Image-data processing device, image-data processing method, image-data distributing device and image-data transmitting system

• US 20040151393A1
• Filed: 12/30/2003
• Published: 08/05/2004
• Est. Priority Date: 01/06/2003
• Status: Active Grant

• Current Assignee: Sovereign Peak Ventures, LLC (Dominion Harbor Enterprises, LLC)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Kurauchi, Nobukazu
• Granted Patent: US 7,369,706 B2
• Time in Patent Office: Days
• US Class Current: 382/239
• CPC Class Codes: G06T 9/007 Transform coding, e.g. discrete cosine transform

Abstract

An original image is divided into a plurality of blocks that are made up of a plurality of picture elements, and in each block, from encoded image-data which is obtained by encoding a spatial-frequency component of the block as a plurality of spatial-frequency coefficients, reduced encoded image-data is produced which is encoded data on a reduced image that is obtained by reducing the original image to a given reduction rate. If the block in the encoded image-data of the original image is in an area where the value of the function is small due to gentle change in brightness or color of the image, for example, only the direct-current component coefficient of is used for the block. On the other hand, if the block is in a area where the value of the function is large because the area is a boundary area, for example, such as an outline in the image, limited number of lower spatial frequency-coefficients are used for the block. The number is based on the reduction rate of the image.

Claims

1. An image-data processing device, in which an original image is divided into a plurality of blocks that are made up of a plurality of picture elements, and in each block, from encoded image-data which is obtained by encoding a spatial-frequency component of the block as a plurality of spatial-frequency coefficients, reduced encoded image-data is produced which is encoded data on a reduced image that is obtained by reducing the original image to a given reduction rate, comprising:

a block abstracting means for abstracting each block as a block to be processed, one after another, from the plurality of blocks;

a DC-coefficient abstracting means for abstracting a direct-current component coefficient from the plurality of spatial-frequency coefficients of the block to be processed;

an adjacent DC-coefficient abstracting means for abstracting the direct-current component coefficient of at least one adjacent block which is adjacent, in any of a horizontal direction, a vertical direction and an oblique direction, to the block to be processed, as at least one adjacent direct-current component coefficient;

a DC-coefficient comparing means for comparing the direct-current component coefficient of the block to be processed and the at least one adjacent direct-current component coefficient, and calculating a value of a predetermined function of the direct-current component coefficient of the block to be processed and the at least one adjacent direct-current component coefficient, the function representing an extent of unevenness between the direct-current component coefficient of the block to be processed and the at least one adjacent direct-current component coefficient;

a coefficient-set setting means for, if the value of the function is larger than a predetermined value, holding a smaller number of spatial-frequency coefficients than the plurality of spatial-frequency coefficients of the block to be processed according to the reduction rate, which have lower frequencies and include the direct-current component coefficient among the plurality of spatial-frequency coefficients of the block to be processed, and setting the other spatial-frequency coefficients to zero; and

a DC-coefficient setting means for, if the value of the function is smaller than the predetermined value, holding only the direct-current component coefficient of the plurality of spatial-frequency coefficients of the block to be processed, and setting the other spatial-frequency coefficients to zero.

2. The image-data processing device according to claim 1, wherein the at least one adjacent block is one adjacent block, and the value of the function is an absolute value of a difference between the adjacent direct-current component coefficient of the one adjacent block and the direct-current component coefficient of the block to be processed.

3. The image-data processing device according to claim 1, wherein the at least one adjacent block is plural adjacent blocks, and the value of the function is an absolute value of a difference between an average of the adjacent direct-current component coefficients of the plural adjacent blocks and the direct-current component coefficient of the block to be processed.

4. The image-data processing device according to claim 1, wherein the at least one adjacent block is plural adjacent blocks, and the value of the function is an absolute value of a difference between a weighted-average obtained by weighted-average calculation, based on adjacent directions, of the adjacent direct-current component coefficients of the plural adjacent blocks, and the direct-current component coefficient of the block to be processed.

5. The image-data processing device according to claim 1, wherein the at least one adjacent block is plural adjacent blocks, and the value of the function is a largest absolute value of the differences between adjacent direct-current component coefficients of the plural adjacent blocks and the direct-current component coefficient of the block to be processed.

6. The image-data processing device according to claim 1, wherein the at least one adjacent block is plural adjacent blocks, and the value of the function is a summation of absolute values of the differences between adjacent direct-current component coefficients of the plural adjacent blocks and the direct-current component coefficient of the block to be processed.

