JP3236821B2 - Hierarchical encoding transmission method and hierarchical decoding method for still image - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for hierarchically encoding and transmitting still images and a method for hierarchically decoding still images, and is particularly useful for exchanging a large amount of image data between hospitals in a telemedicine communication system or the like. The present invention relates to a still image hierarchical coding transmission method and a hierarchical decoding method capable of efficiently transmitting a required portion of image data with a small amount of transmission information.

[0002]

2. Description of the Related Art For example, the required resolution and quality of medical images vary depending on how they are used. Various attempts have been made to hierarchically encode a still image as a method for freely selecting the image quality or resolution of the image. The international standard JPEG method uses multi-valued images as JBI
The G method defines a method of encoding images hierarchically for binary images. In addition, FlashPix divides an image into independent small areas and combines images with multiple resolutions into one. The area is transmitted.

[0003] An example of a conventional hierarchical coding transmission method of a still image will be described below with reference to FIGS. FIG. 9 is a conceptual diagram of an example of a conventional method. Now, an original image of an X-ray photograph as shown in FIG.
048 × 2048 pixels) is input to the region dividing unit 21 in FIG. 9, the region dividing unit 21
As shown in (b), the region is divided into a plurality of partial regions. Next, as shown in FIG. 11, the resolution conversion unit 22 converts the input partial region 30 into a plurality of resolutions and forms a first hierarchical image 31 and a second hierarchical image 32 in descending order of resolution. I do. The hierarchical images 31 and 32 are encoded by the encoding unit 23 and stored in the storage unit 24. If an image transmission request is received from the receiving side, the communication control unit 25 stores the image in the storage unit 24 based on the contents (partial area, resolution, etc.) of the transmission request.
And reads out necessary image data from the receiving side via the line 26 to the receiving side.

Generally, in order to view the entire image of an original image of an X-ray photograph, for example, the receiving side requests that the image 32 having the smallest resolution of each partial area be transmitted for one original image. Next, when the receiving side wants to see a specific partial area of one original image in more detail, it transmits a transmission request signal including the partial area and the resolution to the transmitting side. The transmission request signal enters the communication control unit 25 on the transmission side. The communication control unit 25 analyzes the partial area and the resolution requested for transmission from the transmission request signal, reads out necessary image data from the storage unit 24, and sends it out to the receiving side via the line 26. By decoding the received hierarchical image, the receiving side can view the image of the desired partial area at a higher resolution.

[0005]

However, according to the above-mentioned prior art, when the receiving side requests transmission for a higher resolution image, the hierarchical image of the same partial area,
In other words, coded images of different resolutions are separately and independently coded, and are sequentially transmitted from the lower resolution to the higher resolution, so that the final transmission amount or transmission time However, there is a case where the number of transmissions increases as compared with transmitting one high-resolution image once, and there is a problem that waste is large. Further, in the related art, there is a problem that the encoded data of the partial area that has been transmitted once cannot be reused on the receiving side because the images having different resolutions are handled as separate independent data.

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned problems of the prior art and to provide a still picture hierarchical coding transmission method capable of transmitting image data having a resolution required by a receiving side with a smaller transmission amount or transmission time. And a hierarchical decoding method.

[0007]

In order to achieve the above-mentioned object, the present invention divides an original image into a plurality of partial areas, and provides a plurality of levels of resolution in a direction in which the resolution decreases for each partial area. Performing the conversion, encoding is performed on the image with the lowest resolution among the images of the resolution obtained by the resolution conversion, and the difference between the image with the other resolution and the image with the lower resolution is calculated. Differential encoding, the encoded data for the lowest resolution image in the entire area of the original image is transmitted to the receiving side prior to the differential encoded data, and the partial area and the resolution requested by the receiving side for transmission are transmitted. And selectively transmit the differentially encoded data according to the order from the data for the image with the lower resolution to the image with the higher resolution. Duplicate If there is a first feature in that so as to transmit to the receiving side in accordance with the required differential encoding data non-overlapping area resolution.

