JP2000244744A - Image data compression method and image data management method - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To store image data obtained at a high definition by compressing the image data at a high compression rate, and to enable high-speed reproduction of the stored image data with an image having a small data amount. SOLUTION: 12 pixels per pixel obtained by CCD1.
The bit image data is separated into upper 8 bits of high-order bits having high correlation and lower bits of data having low correlation. JPEG lossless encoding is performed on the upper bit data, and bit shift operation / packing processing for two pixels is performed on the lower bit data. The processed higher-order bit data, lower-order bit data, and position information for individually managing the same are stored in the storage medium 2. A coarse image with a small amount of data can be reproduced at high speed only by decoding high-order bit data having high correlation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for compressing image data and a method for managing image data, and more particularly to a method for compressing image data useful for compressing / decompressing multi-value halftone image data having a large number of gradations. And an image data management method.

[0002]

2. Description of the Related Art With the development of image input devices (for example, CCDs used in digital cameras), image data has been taken in with high definition. The original data (RAW data) thus obtained with high definition is subjected to image processing by a user using a personal computer or the like, and thereafter, desired image data is obtained by an output device (for example, a CRT or a printer). It is supposed to be.

Image data represented by a signal (signal charge) from a CCD is converted into a digital signal of 10 to 12 bits per pixel by, for example, an A / D converter. When converted into a 12-bit digital signal, the maximum gradation is "4096". Thus 10
The image data captured in high definition with bits to 12 bits is changed into image data of about 8 bits per pixel,
The image is reproduced on the output device.

As described above, the reason why the number of bits of image data per pixel is represented by 10 bits to 12 bits at the time of capturing is as follows. This is because it is necessary to obtain image data evenly in the range. On the other hand, at the time of reproduction, since the brightness difference actually represented in one frame (screen) is smaller than that in the shooting environment, the brightness of the image in one frame can be sufficiently expressed by image data of about 8 bits.

The image data captured by the CCD is stored in a storage medium, and the image data is read out from the storage medium as appropriate. Conventionally, the storage medium is changed to 8 bits per pixel. Image data is stored. Here, if the image data of 8 bits per pixel is stored as it is, the amount of data per frame (one screen) becomes enormous. Therefore, the image data is compressed and then stored in a storage medium. I have.

[0006] In general, image data compression processing includes DPCM processing on original data (RAW data),
Huffman coding, arithmetic coding, JP using these as appropriate
EG lossless coding, universal coding represented by the Ziv-Lempel method, and the like are known.

[0007]

However, if 8-bit image data per pixel is stored as original data in the storage medium, the user can process / correct the 8-bit image data per pixel as desired. Is added, the image data after processing / correction becomes 8 bits or less per pixel, and the image quality deteriorates.

Therefore, the original data (10 bits to 12 bits) of the high-definition image obtained by the CCD is stored as the original data in the storage medium, and the original data is read and processed. By performing / correction, the image quality of the processed / corrected image data can be improved. When the high-definition original data is stored in a storage medium, it is necessary to perform the above-described compression processing (especially, lossless compression processing).
Even if the same compression processing is performed on 8-bit image data, a high compression ratio cannot be achieved. This is because when image data is compressed (particularly in the case of DPCM encoding), the higher the correlation between pixel data between adjacent pixels, the higher the compression ratio can be obtained. In the case of data, the correlation of image data between pixels is remarkable in the upper 6 bits to 8 bits, but is lower in the lower 3 to 8 bits.
This is because there is almost no correlation for 4 bits.
Therefore, a high compression rate cannot be obtained even if lossless compression is directly applied to 10-bit to 12-bit image data. Even after compression, a storage medium with large image data and a large capacity is still required. become.

Further, the image data represented by 10 bits to 12 bits has a disadvantage that the processing time is long for reading and reproducing the image data from the storage medium because of the large amount of image data. The present invention has been made in view of such circumstances, and a first object of the present invention is to provide an image data compression method capable of compressing image data obtained with high definition at a high compression ratio.

It is a second object of the present invention to provide an image data management method capable of selectively reproducing a coarse image having a small data amount at a high speed in reproducing image data stored in a storage medium. It is.

