JPH01128674A - Picture compressing system - Google Patents

Abstract

PURPOSE:To adjust a parameter for each picture element and to attain aimed picture quality and compressibility by executing a compressing processing using the reduced picture of an original picture before a main processing and setting the parameter to determine the picture quality and the compressibility of the main processing using the compressed picture of the reduced picture. CONSTITUTION:An original picture 10 is first reduced with a thinning processing 11. A reduction ratio is slightly changed according to an original picture size, however, the ratio is approximately fixed to 1/16. Next, a compressing processing 12 is executed with the same algorithm as that of the main processing. For example, an S/N, the compressibility, etc., are calculated 13 as evaluation values from a reduced and compressed picture obtained here, a visual observation evaluation 14 is executed if necessary, a deciding 15 is executed by the result, a parameter changing 16 is executed in a necessary case, and the returning to the compressing processing 12 again is executed. A main processing (original picture compressing processing) 17 a starts at a stage in which ultimate aimed S/N or compressibility can be obtained. Since a processing parameter to obtain the aimed picture quality and compressibility can be automatically set in the irreversible compressing processing of a variable density picture, practicability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an irreversible compression method for grayscale images, and in particular to a method that facilitates the setting of compression processing parameters and a storage capacity for medical images such as X-ray images. This invention relates to an image compression method suitable for image reduction.

[Conventional technology]

Conventionally, processing parameters that determine image quality and compression rate were set in advance.
The method is to evaluate 00 to 200 options and select from among them (Ta et al., ``Image data compression and its effects on transmission and storage'', Video Information (M).

V o 1, 18, Na 14, ' 86-
7, P719-P724), and in the above-mentioned known example 1, for example, in the irreversible compression method, the compression rate is set to 115.
Some devices have a means for manually selecting, such as 1/10° or 1/20, but most compression processing is performed using a predetermined method and compression rate.

[Problem that the invention seeks to solve]

In the above conventional technology, it is necessary to evaluate various parameters in advance according to the compression method 2w shadow method 2 parts, etc.
The set parameters are not necessarily optimal for each image.

A first object of the present invention is to provide a means for adjusting the above parameters for each image to achieve target image quality and compression ratio. Furthermore, the above-mentioned conventional technology does not take into consideration the importance of images for one diagnosis or research, and for example, because images that are key to one diagnosis are irreversibly compressed, filtering, contrast enhancement, etc. necessary for diagnosis are A situation occurs where image processing cannot be performed. Furthermore, if the overall compression rate is lowered in order to avoid image quality deterioration, there is a problem in that the storage capacity increases.

A second object of the present invention is to solve the above contradictory problems.

[Means for solving problems]

The first purpose is to compress the original image.
This is achieved by performing processing using the same compression algorithm using an image that is a reduced version of the original image, and by adding processing that uses the results to set processing parameters that determine the image quality and compression rate during compression.

The second objective is to select a compression method depending on the importance of the image, such as irreversible compression with no image quality deterioration for some and irreversible compression with a high compression rate for others. achieved.

In medical imaging, an average of 5 to 10 images are created, although this varies depending on the modality.As the images important for diagnosis (key images) are at most 1 to 2, other images are compressed. There is no problem with increasing the rate.

[Effect]

(1) Figure 1 shows an overview of one effect. The original image 10 is first reduced by a thinning process 11 . The reduction rate is about 1/16, although it depends on the original image size.

For example, if the size is 5122, the size is 1282.2048", which is 5123. This level of reduction rate is also required in order to reduce the proportion of the overall processing time.

Next, compression processing 12 is performed using the same algorithm as the single processing. From the reduced compressed image obtained here, calculate evaluation values such as S/N, compression ratio, etc. (13) L. If necessary, perform visual evaluation 14, and judge 1 based on the result.
5, and if necessary, change the parameters 16 and return to the compression process 12 again. Finally, the target S/N
, or when the compression ratio is obtained, the main process 17 is entered.

Assuming that the image size is 1716, processing 11 to 15 takes about 1!16 times of the main processing, and when repeated twice, the processing amount is about 12% of one processing, so there is no problem. This is not the time.

(2) FIG. 5 shows an overview of the operation, and will be explained using a medical image as an example. Consider storing 10 original images for one examination of one patient.1 Normally, there are 1 to 2 key images for one diagnosis, but these are stored after performing reversible compression in consideration of later image processing. (511).

Also, for images of primary importance, irreversible compression with a low compression rate is selected (512), and for images of low importance, irreversible compression with a higher compression rate is selected (513).
). Furthermore, even if the image is a key image, an image that has been used for a long period of time is subjected to irreversible compression with a high compression rate. In this way, by selecting an appropriate method according to the degree of importance for diagnosis, it is possible to increase the compression rate as a whole without reducing diagnostic accuracy. The selection of the compression process described above may be instructed by a doctor, or may be automatically determined using information regarding the key image described in the diagnostic information 100.

