JPH09200753A - Image compressing/extending device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce picture quality degradation and to provide a satisfactory restored image even when any error is generated in compressed image data by performing compressing processing while dividing all the picture elements of a source image into plural picture element groups. SOLUTION: Data for one line of the source image in a source image memory 23 are transferred to a buffer memory 26 and under the control of a division control circuit 27, the data for one line in the buffer 26 are read out while being divided into data belonging to odd-number addresses and data belonging to even-number addresses. Then, a compressing means 28 performs the compressing processing for each picture element group divided by a dividing means 25, and these picture element groups are successively sent out and stored in a storage means 21. When any error is generated in any picture element group in the compressed image data, since that error appears as an error distributedly existent at every other picture element in a restored image 22 without fail, all the information in a specified area can be prevented from being lost by this error.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image compression / decompression device which compresses a captured original image and decompresses the compressed image.

[0002]

2. Description of the Related Art When transmitting / receiving a digital image through a communication line, storing it in a storage device, or reducing the load on the communication path or the storage device, the original image is subjected to image compression processing. We are trying to reduce the amount of data.

FIG. 5 shows a conventional image compression apparatus.
This apparatus includes an original image memory 1 for storing an original image, an address controller 4 for controlling the address of the memory 1, and an original image read from the original image memory 1 under the control of the address controller 4. And a compressor 2 for compressing the compressed image, and the compressed image is stored in a storage means (eg, magnetic disk, optical disk) 3
Is written to.

The compressor 2, for example, as shown in FIG. 6, has an input buffer 5 for temporarily storing the data from the original image memory 1, and a linear input of the next input data based on the already input data. A linear predictor 10 for performing prediction,
An adder 6 that performs addition processing of the output data of the input buffer 5 and the prediction output of the linear predictor 10, a Huffman encoder 7 that performs Huffman coding processing of this addition output, and a byte of Huffman coding output A byte format converter 8 for performing format conversion processing and an output buffer 9 for temporarily storing the converted output are provided, and compressed image data is sent to the storage means 3 via the output buffer 9. It has become.

The image compressed by the above image compression device is restored to the original image by going through the reverse process of the compression process. This device is called an image decompression device, and basically has a decompressor 16 as shown in FIG.
That is, the decompressor 16 includes an input buffer 11, a Huffman decoder 12 that performs a Huffman decoding process on the compressed image data captured via the input buffer 11,
An adder 14 that performs an addition process of the Huffman decoding output and the prediction output of the linear predictor 14, and a linear prediction that performs a linear prediction process of data next input to the adder 13 based on the addition output. It has a digitizer 14 and an output buffer 15 for temporarily storing the addition output of the adder 13, and the output of the output buffer 15 becomes the image data restored to the original image.

By the way, when the compressed image data is stored in a storage means such as a magnetic disk or an optical disk, an error may occur when reading the data.

For example, in the case of a magnetic disk or optical disk,
The unrecoverable error rate is 10 ¹² bits / error, 2000 × 2000 × 10 bit image 25000
An error occurs once per sheet.

Therefore, conventionally, as shown in FIG.
When the compression processing is performed for each line 7 and the processing result is written in the storage unit 3 for each line, for example, when a data error occurs in the Mth line as shown in FIG. The propagation of the data error is suppressed to only one line on the restored image 18.

[0009]

However, even if the data error is 1 bit, since the compressed image data itself is coded, not only the M-th line on the restored image 18 but also the one shown in FIG. As indicated by the shaded area in FIG. 10, even the Mth and subsequent lines are adversely affected, and significant information may be lost over a wide range.

Therefore, the present invention eliminates the above-mentioned drawbacks, and an object of the present invention is to provide an image compression / decompression device capable of obtaining a good restored image with little deterioration in image quality even when an error occurs in compressed image data. .

[0011]

According to the present invention, when a plurality of pixels that are not adjacent to each other on one line in the reading direction in the original image stored in the memory are regarded as one pixel group, all the original images in the original image are stored. Dividing means for dividing a pixel into a plurality of pixel groups, compression means for performing compression processing for each of the pixel groups, and storage means for storing the compressed output.
It has a restoring means for expanding the stored contents of the storing means for each pixel group to obtain each restored image, and a means for returning each restored image by the restoring means to the pixel array of the original image. .

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Before describing the embodiments of the present invention, the gist of the present invention will be briefly described. That is, all the pixels in the original image are divided into a plurality of pixel groups by the dividing means, compressed by the compressing means for each pixel group, and then stored in the storage means. For this reason, even if a data error occurs in any of the pixel groups in the compressed image data, it appears as an interspersed error on the image reconstructed by the reconstructing means, and the information of the specific area is completely lost. Never.

Next, the present invention will be specifically described with reference to examples.

FIG. 1 is a block diagram showing an embodiment of the present invention. As shown in the figure, the apparatus of this embodiment includes an image compression unit 20 for compressing an original image, a storage unit 21 for storing the compressed image, and an image decompression unit for decompressing the compressed image read from the storage unit 21. 22 and.