[0011]

According to a first aspect of the present invention, there is provided an image processing method comprising the steps of: converting image data acquired at a fixed number of bits per pixel by image input means (1); Separating the data of each pixel into upper bit data represented by a predetermined number of upper bits and lower bit data represented by a predetermined number of lower bits; and Performing encoding, packing the lower bit data by a bit shift operation for a plurality of pixels, and individually separating the variable length coded upper bit data and the packed lower bit data. Generating management data for management, the variable length coded upper bit data, the packed lower bit data, and By a step of storing the administrative data in the storage medium (2), in which so as to compress.

According to a second aspect of the present invention, in the image data compression method according to the first aspect, the image input means (1) is an input means (CCD) in which pixels are arranged in a matrix. The variable-length coded upper bit data is divided into blocks for each pixel included in the same row, and the packed lower bit data is divided into blocks for each pixel included in the same row. And generating position information indicating a storage position of each of the higher-order bit data and the blocked lower-order bit data.

According to a third aspect of the present invention, in the image data compression method according to the first or second aspect, the variable length encoding is performed by Huffman encoding and DPCM encoding. Things. According to a fourth aspect of the present invention, in the image data compression method according to any one of the first to third aspects, the fixed number of bits of the data for each pixel is determined by the detection accuracy of the image input means (1). , And the predetermined number of upper bits is the number of upper bits that have a strong tendency to cause a correlation with neighboring pixels, and the value is obtained by an empirical rule.

According to a fifth aspect of the present invention, the image input means (1) in which pixels are arranged in a matrix form provides one pixel.
The image data obtained with a fixed number of bits per pixel is converted into the upper bit data represented by a predetermined upper bit number and the lower bit represented by a lower predetermined bit number of the data of each pixel having the fixed bit number. Separating the higher-order bit data into pixels for each pixel included in the same row; andblocking the lower-order bit data for each pixel included in the same row. Generating position information indicating a storage position of each of the blocked high-order bit data and the blocked low-order bit data; and Storing the side bit data and the generated position information in a storage medium (2).

(Operation) According to the first aspect of the present invention, variable-length encoding can be performed with high compression on high-order bit data having high correlation with neighboring pixels in image data obtained with high definition. , And the bit shift and packing processing can be performed at high speed for the lower-order bit data having low correlation. In addition, by storing the management information, desired image data can be accessed at high speed, and the restoration process can be speeded up.

According to the second aspect of the present invention, the upper bit data and the lower bit data are individually divided into blocks for each row, so that only the image data of a specific row is selectively reproduced. Can be speeded up. In this case, an image can be reproduced at high speed based on the position information indicating the storage position of each block. According to the third aspect of the present invention,
It becomes possible to encode image data at a high compression ratio with respect to high-order bit data having a strong correlation.

According to the fourth aspect of the present invention, it is possible to compress / decompress high-definition image data corresponding to the accuracy of the image input means (1). According to the invention of claim 5,
The high-definition image data obtained by the image input means (1) is separated into upper bit data and lower bit data and stored in the storage medium (2), so that only the upper bit data is selectively stored. To reproduce coarse images at high speed.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) A first embodiment of the present invention will be described below with reference to the accompanying drawings. Note that the first embodiment corresponds to claims 1 to 5. FIG. 1 is a block diagram showing a configuration of an encoding processing device 10 to which an image data compression method and an image management method of the present invention are applied.

The encoding processing device 10 includes an image input device (C
After the image signal input from the CD 1 is digitized, the image data is compressed and stored in the storage medium 2 by JPEG lossless encoding using both DPCM encoding and Huffman encoding. . Here, the encoding processing device 10 is provided integrally with the CCD 1 (for example, in a digital camera). Also, the compressed image data stored in the storage medium 2 is decoded by a decoding processing device 20 (FIG. 6) such as a personal computer, as described later, and then processed / corrected by the user, The image is restored.