7. The image-data processing device according to claim 1, wherein referring to the ratio of the number of the smaller number of spatial-frequency coefficients than the plurality of spatial-frequency coefficients which are held by the coefficient-set setting means to the number of the plurality of spatial-frequency coefficients as a coefficient reduction rate, the coefficient-set setting means divides the reduction rate into a plurality of levels, sets the coefficient reduction rate according to the levels of the reduction rate, and if the value of the function is larger than the predetermined value, holds the smaller number of spatial-frequency coefficients according to the coefficient reduction rate and sets the other spatial-frequency coefficients to zero.

8. The image-data processing device according to claim 1, further comprising:

an input processing means for receiving an input of the reduction rate;

a decoding means for decoding the reduced encoded image-data;

an image-size reducing means for reducing the image size of the reduced encoded image-data which is decoded; and

a screen displaying means for displaying on a screen the reduced encoded image-data which is reduced in a image size.

9. The image-data processing device according to claim 1, wherein:

the encoded image-data is colored; and

the predetermined value is individually given for every color component.

10. The image-data processing device according to claim 1, wherein:

the encoded image-data is colored; and

the coefficient-set setting means determines, individually for every color component, the number of the smaller number of spatial-frequency coefficients than the plurality of spatial-frequency coefficients.

11. The image-data processing device according to claim 1, wherein:

the encoded image-data is colored; and

the block abstracting means abstracts the block to be processed only for limited predetermined color components.

12. The image-data processing device according to claim 1, wherein:

the encoded image data is image data encoded by variable-length coding; and

the coefficient-set setting means and the DC coefficient setting means adds a code which shows an end of bit-string of a block to an end of bit-string of the spatial-frequency coefficients to be held and deletes the other spatial-frequency coefficients, and thereby, sets the other spatial-frequency coefficients to zero.

13. An image-data processing method, in which an original image is divided into a plurality of blocks that are made up of a plurality of picture elements, and in each block, from encoded image-data which is obtained by encoding a spatial-frequency component of the block as a plurality of spatial-frequency coefficients, reduced encoded image-data is produced which is encoded data on a reduced image that is obtained by reducing the original image to a given reduction rate, comprising:

a first step of abstracting a direct-current component coefficient from the plurality of spatial-frequency coefficients;

a second step of abstracting the direct-current component coefficient of at least one adjacent block which is adjacent, in any of a horizontal direction, a vertical direction and an oblique direction, to a block including the abstracted direct-current component coefficient, as at least one adjacent direct-current component coefficient;

a third step of comparing the direct-current component coefficient of and the at least one adjacent direct-current component coefficient, and calculating a value of a predetermined function of the direct-current component coefficient and the at least one adjacent direct-current component coefficient, the function representing an extent of unevenness between the direct-current component coefficient and the at least one adjacent direct-current component coefficient;

a fourth step of, if the value of the function is larger than a predetermined value, holding a smaller number of spatial-frequency coefficients than the plurality of spatial-frequency coefficients according to the reduction rate, which have lower frequencies and include the direct-current component coefficient among the plurality of spatial-frequency coefficients, and setting the other spatial-frequency coefficients to zero; and

a fifth step of, if the value of the function is smaller than the predetermined value, holding only the direct-current component coefficient of the plurality of spatial-frequency coefficients, and setting the other spatial-frequency coefficients to zero,

wherein each step is executed on each block, so that the reduced encoded image-data is produced which is encoded data on a reduced image that is obtained by reducing the original image to the reduction rate.

14. The image-data processing method according to claim 13, wherein the at least one adjacent block is one adjacent block, and the value of the function is an absolute value of a difference between the adjacent direct-current component coefficient of the one adjacent block and the direct-current component coefficient.

15. The image-data processing method according to claim 13, wherein the at least one adjacent block is plural adjacent blocks, and the value of the function is an absolute value of a difference between an average of the adjacent direct-current component coefficients of the plural adjacent blocks and the direct-current component coefficient.

16. The image-data processing method according to claim 13, wherein the at least one adjacent block is plural adjacent blocks, and the value of the function is an absolute value of a difference between a weighted-average obtained by weighted-average calculation, based on adjacent directions, of the adjacent direct-current component coefficients of the plural adjacent blocks, and the direct-current component coefficient.

