JP3080937B2 - JBIG encoding method and recording medium recording JBIG program - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an encoding method based on JBIG.

[0002]

2. Description of the Related Art ITU-T recommendation T. JBI by 85
G (Joint Bi-level Image Gro)
Up), an example of the conventional data encoding method is disclosed in
149264.

As shown in FIG. 9, this apparatus has a CPU for performing arithmetic processing, data processing, control processing for each unit, and the like.
(Central processing unit) 100; an image data memory 400 for storing binary image data of an original read at the time of transmission; an encoding program 201 by JBIG and converting the image data into encoded data; A ROM 200 in which a probability estimation table memory 202 for converting to data is stored, a learning table memory 300 which is referred to in order to predict whether an encoding target image is white or black and to increase a hit probability, and The FIFO memory 500 that manages the resulting code data in a FIFO (first in first out) manner is connected to a bus 60.
0 are connected to each other.

[0004] The CPU 100 has a register 101 for holding image data read out in blocks from the line to be coded, and a register 102 for holding image data read out in blocks from the line immediately before the line to be coded. A register 103 for holding image data read out in blocks from a line two lines before the line to be coded, a register 104 for holding the address of a pixel to be coded in the line to be coded, A register 105 for holding the address of the pixel immediately above the pixel to be coded on the previous line, a register 106 for holding the address of a pixel immediately above the pixel to be coded on the line immediately before the line to be coded, and a context Has a register 107 for holding the contents.

[0005] The CPU 100 executes an encoding program 201 based on JBIG described later to
Implement a data encoding method.

Next, the overall operation will be described with reference to FIG.

At step 721, it is determined whether or not to make a typical prediction.
In step 6 , one-line encoding processing is performed. Next, step 710
It is determined whether or not the processing for the number of original lines has been completed, and if not completed, the process returns to step 721 to repeat the encoding processing.

When it is determined whether or not the typical prediction is performed (step 721), when the typical prediction is performed, the line to be encoded is compared with the line immediately before the line to be encoded in step 707. , Step 708 determines whether the two lines are the same. If the result of this determination is not the same, one-line encoding processing (step 709)
And if they are the same, the encoding target line is not set as the encoding target.

Next, as in the case where typical prediction is not performed in step 710, it is determined whether or not the processing for the number of original lines has been completed. If not completed, the process returns to step 721.
The encoding process is repeated. The encoding process is performed by repeating the above process for the number of original lines.

Next, the encoding process for one line will be described with reference to FIG.

First, in step 802, image data in block units is created for the line immediately before the line to be encoded.

Here, details of the image data creation processing will be described with reference to FIG.

First, in step 811, an address for reading image data is set, and in step 812, image data is read from the set address. Further, since the data before the pixel to be encoded is necessary due to the structure of the context, the read image data is shifted in step 813 and combined with the remaining image data of the previous block processing in step 814 to form a block. Create image data of

Next, in step 803, the image data creation processing is performed for the line immediately before the line to be encoded, and image data is created in block units. further,
In step 804, the image data creation processing is performed on the encoding target line to create image data in block units. Next, in step 752, it is determined whether or not the three created image data blocks are all white. If the result of the determination is all white, the one-pixel encoding process is repeated in step 757 until the block process ends in step 758.

If the result of the determination is other than all white,
Until the block processing is completed in step 755, in step 753, a context is created in which the peripheral pixels of the encoding target pixel are converted into one dimension. In step 754, one-pixel encoding processing is performed. Each of the image data is shifted by one bit, and the creation of the next peripheral pixel is repeated.

When the processing for each block is completed,
Returning to the beginning of the one-line encoding process, in step 801, 1
It is determined whether or not the encoding process for the line has been completed. The encoding process is performed by repeating the above process for the number of original lines.

[0017]

However, this conventional technique has a problem that the encoding processing speed is slow when typical prediction which is an option of JBIG is not performed.

The first reason is that the process of creating an image data block for creating a context is frequently performed on a block-by-block basis with respect to three lines, ie, the line to be encoded, the previous line, and the previous line. This is because it is performed.