Here, the CCD 1 connected to the input side of the encoding processing device 10 has pixels (cells) arranged in a matrix of m rows × n columns and, as shown in FIG. Color filters (in the illustrated example, “R”, “G”, and “B”) are arranged. The encoding processing device 10 includes an A / D converter 1 for converting a signal (signal charge) from the CCD 1 into a digital signal (12 bits) of 4096 gradations.
1. Input data buffer 12 for temporarily storing digitized signal (original data), input data buffer 1
2, a CPU 13 for encoding a signal (original data) temporarily stored in the main memory 2, a main memory 14 for storing a program executed by the CPU 13, and a signal for temporarily storing a signal (compressed image data) encoded by the CPU 13. The output data buffer 15 and the like output the data to the storage medium 2 at a predetermined timing and store the data.

The input data buffer 12 includes a CC
Pixel data for each pixel obtained by D1 (m × n)
Is stored for each row (line), and is shifted from the target line buffer 12A and the target line buffer 12A which collectively store data (n pixel data) for one row to be encoded. The buffer for one line before 12B that stores the data of one line before that is stored and the buffer 12C for two lines before that stores the data of two lines before shifted from the buffer for one line 12B.

The output data buffer 15 includes an address buffer 15A, a high buffer 15B, and a low buffer 15C. Among them, the "high-order compressed data block position information" described later in the address buffer 15A, and the address buffer 15A described later in the high buffer 15B. "Higher side compressed data" and "lower side data block position information"
“Lower data” is stored in C.

Next, the encoding process of image data for one frame (screen) executed by the CPU 13 of the encoding processing device 10 will be described with reference to the program flowchart of FIG. When the encoding process is started (start), first, in step S1, n pieces of pixel data (12-bit original data) stored in the target line buffer 12A of the input data buffer 12 for each row are n. ,
The data of the pixel of interest is read.

In step S2, the read pixel data (12 bits) of the target pixel is separated into upper 8 bits (upper bit data) and lower 4 bits (lower bit data). Separating the 12-bit pixel data (original data) into the upper 8 bits and the lower 4 bits in this way, in the image data obtained by 12 bits, generally, the data from the upper 6 bits to the upper 8 bits is used. Has a high correlation with other image data in the vicinity and can be encoded at a high compression ratio. On the other hand, when the lower 4 bits are reached, the lower 4 bits of other neighboring pixels This is because the correlation becomes low.

In step S3, the upper 8 bit data is encoded by JPEG lossless encoding, and the encoded pixel data is stored in the high buffer 15B as "upper compressed data". In the first embodiment, the JPEG lossless encoding in step S3 is generally performed by DPCM encoding and Huffman encoding according to the following procedure.

First, the prediction value of the pixel of interest is based on the pixel value (value of higher-order bit data) of a neighboring pixel of the same color filter (same color pixel) or the pixel value of an adjacent pixel (value of higher-order bit data). Is calculated according to a predetermined prediction formula. Here, as a neighboring pixel, a pixel of the same color on the same line (for example, R4 which is two pixels earlier than the pixel of interest (R44 in FIG.
2) or the same-color pixel (R24, R22) two lines before, or the pixel which gives the pixel value with the smallest prediction error among the adjacent pixels (G43, B33, G34) is used.

Specifically, which pixel value is used for calculation of the predicted value (which pixel value is used as a variable for the prediction formula) is, specifically, a pixel of the same color in the vicinity of the pixel two pixels before or the pixel two pixels before. A plurality of temporary prediction values are obtained by a plurality of prediction formulas using the respective pixel values of the higher-order bit data of the adjacent pixel of, and the pixel value two pixels before and the plurality of the temporary prediction values are respectively determined. Compare,
A prediction formula (optimal prediction formula) that minimizes the prediction error is stored. Then, the prediction value of the target pixel in the current loop is calculated using the optimal prediction formula stored two pixels before.

The predicted value of the high-order bit data calculated in this way is compared with the pixel value of the high-order bit data (8 bits) separated in step S2 to obtain a prediction error Δ (DPCM). Coding). Then, the prediction error Δ is subjected to Huffman encoding according to the occurrence distribution, and the upper bit data is encoded (variable length encoding).

Here, in calculating the prediction value, a prediction formula using the pixel value of the same color pixel in the same row and the pixel value of the same color pixel two rows before is used as the same color pixel, as shown in FIG. In the case of a three-primary-color CCD, the pixels on which color filters of the same color component are arranged for one row (1
This is because it does not exist before (line before) but there is a neighboring pixel of the same color two lines before.

