JPH0522611A - Image coding system - Google Patents

Abstract

PURPOSE:To code the document image data having many line and blank spaces with high efficiency. CONSTITUTION:A full white line deciding means 101 inputs the original image data and outputs a line deciding signal 12 which decides a full white line or a line including a black picture element and the partial image data 13 excluding the full white lines. Then a two-dimensional coding means 103 codes the signal 12 and then the data 13 and transmits the original image coding data 14 to a decoding part to decode the data. The full white line is put into the decoded partial image data 16 and the original image data are decoded. In such a constitution, the number of lines to be coded is decreased and at the same time the coding efficiency of the image data is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image coding method for coding an image including many white lines appearing between lines and in upper and lower margins, such as a document created by a word processor or a typewriter. is there.

[0002]

2. Description of the Related Art In many conventional coding systems, the coding efficiency is improved by utilizing the correlation between pixels. Among them, 2 using correlation between lines
There are MR and MMR coding methods as dimensional coding methods.
In the MR / MMR encoding method, the change pixels on the encoding line are encoded with reference to the change pixels on the immediately preceding line (reference line). FIG. 4 shows the definition of the starting pixel and the change pixel used for encoding, and Table 1 shows the code allocation of the MR encoding method.

[Table 1] In the two-dimensional coding method such as the MR coding method, MH coding, which is a one-dimensional coding method, is performed for every certain line in order to prevent a coding error from propagating to subsequent lines. The MMR coding method aims to improve the coding efficiency by partially changing the MR coding method, and is basically the same as the MMR coding method. Describe.

The MR coding method is a method belonging to two-dimensional coding, and the change pixel a1 next to the starting point pixel a0 in FIG. 4 is coded with reference to the change pixel of the reference line.
The encoding procedure is shown below. Procedure 1 1 When b2 exists on the left side of a1, it is detected as a pass mode, and this mode is encoded using the code word “0001”. After that, the pixel immediately below b2 is set as a new starting pixel a0. If the 2-pass mode is not detected, proceed to step 2.

Procedure 2 1 The distance between a1 and b1 is measured. 2 If the distance between a1 and b1 is 3 or less, it is detected as the vertical mode, and the distance of a1b1 is encoded as shown in Table 1. After that, the pixel a1
Becomes the new starting pixel a0. 3 When the distance between a1 and b2 is larger than 3, it is detected as the horizontal mode, and as shown in Table 1, the code “001” is followed by a0a1 and a1.
Each a2 is encoded by one-dimensional encoding. After that, the pixel a2 becomes the starting point pixel a0.

In the decoding of the MR coding method, the coded data is decoded according to the code word allocation in Table 1, and the position of the changed pixel of the decoded line with respect to the changed pixel of the reference line (previous line) is measured. Done.

[0006]

In the conventional MR and MMR encoding method, an image in which a lot of white lines appear between lines or in the upper and lower margins, such as a document created by a word processor or a typewriter, is used. If you are encoding without paying attention to such characteristics, and the reference line is all white,
Since almost all the change points are coded in the horizontal mode in which long code words are assigned, there is a problem that the coding efficiency of the coding line using the all-white line as a reference line decreases. .

The present invention is an image coding system made to solve the above problems, and an object thereof is to improve the coding efficiency.

[0008]

The image coding system according to the first aspect of the present invention determines an all-white line or a line including a black pixel in binary image data and generates a line determination signal. A means for generating partial image data excluding all white lines from an original image, a frame memory for accumulating partial image data, a code for sequentially encoding the line determination signal and partial image data, and a code for transmitting them A decoding unit that decodes the received encoded data in the order of the line determination signal and the partial image data, the line determination storage memory that stores the decoded line determination signal, and the decoded partial image data And a decoding unit for obtaining original image data by using means for inserting an all-white line based on the line determination signal.

The image coding system according to the second invention is included in the two-dimensional coding system in which the line determination signal is used for coding / decoding partial image data in addition to the configuration of the first invention. Encoding / decoding is performed by a one-dimensional encoding method.

[0010]

According to the first aspect of the present invention, the determination signal is generated by determining whether all the lines of the image data are all white lines or lines including black pixels, and After reducing the number of lines to be encoded by removing all white lines and generating partial image data, encode the partial image data and the judgment signal and send them to the decoding unit in the order of the partial image data and the judgment signal. Decode, insert an all-white line between each partial image data according to the line determination signal,
Get the original image data.

