of the text region can be compressed without loss.

Claims (3)

A first step of converting color data input into a unit area having a predetermined pixel into gray scale data; A second step of inputting gray scale data converted by performing the first step by one pixel, and determining the number of colors based on the input gray scale data; A third step of repeating, based on a unit area, a determination as to whether the number of colors determined by the second process is equal to a value of a pixel previously input; A fourth step of counting an area in which the number of colors determined by the execution of the second step is different from a value of a previously input pixel; A fifth step of determining as image data when the count value is greater than or equal to a preset value by performing the fourth step; And A sixth process of determining as text data when the value counted by the execution of the fourth process is equal to or less than a preset count value; And image / text area data detection method of a document. A gray scale conversion unit converting color data input to a unit area of a predetermined pixel into gray scale data based on Equation 2; An image / text data detection unit receiving gray scale data of a unit area converted by the gray scale converter and detecting data of an image area or data of a text area based on the number of colors represented by the gray scale data; A loss compression unit for compressing the number of colors according to a flow of a loss algorithm when the image / text data detector determines the number of colors as data of an image area and detects the result as data of an image area; And A lossless compression unit configured to compress the number of colors according to a flow of a lossless algorithm when the image / text data detector determines the number of colors as data of a text area and detects the result as data of a text area; And image / text area data compression device of a document. [Equation 2] Luminance signal = R + G + B The apparatus of claim 2, wherein the image / text data detector; The pixel value is determined based on the number of colors represented by the gray scale data, the pixel value of the image area or the text area of the image area is determined using a count value of a different pixel by comparing the pixel value of the pixel with the predetermined pixel value. And image / text area data compression device of said document.

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