JP3363536B2 - Color image processing apparatus and color image processing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image processing apparatus and a color image processing method for encoding color image data.

[0002]

2. Description of the Related Art In recent years, JPEG (Joint
Proposed by Photographic Experts Group) (hereinafter referred to as JPEG encoding method). The JPEG encoding system is composed of a plurality of systems, and the most basic one is the baseline system.

FIG. 9 is a diagram showing a data compression procedure of the baseline system. First, the input image data read by a document reading device such as a scanner is 8 pixels x
It is divided into blocks of 8 pixels, and subsequent compression processing is performed in units of this block. In the JPEG encoding system, the image data read by the document reading device
Although there is no stipulation for the color space to be encoded, the conversion process of the color space is often performed as a process prior to the encoding process. As the color space to be converted, a color space capable of performing the encoding process with high efficiency, for example, a color space composed of a luminance signal and a color signal (YC _b C _r , YIQ, Lab).
Etc.) are many.

In the baseline system, a discrete cosine transform (hereinafter referred to as DCT), which is a kind of orthogonal transform, is applied to the divided image data of each block (original color space or image data after color space conversion). It is given (301). After the original input image data is converted to the data of the spatial frequency component by the DCT, the coefficient at the upper left of the 8 × 8 block is called the direct current (DC) component. It is a corresponding value. The other 63 coefficients are called alternating current (AC) components, and are values indicating how many spatial frequency components corresponding to the position are included in the image data of the block before conversion.

The transformed DCT transform coefficient is divided by a value obtained by multiplying 8 × 8 threshold values by a scale factor that determines how many times the threshold value is used, and quantized. (302). For the quantized DCT coefficient, D
Different encoding processes are performed on the C component and the AC component. That is, for the DC component, the difference between the DC component of the processing block and the DC component of the previous block is Huffman-coded using the strength of correlation between adjacent blocks (303, 304). A
The C components are rearranged in a one-dimensional array by a zigzag scan from a low spatial frequency region to a wide spatial region within the block (3
05), two-dimensional Huffman coding is performed by combining a coefficient other than zero (effective coefficient) and the number of consecutive zeros (ineffective coefficient) (run length) (306 to 309).

On the other hand, on the coding side of the color image communication device, it is necessary to perform margin processing in addition to the coding processing. The margin processing is to add a margin required on the transmitting side to match the size of the transmitted image with the size of the reproduced image on the receiving side. Therefore, when the baseline system of the JPEG encoding system is applied, color space conversion processing and DCT processing are not performed only on image data read by an image reading unit such as a scanner, but are added on the transmission side. The margin data to be processed must be processed in the same way as the image data.

Therefore, in the color image communication apparatus to which the JPEG coding method is applied, the space data in the blank area and the color image data read by the scanner or the like must be subjected to color space conversion processing, DCT processing, quantization processing and the like. .

[0008]

The present invention is trying to solve] As described above,
In the JPEG encoding system, each encoding target block is
Is a coding method that uses correlation (corresponding to the differential coding of the DC component).
This is also performed, which corresponds to the blank area.
Even if it is the block to be encoded, the JPEG encoding process
There is no reason not to do it. Because it ’s a blank area
Also, the final encoded data after JPEG encoding is uniquely determined.
Because it doesn't help .

The present invention has been made in view of the above problems.
And the purpose is to add color image data
As much as possible in the form of performing JPEG encoding
This is to reduce the encoding process .

[0010]

In order to achieve the above object, the present invention provides a JPEG encoding system for color image data.
A color image processing device for encoding using
Input means for inputting color image data represented in the color space of the above, and the input color image data in the second color space.
Color space conversion means for converting to color image data of
Color image of the second color space obtained by the color space conversion means
DCT processing means for DCT processing image data, and first color
The color image data of the blank area represented by the space is the second color.
Converted to spatial color image data and DCT processing
Storage means for storing intermediate data obtained in advance ,
A judgment means for judging whether or not the block to be encoded in the input color image data corresponds to a blank area.
And the block to be encoded based on the judgment result.
Tsu when click is blank area, the processing target of the block
Read the intermediate data stored in the storage means,
The data is subjected to the JPEG encoding process after the DCT process.
However , if the block to be encoded is not a blank area, the color space conversion unit and the DCT processing unit are used to
The data obtained after processing the block to be encoded
And a coding means for performing a JPEG coding process .