According to the second aspect of the invention, the line determination signal is MH (Modified Huffman) encoding supported by the MR encoding method which is one of the two-dimensional encoding methods of partial image data. The method is applied to perform one-dimensional encoding.

[0012]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an encoding unit in this encoding method. In FIG. 1, reference numeral 101 is an input of the original image data 11, and an all-white line determination means for generating a line determination signal and partial image data obtained by removing all white lines from the original image. Reference numeral 102 is a frame memory for storing the partial image data. , 103 are encoding means for sequentially encoding the line determination signal generated by the all-white line determination means 101 and the partial image data accumulated in the frame memory 102.

FIG. 2 is a block diagram showing a decoding unit in the present encoding system. Reference numeral 201 is a decoding means for decoding the received original image encoded data, 202 is a line determination signal storage memory for storing the decoded line determination signal, 203
Is an all-white line synthesizing means for inserting all-white lines into the decoded partial image data based on the line determination signal.

FIG. 3A shows an example of MR coding for the coded line when the reference line includes black pixels and FIG. 3B is for the coded line when the reference line is all white. FIG. 3A shows a vertical mode, in which the subscripts R and L of V indicate whether a ₁ is on the right side or the left side of b ₁ , and the numbers in parentheses indicate the distance. The values of a ₁ and b ₁ are shown.

Note that a ₁ indicates the first change pixel on the coding line to the right of a ₀ (reference or starting point change pixel on the coding line). Further, b ₁ denotes a first change pixel on the reference line having a color opposite to that of a ₀ in the right of a _0.

Further, FIG. 3B shows a horizontal mode, where H is a flag code "000" in the two-dimensional code table.
1 ”. H (a ₀ , a ₁ ) and H (a ₁ , a ₂ ) are codes indicating the length of each line a ₀ , a ₁ and a ₁ , a ₁ indicating“ color ”. CCITT Bull Book VII-F
ASCIILE VII. 3 Terminal devices and protocols for telematic services (Recommendations T.0 to T.63)
Medium Recommendation T. 4 See P18-31) (Foundation Japan I
TU Association, issued September 20, 1990)

The encoding unit in this encoding method will be described with reference to FIG. The all-white line determination means 101 having the input as the original image data 11 outputs a line determination signal 12 which determines whether all the lines of pixels are all-white lines or lines including black pixels, and , The partial image data 13 formed of lines including black pixels excluding all-white lines is accumulated in the frame memory 102.

Subsequently, the line determination signal 12 and the partial image data 13 stored in the frame memory 102 are sequentially input to the encoding means 103 for encoding. However, the encoding of the line determination signal is one-dimensional encoding,
For this, for example, the modified Huffman (hereinafter abbreviated as MH) coding is applied by regarding an all-white line as white and a line including even one pixel as black. Since the MH coding system is a one-dimensional coding system supported by the MR coding system,
It depends on the fact that it can be easily made into a device.

The data obtained by encoding the line determination signal and the data obtained by encoding the partial image data are combined to form original image encoded data 14. At this time, the line determination signal and the partial image data 14 are used. At this time, the total number of lines is transmitted in advance by, for example, 32-bit constant length header information or the like so that the receiving side can recognize the break between the line determination signal and the partial image data, or the EOL signal is added to the end of the line determination signal. Shall be inserted. As described above, it is possible to reduce the number of encoded lines by first encoding whether all the lines of the image data are all-white lines and excluding the all-white lines from the image data.

Further, since the positions of the characters in the document created by a word processor or typewriter are aligned in the vertical direction, there is a correlation in the distribution of black pixels between the lines sandwiching the all-white line and the reference line. It is possible to reduce the number of change pixels to be coded in the horizontal mode and improve the coding efficiency by coding with the line including the black pixel as the reference line, rather than coding with all white lines. You can

Next, the decoding unit in the present encoding system will be described with reference to FIG. First, the decoding unit 201 decodes the line determination signal of the received original image encoded data 14 into M
Decoding is performed based on the H encoding method. At this time, when the number of lines transmitted immediately before in the header information is reached,
Alternatively, decoding of the line determination signal is completed upon detection of the EOL signal.