After the upper bit data is encoded in step S3, the lower 4 bits of the pixel of interest are replaced with the adjacent pixel (in the example shown in FIG. The pixel is combined with the lower bit data and processed as 8-bit data as a whole.
That is, of the pixels (n) included in the same row among the pixels (FIG. 2) arranged in a matrix, the odd-numbered pixels or the even-numbered pixels from the extreme end position (B11 in the first row of FIG. 2). It is determined whether or not there is an odd number (B11, B13, B1).
If 5), the lower 4-bit data is stored in row buffer 1
The upper 4 bits of 5C (8 bits) are shifted and stored. If it is an even number (G12, G14), the lower bit data is directly stored in the lower 4 bits of the row buffer 15C. As a result, in the row buffer 15C, the odd 4 bits (B11,
B13, B15) are stored, and even-numbered lower-order bit data (4 bits) are stored in the lower 4 bits of the row buffer 15C (bit shift processing, packing processing).

In step S5, step S1 described above is performed.
It is determined whether or not the processing of Step S4 has been performed for one row, that is, all of the n pixels included in the current target row, and when the processing for one row has been completed ( The determination result is “Yes”, and the process proceeds to the next step S6.
In step S6, upper compressed data obtained for one row (n pixels) is combined as an upper compressed data block, and similarly, lower data is combined as a lower data block (blocking). .

In step S7, the position information of the lower data block in the same row is added to the head position of the upper compressed data block. In step S8, position information indicating the head position of the upper compressed data block of each row is added to the address buffer 15A. In this manner, the upper-side compressed data and the lower-side data of one row to which the position information of the upper-side compressed data block and the position information of the lower-side data block stored in the address buffer 15A are added are stored in the storage medium 2. It is stored at a predetermined timing.

When the encoding of the image data for one line of interest this time is completed, in the next step S9, the processing of the above-described steps S1 to S8 is performed by m lines constituting one frame (one screen). It is determined whether or not all the operations have been performed. If the processing for one frame (processing for m rows) has not been completed yet, the determination result of step S9 is “No”.
Then, the above-described steps S1 to S8 are repeatedly executed.

On the other hand, if the decision result in the step S9 is "Ye
In the case of s ", that is, when the processing for all the rows (m rows) of one frame is completed, the present program is terminated. The encoded image data ( 1 shows a data format (for one frame).

As shown in this figure, for one frame of image data, the uppermost compressed data block position information for one frame (m lines) is stored at the earliest position, and thereafter the image data for each line is stored. Data blocks are stored in a repeating pattern from the first row to the m-th row. One row of lower data block position information is added to the head position of each row of image data blocks, followed by one row of upper compressed data blocks and one row of lower data blocks. Are sequentially stored.

The upper compressed data block position information provided at the earliest position of one frame of image data is 1
4 shows positional information (information on the upper compressed data position indicated by ↓ in FIG. 4) of the image data block of each line of the image data of the frame (m lines). Further, the lower data block position information provided at the head position of the image data block of each row indicates the position information of the lower data block in the image data block of each row (information of the position indicated by ↑ in FIG. 4). Things.

More specifically, as shown in a partially enlarged manner in FIG. 4 (the image data block in the second row is enlarged in the figure), the upper data block following the lower data block position information in the second row is shown. In the side compressed data block, the upper side compressed data of all the pixels (for n pixels) included in the second row are divided into blocks. The lower-side data (8 bits) packed and addressed to two pixels and represented by one byte is for one row (for n pixels).
Are divided into lower data blocks.

As described above, the uppermost compressed data block position information is stored at the earliest position of one frame of image data, whereby the upper compressed data of a specific row in one frame of image is randomly stored. Can be read. Here, the upper compressed data block position indicating the position of the upper compressed data block simultaneously indicates the position of the image data block of each row. Therefore, both the upper compressed data and the lower data of a specific row can be read at random.

The reason why the lower-side data block position information is added to the head position of the image data block in each row as described above is that the length of the upper-side compressed data block is determined by the JPEG lossless encoding. This is because the data length is variable and the data length is different for each row. FIG.
Shows another data format example when the upper compressed data block and the lower data block are stored in the storage medium 2.