17. The image-data processing method according to claim 13, wherein the at least one adjacent block is plural adjacent blocks, and the value of the function is a largest absolute value of the differences between adjacent direct-current component coefficients of the plural adjacent blocks and the direct-current component coefficient.

18. The image-data processing method according to claim 13, wherein the at least one adjacent block is plural adjacent blocks, and the value of the function is a summation of absolute values of the differences between adjacent direct-current component coefficients of the plural adjacent blocks and the direct-current component coefficient.

19. The image-data processing method according to claim 13, wherein:

the fourth step, referring to the ratio of the number of the smaller number of spatial-frequency coefficients than the plurality of spatial-frequency coefficients which are held in the fourth step to the number of the plurality of spatial-frequency coefficients as a coefficient reduction rate, divides the reduction rate into a plurality of levels, sets the coefficient reduction rate according to the levels of the reduction rate, and if the value of the function is larger than the predetermined value, holds the smaller number of spatial-frequency coefficients according to the coefficient reduction rate and sets the other spatial-frequency coefficients to zero.

20. The image-data processing method according to 13, further comprising:

a sixth step of receiving an input of the reduction rate;

a seventh step of decoding the reduced encoded image-data;

an eighth step of reducing an image size of the reduced encoded image-data which is decoded; and

a ninth step of displaying on a screen the reduced encoded image-data which is reduced in an image size.

21. The image-data processing method according to claim 13, wherein:

the encoded image-data is colored; and

the predetermined value is individually given for every color component.

22. The image-data processing method according to claim 13, wherein:

the encoded image-data is colored; and

in the fourth step, the number of the smaller number of spatial-frequency coefficients than the plurality of spatial-frequency coefficients is determined individually for every color component.

23. The image-data processing method according to claims 13, wherein:

the encoded image-data is colored; and

the first to fifth steps for each block are executed only for limited predetermined color components.

24. The image-data processing method according to claims 13, wherein:

the encoded image data is image data encoded by variable-length coding; and

the fourth and the fifth steps adds a code which shows an end of bit-string of a block to an end of bit-string of the spatial-frequency coefficients to be held and deletes the other spatial-frequency coefficients, and thereby, sets the other spatial-frequency coefficients to zero.

25. An image-data distributing device, in which an original image is divided into a plurality of blocks that are made up of a plurality of picture elements, in each block, from encoded image-data which is obtained by encoding a spatial-frequency component of the block as a plurality of spatial-frequency coefficients, reduced encoded image-data is produced which is encoded data on a reduced image that is obtained by reducing the original image to a given reduction rate, and the reduced encoded image-data is transmitted over a network, comprising:

an encoded image-data storing means for storing a plurality of pieces of the encoded image-data;

an encoded image-data reading means for reading encoded image-data which corresponds to one image, from among the plurality of pieces of encoded image-data which is stored in the encoded image-data storing means; and

an image-data processing device, including;

a block abstracting means for abstracting each block as a block to be processed, one after another, from the plurality of blocks;

a DC-coefficient abstracting means for abstracting a direct-current component coefficient from the plurality of spatial-frequency coefficients of the block to be processed;

an adjacent DC-coefficient abstracting means for abstracting the direct-current component coefficient of at least one adjacent block which is adjacent, in any of a horizontal direction, a vertical direction and an oblique direction, to the block to be processed, as at least one adjacent direct-current component coefficient;

a DC-coefficient comparing means for comparing the direct-current component coefficient of the block to be processed and the at least one adjacent direct-current component coefficient, and calculating a value of a predetermined function of the direct-current component coefficient of the block to be processed and the at least one adjacent direct-current component coefficient, the function representing an extent of unevenness between the direct-current component coefficient of the block to be processed and the at least one adjacent direct-current component coefficient;

a coefficient-set setting means for, if the value of the function is larger than a predetermined value, holding a smaller number of spatial-frequency coefficients than the plurality of spatial-frequency coefficients of the block to be processed according to the reduction rate, which have lower frequencies and include the direct-current component coefficient among the plurality of spatial-frequency coefficients of the block to be processed, and setting the other spatial-frequency coefficients to zero; and

a DC-coefficient setting means for, if the value of the function is smaller than the predetermined value, holding only the direct-current component coefficient of the plurality of spatial-frequency coefficients of the block to be processed, and setting the other spatial-frequency coefficients to zero, wherein

the image-data processing device produces the reduced encoded image-data, from encoded image-data which is read by the encoded image-data reading means, and

the image-data distributing device further comprises a transmitting means for transmitting, to the network, the reduced encoded image-data which is produced by the image-data processing device.