The decoded line determination signal 15 is stored in the line determination signal storage memory 202, and the partial image data 16 subsequently decoded by 201 is input to the all-white line synthesizing means 203. In the all-white line synthesizing means 203, the line determination signal 15 is applied to the decoded partial image data 16.
All white lines are inserted based on, and restored to the original image data 17.

Although the MR coding method is used as the coding method in the above description, the same effect can be obtained by using the MMR coding method or another two-dimensional coding method.

[0024]

As described above, according to the first aspect of the present invention, it is determined whether all the lines of the image are all white lines or lines including black pixels, and all lines are excluded. Since it suffices to encode the image, the number of lines to be encoded can be reduced, and the code of the line in which the preceding line is all white can be shortened, so that the encoding efficiency of the image data can be improved.

According to the second aspect of the invention, the line determination signal is encoded / decoded by the one-dimensional encoding method included in the two-dimensional encoding method used for encoding / decoding the partial image data. In particular, the line determination signal can be easily encoded / decoded without using a specific encoding / decoding device.

[Brief description of drawings]

FIG. 1 is a block diagram showing an encoding unit in an encoding method.

FIG. 2 is a block diagram showing a decoding unit in the encoding system.

FIG. 3 is an array diagram of pixels showing an MR encoding example in the case a including a black pixel and in the case b in which the reference line is all white.

FIG. 4 is an array diagram of pixels showing a starting pixel and a change pixel used for encoding.

[Explanation of symbols]

11 Original image data 12 line judgment signal 13 partial image data 14 Original image coded data 15 Decoded line decision signal 16 Decoded partial image data 17 Decoded original image data 101 all white line determination means 102 frame memory 103 encoding means 201 Decoding means 202 line judgment signal memory 203 All-white line synthesizing means

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[Procedure amendment]

[Submission date] October 9, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title of image coding method

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image coding method for coding an image including many white lines appearing between lines and in upper and lower margins, such as a document created by a word processor or a typewriter. is there.

[0002]

2. Description of the Related Art In many conventional coding systems, the coding efficiency is improved by utilizing the correlation between pixels. Among them, 2 using correlation between lines
There are MR and MMR coding methods as dimensional coding methods.
In the MR / MMR encoding method, the change pixels on the encoding line are encoded with reference to the change pixels on the immediately preceding line (reference line). FIG. 4 shows the definition of the starting pixel and the change pixel used for encoding, and Table 1 shows the code allocation of the MR encoding method.

[0003]

[Table 1]

In the two-dimensional coding method such as the MR coding method, the MH coding, which is a one-dimensional coding method, is performed for every certain line in order to prevent a coding error from propagating to subsequent lines. . The MMR coding method aims to improve the coding efficiency by partially changing the MR coding method, and is basically the same as the MMR coding method. Describe.

The MR encoding system belongs to the two-dimensional encoding system, and the change pixel on the reference line is used as a reference to encode the change pixel a1 next to the starting pixel a0 in FIG.
The encoding procedure is shown below. Step 11 b2 on the left side of a1
Is detected as a pass mode, and this mode is encoded using the codeword “0001”. After this, b
The pixel directly under 2 is set as a new starting pixel a0. If the 2-pass mode is not detected, proceed to step 2.

Procedure 21: Measure the distance between a1 and b1.
2 If the distance between a1 and b1 is 3 or less, it is detected as the vertical mode, and the distance of a1b1 is encoded as shown in Table 1. After that, the pixel a1 becomes the new starting pixel a0. Three
When the distance between a1 and b2 is greater than 3, the horizontal mode is detected, and as shown in Table 1, the code "001" is followed by a0a1 and a1a2, which are each coded by one-dimensional coding. After that, the pixel a2 becomes the starting point pixel a0.

The decoding of the MR coding method is performed by decoding the coded data according to the code word assignment of Table 1 and measuring the position of the changed pixel of the decoded line with respect to the changed pixel of the reference line (previous line). Done.

[0008]

In the conventional MR and MMR encoding method, an image in which a lot of white lines appear between lines or in the upper and lower margins, such as a document created by a word processor or a typewriter, is used. If you are encoding without paying attention to such characteristics, and the reference line is all white,
Since almost all the change points are coded in the horizontal mode in which long code words are assigned, there is a problem that the coding efficiency of the coding line using the all-white line as a reference line decreases. .