The image compressing section 20 comprises an original image memory 23, an address controller 24, a dividing means 25, and a compressing means 28. The original image memory 23 stores an original image (non-compressed image) fetched from the outside, and the address control of the original image memory 23 is performed by an address controller 24. The dividing means 25 divides all the pixels in the original image into a plurality of pixel groups when a plurality of pixels which are not adjacent to each other on the original image are made into one pixel group, and is sent out from the original image memory 23. It comprises a buffer memory 26 for storing data for one line of the original image, and a division control circuit 27 for enabling data transfer for each pixel group to the compression means 28 by address control of the buffer memory 26. Compression means 28
Performs a compression process for each pixel group, and the compressed image data generated by this process is stored in the storage means 21. As the storage means 21, for example, a magnetic disk or an optical disk is applied.

The image decompression unit 22 also includes a restoring means 29,
Interpolation means 33, restored image memory 34, address controller 3
5 is included. The decompression unit 29 expands the stored contents of the storage unit 21 for each pixel group to obtain a decompressed image, and the decompressor 30 that decompresses the compressed image data sent from the storage unit 21 for each pixel group. A buffer memory 31 for storing the decompressed output and this buffer memory 3
And a restoration control circuit 32 that rearranges data by address control of 1. The interpolating means 33 interpolates a data error portion on the restored image from adjacent pixels. Then, the formed restored image is transmitted to the outside via the restored image memory 34 arranged in the subsequent stage. The address control unit 35 uses the restored image memory 3
4 address control is performed.

Next, the operation of the above configuration will be described.

<Image compression> First, the data for one line of the original image in the original image memory 23 is transferred to the buffer memory 26, and the data for one line in the buffer 26 is controlled by the division control circuit 27. Are read separately for data belonging to odd addresses and data belonging to even addresses. FIGS. 2A, 2B and 2C show changes in addresses in this case. When writing data to the buffer memory 26, as shown in FIG.
Addressing is performed in the order of 2, 3, 4, ..., N. Then, when reading, as shown in FIG.
3, 5, ..., N-1 in order of odd number address control, and as shown in FIG.
..., N, and even-numbered address control for addressing are executed in this order. By such read address control, one line of data is divided into data belonging to odd addresses and data belonging to even addresses. In other words, it is divided into an odd-numbered pixel group and an even-numbered pixel group, which are composed of a plurality of pixels that are not adjacent to each other.

Such pixel group division processing is executed for every line of the original image. Then, the compression means 28 performs compression processing for each pixel group divided by the division means 25, and the processing results are sequentially sent to and stored in the storage means 21. FIG. 3 shows the relationship between the original image 17 and the compressed image data in the storage means 21. As shown in FIG. 3, the compressed image data obtained for each pixel group is written in different areas in the storage means 21. Be done. In the figure, "O" means that the data is an odd-numbered pixel group, and "E" means that it is an even-numbered pixel group.

<Image Decompression> The compressed image data in the storage means 21 is taken into the decompressor 30 for each pixel group,
The data is decompressed here and then written in the buffer memory 31. In writing this decompressed data, the restoration control circuit 3
By the write address control by 2, the decompressed data for each pixel group is returned to the pixel array of the original image. That is, as a result of the decompression processing performed by the decompressor 30 for each pixel group as described above, the processing output is a pixel array for each odd address and even address. Therefore, the restoration control circuit 32 causes the buffer memory 31. By controlling the write address of, the array of decompressed data on the buffer memory 31 is restored to the original pixel array before division.
As a result, a restored image is obtained. FIG. 4 shows a restored image, and this pixel array matches the original image. When an error occurs in any pixel group in the compressed image data, the error always appears as an error scattered every other pixel in the decompressed image 22, so that the error completely eliminates the information on the specific area. There is no such thing. Therefore, the interpolation unit 33 can easily interpolate the abnormal pixel from the pixels (adjacent pixels) around the abnormal pixel, and it is possible to obtain a good restored image with little image quality deterioration. This restored image is the restored image memory 3
It is sent to the outside via the No. 4.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications can be made. For example, in the above-described embodiment, a description has been given of a case where the pixel is divided into pixel groups every other pixel, such as an odd-numbered pixel and an even-numbered pixel. Further, the present invention can be applied even when a communication line is included in the transmission path of the compressed image data.

[0022]

As described above in detail, according to the present invention, it is possible to provide an image compression / expansion device capable of obtaining a good restored image with little deterioration in image quality even when an error occurs in compressed image data. it can.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory view of the operation of the device of this embodiment.

FIG. 3 is an explanatory view of the operation of the device of this embodiment.

FIG. 4 is an explanatory view of the operation of the device of this embodiment.

FIG. 5 is a block diagram of a conventional example.

FIG. 6 is a block diagram of a conventional example.

FIG. 7 is a block diagram of a conventional example.

FIG. 8 is an operation explanatory view of a conventional example.

FIG. 9 is an operation explanatory view of a conventional example.

FIG. 10 is an operation explanatory view of a conventional example.

[Explanation of symbols]

21 ... storage means, 25 ... division means, 28 ... compression means, 2
9 ... Restoration means, 33 ... Interpolation means.

Claims (1)

[Claims] 1. When a plurality of pixels which are not adjacent to each other on one line in the reading direction in the original image stored in the memory are regarded as one pixel group, all the pixels in the original image are divided into a plurality of pixel groups. Dividing means for dividing into, a compression means for performing compression processing for each of the pixel groups, a storage means for storing the compressed output, and a storage content of the storage means for decompressing each pixel group. An image compression / decompression device comprising: a restoring unit for obtaining a restored image, and a unit for returning each restored image by the restoring unit to the pixel array of the original image.