【Example〕

A first embodiment of the present invention will be described below with reference to FIGS. 2 to 4.

FIG. 2 shows the overall configuration of a medical X-ray film image processing apparatus. The film image 200 is digitized by the film digitizer 20 and the image processing device 2
The compressed image 210 is stored in the external storage device 23 after the compression process is performed according to the procedure described in FIG. 2
10 is restored at the time it is displayed on the display 22, photo printer 24, etc. Incidentally, in FIG. 1, evaluation values are usually determined based on a numerical range set within a computer.

Further, FIG. 3 shows the contents of block encoding, which is one of the typical compression methods. In this figure, the image size of the original image 30 is 20482, and this is divided into a large number of 4×4 size blocks 301.

Processing is performed to change the encoding mode for each block 6 Therefore, in the present invention, it is sufficient to create 5122 images from the original image 30 and perform exactly the same processing using them as the original image 3o. Further, FIG. 4 shows adaptive cosine transformation, which is another typical method.

In this method as well, the original image 40 is divided into a large number of blocks 41 (
A cosine transform 42 is performed for each block, and the transformed blocks 43 are divided into classes according to the magnitude of AC energy, a bit allocation table 47 is created for each class, and a quantizer 48 Encoded data 49 is generated. Here again, after creating a reduced image from the original image 40, the number of blocks 41 decreases when encoding is performed using the same processing steps as 41 to 49 above, so the number of blocks in the class after cosine transformation is For example, when the reduction ratio is set to 1/16, the result is 1716, so the result is not exactly the same as when using the original image, but this poses no problem when used for the purpose of parameter setting.

Next, a second embodiment of the present invention will be described with reference to FIGS. 6 and 7.

Figure 6 shows the X-ray film being transferred to a film scanner 62.
After being digitized by 0 and taken into the image processing device 621 and subjected to various image processing, the image is displayed on the image display 62.
2 shows a system in which diagnosis is performed by displaying on a photo printer 623 or the like.

The digital image input here has been compressed.

It is stored on a magnetic disk 624 or an optical disk 625 depending on the purpose. Here, the doctor 626 proceeds with the diagnosis while observing the image displayed at 622 or 623. At this time, the key image for diagnosis may be directly designated manually using the input device 627, or an image interpretation report may be created and the designation of the key image may be included in the report.

FIG. 3 shows supplementary information 731 of the original image 610. For example, image ID 310. Patient name 3112
Information such as the image file name 313 is stored, and by storing the selected compression information 312 in this, for example, for the image numbered ff1NID100,
When an instruction for some kind of image processing is given, it is known that it can be executed. Similarly, it can be seen that the image (i) oto2, 1034 is irreversibly compressed, so that the processing content of one image is limited.

According to this embodiment, it is possible to compress large-capacity images such as X-ray images without reducing diagnostic accuracy.

〔Effect of the invention〕

According to the present invention, there are the following effects.

(1) In irreversible compression processing of grayscale images, processing parameters for obtaining acceptable image quality and compression ratio are automatically set, thereby improving practicality.

(2) Since it is possible to select the compression processing content according to the importance of the image, it is possible to increase the overall compression rate and compress the image while maintaining diagnostic accuracy.

Further, by adding information regarding the selected compression process to the supplementary information, execution of image processing can be restricted, so image deterioration does not need to be exposed.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the basic principle of the present invention, Fig. 2 is a block diagram of the first embodiment of the invention, Fig. 3 is a diagram showing a block encoding method, and Fig. 4 is an adaptive cosine diagram. A diagram showing the encoding method, FIG. 5 is a diagram showing an outline of the second embodiment of the present invention, FIG. 6 is a block diagram of the X-ray film processing apparatus according to the second embodiment, and FIG. 7 is a diagram showing the compression method. Additional information / [! ] 16 Hara 7 Ichiri Chichisara Prefecture 2 Exit 210 Cliff IiJ/# f” r1
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Claims (1)

[Claims] 1. In irreversible compression processing of grayscale images, before the main processing for compressing the original image, compression processing is performed using an image obtained by reducing the original image, and the compression processing of the reduced image is performed. Using compressed images,
An image compression method characterized by setting parameters that determine the image quality, compression rate, etc. of this processing. 2. An image compression method characterized by providing means for selecting a reversible compression method and an irreversible compression method and a means for selecting a compression rate of the irreversible compression according to the importance of the image in compression and storage processing of grayscale images. . 3. The image compression method of item 2, characterized in that the selection means comprises a manual selection by a human or a selection means using incidental information of the image. 4. Information regarding the selection means is registered as incidental information of the image. The image compression method according to item 1, characterized in that: