JPH0799576A - Picture compressor, picture decoder and picture processing unit using them - Google Patents

Abstract

PURPOSE:To compress/decode a picture at a high compression rate without deterioration in quality of a reproduced picture by compressing a difference picture between an original picture and a picture obtained by decoding the original picture compressed by a 1st compression means and decoded by a decoding means at a 2nd compression means, decoding the compressed picture and synthesizing the picture. CONSTITUTION:An original picture A1 is inputted to a high compression rate coder 3 and a differential picture generating section 4 via a picture input device 1 and a picture memory 2. The coder 3 compresses the original picture A1 at a high compression rate by the DCT system to generate a compressed picture A2. The picture A2 is stored in a database 7 and inputted to a high compression rate decoder 5. The decoder 5 decodes the picture A2 to generate a decoded picture A3. A difference picture generating section generates a positive difference picture C1 and a negative difference picture D1 based on the difference calculation between the picture A3 and the original picture A1 and they are stored in the database 7. The picture A2 is sent to the decoder 5 by an external output request and pictures C2, D2 are fed to a decoder 8. The decoder 5 generates the decoded picture A1 and the decoder 8 generates the pictures C2, D2. A synthesis section 9 generates a decoded picture E1 from the original picture based on the pictures as above.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for compressing / decompressing image data.

[0002]

2. Description of the Related Art In recent years, the purpose of the present invention is to reuse image data for printing as an original for printing such as commercial printing and leaflets, or to provide high-definition printing images on various electronic media. The construction of an image database is being considered.

A problem in constructing this image database is establishment of a compression technique. The image data for printing generally has a data size of about 30 MB,
It is extremely large. If such image data with a large data size is stored and managed as it is, the storage area of the database will be squeezed, the work efficiency during data processing will be significantly reduced, and the image transfer efficiency will be further reduced. . At present, there is a discrete cosine transform (DCT) method as a compression method often used not only for data compression of print image data but also for various data compression. This D
The CT method is a method that pays attention to a component (spatial frequency) in which a pixel value of an image changes, and can realize data compression with a high compression rate.

However, the data compression by the DCT method is
Although it is possible to compress at a high compression rate, the quality of the reproduced image deteriorates to some extent. The printed matter provided as a still image is
Evaluation is made from each angle such as resolution, color tone, and gradation. Therefore, when a complete image reproduction without any information loss is required, a reversible coding system such as a reversible coding system is mainly adopted instead of the DCT system.
However, the lossless coding method cannot realize a high compression rate that can replace the DCT method.

[0005]

As described above, in the conventional image compression method, the image data could not be compressed at a high compression rate without degrading the quality of the reproduced image. Therefore, the image data can be compressed by the DCT method or the like. Compared with such a high compression rate, it is necessary to handle image data having a low compression rate, which causes a problem that the memory area of a database or the like is pressed and work efficiency and image transfer efficiency are reduced.

The present invention has been made in view of the above circumstances, and it is possible to compress image data at a high compression rate without degrading the quality of a reproduced image, save the memory area, and perform the work. An object of the present invention is to provide an image compression device capable of improving the efficiency and the efficiency of image transfer.

Another object of the present invention is to provide an image decompression device capable of decompressing image data compressed at a high compression rate without degrading the quality of reproduced images.

Further, according to the present invention, it is possible to compress image data at a high compression rate without degrading the quality of reproduced images.
Moreover, it is an object of the present invention to provide an image processing apparatus capable of restoring image data having a high compression rate without deteriorating quality of a reproduced image.

[0009]

In order to achieve the above object, the present invention has taken the following means.

According to the first aspect of the image compression apparatus, the first compression means for compressing the original image, the restoration means for restoring the compressed image created by the first compression means, and the restoration means for restoring the compressed image. A difference means for creating a difference image between the restored image and the original image, a second compression means for compressing the difference image created by the difference means, and a compressed image of the difference image created by the second compression means A storage unit that stores the compressed image of the original image created by the first compression unit is provided.

According to a second aspect of the present invention, there is provided an image compression apparatus, wherein the first compression means uses a high compression rate compression system and the second compression means.
As the compression means, a high compression rate compression method or a reversible compression method is used.

An image restoration apparatus according to a third aspect stores a compressed image obtained by compressing an original image and a compressed image obtained by compressing a difference image between the original image and a compressed image obtained by compressing the original image. Means, decompressing means for decompressing the compressed image of the original image and the compressed image of the differential image in the storage means, and a synthesizing means for synthesizing the decompressed image of the original image and the decompressed image of the differential image restored by the decompressing means. And is configured to include.

