JP3280120B2 - Communication device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication apparatus for performing coding using DCT operation.

[0002]

2. Description of the Related Art Conventionally, DCT (Discrete Cosine Transform)
Coding using arithmetic operations, for example, JPEG (Joint Photo
In a communication device that uses a graphic expert group, the DC
The T operation is performed and JPEG encoding is performed.

[0003]

However, in the above-mentioned conventional communication apparatus, since the DCT operation is performed irrespective of the state of the image, there is a problem that it is difficult to improve the encoding processing speed. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to increase the encoding processing speed of an image portion composed of white pixels having a high appearance probability,
It is an object of the present invention to provide a communication device which aims to increase the processing speed of PEG encoding.

[0004]

In order to achieve the above object, the present invention provides a method for JPEG encoding / decoding image data.
In a communication device for performing decoding, means for storing in advance an operation value obtained by performing a DCT operation on a pixel block in which all pixels of an 8 × 8 pixel block among the pixel blocks constituting the image data are white. And first determining means for determining whether or not all the pixels of the first 8 × 8 pixel block to be encoded at the present time are white pixels, and regarding the scanning direction of the encoding, 1 x 8
A second determination is made as to whether or not all the pixels of the second 8 × 8 pixel block located immediately before the eight pixel block are white pixels.
And if all the pixels of the first 8 × 8 pixel block are white pixels and all the pixels of the second 8 × 8 pixel block are white pixels, 8
Means for performing an encoding process on the pixel block using the operation value.

[0005]

With the above arrangement, the function of the present invention is to increase the processing speed of JPEG encoding.

[0006]

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram illustrating a configuration of a facsimile apparatus that is a communication apparatus according to an embodiment of the present invention. In the figure, reference numeral 2 denotes a central control unit (CPU).
M3 and RAM4. The ROM 3 stores a program for operating the CPU 2.
The CPU 2 controls the operation of the entire apparatus according to the program. The RAM 4 is used as a work area of the CPU 2. The crystal oscillator 1 for generating the operation clock is connected to the CPU 2.

The reading unit in the facsimile apparatus includes:
A document image is mainly read by the CCD line sensor 11, and further includes a reading motor 12. The image recording unit includes a recording head 10 that is a thermal head, a recording motor 13, and a motor drive IC 17 that drives the recording motor 13. In the facsimile apparatus, the received image or the copy image is recorded in the reading unit and the image recording unit.

A modem (MODEM) 14 modulates / demodulates image data and control procedure data, and is connected to a line 23 via a network control unit (NCU) 15. This N
The CU holds the loop current of the line 23 or performs line switching with the telephone 24. Reference numeral 9 denotes a JPEG encoding LSI, which will be described later.
A plurality of DSPs for performing encoding are built in.

FIG. 2 is a schematic flowchart showing a communication control procedure of the facsimile apparatus according to the embodiment. In the figure, when the power of the facsimile apparatus is turned on, C
The PU2 initializes parameters in step S1, and in steps S2, S4, S6, and S8, whether copy, transmission, reception, and functions have been selected as operation modes, that is, whether the device has been activated. Is determined, a copy process (step S3), a transmission process (step S5),
A reception process (step S7) and a function process (step S9) are executed. For example, step S4
Now, it is determined by the CPU that a document is set on the apparatus and a one-touch key (not shown) constituting the key 29 is pressed.
2 is detected via the gate array 10, step S
The process proceeds to the transmission process of No. 5.

FIG. 3 is a detailed flowchart of the transmission process shown in step S5 in the communication control procedure shown in FIG. In the figure, the CPU 2 initializes parameters in step S11, and executes steps S12, S13, S
In a loop of 14, reading of an image in units of one page and storage processing of image information are performed, and if processing of one page is completed, that is, the determination in step S14 is YES.
If so, memory data loading is performed in step S15, and encoding and memory storage processing are performed in step S16. Then, in step S17, it is checked whether or not all pages have been processed.

Here, steps S15, S16
Image processing for one page is performed each time the processing is passed. When the processing for all pages is completed, the process proceeds to step S18, where the memory transmission processing for each page is performed.
Then, in the subsequent step S19, it is checked whether transmission has been completed for all pages, and if it is determined that the processing has been completed, return processing is performed.

FIG. 4 is a detailed flowchart of the page processing end determination in step S14 in the transmission processing procedure shown in FIG. FIGS. 5 and 6 are diagrams showing a unit of a pixel group when determining whether or not all data of the document image data is white data (hereinafter, all white), which will be described later.
Each square corresponds to one pixel unit at the time of DCT calculation.