In order to achieve the above object, the present invention encodes color image data using a JPEG encoding system.
A color image processing method for encoding, the input step of inputting color image data represented in a first color space,
The input color image data is colored in a second color space.
-Color space conversion step of converting to image data, and the color
Color image of the second color space obtained in the space conversion step
A DCT processing step for DCT processing the data;
The color image data of the blank area represented by the color space is the second
Converted to color image data in color space and processed by DCT
A storing step of preliminarily storing intermediate data obtained by the processing, and determining whether or not the block to be encoded in the input color image data corresponds to a blank area.
A determination step and the encoding based on the determination result.
If the target block is in the margin area, the processing of the block
Intermediate data stored in the storage step as a target
And read the data as JPEG after the DCT processing.
When the encoding process is performed and the block to be encoded is not the blank area, the color space conversion step and the DCT
After processing the coding target block in the processing step
And an encoding step of subjecting the obtained data to a JPEG encoding process .

[0012]

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described in detail below with reference to the drawings. <First Embodiment> FIG. 1 is a block diagram showing the arrangement of a color image communication apparatus according to the first embodiment. In the figure, reference numeral 101 denotes a document reading unit, which reads image data of a document with a scanner or the like. 102 is direct
A memory access controller (hereinafter, DMAC), which transfers the image data read by the document reading unit 101 to an image memory described later. An image memory 103 stores the image data read by the document reading unit 101. Reference numeral 104 denotes a digital signal processor (hereinafter referred to as DSP), which encodes image data stored in the image memory 103. A margin value setting register 105 stores data to be added as a margin.

An instruction memory 106 stores the processing program of the DSP 104. 108
Is a code memory for storing the data coded by the DSP 104. 109 is a line control device (hereinafter, CC
U), the code data stored in the code memory 108 is read and sent to the communication transmission path. Reference numeral 107 denotes a microprocessor (hereinafter referred to as main CPU), which is an image memory 1
03, the code memory 108, and the DSP 104, and further, write data to be added as a margin to the margin value setting register 105, and D to the instruction memory 106.
Download the processing program of SP104.

With the above arrangement, the encoding process in the first embodiment will be described below with reference to the flowcharts shown in FIGS. At startup, the main CPU 107 downloads the processing program of the DSP 104 to the instruction memory 106, and simultaneously writes the margin data to be added as a margin into the margin value setting register 105 for each color component. For example, when the data to be added as a margin is “white”, the color space read by the document reading unit 101 is red (R), green (G), and blue (B), and the data precision of each color signal is 8 bits. , R = G = B = 255 (0F
FH) is written in the margin value register 105.

Here, the main CPU 107 causes the DS
When the processing program of P104 is downloaded (step S101), the DSP 104 performs initialization and holds the standby state of the encoding process. Main CPU1
When the encoding process is started from 07 (step S10)
2), the DSP 104 performs the initial process of the encoding process (step S103). If the encoding process is not started, the DSP 104 keeps the encoding process standby state.

Next, the DSP 104 reads the margin value set in the margin value setting register 105 (step S1).
04). In this example, R = G = B = 255 (0F
FH) data is taken into a memory such as an internal register of the DSP 104. The DSP 104 converts the captured blank value data into data on a color space to be encoded, for example, the YC _b C _r color space (step S105), and stores it in the internal RAM of the DSP 104 (step S106). Further, when the color space to be encoded is the RGB color space, the blank space value data fetched from the blank space value setting register 105 is processed by the DSP.
The data is stored in the internal RAM 104 and the subsequent processing is performed. That is, without performing the process of step S105,
The processing of 06 is performed.