[0008]

According to the above feature, the image having the lowest resolution is encoded, but the image having the other resolution is differentially encoded. The transmission amount or transmission time at the transmission stage can be greatly reduced as compared with the conventional method of encoding and transmitting images of each resolution. Further, the difference coded data corresponding to the partial area requested to be transmitted from the receiving side and the resolution can be selectively transmitted in order from the data for the image having the lower resolution to the image having the higher resolution.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. 1 to 4 are views for explaining the principle of the present invention. FIG. 1 is a diagram for explaining the same partial area division processing as in FIG. 9, and a description thereof will be omitted.

FIG. 2 is an explanatory diagram of a hierarchical coded transmission method according to the present invention, wherein 1 is a first hierarchical image which is a partial area obtained by dividing the original image into areas, These are a second hierarchical image and a third hierarchical image obtained by converting the first hierarchical image 1 into a plurality of levels of resolution. The resolution decreases in the order of the first, second, and third hierarchical images. The first and second hierarchical images 1 and 2 are differentially encoded, and the third hierarchical image 3 with the lowest resolution is encoded (for example, MGR encoded) and stored in the storage device. The encoded data stored in the storage device is read out according to a transmission request from a receiving side, which will be described later, and transmitted to the receiving side.

As described above, according to the present invention, since the images other than the third-layer image 3 having the lowest resolution are created by differential encoding, the amount of data transmission and the transmission time are significantly reduced as compared with the conventional one. Will be able to

FIGS. 3 and 4 are explanatory diagrams of processing on the receiving side. The receiving side firstly converts a partial image of a required area in the entire image into a third hierarchical image 3 of the lowest resolution. Requests the sender to be transmitted in Upon receiving this request, the transmitting side transmits the third hierarchical image 3 of the requested partial image to the receiving side. The receiving side decodes the received partial image and displays the divided image on the display unit. In general, the receiver initially has the entire area 5 of the entire image, as shown in FIG.
Are requested, the partial images are transmitted as the third hierarchical image and displayed on the display unit.

Next, when the receiving side wants to see the area 6 in the whole area 5 in more detail, the image data of the partial areas 6a, 6b, 6c, and 6d is further raised from the receiving side to the transmitting side. Requests transmission at resolution. Then, the transmission side transmits the differentially encoded second layer image 2 to the partial areas 6a, 6b, 6c, and 6d. When the receiving side receives the differentially coded image, the partial areas 6a, 6b, 6c, and 6d previously received
The differential decoding process is performed using the first hierarchical image data of the above, and is displayed on the display unit. Therefore, the display area includes the area 6
Only at a higher resolution.

[0015] When the receiving side desires to display at a higher resolution, a transmission request signal including the partial area of the area desired to be displayed and the resolution is sent to the transmitting side. Then,
The transmitting side transmits the first layer image 1 of the partial area included in the requested area in the same manner as described above. The receiving side can display the image of the area at a higher resolution by performing the differential decoding process on the first hierarchical image 1 using the received image data.

When the receiving side wants to see the area 7 slightly below the area 6 in more detail, the area 6 is continuously moved as shown in FIG. An area 7 where a part overlaps is designated. Then,
The transmitting side does not need to transmit a partial area that has already been transmitted at high resolution, and transmits differentially encoded data only to a partial area that has not been transmitted at high resolution. That is, the data in the partial areas 6b and 6d need not be transmitted, and the partial areas 7a, 7b,
Only the differentially encoded data of 7c and 7d are transmitted. Therefore, on the receiving side, the partial areas 7a, 7b, 7c, and 7 are combined with the already received image data.
d by performing the differential decoding process on the designated area 7
Resolution can be improved. As described above, according to the present invention, when the receiving side specifies an area for which high-resolution display is desired, the transmitting side only needs to transmit only differentially encoded data of a partial area included in the area, On the other hand, the receiving side only needs to perform the difference decoding process using the already received low-resolution image data. Therefore, the already received image data can be effectively used without being wasted, and the transmission efficiency can be improved.

Next, an example of a specific process for performing the resolution conversion and the hierarchical coding described in FIG. 2 will be described with reference to FIGS. Now, assuming that the partial area 1 (LL0) in FIG. 1 or FIG. 2 is input as an original image, a certain numeral n is set to 1 in step S1, and steps S2 and S
Proceed to 3. The number n is a number related to the level of the resolution, and the resolution decreases as n increases.
In step S2, low-frequency horizontal processing is performed, and in step S3, high-frequency horizontal processing is performed. Further, in step S4, vertical processing on the low frequency side is performed, and in step S5, vertical processing on the high frequency side is performed. On the other hand, in step S6, low-frequency vertical processing is performed, and in step S7, high-frequency vertical processing is performed. By the above processing, the images (LL1, LH1, HL1, H1) corresponding to the first hierarchical image 1 are obtained.
H1) (see FIG. 6A).

Next, at step S8, it is determined whether or not n = 4. If the determination is negative, the process proceeds to step S9, where 1 is added to n, and n = 2. Then, the processing of steps S2 to S7 is repeated for the image LL1.

On the other hand, in step S10, the image LH
1, HL1, and HH1 are divided into regions. In step S11, the divided image LH
1, HL1, and HH1 are MGR encoded. The MG
The R encoding is performed as shown in FIG. 10, but since it is well known, detailed description is omitted. In step S12, blocking is performed using the detection code.

When the above processing is repeatedly performed, images (LL2, LH2, HL) corresponding to the second hierarchical image 2 are obtained.
2, HH2), an image (LL) corresponding to the third hierarchical image 3
3, LH3, HL3, HH3), and the fourth hierarchical image 4
(LL4, LH4, HL4, HH4)
(See FIG. 6A) are sequentially obtained, and in step S11, (LHn, HLn, HHn) (where n = 2, 3,
4), MGR encoding is performed, and in step S12, these MGR encodings are blocked by detection codes.

On the other hand, LLn (where n = 2, 3, 4)
With regard to, the resolution conversion is repeated until the determination in step S8 becomes affirmative.
Proceeding to 13, the MGR encoding process is performed on the image LL4. In step S14, the MGR encoded data obtained in step S13 and the block code data obtained in step S12 are merged into an encoded segment and stored in a storage device (not shown).

The processing in steps S1 to S9 is based on Wa.
This is resolution conversion processing by velet conversion, and the band division processing on the low band side and the high band side indicated by oblique lines can be performed using the equations 11 and 12 shown in the figure.

Next, an example of a specific process for performing the decoding process described with reference to FIG. 3 will be described with reference to FIG. In step S21, LL4 encoded code data, that is, data of the fourth hierarchical image 4 having the lowest resolution is received. In step S22, the LL4 encoded code data is decoded,
Proceed to step S23. In step S23, n = 4 is set, and the process proceeds to step S24, where LH4, HL4, H
The H4 block area is decoded. Step S2
The LL4 image data decoded in step 2 is transferred to step S25 via the bus. In step S26, Wa is determined based on the data decoded in steps S24 and S25.
Image restoration processing by velet transformation is performed. The image data subjected to the image restoration processing passes through the bus and goes to step S25.
And is also sent to the display unit 11 to be displayed hierarchically. In step S25, LLn is decoded using the image restoration data obtained by the Wavelet transform.

In step S27, it is determined whether or not n = 1 is satisfied. When the determination is negative, the process proceeds to step S28, and 1 is subtracted from n. Subsequently, the process returns to step S24, and the operations of steps S24 to S26 are repeated. As a result of repeating the above processing, if the determination in step S27 is affirmative, it means that decoding up to the first hierarchical image 1 having the highest resolution has been completed.

Therefore, when the present invention is put to practical use, if step S27 is set to "n = 4?", Decoding up to the fourth hierarchical image 4 having the lowest resolution can be performed. If it is desired to perform another stage of decoding up to the third hierarchical image 3 with a high resolution, step S27
Is set to “n = 3?”, This can be realized.