In step S21 of FIG. 4, the parameters are initialized, and in step S22, it is determined whether or not the pixels in the eight columns of the image data in the main scanning direction are all white. Note that this determination is made for each pixel group shown in FIG.
If the decision result in the step S22 is YES, the process advances to a step S23, where the result of executing the DCT operation when the pixels of eight columns in the main scanning direction stored in the ROM 3 in advance are all white. Is stored in the memory, and in a succeeding step SS24, +8 of the sub-scanning pointer which is a control parameter is incremented.

In step S25, it is checked whether or not 8 * 8 pixels which are units of JPEG encoding are all white. At this time, the process is performed in units of the pixel group shown in FIG. If the check result is YES, in step S26, the above 8 * 8
It is checked whether the 8 * 8 pixel immediately before the pixel (also a unit of JPEG encoding) is also all white. And
If the decision result in the step S26 is YES, a result in the case where 8 * 8 pixels are all white, that is, a value previously stored in the ROM 3 is stored in the memory in a step S27, and the process proceeds to the step S29. .

On the other hand, when the current processing target 8 * 8 pixel is not all white (the determination result in step S25 is N
O) Or, if those pixels are all white but the immediately preceding 8 * 8 pixels are not all white, step S2
In step 8, a well-known DCT operation is performed, and the result of the JPEG encoding is stored in a memory. In step S29, the value of the main scanning pointer, which is a control parameter, is advanced (increment of +8), and in step SS30, it is checked whether the processing for one page has been completed. If it is determined that the processing for one page has been completed, a return processing is performed.

As described above, in JPEG, an 8 × 8 pixel block of an original image is subjected to DCT operation and encoded, but when the 8 × 8 pixel block of the original image is completely white,
The result of the DCT operation is already obvious. In addition, the appearance probability of an all-white part in a document is generally very high. Therefore, if the encoding processing speed of the image portion having a very high appearance probability, that is, the entire white portion is increased by processing as described above, the processing speed of JPEG encoding can be increased.

FIG. 7 is a detailed flowchart of the all-white determination process in step S25 shown in FIG. In step S41 of FIG. 7, parameters (i, j...) Are initialized, and in step S42, image data (i, j) for one pixel is loaded. Then, in a step SS43, it is checked whether or not the pixel is white. As a result, if the pixel is not white, in step S44, the control parameter NOT-WH
Set "1" to the ITE flag and perform return processing.

However, the determination in step S43 is YES
If so, in step S45, the pixel pointer (i) which is a control parameter is incremented by +1 and the process proceeds to step SS46. In this step S46, it is checked whether or not the processing in steps S42, S43, and S45 has been performed a total of eight times. If the processing has not been performed eight times, the process returns to step S42.

If the result of the eight-loop search in step S46 is YES, in step S47, the pixel pointer (j), which is a control parameter, is incremented by +1 and then the process proceeds to step S48. This step S48
Then, steps S42, S43, S45, S46,
It is checked whether or not the process of S47 has been performed for 8 * 8 pixels. If the result is NO, the process returns from step S48 to step S42.

If the result of the determination in step S48 is Y
If it is ES, it is a control parameter in step S49.
Set "1" to the ALL-WHITE flag and perform return processing. Note that, in the processing shown in FIG.
If a return is made after the process in FIG.
The determination in step S25 is branched to the YES side. Further, in the processing shown in FIG. 7, when the processing returns to the processing after the processing in step S44, the processing returns to step S25 in FIG.
Is branched to the NO side.

FIG. 8 is a detailed flowchart of the all-white determination process in step S22 shown in FIG. In the processing shown in FIG. 7 and the processing shown in FIG. 8, since the reading of one page and the storage of the uncompressed data in the memory have been completed in steps S12 and S13 in FIG. 3 before the processing is performed. Steps S22 and S25 in FIG. 4 are collective processes for checking all white of the uncompressed data in the RAM 4.

Further, the processing shown in FIG.
8 relates to an 8 * 8 pixel block corresponding to the pixel (8, 8), whereas the processing shown in FIG. 8 performs the main scanning 8 corresponding to the pixel (1, 1) to the pixel (8, m). This is a process in which pixel blocks for lines are collectively performed. FIG.
In step S51, parameters (i, j...) Are initialized, and in step S52, image data (i, j) for one pixel is loaded. Then, step SS53
Then, it is checked whether the pixel is white. If it is determined that the pixel is not white, in step S54, "1" is set to a NOT-WHITE flag which is a control parameter, and a return process is performed.