According to another aspect of the image restoration apparatus of the present invention, the storage means compresses the original image compressed by the high compression rate compression method and the high compression rate compression method or the reversible compression method. The differential image is stored, and the decompression means uses a decompression method corresponding to each compression method of the original image and the differential image.

According to a fifth aspect of the present invention, there is provided an image processing apparatus which comprises a first compression means for compressing an original image, a first decompression means for decompressing a compressed image created by the first compression means, and a first decompression means. Difference means for creating a difference image between the restored image restored by the restoring means and the original image, a second compression means for compressing the difference image created by this difference means, and a second compression means Storage means for storing the compressed image of the difference image and the compressed image of the original image created by the first compression means;
Second restoring means for respectively restoring the compressed image of the original image and the compressed image of the differential image in the storage means, and the restored image of the original image restored by the second restoring means and the restored image of the differential image are combined. And a synthesizing means for doing so.

[0015]

The present invention has the following effects by taking the above means.

In the image compressing apparatus according to the first aspect, the original image is compressed by the first compressing means, and the compressed image is restored by the restoring means. The restored image and the original image are input to the difference means to create a difference image between them. This difference image is compressed by the second compression means. Then, the compressed image of the difference image and the compressed image of the original image are stored in the storage means.

In the image compression apparatus according to the second aspect, the original image is compressed by the first compression means using the high compression rate compression method, and the differential image is compressed by the second compression means. Alternatively, the compression is performed using one of the lossless compression methods.

Here, the original image compressed at a high compression rate is restored by correcting the image deteriorated in the compression process at a high compression rate by synthesizing with the difference image, so that a restored image without deterioration is obtained. Will be obtained. Further, since the difference image is a flat image, a sufficient compression rate can be expected even with lossless compression. Therefore, the data size can be significantly reduced compared to the case where the original image is compressed by the lossless compression method.

In the image restoration apparatus according to the third aspect, the compressed image of the original image and the compressed image of the difference image stored in the storage means are restored by the restoration method by the restoration method corresponding to each compression method. It Then, the restored image of the original image restored by the restorer and the restored image of the difference image are combined by the combiner to restore the original image.

In the image restoration apparatus according to the fourth aspect, the original image is compressed by using a compression method with a high compression rate, and the differential image is compressed by either a compression method with a high compression rate or a reversible compression method. Compressed and stored in the storage means. When the original image is compressed at a high compression rate, a part of the information deteriorates, and the deteriorated information is corrected by combining it with the difference image. Therefore, the reproduced image does not show image quality deterioration due to data compression at a high compression rate. Further, if the reversible compression method is used for the difference image, there is no information deterioration, so that the restoration accuracy of the original image is improved. Also, even if a compression method with a high compression rate is used, the difference image is a flat image,
There is no significant deterioration like the original image, and the restoration accuracy of the original image can be sufficiently improved.

In the image processing apparatus according to the fifth aspect, when the original image is compressed and saved, the original image is compressed by the first compression means, saved in the storage means, and sent to the first decompression means. Given. The original image restored by the first restoring unit and the original image that has not been compressed are input to the difference unit to create a difference image between them. This difference image is the second
It is compressed by the compression means and stored in the storage means.

On the other hand, when restoring the compressed image stored in the storage means, the compressed image of the original image and the compressed image of the difference image stored in the storage means are respectively compressed by the second restoring means. It is restored by the corresponding restoration method. Then, the restored image of the original image restored by the second restoring unit and the restored image of the difference image are combined by the combining unit to restore the original image.

[0023]

Embodiments will be described below with reference to the drawings.

FIG. 1 shows functional blocks of an image processing apparatus according to an embodiment of the present invention.

The image processing apparatus of this embodiment uses the image data captured by the color image input apparatus 1 such as an image scanner as an original image in the image memory 2 in units of R,
It is stored for each G and B.

The image data of the original image stored in the image memory 2 is given to the high compression rate encoder 3 which serves as the first compression means and the difference image creating section 4 which serves as the difference means when the data is compressed.

The high compression rate encoder 3 executes data compression processing by the DCT method as one of the compression methods with a high compression rate. The compressed image compressed by the high compression rate encoder 3 is given to the decompression means, the high compression rate decoder 5 which is a part of the first decompression means or the second decompression means, and a database described later.

The high compression rate decoder 5 restores the compressed image by a decoding method corresponding to the DCT method. In the high compression rate decoder 5, the restored image of the image input from the high compression rate encoder 3 is output to the difference image creating unit 4, and the restored image of the image input from the database is output to the synthesizing unit described later. The output direction is switched as described above.