In the data format shown in FIG.
In compressing and storing the image data for one frame, the point that the upper compressed data block position information and the lower data block position information are alternately stored for each row at the earliest position, This is different from the data format shown in FIG. For this reason, in the second data format example, random reading of the upper-side compressed data of a specific row based on the upper-side compressed data block position information, and upper-side compression of the specific row based on the upper-side compressed data block position information are performed. In addition to being able to read both the compressed data and the lower data at random, it is also possible to perform random reading of the lower data of a specific row based on the lower position data.

Next, decoding of the compressed image data encoded according to the above procedure will be described. FIG. 6 is a block diagram showing a decoding processing device 20 for decoding the compressed image data stored in the storage medium 2. The decoding processing device 20 decodes the compressed image data from the storage medium 2 and outputs the decoded image data (12-bit original data) to an image processing / correction device (personal computer) 30. An input data buffer 21 for reading compressed image data from the storage medium 2;
CPU for restoring the compressed image data from the CPU, a restored data buffer 23 for temporarily storing and outputting the restored image data (original data) for each row, and a main memory 24 for storing programs executed by the CPU 22, etc. And is constituted by.

Further, an image processing / correcting device 30 is connected to the decoded data buffer 23 of the decoding processing device 20. The image processing / correction device 30 restores image data (1) based on processing / correction information (information input by a user's keyboard operation or the like) input from outside.
2 bits (original data) is processed / corrected.
The processed / modified image data (for example, 8-bit image data) is output to an image output device (for example, a CRT or a printer) 40 so that a desired image can be obtained. When the above-described decoding device 10 is used in a digital camera, the decoding device 2
0, the image processing / correcting device 30 is mainly configured by a personal computer.

Here, the input data buffer 21 of the decoding processing device 20 constitutes an address buffer 21A, a high buffer 21B, and a low buffer 21C. Then, “upper side compressed data block position information” from the storage medium 2 is temporarily stored in the address buffer 21A,
The “upper compressed data” and “lower data block position information” from the storage medium 2 are temporarily stored in the high buffer 21B. The “lower data” from the storage medium 2 is temporarily stored in the row buffer 21C.

The restored data buffer 23 of the decoding processor 20 constitutes a buffer 23A for the target line, a buffer 23B for the previous line, and a buffer 23C for the previous line. Then, the restored image data (12-bit original data) of the current line to be restored (restoration target line) is temporarily stored in the target line buffer 23C. The one-line preceding buffer 23B temporarily stores the one-line preceding image data (12-bit original data) shifted from the target line buffer 23A, and the one-line preceding buffer 23C stores the one-line preceding buffer 23C. 23
The image data (the original data of 12 bits) two rows before shifted from B is temporarily stored.

FIG. 7 shows the C of the above-mentioned decoding device 20.
It is a program flowchart which shows the image decoding process performed by PU22. When the image decoding program is started, first, in step S21,
The position information (upper compressed data block position information, lower data block position information) taken into the input data buffer 21 from the storage medium 2 is read by the CPU 22.

In step S22, based on the read upper compressed data block position information (information indicating the position indicated by ↓ in FIG. 4), the row (1
All data in the image data block of (line) is read. In step S23, the lower data block position information read in step S21 (# in FIG. 4)
The data read in step S22 is separated into an upper compressed data block and a lower data block on the basis of the information indicating the position of.

In step S24, well-known JPEG lossless decoding is performed on the upper compressed data stored in the separated upper compressed data block. The JPEG lossless decoding is performed in a procedure reverse to the coding procedure performed in step S3 of the above-described image coding processing (FIG. 3). That is, when decoding the higher-order bit data (8 bits) of the pixel of interest, first, the pixel value two pixels before (same color pixel) decoded two loops before is obtained. Next, a plurality of temporary prediction values of the same color pixel two pixels before are obtained based on a plurality of prediction formulas using pixel values of neighboring pixels of the same color or adjacent pixels. Then, the pixel value two pixels before is compared with these temporary predicted values to determine the prediction error Δ, and a prediction formula (optimal prediction formula) that minimizes this is determined. Finally, the prediction value of the target pixel in the current loop is obtained using this optimal prediction formula, and the upper bit data (8 bits) of the target pixel is decoded from the stored prediction error Δ and this prediction value. .