However, the determination in step S53 is YES
If so, in step S55, the pixel pointer (i) which is a control parameter is incremented by +1. In the next step S56, it is checked whether or not the processes in steps S52, S53 and S55 have been performed a total of m times, and if not, the process returns to step S52.

If the result of the loop search m times in step S56 is YES, the pixel pointer (i) is set to 1 in step S57. Then, in step S58, the pixel pointer (j), which is a control parameter, is incremented by +1 and then the process proceeds to step S59. In this step S59, the above steps S52, S53, S55
It is checked whether or not the processing of steps S58 to S58 has been performed for 8 * 8 pixels. If the result is NO, the processing returns to step S52.

Then, the judgment result at step S59 is Y
If it is ES, it is a control parameter in step S60.
Set "1" to the ALL-WHITE flag and perform return processing. As described above, the difference between the processing shown in FIG. 7 and the processing shown in FIG. 8 is that, in FIG. 7, in step S46, a check is made for eight pixels in the horizontal direction (main scanning direction). In step 8, the main scanning is performed from end to end in step S56. 8 differs from the processing shown in FIG. 7 in that the value of the control parameter (pixel pointer) i needs to be reinitialized in step S57 when the main scanning line moves to the next line. .

As described above, according to the present embodiment,
Focusing on the high probability of appearance of all white portions in the original image, the encoding processing speed of all white portions is increased in advance by using the result of DCT operation on all white portions of a predetermined pixel block portion. , The processing speed of JPEG encoding can be increased. The present invention may be applied to a system including a plurality of devices or an apparatus including a single device. Needless to say, the present invention can be applied to a case where the present invention is achieved by supplying a program to a system or an apparatus.

[0027]

As described above, according to the present invention,
When the predetermined pixel block is all white, the encoding processing is performed using a predetermined value without performing the DCT operation, thereby improving the encoding processing speed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a facsimile apparatus that is a communication apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic flowchart illustrating a communication control procedure of the facsimile apparatus according to the embodiment.

FIG. 3 is a step S5 in the communication control procedure shown in FIG. 2;
6 is a detailed flowchart of a transmission process shown in FIG.

FIG. 4 shows a step S14 in the transmission procedure shown in FIG. 3;
7 is a detailed flowchart of a page processing end determination.

FIG. 5 is a diagram illustrating a unit of a pixel group when determining whether or not original image data is all white.

FIG. 6 is a diagram illustrating a unit of a pixel group when determining whether or not original image data is all white.

FIG. 7 is a detailed flowchart of an all-white determination process in step S25 shown in FIG. 4;

FIG. 8 is a detailed flowchart of an all-white determination process in step S22 shown in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crystal oscillator 2 CPU 3 ROM 4 RAM 5, 7, 10, 18 Gate array 9 JPEG encoding LSI 11 CCD 12 Reading motor 13 Recording motor 14 Modem 15 NCU 16 Sensor 17 Motor drive IC 19 Speaker 23 Line 24 Telephone 25 Speaker drive Circuit 30 bus

Claims (2)

(57) [Claims] 1. An image processing system comprising: JPEG (Joint Pho
tographic Expert Group) In a communication device that performs encoding / decoding, a DCT (discrete cosine transform) operation is performed on a pixel block in which all pixels of an 8 × 8 pixel block among pixel blocks constituting the image data are all white. Means for preliminarily storing the operation value obtained by performing the above-mentioned, and first judging means for judging whether or not all the pixels of the first 8 × 8 pixel block to be encoded at the present time are white pixels A second determination for determining whether all pixels of a second 8 × 8 pixel block located immediately before the first 8 × 8 pixel block are white pixels with respect to the encoding scanning direction. Means, if all of the pixels of the first 8 × 8 pixel block are white pixels and all of the pixels of the second 8 × 8 pixel block are white pixels, the first 8 × 8 pixel For blocks, Serial communication apparatus characterized by comprising means for performing an encoding process using a calculated value. 2. When all pixels of an 8 × 8 pixel block for one column in the main scanning direction of the image data are white pixels, the DCT operation is not performed on the pixel block and the calculated value is used. 2. The communication device according to claim 1, wherein the encoding process is performed by using.