The differential image creating unit 4 creates a differential image by taking the difference between the original image given from the image memory 2 and the restored image of the same original image given from the high compression rate decoder 5. This difference image is composed of two pieces of image data of a + difference image and a −difference image created for one original image. The difference image created by the difference image creating unit 4 is given to the lossless compression encoder 6 serving as the second compression means.

The lossless compression encoder 6 data-compresses the difference image using a lossless compression method. The compression difference image losslessly compressed by the lossless compression encoder 6 is stored in the database 7. The database 7 stores the compressed image of the original image compressed by the high compression rate encoder 3 and the compressed differential image of the same original image from the lossless compression encoder 6 in association with each other. Various image data are stored in the database 7 after being compressed by the above-mentioned elements.

The compression source image and the compression difference image of the same original image stored in the database 7 are given to the high compression rate decoder 5 at the time of data restoration, and the compression difference image is converted to the lossless compression decoder. Given to 8. The lossless compression decoder 8 restores the compressed difference image by a restoration method corresponding to the lossless compression method of the lossless compression encoder 6.

The reconstruction source image restored by the high compression rate decoder 5 and the difference image restored by the lossless compression decoder 8 are combined by a synthesizing unit 9
Given to. The synthesizing unit 9 creates the original image completely restored.

Next, the operation of this embodiment configured as described above will be described.

2 to 5 show the compression process of the original image, and FIGS. 6 to 8 show the decompression process.

The original image A1 of the data example shown in FIG. 2 from the image memory 2 is the high compression rate encoder 3 and the difference image creating unit 4.
To enter. The high compression rate encoder 3 converts the original image A1 into a DC image.
Data is compressed at a high compression rate by the T method to create a compressed image A2. The compressed image A2 is stored in the database 7 and also input to the high compression rate decoder 5. The high compression rate decoder 5 restores the compressed image A2 to create a restored image A3, as shown in FIG. This restored image A3
Indicates that data of pixels indicated by circles in the figure are deteriorated due to data compression with a high compression rate.

When the restored image A3 is input from the high compression rate decoder 5, the difference image generator 4 has already input the image memory 2
The difference calculation with the original image A1 given by The process of creating this difference image is shown in FIG. The restored image A3 is subtracted from the original image A1 to create a + difference image C1 and a −difference image D1. In the + difference image C1 and the −difference image D1, the degraded data appears only in the degraded pixels of the restored image A3, and the other non-degraded pixels have a pixel value of 0.

The + difference image C1 and the −difference image D1 created by the difference image creation unit 4 are input to the lossless compression encoder 6, where they are losslessly compressed as shown in FIG. C2 and-a differential compression image D2 is created. Here, since the + difference image C1 and the −difference image D1 are flat images with all 0s except for the deteriorated pixels, a sufficient compression rate can be achieved even by reversible compression.

The + differential compressed image C2 and the −differential compressed image D2 created as described above are stored in the database 7.

On the other hand, the database 7 manages the compressed image A2 of the original image and the + differential compressed image C2, −the differential compressed image D2 of the original image in association with each other. Then, if there is an output request by designating the original image from the outside, the compressed image A2 of the designated original image is sent to the high compression rate decoder 5, and the + difference compressed image C2 of the designated original image and − The differential compressed image D2 is sent to the lossless compression decoder 8.

In the high compression rate decoder 5, since the same decompression process is performed on the same compressed image A2 as the decompression in the compression process described above, as shown in FIG. The image A3 is created.

On the other hand, since the lossless compression decoder 8 restores the losslessly compressed image data, the + differential compressed image C2 and the −differential compressed image D2 are losslessly decoded as shown in FIG. It

The restored image A3, the + difference image C1 and the −difference image D1 respectively restored as described above are given to the synthesizing section 9. As shown in FIG. 8, the synthesizing unit 9 adds a + difference compressed image C2 to the restored image A3, subtracts the −difference image D1 from the added value, and creates a final restored image E1.

In the synthesizing section 9, the restored image A3 and the difference image C1,
The restored image E1 obtained by the synthesis process of D1 is the original image A
Since 1 and the pixel value completely match, it means that the image can be completely restored without deterioration in image quality.

For example, as a compression method with a high compression rate, JPE is used.
When the DCT method of G is used and the special method of JPEG is used as the reversible compression method, assuming that the data size of the original image is 40 MB, the data size of the compressed original image and difference image is the original image = 40 × (1/40) = 1 MB Difference image = 40 × (1/5) × 2 = 17 MB.