FIG. 8 shows an outline of an image transmission method according to the present invention. When a transmission request is sent from the receiving side to the transmitting side, the requested resolution is selected from the hierarchical data stored in the storage device on the transmitting side. Is transmitted to the receiving side.

[0027]

As is clear from the above description, according to the present invention, an image having the lowest resolution is encoded, but an image having another resolution is differentially encoded. Therefore, the transmission amount or transmission time at the stage of transmitting the image with the highest resolution, that is, the original image, can be significantly reduced as compared with the conventional method of encoding and transmitting the image at each stage of resolution. it can.

For example, an X-ray radiograph is transmitted at a transmission speed of 6.
As a result of transmission over a 4 kbit / s digital communication line, it takes 540 seconds to transmit and receive uncompressed image data. On the other hand, the entire hierarchically coded image according to the present invention is converted from the lowest resolution nth hierarchy to the next resolution. 6 seconds to transmit and display up to the (n-1) th layer,
It took 30 seconds to select and display 12 pixels to the final stage.

Further, according to the present invention, the next high-resolution image is decoded using the encoded data received once, so that the data received once can be reused and waste can be eliminated.

Further, when the present invention is used in a telemedicine communication system, a transmission server (transmission side) transmits data of an image portion requested by a client (reception side) at a requested resolution in a short time. Therefore, the effect of selectively providing high-definition, large-capacity medical image data, such as radiographs, to the client is very large.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram of a partial area dividing process according to the present invention.

FIG. 2 is a schematic explanatory diagram of an encoding process of the present invention.

FIG. 3 is a schematic explanatory diagram of a decoding process of the present invention.

FIG. 4 is another schematic explanatory diagram of the decoding process of the present invention.

FIG. 5 is an explanatory diagram showing a specific example of a partial area division and encoding process according to the present invention.

FIG. 6 is an explanatory diagram of the operation of FIG. 5;

FIG. 7 is an explanatory diagram showing a specific example of the decoding process of the present invention.

FIG. 8 is an explanatory diagram of the operation of the image transmission method of the present invention.

FIG. 9 is a conceptual diagram of a conventional hierarchical encoding method.

FIG. 10 is a schematic explanatory diagram of a conventional partial area dividing process.

FIG. 11 is a schematic explanatory diagram of a conventional encoding process.

[Explanation of symbols]

Reference numeral 1: first hierarchical image (partial area), 2: second hierarchical image, 3
... 3rd hierarchical image, 5 ... all area, 6 ... area, 6a-6d ...
... Partial areas, 7... Areas, 7a to 7d.

Continuation of the front page (56) References JP-A-9-148938 (JP, A) JP-A-9-182069 (JP, A) JP-A-9-238338 (JP, A) IEICE Technical Report, IE98 7, 1998-4-17, p. 49−55 (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 1/41-1/419 H04N ^7/ 24-7/68

Claims (3)

(57) [Claims] An original image is divided into a plurality of partial areas, and a plurality of levels of resolution conversion are performed on each of the partial areas in a direction in which the resolution becomes lower. For low-resolution images, encoding is performed, and for other-resolution images, difference encoding is performed by taking the difference from the lower-resolution image. The encoded data for the lower image,
The differentially encoded data is transmitted to the receiving side prior to the differentially encoded data, and the differentially encoded data corresponding to the partial area and the resolution requested by the receiving side is selectively selected from the data for the low resolution image in the order of increasing resolution. Transmit, and the partial area for which the transmission request was
If the area partially overlaps the existing partial area,
Send the differentially encoded data to the receiving side according to the requested resolution.
Hierarchical encoding method for transmitting still images which is characterized in that so as to transmit. 2. The method according to claim 1, wherein the resolution conversion is performed by a wavelet transform, and the difference encoding is performed.
Is performed by MGR coding . 3. The method according to claim 1 , wherein
Encoded data for the lowest resolution image sent
Data is first decoded and then the location of the image in the desired partial area
Decode the differentially encoded data according to the desired resolution, and
Restore the image at the desired resolution to the image in the desired area
A hierarchical decoding method for a still image.