If the area to be encoded is a blank area (step S107), the DSP 104 configures the blank value data stored in the internal RAM of the DSP 104 by the above-described processing into data of a block unit of 8 × 8 pixels. Then, the subsequent process, that is, the DCT process is performed (step S1).
08). Next, the data after the DCT processing is quantized (step S109), rearranged into a one-dimensional array by zigzag scanning (step S113), and Huffman coding processing is performed (step S114).

When the coding process of all the image data is completed, the DSP 104 finishes the coding process, but if it is in the middle of the coding process, the process returns to step S107 to perform the process. In step S107, when the area to be encoded is not the blank area, the DSP 104 causes the image memory 10
The image data is read in blocks from 3 (step S110). Then, the read image data is converted into data on the color space to be encoded (step S11).
1).

If the color space to be encoded is the same as the color space read by the document reading section 110, the process in step S111 is not performed. Next, the DSP 104
Performs DCT processing on the block-unit data processed in step S110 or S111 (step S11
2) Quantization (step S109) and zigzag scanning (step S) as in the processing of the margin value data described above.
113) and Huffman coding (step S114) are sequentially performed.

Thereafter, the code data coded by the DSP 104 is written in the code memory 108, and the CCU
It is read from the code memory 108 by 109 and transmitted to the communication line. Then, the DSP 104 performs steps S107 to S until the encoding process of all the image data is completed.
The processing up to 114 is performed for each of the blank area and the image data area. When the encoding process of all the images is completed, the DSP 104 holds the standby state of the encoding process again.

As described above, according to the first embodiment, the data of the blank area is subjected to the DCT processing or the like using the blank value data which has been subjected to the color space conversion processing in advance. The conversion processing of the color space applied to the data becomes unnecessary. As a result, in the DSP processing program,
The number of processing steps required for color space conversion is reduced, and the coding processing time of all image data can be shortened.

<Second Embodiment> Next, a second embodiment according to the present invention will be described in detail with reference to the drawings. FIG. 4 is a block diagram showing the configuration of the color image communication apparatus in the second embodiment. The same parts as those in FIG. 1 are designated by the same reference numerals and the description thereof is omitted. In FIG. 4, reference numeral 110 denotes an external memory that stores data after the color space conversion processing of the blank value and the DCT processing. The external memory 110 is a memory that the main CPU 107 and the DSP 104 can access at high speed.

With the above arrangement, the encoding process in the second embodiment will be described below with reference to the flowcharts shown in FIGS. At the time of startup, the main CPU 107 downloads the processing program of the DSP 104 to the instruction memory 106, and simultaneously writes the data after the color space conversion processing of the blank value added and the DCT processing to the external memory 110 for each color component.

Here, the main CPU 107 causes the DS
When the download of the processing program of P104 is completed (step S201) and the data after the space value color space conversion processing and DCT processing is written to the external memory 110 (step S202), the DSP 104 performs initial setting (step S203). , Holds the standby state of the encoding process. When the encoding process is activated by the main CPU 107 due to an interrupt or the like (step S204), the DSP 1
04 performs an initial process of the encoding process (step S
205). Also, if the encoding process is not started,
The DSP 104 continues to hold the standby state of the encoding process.

When the area to be encoded is a blank area (step S206), the DSP 104 causes the main CPU 107
By using the data after the color space conversion processing and the DCT processing of the blank value written in the external memory 110, the subsequent processing in the JPEG encoding system is performed. That is, DSP104
Reads the blank value data after DCT processing for each signal from the external memory 110, quantizes the read data (step S207), and rearranges the two-dimensional array data into a one-dimensional array by zigzag scanning (step S207). S2
08), Huffman encoding processing is performed (step S20).
9).

When the encoding process of all the image data is completed, the DSP 104 terminates the encoding process, but if it is in the middle of the encoding process, the process returns to step S206 to continue the process (step S210). Step S206
In, if the area to be encoded is not a blank area,
The DSP 104 reads the image data read by the document reading unit 101 and transferred to the image memory 103 by the DMAC 102 in block units (step S2).
11) The read image data is converted into data in the color space to be encoded (step S212).