As described above, according to this embodiment, the original image is image-compressed by the high compression rate DCT system and stored, and the compressed image is created by the decompression system corresponding to the DCT system. Since the difference image between the restored image and the original image is compressed and stored, the original image with almost no image deterioration can be restored only by combining the restored image and the difference image in the restoration process. Therefore, image data with a high compression rate can be accumulated and processed, and the amount of image data that can be stored in the database 7 can be greatly increased, and at the same time,
The efficiency of the work can be improved because the data compressed or compressed is transferred or processed.

In the above embodiment, the reversible compression is used for compressing the difference image, but other compression methods can be used. For example, DCT, which is a high compression ratio compression method.
The method can also be applied. Further, as a compression method with a high compression rate, a method other than the DCT method can be adopted.

In the above embodiment, the case where the compression process and the decompression process are performed by one system has been described, but the compression process and the decompression process may be performed by separate devices. In this case, the high compression rate decoder 5 is installed in each of the compression process and the decompression process.

The present invention is not limited to the above embodiments, but various modifications can be made without departing from the gist of the present invention.

[0049]

As described in detail above, according to the present invention, image data can be compressed at a high compression rate without deterioration of the quality of a reproduced image, the memory area can be saved, and the work efficiency can be improved. An image compression device that can improve the efficiency of image transfer can be provided.

Further, according to the present invention, it is possible to provide an image decompression device capable of decompressing image data compressed at a high compression rate without deteriorating the quality of a reproduced image.

According to the present invention, it is possible to compress image data at a high compression rate without degrading the quality of the reproduced image, and to cause the image data having the high compression rate to deteriorate the quality of the reproduced image. It is possible to provide an image processing device that can be restored without any problem.

[Brief description of drawings]

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

FIG. 2 is a process diagram of compressing an original image by a DCT method.

FIG. 3 is a process diagram of restoring a compressed image of an original image to create a difference image.

FIG. 4 is a process diagram of creating a difference image of an original image.

FIG. 5 is a process diagram of compressing a difference image by a lossless compression method.

FIG. 6 is a process diagram of restoring a compressed image of an original image to restore the original image.

FIG. 7 is a process diagram of restoring a compressed image of a difference image.

FIG. 8 is a process diagram of combining an original image and a restored image of a difference image.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image scanner, 2 ... Image memory, 3 ... High compression rate encoder, 4 ... Difference image creation part, 5 ... High compression rate decoder, 6 ... Reversible compression encoder, 7 ... Database, 8 ... Reversible Compressor / decoder 9, synthesis unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomohiko Matsuda 1-5-1 Taito, Taito-ku, Tokyo Toppan Printing Co., Ltd.

Claims (5)

[Claims] 1. A first compression unit for compressing an original image, a restoring unit for restoring a compressed image created by the first compression unit, and a difference between the restored image restored by the restoring unit and the original image. A difference means for creating an image, a second compression means for compressing the difference image created by the difference means, a compressed image of the difference image created by the second compression means, and a first compression means An image compression apparatus comprising: a storage unit that stores a compressed image of an original image. 2. The first compression means performs image compression according to a high compression rate compression method, and the second compression means uses a high compression rate compression method or a reversible compression method. The image compression apparatus according to claim 1, wherein image compression is performed. 3. A storage unit for storing a compressed image obtained by compressing an original image and a compressed image obtained by compressing a difference image between the original image and a compressed image obtained by compressing the original image, and an original image stored in the storage unit. It is characterized by further comprising: decompressing means for decompressing each of the compressed image and the compressed image of the difference image; Image restoration device. 4. The storage means stores an original image compressed by a high compression rate compression method and a differential image compressed by a high compression rate compression method or a reversible compression method. 4. The image decompression apparatus according to claim 3, wherein the decompression unit decompresses each compressed image using a decompression method corresponding to each compression method of the original image and the difference image. 5. A first compression means for compressing an original image, a first decompression means for decompressing a compressed image created by this first compression means, and a decompressed image decompressed by this first decompression means. A difference unit that creates a difference image from the original image, a second compression unit that compresses the difference image created by this difference unit, a compressed image of the difference image created by this second compression unit, and the first image Storing means for storing the compressed image of the original image created by the compressing means, second decompressing means for decompressing the compressed image of the original image and the compressed image of the difference image in the storing means, and the second decompressing means. An image processing apparatus comprising: a synthesizing unit for synthesizing a restored image of an original image restored by a restoring unit and a restored image of a difference image.