Further, data before the pixel to be coded is required due to the structure of the context. After loading the image data of the pixel to be coded, the image data block is created by combining the data with the previous data. Therefore, the next image data from the encoding target pixel cannot be loaded into the entire register width, and the image data is loaded with a width smaller than the register width.
This is because the number of data loads has increased.

An object of the present invention is to achieve a high encoding processing speed,
An object of the present invention is to provide an encoding method using JBIG.

[0021]

According to the present invention, when typical prediction is not performed, it is searched whether or not the image data of the line to be coded is all white, and the image data from the line to be coded to (n-1) lines before is searched. Based on the search results for n lines (n is an integer of 3 or more), n lines are all white or 1 to (n-1)
It is determined whether the line is all white or there is no all white line. If the n lines are all white, the processing for creating image data for n lines and the block determination processing are not performed and the 1 to (n−1) lines Is characterized by not creating image data for an all-white line.

It is searched whether the image data of one line is all white, and based on the search results for n lines, the n lines are all white, the 1 to (n-1) lines are all white, or all white. It is determined whether there is a line or not, and the process branches to each dedicated process. If the n lines are all white, the process is reduced by not performing the process of creating image data for n lines and the block determination process. When the lines 1 to (n-1) are all white, the processing is reduced by not performing the image data creation processing on the all white lines.

Conventionally, image data could not be loaded to the entire register width due to the structure of the context. However, by loading the entire register width at the time of one-line all-white search, the number of times of loading image data is reduced.

Accordingly, the encoding speed is improved particularly for an image with a tendency to white-eye, such as an image having many all-line white lines, that is, a document image often handled by facsimile.

[0025]

Next, embodiments of the present invention will be described with reference to the drawings.

Referring to FIG. 1, a first embodiment of the present invention includes a CPU (Central Processing Unit) 100 for performing arithmetic processing, data processing, control processing for each unit, and the like, and a document read at the time of transmission. An image data memory 400 for storing value image data, a ROM 200 storing an encoding program 201A by JBIG and a probability estimation table 202 for converting image data into code data or converting code data into image data; A learning table memory 300 referred to in order to predict whether the image to be encoded is white or black and to increase the probability of hitting the image, and a FIFO (first-in first-out) management of code data as a result of the conversion. The memory 500 is connected to each other by a bus 600.

The CPU 100 has a register 101 for storing image data read out from the line to be encoded in blocks, and a register 102 for storing image data read out in blocks from the line immediately preceding the line to be encoded. A register 103 for holding image data read out in blocks from a line two lines before the line to be coded, a register 104 for holding the address of a pixel to be coded in the line to be coded, A register 105 for holding the address of the pixel immediately above the pixel to be coded on the previous line, a register 106 for holding the address of a pixel immediately above the pixel to be coded on the line immediately before the line to be coded, and a context 107 that holds the contents of the above, and the result of searching whether the encoding target line is all white Previous line and the encoding target line has a register 108 for holding a flag of the results two previous line results was searched whether all white and coded line is searched whether all white.

The CPU 100 executes an encoding program 201A based on JBIG described below.

Next, the procedure of the JBIG encoding program 201A of this embodiment will be described with reference to the flowcharts of FIGS.

First, the overall operation will be described with reference to FIG.

At the beginning of the encoding process for one page, in step 700, all the three flags of the line to be encoded, one line before and two lines before are reset for the all white line flag.

Next, in step 701, it is determined whether or not a typical prediction for comparing the line to be encoded with the line immediately before the line to be encoded is performed. When typical prediction is not performed, a one-line search process is performed in step 702 to determine whether all the lines to be coded are white pixels. In step 703, the image data of three lines is all white, the image data of one or two lines is all white, and the all white line is determined by the search result flag of the encoding target line and the search result flags of the previous two lines. It is determined whether or not there is, and the process branches to three processing routines.

If the result of the determination is that the three lines of image data are all white, then in step 704, one line encoding process is performed exclusively for all three lines of white pixels. If the result of the determination is that one or two lines are all white pixels, then in step 705 one or two lines are all dedicated to white pixels.
Perform line encoding processing. If the result of the determination is that there is no line of all white pixels, the routine proceeds to step 706, where 1
Perform line encoding processing.

Next, in step 710, it is determined whether the processing for the number of original lines has been completed. If not completed, the flow returns to step 701 to repeat the encoding processing.

In the case of performing typical prediction by determining whether or not to perform the above-described typical prediction, the line to be encoded is compared with the line immediately before the line to be encoded in step 707 as in the conventional case. Then, in step 708, it is determined whether the two lines are the same. If the result of this determination is that they are not the same, one-line encoding processing is performed in step 709, and if they are the same, the encoding target line is not set as the encoding target. Next, as in the case where typical prediction is not performed in step 710, it is determined whether the processing for the number of document lines has been completed. If not completed, the process returns to step 701 to repeat the encoding processing.

Next, one line search processing (step 70)
2) will be described with reference to FIG.

First, in step 721, an all white line
The flag is substituted into the flag two lines before the line one line before and the flag one line before the flag of the encoding target line, and reset from the state of the previous line to the state of the current line.

Next, in step 722, initialization is performed using the head address of the encoding target line for determining all white as an address for reading image data. Next, in step 723, image data is read from the address. Conventionally, reading at the time of creating an image data block could not be performed over the entire register width. Reading is possible, and the number of times of loading image data can be reduced.

Next, at step 724, it is determined whether or not the image data is all white.
The address is incremented to set the address of the next image data, and it is determined in step 726 whether one line has been completed. If the processing has not been completed, the process returns to step 723, and the above processing (steps 723 to 725) is repeated from the reading of the image data. When the processing is completed, one line is set to all white in step 727, and the all white line flag of the encoding target line is set.
The search processing for one line is terminated. On the other hand, in the all-white discrimination process (step 724) of the read image data, if anything other than all-white is detected, the all-white line flag of the encoding target line is reset in step 728 to search for one line. The process ends.

Next, the encoding process for one line when all three lines are all white (step 704) will be described with reference to FIG.

In the encoding process for one line, only the one-pixel encoding process (step 732) is repeatedly performed until the process for one line is completed (step 31). Here, the processing of creating image data for the encoding target line, one line before and two lines before, the all-white determination processing in block units, and the block end determination processing, which are conventionally performed, are not performed. This is because, when all three lines are white pixels, the model template during the one-line encoding process is all 0 and there is no change. By not performing the processing, the processing speed can be improved.

Next, the encoding process for one line when one or two lines are all white (step 705) will be described with reference to FIG.

First, in step 742, the three all white line flags of the line to be encoded, one line before and two lines before are referred to to set / set the three flags.
For each reset state, the process branches into six patterns excluding two patterns of all set and all reset. The process of creating the image data of each pattern only performs the image data creation process for the line for which the flag is reset, but does not perform the image data creation process for the line for which the flag is set. For example, when the all white flag of the line to be coded and the line immediately before is set, step 7
At 43, only the image data creation processing is performed for the two lines before, and the image data creation processing for the encoding target line for which the flag is set and the immediately preceding line is not performed. Similarly, steps 744 to 751 are image data creation processing for each pattern.

The reason why the above-described image data creation processing is not performed is that, since it is known that one line is all white for the line on which the flag is set, the image data can be processed as all white. That's why. By not performing the above processing, the processing speed is improved.

Next, at step 752, it is determined whether or not the three image data blocks created are all white.
If the result of the determination is all white, the one-pixel encoding process (step 757) is repeated until the block process ends in step 758.

If the result of the determination is other than all white,
Until the block processing is completed in step 755, a context is created in which the peripheral pixels of the encoding target pixel are converted into one dimension in step 753, one-pixel encoding processing is performed in step 754, and image data for three blocks is generated in step 756. Are shifted by one bit, and the creation of the next peripheral pixel is repeated.

When the processing for the block unit is completed,
Returning to the top of the one-line encoding process, at step 741, 1
It is determined whether or not the encoding process for the line has been completed. The encoding process is performed by repeating the above process for the number of original lines.