Next, the DSP 104 performs DCT processing on the image data after the color space conversion (step S213) and quantizes it (step S214). The quantized data is subjected to zigzag scanning (step S208) and Huffman coding (step S209) in the same manner as the blank value data processing. Thereafter, the code data encoded by the DSP 104 is written in the code memory 108, read out from the code memory 108 by the CCU 109, and transmitted to the communication line. And DSP104
Performs the processing of steps S206 to S210 for the blank area or the image data area, respectively, until the encoding processing of all the image data is completed. When the encoding process of all the images is completed, the DSP 104 holds the standby state of the encoding process again.

In the second embodiment, the main CPU 10
7 is a space value color space conversion process for the external memory 110, DC
I explained how to write data after T processing,
When the color space encoded by the DSP 104 is the same as the color space read by the document reading unit 101, the data obtained by performing the DCT process on the margin value data is used as the main CPU 107.
May be written in the external memory 110.

<Third Embodiment> Next, a third embodiment of the present invention will be described in detail with reference to the drawings. In the second embodiment, the main CPU 107 writes the data after the color space conversion of the blank value and the DCT process to the external memory 110, and D
The SP 104 uses the data to perform the blank area coding processing, but similar processing can be performed by other than this method.

The encoding process in the third embodiment will be described below with reference to the flowcharts shown in FIGS. 7 and 8. At the time of startup, the main CPU 107 downloads the processing program of the DSP 104 to the instruction memory 106, and simultaneously writes the margin data to be added as a margin into the external memory 110 for each color component. For example, when the data to be added as the margin is “white”, the document reading unit 10
The color space read in 1 is red (R), green (G), blue (B)
When the data precision is 8 bits, R = G = B = 25
5 (0FFH) is written in the external memory 110.

Here, the main CPU 107 causes the DS
When the processing program of P104 is downloaded (step S301), the DSP 104 performs initialization and holds the standby state of the encoding process. Main CPU1
When the encoding process is activated by an interrupt or the like from 07 (step S302), the DSP 104 performs the initial process of the encoding process (step S303). If the encoding process is not started, the DSP 104 keeps the encoding process standby state.

Next, the DSP 104 operates the external memory 110.
The margin value written in is read (step S30
4). In this example, R = G = B = 255 (0FF
The data of H) is taken into the memory such as the internal register of the DSP 104. The DSP 104 converts the captured blank value data into a color space for encoding processing (step S305),
The data is stored in the internal RAM of the DSP 104. At this time, the blank R, G, B data read in the previous step may be erased. That is, it is only necessary that the color space converted blank data is stored in the internal RAM of the DSP 104. And DSP1
Reference numeral 04 expands the stored margin data for each signal component into block data which is a subsequent encoding processing unit, and performs DCT processing on the expanded data. The blank data after the DCT processing is stored in the external memory 110 which can be accessed by the DSP 104 at high speed by the DSP 104 (step S306).

The processing from the next step S307 is the second step.
This is the same as the processing after step S206 in the embodiment. Therefore, the DSP 104 performs the subsequent processing under the same conditions as in the second embodiment. That is, the processes of steps S307 to S315 are performed for the blank area or the image data area, respectively, until the encoding processing of all the image data is completed. Thereafter, the code data encoded by the DSP 104 is written in the code memory 108,
Read from the code memory 108 by the CCU 109,
It is transmitted to the communication line. Then, when the encoding process of all the images is completed, the DSP 104 holds the standby state of the encoding process again.

In the description of the third embodiment, the DSP 10
4 performs color space conversion processing and DCT processing on the blank space data set in the external memory 110 and writes the processing result data to the external memory 110. However, the color space encoded by the DSP 104 is the original reading unit 101. If the color space is the same as the color space to be read in, the DSP 1 is the margin data set in the external memory 110 and is only DCT processed.
04 may be written in the external memory 110.