In step S25, the lower-order data (two pixels are represented by 8 bits) packed in step S4 of the above-described image encoding process (FIG. 3) is replaced with the upper 4 bits in odd numbers. , The lower 4 bits are restored as even-numbered image data (lower-order bit data).

In step S26, the above-mentioned step S24
The 12-bit image data (original data) is obtained from the high-order bit data (8 bits) restored in step S25 and the low-order bit data (4 bits) restored in step S25. In step S27, the above-described step S
It is determined whether or not the processing from step S24 to step S26 has been performed for one row, that is, all the n pixels included in the same row. When the decoding processing for one row is completed, the process proceeds to step S28. move on.

In step S28, the above-described step S
It is determined whether or not the processing from step 22 to step S27 has been performed for all rows (m rows) constituting one frame (one screen). If the processing for one frame has not been completed yet, Returning to step S22, the process is repeated.
When the processing has been completed for all the rows (m rows) of one frame (the determination result in step S28 is "Yes"), the program is terminated as it is (END).

As described above, according to the image data encoding method and the image data decoding method of the first embodiment,
The image data (12
Bit image data), high-order bit data (8 bits) with high correlation is compressed at a high compression rate by JPEG lossless coding, and low-order bit data (4 bits) with low correlation is processed. Since the bit shift and packing processes are performed to increase the speed, the speed of the encoding process can be increased while securing a high compression ratio for the entire 12-bit image data (original data).

By decoding only the upper-side compressed data of the encoded image data, a coarse image can be reproduced at a high speed. At this time, the upper compressed data block position information is stored at the earliest position of the compressed image data for one frame, and the upper compressed data block position (the position indicated by ↓ in FIG. 4) can be immediately recognized. For,
Reproduction of coarse images is performed easily and at high speed. In addition, a specific line can be selected from the m lines to partially reproduce an image at high speed. In the first embodiment, in order to perform the process efficiently, the process returns to step S24 while the determination result in step S27 is “No”, and
While the process returns to step S22 and repeats the process while the determination result in step S28 is “No”, as shown in FIG. 8, when the determination result in step S27 is “No”, or When the determination result in step S28 is "No", the processing may be repeated from the reading of the position information in step S21.

(Second Embodiment) Next, a second embodiment of the present invention will be described.
The embodiment will be described with reference to FIGS. 9 and 10. FIG. This second embodiment also corresponds to claims 1 to 5. In the second embodiment, when the upper compressed data block and the lower data block are stored in the storage medium 2, the upper compressed data of all rows (m rows) for one frame of image data is stored. A data block and a lower data block of all rows (m rows) are separately stored.

FIG. 9 shows the data format in this case. Note that the configuration of the encoding processing device and the decoding processing device for realizing the second embodiment is the same as that of the encoding processing device 10 (FIG. 1) of the first embodiment described above. 20 (FIG. 6), and the description thereof is omitted. Also, the encoding of the upper bit data (JPEG lossless encoding) differs only in the procedure of storage in the storage medium 2 performed in steps S6 to S9 of the image encoding process shown in FIG. That is, in the second embodiment, as shown in FIG. 9, both the upper compressed data block position information and the lower data block position information are stored at the earliest position of one frame of image data. ,
The upper data blocks are stored collectively for m rows, and then the lower data blocks are stored collectively for m rows.

As described above, the upper data blocks for m rows are collected, and the lower data blocks for m rows are collected.
By storing the data in the storage medium 2 in a separated state, when the image data is reproduced, for example, when only the upper 8 bits of data are decoded and output (when only the coarse 8 bit image is reproduced), Only the upper-side compressed data need be decoded based on the upper-side compressed data block position information stored in, and the processing speed is increased.

In the data format of the compressed image in the second embodiment, the upper compressed data block position information and the lower data block position information are stored together. Also, the upper compressed data and the lower data are stored together. Therefore, it is possible to read out all the upper compressed data or all the lower data included in one screen at a high speed based on each position information.

The procedure for decoding only the upper compressed data and reproducing a coarse image (upper 8 bits) at high speed will be described below with reference to the program flowchart shown in FIG. This program is executed by the CPU 22 of the decryption processing device 20 (FIG. 6). First, in step S31, the upper data block position information is read.

In step S32, data in the upper compressed data block (upper compressed data) for one row is read using the upper data block position information. In step S33, JPEG is performed in a procedure reverse to the JPEG lossless encoding performed in the encoding process.
By the lossless decoding, decoding of one pixel of the read high-order side compressed data is performed. This step S3
3 is performed in the same procedure as in step S24 in FIG.

In step S34, the above-described step S
It is determined whether or not the processing of 33 is performed for one row, that is, n pixels included in the same row. When the processing of one row is completed, the process proceeds to the next step S35. In step S35, the above-described steps S32 to S33
All lines (m lines) that make up one frame (one screen)
Is determined, and if the processing for one frame has not yet been completed, the above-described step S3
2 and the process is repeated.

On the other hand, if it is determined in step S35 that the decoding process has been completed for all the lines of one frame, the present program is terminated (END). According to the second embodiment described above, when restoring the image data from the storage medium 2 in which the high-definition original data (RAW data) represented by 12 bits per pixel is compressed and stored. By restoring only the upper 8 bits having strong correlation, a coarse image can be reproduced at high speed. It should be noted that also in the second embodiment, in order to perform the processing efficiently, the determination result in step S34 is “No”.
Is returned to step S33, and step S35
While the determination result is “No”, the process returns to step S32 to repeat the processing. However, as shown in FIG. 11, when the determination result in step S34 is “No”, or when the determination result in step S35 is “No”. When the determination result is “No”, the process may be repeated from step S31.

In the first and second embodiments, the case where the original data (RAW data) of an image is 12 bits has been described. However, image data larger than 12 bits and image data smaller than 12 bits are described. In any case, the present invention is applicable, and in this case, the processing speed can be increased while securing a high compression ratio.
In the first and second embodiments, an example has been described in which the original 12-bit data (RAW data) is separated into upper 8 bits and lower 4 bits. In the case of 12-bit image data, it is generally empirically known that the range is from 6 bits to 9 bits.), However, the number of bits other than 8 bits can be set. In this case, the number of upper bits to be used as upper bit data may be determined for each frame (one screen).

In the first and second embodiments described above, both the encoding processing device and the decoding processing device are configured separately (for example, when the encoding processing device is a digital camera side, Although the decoding device has been described on the personal computer side, these two devices may be incorporated in one device (for example, both may be incorporated in a digital camera or the like).

In the first and second embodiments, the processing for separating the image data into the upper side and the lower side, and the encoding processing by the DPCM encoding of the upper bit data,
In both cases, an example has been described in which the processing is performed by the CPU 13 in the encoding processing apparatus 10. However, the present invention is not limited to this, and the encoding by the dedicated LSI integrated on an external chip is performed by performing the DPCM encoding. The CPU 13 in 10 may be configured to separate only the upper side and the lower side. In this case, the external dedicated LSI is replaced with DPCM encoding.
An LSI that performs encoding by Ziv-Lempel or the like may be used. Also, for decoding, a chip in which dedicated LSIs are similarly integrated is externally attached to the decoding processing device 20, and DPCM decoding of higher-order bit data is performed by a dedicated LSI in the chip (or by Ziv-Lempel or the like). (Decoding). In this case, the CPU 22 of the decoding processing device 20 may combine the upper bit data and the lower bit data after decoding.

Although the first and second embodiments have been described on the assumption that a still image is obtained by a digital camera or the like, the present invention is also applicable to the case of obtaining a moving image. It is.

[0065]

According to the first aspect of the present invention described above,
The image data obtained with high definition is separated into upper bit data having a high correlation with neighboring pixels and lower bit data having a low correlation, and the image data is encoded. Therefore, by performing encoding with a high compression rate for the high-order bit data and increasing the processing speed for the low-order bit data, the image data as a whole is encoded at a high compression rate, and the processing speed is increased. Can be enhanced. Further, the management information achieves high-speed processing when selectively encoding / decoding the image data of a specific row.

According to the second aspect of the present invention, since the upper bit data and the lower bit data are individually divided into blocks for each row, the image of the specific row is restored by restoring the upper bit data. Can be further accelerated when selectively reproducing. According to the third aspect of the present invention, image data is compressed at a high compression ratio with respect to high-order bit data having high correlation.

According to the fourth aspect of the present invention, image data captured with high definition can be restored with high definition, and the user can process / modify this high-definition image data, The image data after the correction can have an image quality according to the specifications of the output device. According to the fifth aspect of the present invention, only the high-order bit data of the high-definition image data can be selectively restored, a coarse image can be reproduced at high speed by the position information, and the image of the specific row can be reproduced. It is possible to speed up the process of partially reproducing only.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of an encoding processing device according to a first embodiment of this invention.

FIG. 2 is a diagram showing a layout of a color filter arranged on a light receiving surface of the image input device 2.

FIG. 3 is a flowchart illustrating an image encoding process according to the first embodiment.

FIG. 4 is a diagram showing a first example of a format of compressed image data obtained according to the first embodiment.

FIG. 5 is a diagram illustrating a second example of a format of compressed image data obtained according to the first embodiment.

FIG. 6 is a block diagram illustrating a configuration of a decoding processing device according to the first embodiment of this invention.

FIG. 7 is a flowchart illustrating an image decoding process according to the first embodiment.

FIG. 8 is a flowchart illustrating a different mode of the image decoding process according to the first embodiment.

FIG. 9 is a diagram showing a format of compressed image data obtained according to the second embodiment.

FIG. 10 is a flowchart illustrating an image decoding process according to the second embodiment.

FIG. 11 is a flowchart illustrating a different mode of the image decoding process according to the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image input apparatus (CCD) 2 Storage medium 10 Encoding processing unit 12 Input data buffer 13 CPU 15 Output data buffer 20 Decoding processing unit 21 Input data buffer 22 CPU 23 Restoration data buffer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 5/92 H04N 5/92 H 7/24 7/13 Z

Claims (5)

[Claims] 1. An image data compression method for compressing image data obtained with a fixed number of bits per pixel by an image input means, wherein the data of each of the fixed number of pixels is represented by a predetermined number of upper bits. Separating upper bit data into lower bit data represented by a predetermined number of lower bits, applying variable length coding to the upper bit data, and converting the lower bit data into a plurality of pixels. Packing by a destination bit shift operation; generating management data for individually managing the variable length coded upper bit data and the packed lower bit data; and the variable length code. And storing the encoded upper bit data, the packed lower bit data, and the generated management data in a storage medium. Image data compression method, characterized in that comprising the step of 憶. 2. The image data compression method according to claim 1, wherein said image input means is input means in which pixels are arranged in a matrix, and said variable-length coded upper bit data is in the same row. The packed lower-order bit data is blocked for each included pixel, and the packed lower-order bit data is blocked for each pixel included in the same row. As the management data, the blocked upper-order bit data and the blocked An image data compression method, wherein position information indicating each storage position of lower-order bit data is generated. 3. The image data compression method according to claim 1, wherein said variable-length encoding is performed by Huffman encoding and DPCM encoding. 4. The image data compression method according to claim 1, wherein the fixed number of bits of the data for each pixel is a value corresponding to a detection accuracy of the image input unit. The image data compression method, wherein the predetermined number of bits on the side is the number of bits on the high-order side where there is a strong tendency to cause a correlation with neighboring pixels, and the value is obtained by an empirical rule. 5. An image data management method for managing image data obtained with a fixed number of bits per pixel by image input means in which pixels are arranged in a matrix, wherein the data for each pixel having the fixed number of bits is stored in a higher order Separating upper bit data represented by a predetermined number of bits from lower bit data represented by a predetermined number of lower bits, and blocking the upper bit data for each pixel included in the same row. And blocking the lower bit data for each pixel included in the same row; and storing the storage locations of the blocked upper bit data and the blocked lower bit data. Generating position information indicative of: the higher-order bit data blocked and the lower-order bit data blocked Image data management method characterized by comprising the step of storing the positional information the generated in the storage medium.