The present invention is an image coding system made to solve the above problems, and an object thereof is to improve the coding efficiency.

[0010]

Means for Solving the Problems The image encoding method according to the first invention, the binary image data, all white line
Or it is, or to determine whether a line containing black pixels,
A unit for generating a line determination signal and generating partial image data by removing all white lines from the original image, a frame memory for accumulating the partial image data, the line determination signal and the partial image data are sequentially coded. And a decoding unit that decodes the received encoded data in the order of the line determination signal and the partial image data,
A line determination storage memory that stores the decoded line determination signal, and a decoding unit that obtains original image data by using means for inserting an all-white line into the decoded partial image data based on the decoded line determination signal, Is provided.

Further, the image coding method according to the second invention, without changing the configuration of the first invention, the line determination signal, the two-dimensional coding to be used for encoding and decoding of the partial image data The encoding / decoding is performed by the one-dimensional encoding method included in the method.

[0012]

[Action] The first invention is either all white lines for all lines of the image data, or whether to generate a line-size constant signal to determine a line including the black pixels, the image after reducing the number of lines to be encoded by generating a partial image data by removing the all-white line from the data, a line determination signal and the part of image data is encoded, decrypt
Transmission line-determination signal to the part, part of image data, decoded in the order of decision signals, and insert the all-white line according the line determination signal during each partial image data to obtain original image data.

According to the second aspect of the invention, the line determination signal is MH (Modified Huffman) encoding supported by the MR encoding method which is one of the two-dimensional encoding methods of the partial image data. The method is applied to perform one-dimensional encoding.

[0014]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an encoding unit in this encoding method. In FIG. 1, reference numeral 101 is an input of the original image data 11, and an all-white line determination means for generating a line determination signal and partial image data obtained by removing all white lines from the original image. Reference numeral 102 is a frame memory for storing the partial image data. , 103 are encoding means for sequentially encoding the line determination signal generated by the all-white line determination means 101 and the partial image data accumulated in the frame memory 102.

FIG. 2 is a block diagram showing a decoding unit in the present encoding system. Reference numeral 201 is a decoding means for decoding the received original image encoded data, 202 is a line determination signal storage memory for storing the decoded line determination signal, 203
Is an all-white line synthesizing means for inserting all-white lines into the decoded partial image data based on the line determination signal.

FIG. 3A shows an example of MR coding for the coded line when the reference line includes black pixels and FIG. 3B is for the coded line when the reference line is all white. Subscripts R and L of the vertical <br/> Oite the mode, V in FIG. 3 (a), indicates whether a left or a ₁ is a right b ₁ respectively, the numbers in parentheses distance The values of a ₁ and b ₁ are shown.

Note that a ₁ indicates the first change pixel on the coding line to the right of a ₀ (reference or starting point change pixel on the coding line). Further, b ₁ denotes a first change pixel on the reference line having a color opposite to that of a ₀ in the right of a _0.

Furthermore, in the horizontal mode of FIG.
(A ₀ a ₁ , a ₁ a ₂ ) is H + M (a ₀ a ₁ ) + M (a
₁ a ₂ ) is meant. H is the flag code "001", M
(A ₀ a ₁ ) and M (a ₁ a ₂ ) are each run a ₀ a ₁ , a
It is a code indicating the length and color of ₁ a ₂ . (See CCITT Bull Book VII-FASCICLE VII.3 Terminal Devices and Protocols for Telematic Services (Recommendations T.0 to T.63) Recommendations T.4 P18 to 31) (Japan ITU Association Heisei 2) (Published September 20, 2012)

An encoding unit in this encoding method will be described with reference to FIG. The all-white line determination means 101 having the input as the original image data 11 outputs a line determination signal 12 which determines whether all the lines of pixels are all-white lines or lines including black pixels, and , The partial image data 13 formed of lines including black pixels excluding all-white lines is accumulated in the frame memory 102.

Subsequently, the line determination signal 12 and the partial image data 13 stored in the frame memory 102 are sequentially input to the encoding means 103 for encoding. However, the encoding of the line determination signal is one-dimensional encoding,
For this, for example, the modified Huffman (hereinafter abbreviated as MH) coding is applied by regarding an all-white line as white and a line including even one pixel as black. Since the MH coding system is a one-dimensional coding system supported by the MR coding system,
It depends on the fact that it can be easily made into a device.