In this embodiment, the model template is 3
Although the case of lines has been described, as another embodiment, a case where the model template is n lines will be described.

Referring to FIG. 6, in the present embodiment, the CPU register configuration in the embodiment shown in FIG. 1 is different from the embodiment shown in FIG. Registers 104-106 for three lines,
The difference is that it has n lines.

Next, the overall operation will be described with reference to FIG.

This embodiment is different from the embodiment shown in FIG. 2 in that the number of all white line flags is
The difference is that the number of all white lines to be determined is three, whereas the number of all white lines to be determined is three, whereas the number of all white lines is n.

First, at the beginning of the encoding process for one page,
In step 761, all the n flags from the line to be encoded to the line before the n-th line are reset for the all white line flag.

Next, after one-line search processing (step 76)
2) In step 763, whether all the n lines are white pixels
It is determined whether the 1st line to the (n-1) th line are all white pixels or there are no all white pixel lines, and the process branches to three processing routines. If the result of the determination is that all the n lines are white pixels, a one-line encoding process for exclusive use of all the n lines is performed in step 764. This is the same as the dedicated one-line encoding process (step 704). When the discrimination result is that all the 1 to n-1 lines are white pixels,
In step 765, one-line encoding processing exclusively for white pixels is performed for all of the one to n-1 lines. If the result of the determination is that there is no line of all white pixels, step 706
Performs a one-line encoding process as before.

Next, the encoding process of one line when all the one to n-1 lines are white pixels (step 76)
5) will be described with reference to FIG.

This embodiment is different from the embodiment shown in FIG. 5 in the process of creating image data. First, in step 771, two patterns of all set and all reset are set for each set / reset state of the n flags with reference to the n all white line flags from the encoding target line to the nth line before. Exclude ( ²ⁿ
-2) Branch into patterns. In the process of creating the image data of each pattern, the image data creating process is performed only on the line for which the flag is reset, and the image data creating process is not performed for the line for which the flag is set. For example, when the all-white flag is set only for the line to be encoded, image data creation processing is performed for the line n lines before the line immediately before (steps 772 and 744).
Only, the image data creation processing of the encoding target line for which the flag is set is not performed. Similarly, step 74
Steps 5 to 748 are image data creation processing for each pattern.

[0056]

According to the present invention as described above, the encoding speed is improved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart showing an encoding procedure according to the first embodiment.

FIG. 3 is a flowchart showing a procedure of a process of step 702 in FIG. 2;

FIG. 4 is a flowchart showing a procedure of a process of step 704 in FIG. 2;

FIG. 5 is a flowchart showing a procedure of a process of step 705 in FIG. 2;

FIG. 6 is a block diagram showing a second embodiment of the present invention.

FIG. 7 is a flowchart showing an encoding procedure according to the second embodiment.

FIG. 8 is a flowchart showing a procedure of a process of step 765 in FIG. 7;

FIG. 9 is a block diagram of a conventional example.

FIG. 10 is a flowchart showing a conventional encoding procedure.

FIG. 11 is a flowchart showing the procedure of the process of step 706 in FIG. 10;

FIG. 12 shows steps 802, 803, and 804 in FIG.
Is a flowchart showing the procedure of the processing of FIG.

[Explanation of symbols]

100 CPU 101-108 Register 200 ROM 201A, 201B, 201 JBIG program 202 Probability estimation table 300 RAM (learning table memory) 400 RAM (image data memory) 500 RAM (FIFO memory) 600 Bus 700-710, 721-728, 731 , 732, 7
41-758 Steps 761-765, 771-7
73,801-804,811-814 steps

Claims (8)