26. An image-data transmitting system, comprising an image-data distributing device, in which an original image is divided into a plurality of blocks that are made up of a plurality of picture elements, in each block, from encoded image-data which is obtained by encoding a spatial-frequency component of the block as a plurality of spatial-frequency coefficients, reduced encoded image-data is produced which is encoded data on a reduced image that is obtained by reducing the original image to a given reduction rate, and the reduced encoded image-data is transmitted over a network, including:

an encoded image-data storing means for storing a plurality of pieces of the encoded image-data;

an encoded image-data reading means for reading encoded image-data which corresponds to one image, from among the plurality of pieces of encoded image-data which is stored in the encoded image-data storing means; and

an image-data processing device, in which an original image is divided into a plurality of blocks that are made up of a plurality of picture elements, and in each block, from encoded image-data which is obtained by encoding a spatial-frequency component of the block as a plurality of spatial-frequency coefficients, reduced encoded image-data is produced which is encoded data on a reduced image that is obtained by reducing the original image to a given reduction rate, having;

a block abstracting means for abstracting each block as a block to be processed, one after another, from the plurality of blocks;

a DC-coefficient abstracting means for abstracting a direct-current component coefficient from the plurality of spatial-frequency coefficients of the block to be processed;

an adjacent DC-coefficient abstracting means for abstracting the direct-current component coefficient of at least one adjacent block which is adjacent, in any of a horizontal direction, a vertical direction and an oblique direction, to the block to be processed, as at least one adjacent direct-current component coefficient;

a DC-coefficient comparing means for comparing the direct-current component coefficient of the block to be processed and the at least one adjacent direct-current component coefficient, and calculating a value of a predetermined function of the direct-current component coefficient of the block to be processed and the at least one adjacent direct-current component coefficient, the function representing an extent of unevenness between the direct-current component coefficient of the block to be processed and the at least one adjacent direct-current component coefficient;

a coefficient-set setting means for, if the value of the function is larger than a predetermined value, holding a smaller number of spatial-frequency coefficients than the plurality of spatial-frequency coefficients of the block to be processed according to the reduction rate, which have lower frequencies and include the direct-current component coefficient among the plurality of spatial-frequency coefficients of the block to be processed, and setting the other spatial-frequency coefficients to zero; and

a DC-coefficient setting means for, if the value of the function is smaller than the predetermined value, holding only the direct-current component coefficient of the plurality of spatial-frequency coefficients of the block to be processed, and setting the other spatial-frequency coefficients to zero, wherein

the image-data processing device produces the reduced encoded image-data, from encoded image-data which is read by the encoded image-data reading means,

the image-data distributing device further comprises a transmitting means for transmitting, to the network, the reduced encoded image-data which is produced by the image-data processing device, and

the image-data transmitting system further comprises a terminal device which is connected over the network to the image-data distributing device, wherein the terminal device includes;

a reduced encoded image-data receiving means for receiving the reduced encoded image-data which is transmitted by the transmitting means;

a decoding means for decoding the reduced encoded image-data which is received;

an image-size reducing means for reducing an image size of the reduced encoded image-data which is decoded; and

a screen displaying means for displaying on a screen the reduced encoded image-data which is reduced in an image size.

27. The image-data transmitting system according to claim 26, wherein:

the terminal device further includes,

an image-request inputting means for receiving a request to designate encoded image-data which corresponds to one image, from among the plurality of pieces of encoded image-data which is stored in the encoded image-data storing means, and

an image-request transmitting means for transmitting the received request, over the network, to the image-data distributing device;

the image-data distributing device further includes an image-request receiving means for receiving the transmitted request; and

the encoded image-data reading means reads encoded image-data which corresponds to the request, from among the plurality of pieces of encoded image-data which is stored in the encoded image-data storing means.

28. The image-data transmitting system according to claim 26, wherein:

the terminal device further includes,

a reduction rate inputting means for receiving an input of the reduction rate, and

a reduction rate transmitting means for transmitting the received reduction rate, over the network, to the image-data distributing device;

the image-data distributing device further includes a reduction rate receiving means for receiving the transmitted reduction rate; and

the image-data processing device produces the reduced encoded image-data by setting the received reduction rate as the given reduction rate.