The data obtained by encoding the line determination signal and the data obtained by encoding the partial image data are combined to form original image encoded data 14. At this time, the line determination signal and the partial image data 14 are used. At this time, the total number of lines is transmitted in advance by, for example, 32-bit constant length header information or the like so that the receiving side can recognize the break between the line determination signal and the partial image data, or the EOL signal is added to the end of the line determination signal. Shall be inserted. As described above, it is possible to reduce the number of encoded lines by first encoding whether all the lines of the image data are all-white lines and excluding the all-white lines from the image data.

Further, since the positions of the characters in the document created by a word processor or typewriter are aligned in the vertical direction, the black pixel distribution between the lines sandwiching the all-white line has a correlation, and the reference line It is possible to reduce the number of change pixels to be coded in the horizontal mode and improve the coding efficiency by coding with the line including the black pixel as the reference line, rather than coding with all white lines. You can

Next, the decoding unit in this encoding system will be described with reference to FIG. First, the decoding unit 201 decodes the line determination signal of the received original image encoded data 14 into M
Decoding is performed based on the H encoding method. At this time, when the number of lines transmitted immediately before in the header information is reached,
Alternatively, decoding of the line determination signal is completed upon detection of the EOL signal.

The decoded line determination signal 15 is stored in the line determination signal storage memory 202, and the partial image data 16 subsequently decoded by 201 is input to the all-white line synthesizing means 203. In the all-white line synthesizing means 203, the line determination signal 15 is applied to the decoded partial image data 16.
All white lines are inserted based on, and restored to the original image data 17.

Although the MR coding method is used as the coding method in the above description, the same effect can be obtained by using the MMR coding method or another two-dimensional coding method.

[0026]

As described above, according to the first aspect of the present invention, it is determined whether all the lines of the image are all white lines or lines including black pixels, and all lines are excluded. Since it suffices to encode the image, the number of lines to be encoded can be reduced, and the code of the line in which the preceding line is all white can be shortened, so that the encoding efficiency of the image data can be improved.

According to the second aspect of the invention, the line determination signal is encoded / decoded by the one-dimensional encoding method included in the two-dimensional encoding method used for encoding / decoding the partial image data. In particular, the line determination signal can be easily encoded / decoded without using a specific encoding / decoding device.

[Brief description of drawings]

FIG. 1 is a block diagram showing an encoding unit in an encoding method.

FIG. 2 is a block diagram showing a decoding unit in the encoding system.

FIG. 3 is an array diagram of pixels showing an MR encoding example in the case a including a black pixel and in the case b in which the reference line is all white.

FIG. 4 is an array diagram of pixels showing a starting pixel and a change pixel used for encoding.

[Description of Codes] 11 original image data 12 line determination signal 13 partial image data 14 original image encoded data 15 decoded line determination signal 16 decoded partial image data 17 decoded original image data 101 all-white line determination means 102 frame memory 103 encoding means 201 decoding means 202 line determination signal memory 203 all-white line synthesizing means a ₀ starting point pixel a ₁ first change pixel a ₂ on the right of a ₀ on the encoding line a on the encoding line a ₂ opposite color of a pixel is the first change pixel b ₁ reference b ₁ a ₀ on the right than on the opposite color of the pixel b ₂ reference line serving as a ₀ from the right a ₀ on line in from ₁ to the right

[Procedure Amendment 2]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (2)

[Claims] 1. An all white line in binary image data,
Alternatively, a line that includes a black pixel is determined, a line determination signal is generated, and partial image data that is obtained by removing all white lines from the original image is generated; a frame memory that stores the partial image data; The line determination signal and the partial image data are sequentially encoded, an encoding unit that transmits them, a decoding unit that decodes the received encoded data in the order of the line determination signal and the partial image data, and the decoded line determination signal A line determination storage memory for storing, and a decoding unit for obtaining original image data by using means for inserting an all-white line based on the decoded line determination signal into the decoded partial image data. Image coding method. 2. The image coding method according to claim 1, wherein the line determination signal is coded / decoded by a one-dimensional coding method included in a two-dimensional coding method used for coding / decoding partial image data. An image coding method characterized by the above.