(57) [Claims] 1. In a data encoding method based on JBIG, when typical prediction is not performed, it is searched whether or not image data of an encoding target line is all white, and from the encoding target line to (n-1) th line before. Based on the search results for n lines (n is an integer of 3 or more), whether n lines are all white,
It is determined whether the lines 1 to (n-1) are all white or there are no all white lines. If the n lines are all white, the process for creating image data for n lines and the block determination process are not performed. To (n-1) lines are all white, and image data is not created for all white lines. 2. An image processing apparatus according to claim 1, wherein the line from the line to be encoded to n lines before is
nAll white lineStep to reset all flags
A line to be coded and a line immediately before the line to be coded.
NToSteps to determine whether to make a typical prediction or not
If the typical prediction is not performed, the line to be encoded is one line
Perform one-line search processing to determine whether all pixels are white pixels.
Step and the encoding target lineAll white lineFlag and the previous (n
-1) for lineAll white lineBy flag, n
Image data is all white or 1 to (n-1) lines
Image data is all white or there is no all white line
And if the image data of the n lines is all white,
Performing a one-line encoding process exclusively for white pixels by usingFromWhen (n-1) lines are all white pixels, 1From
(N-1) performs one-line encoding processing exclusively for white pixels.
If there is no line of all white pixels, one-line encoding
An encoding method according to JBIG, comprising a step of performing. 3. The method according to claim 2, wherein the one-line encoding processing for exclusive use of white pixels for all n lines includes repeating the encoding processing for one pixel until the processing for one line is completed. 4. A one-line encoding process in which all of the lines from 1 to (n-1) are dedicated to white pixels is performed by referring to n all-white-line flags from the line to be encoded to the line before n. 2 sets of all sets and all resets for each set / reset state of all white line flags
The method according to claim 2, further comprising branching into (2 ⁿ −2) patterns, excluding the pattern, and performing image creation only on lines for which the all white line flag is reset. 5. An image processing apparatus according to claim 1, wherein the line from the line to be encoded to the line before n lines is
nAll white lineProcedure to reset all flags
A line to be coded and a line immediately before the line to be coded.
NToSteps to determine whether to make a typical prediction or not
When typical prediction is not performed, one line to be coded is
Hand to perform one-line search processing to determine whether all are white pixels
Order and the encoding target lineAll white lineFlag and the previous (n
-1) for lineAll white lineBy flag, n
Image data is all white or 1 to (n-1) lines
Image data is all white or there is no all white line
And if the image data of the n lines is all white,
Performing a one-line encoding process exclusively for white pixels by usingFromWhen (n-1) lines are all white pixels, 1From
(N-1) performs one-line encoding processing exclusively for white pixels.
If there is no line of all white pixels, one-line encoding
Steps to take and, When making a typical prediction, the line to be encoded and the encoding pair
Compare the line before the elephant line and compare the two lines
The procedure for determining whether they are the same and the procedure for performing one-line encoding if they are not the same,
Procedures to determine whether or not to make typical predictions
Is repeated for the number of original lines, and a JBIG program is recorded.
Recording medium. 6. The recording medium according to claim 5, wherein the one-line encoding process exclusively for white pixels for all n lines includes repeating the encoding process for one pixel until the processing for one line is completed. 7. A one-line encoding process in which all of the lines from 1 to (n-1) are dedicated to white pixels is performed by referring to n all-white-line flags from the line to be encoded to the line before n. For each set / reset state of all white line flags, branch to (2 ⁿ -2) patterns, excluding 2 patterns of all sets and all resets,
7. The recording medium according to claim 5, wherein image recording is performed only for a line for which the all white line flag is reset. 8. A one-line encoding process in which all of the lines from 1 to (n-1) are dedicated to white pixels is performed by referring to n all-white-line flags from the line to be encoded to n-th line before, For each set / reset state of the all white line flags, except for the two patterns of all sets and all resets, (2 ⁿ −
2) branching into patterns and performing image creation only on lines for which the all-white line flag is reset; determining whether the created n image data blocks are all white; If the discrimination result is all white, a procedure for performing one-pixel encoding until the block processing is completed; and if the discrimination result is not all white, a peripheral image of the encoding target image until the block processing is completed. Is created into a one-dimensional context, and one-pixel encoding is performed.
6. The method according to claim 5, further comprising the step of, after shifting the image data of n blocks by 1 bit, repeatedly creating the next peripheral pixel, and, upon completion of the processing in units of blocks, determining whether the processing for one line has been completed. recoding media.