As described above, according to the second and third embodiments, when the encoding process by the JPEG encoding method is performed, the margin area data is subjected to the color space conversion process and the DCT process in advance. Since the quantization, zigzag scanning, and Huffman coding are performed using the value data, the color space conversion process and the DCT process performed on the blank area data are unnecessary. As a result, the number of steps required for color space conversion processing and DCT processing in the DSP processing program is reduced, so that it is possible to shorten the encoding processing time for all image data.

The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0038]

According to the present invention as described above, according to the present invention, Ca
In the form of performing JPEG encoding on the color image data
Stomach, it is possible to Rukoto to reduce only the encoding process can be.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a color image communication device according to a first embodiment.

FIG. 2 is a flowchart showing an encoding process in the first embodiment.

FIG. 3 is a flowchart showing an encoding process in the first embodiment.

FIG. 4 is a block diagram showing a configuration of a color image communication device according to a second embodiment.

FIG. 5 is a flowchart showing an encoding process in the second embodiment.

FIG. 6 is a flowchart showing an encoding process in the second embodiment.

FIG. 7 is a flowchart showing an encoding process in the third embodiment.

FIG. 8 is a flowchart showing an encoding process in the fourth embodiment.

FIG. 9 is a processing block diagram at the time of encoding in the JPEG encoding method.

[Explanation of symbols]

101 original reading section 102 DMAC 103 image memory 104 DSP 105 Margin value setting register 106 instruction memory 107 CPU 108 code memory 109 CCU

Continuation of the front page (56) Reference JP-A-5-114993 (JP, A) JP-A-4-20073 (JP, A) JP-A-1-144862 (JP, A) JP-A-4-217176 (JP , A) JP 7-30762 (JP, A) JP 7-23234 (JP, A) JP 61-32664 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB Name) H04N 1/41

Claims (4)

(57) [Claims] 1. A JPEG encoding method for color image data
A color image processing apparatus which encodes the color image data using an input means for inputting color image data represented in a first color space, and the input color image data in a second color space.
-Color space conversion means for converting into image data, and a color space of the second color space obtained by the color space conversion means
-DCT processing means for performing DCT processing on image data, and color image data of a blank area represented by the first color space
Converted to color image data in the second color space, and D
Storage means for storing intermediate data obtained by CT processing in advance, and a judgment means for judging whether or not the block to be encoded in the input color image data corresponds to a blank area.
If the block to be coded is a blank area based on the determination result and the determination result, the block is processed as the processing target of the block.
Read the intermediate data stored in the storage means
Is subjected to the JPEG encoding process after the DCT process,
If the block of serial encoded is not a blank area of the previous
The above-mentioned code using the color space conversion means and the DCT processing means
JPE is applied to the data obtained after processing the block to be digitized.
A color image processing apparatus comprising: an encoding unit that performs G encoding processing. 2. The color image processing apparatus according to claim 1, further comprising a transmission means for transmitting encoded data obtained by each encoding process via a communication line. 3. Processing JPEG coding of subsequent said DCT processing
The sense, the color image processing apparatus according to claim 1, wherein Rukoto includes quantization and Huffman coding. 4. A JPEG encoding method for color image data
A color image processing method for encoding using the above , comprising an input step of inputting color image data represented in a first color space, and a step of inputting the input color image data in a second color space.
A color space conversion step that converts the over image data, color of the second color space obtained by the color space conversion step
-The DCT processing step of performing DCT processing on the image data and the color image data of the blank area represented by the first color space are
Converted to color image data in the second color space, and D
A storage step of storing intermediate data obtained by CT processing in advance, and a determination step of determining whether or not the block to be encoded in the input color image data corresponds to a blank area .
If the block to be encoded is a blank area based on the step and the determination result, the block is processed as the target of the block.
The intermediate data stored in the storing step is read and the
Data to the JPEG encoding process after the DCT process.
If the block to be encoded is not a blank area, the color space conversion step and the DCT processing step are performed.
Data obtained after processing the block to be encoded
And a coding step of performing JPEG coding processing on the color image processing apparatus.