IMAGE CODING METHOD AND APPARATUS AND IMAGE DECODING METHOD AND APPARATUS, BASED ON CHARACTERISTICS OF REGIONS OF IMAGE

• US 20130202201A1
• Filed: 08/10/2012
• Published: 08/08/2013
• Est. Priority Date: 02/02/2012
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: PARK, Pil-kyu, CHO, Dae-sung, PARK, Min-woo
• Granted Patent: US 8,879,838 B2
• Time in Patent Office: Days
• US Class Current: 382/165
• CPC Class Codes: H04N 19/12 Selection from among a plurality of transforms or standards, e.g. selection between discrete cosine transform [DCT] and sub-band transform or selection between H.263 and H.264
• CPC Class Codes: H04N 19/136 Incoming video signal characteristics or properties
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/176 the region being a block, e.g. a macroblock
• CPC Class Codes: H04N 19/186 the unit being a colour or a chrominance component
• CPC Class Codes: H04N 19/59 involving spatial sub-sampling or interpolation, e.g. alteration of picture size or resolution
• CPC Class Codes: H04N 19/60 using transform coding

Abstract

Methods of efficiently coding and decoding an image by analyzing each of regions of the image are provided. In the image coding method, an image format and a coding mode of a first region of an image are determined, whether a current image format of the first region is to be switched is determined based on the determined image format, and the first region is coded based on the determined image format and coding mode.

Claims

1. A method of coding an image, the method comprising:

determining an image format and a coding mode of each of regions of the image;

determining whether a current image format of a first region from among the regions of the image is to be switched, based on the determined image format; and

coding the first region, based on the determined image format and coding mode.

2. The method of claim 1, wherein the coding of the first region comprises switching the current image format of the first region to the determined image format, based on a result of the determining of whether the current image format of the first region is to be switched.

3. The method of claim 1, wherein the determining of the image format and the coding mode comprises:

analyzing image characteristics of the first region; and

determining the image format and the coding mode of the first region, based on a result of the analyzing.

4. The method of claim 3, wherein the analyzing of the image characteristics of the first region comprises:

determining a number of colors of the first region; and

determining a gradation of a chroma component of the first region.

5. The method of claim 4, wherein the analyzing of the image characteristics of the first region further comprises determining the first region as a synthetic image region, a natural image region, a text region, or a gradation region, based on the determined number of colors and the determined gradation of the chroma component.

6. The method of claim 5, wherein, during the analyzing of the image characteristics of the first region, the first region is determined as the synthetic image region or the natural image region when the number of colors of the first region is equal to or greater than a first threshold, and the first region is determined as the text region or the gradation region when the number of colors of the first region is less than the first threshold.

7. The method of claim 5, wherein, during the analyzing of the image characteristics of the first region, the first region is determined as the synthetic image region or the text region when the gradation of the chroma component of the first region is equal to or greater than a second threshold, and the first region is determined as the natural image region or the gradation region when the gradation of the chroma component of the first region is less than the second threshold.

8. The method of claim 5, wherein the determining of the image format and the coding mode comprises:

determining a color format of the first region as a first color format for the synthetic image region, a second color format for the natural image region, a third color format for the text region, or a fourth color format for the gradation region; and

determining the coding mode of the first region as a first coding mode for the synthetic image region, a second coding mode for the natural image region, a third coding mode for the text region, or a fourth coding mode for the gradation region.

9. The method of claim 1, wherein the coding of the first region comprises coding the first region based on at least one of transformation domain coding and pixel domain coding, according to the determined coding mode.

10. The method of claim 2, wherein the switching of the current image format of the first region comprises switching at least one of a color model and a color resolution of the current color format of the first region, according to the determined image format.

11. The method of claim 3, wherein the determining of the image format and the coding mode of the first region comprises determining the image format and the coding mode of the first region, based on the result of the analyzing and a control signal.

12. The method of claim 2, wherein the switching of the current image format of the first region comprises switching the current image format to the determined image format when the determined image format and the current image format of the first region are different from each other.

27. A computer readable recording medium having recorded thereon a computer program for executing the method of claim 1.

13. A method of decoding an image, the method comprising:

parsing image format information, coding mode information, and code image data in units of regions of a coded image, from a bit stream containing the coded image;

determining an image format and a decoding mode of a first region, based on the image format information and the coding mode information parsed in the units of the regions of the coded image;

decoding coded image data of the first region, based on the determined image format and decoding mode; and

determining whether a current image format of the first region is to be inversely switched, based on the determined image format.

14. The method of claim 13, wherein the determining of whether the current image format of the first region is to be inversely switched comprises inversely switching the current image format to the determined image format, based on a result of the determining of whether the current image format of the first region is to be inversely switched.

15. The method of claim 13, wherein the determining of the image format and the decoding mode comprises obtaining an image format and a coding mode that are determined by analyzing image characteristics of the first region.

16. The method of claim 15, wherein the analyzing of the image characteristics of the first region comprises determining a number of colors of the first region and a gradient of a chroma component of the first region.

17. The method of claim 16, wherein the first region is determined as a synthetic image region, a natural image region, a text region, or a gradation region, based on the number of colors of the first region and the gradient of the chroma component of the first region.

18. The method of claim 17, wherein the first region is determined as the synthetic image region or the natural image region when the number of colors of the first region is equal to or greater than a first threshold, and is determined as the text region or the gradation region when the number of colors of the first region is less than the first threshold.

19. The method of claim 17, wherein the first region is determined as the synthetic image region or the text region when the gradation of the chroma component of the first region is equal to or greater than a second threshold, and is determined as the natural image region or the gradation region when the gradation of the chroma component of the first region is less than the second threshold.

20. The method of claim 17, wherein a color format of the first region is determined as a first color format for the synthetic image region, a second color format for the natural image region, a third color format for the text region, or a fourth color format for the gradation region;

and

the coding mode of the first region is determined as a first coding mode for the synthetic image region, a second coding mode for the natural image region, a third coding mode for the text region, or a fourth coding mode for the gradation region.

21. The method of claim 13, wherein the decoding of the coded image data of the first region comprises decoding the first region based on at least one of transformation domain decoding and pixel domain decoding, according to the determined decoding mode.

22. The method of claim 14, wherein the inverse switching of the current image format of the first region comprises inversely switching at least one of a color model and a color resolution of the current color format of the first region, according to the determined image format.

23. The method of claim 15, wherein the image format and the decoding mode of the first region are determined based a result of the analyzing and a control signal.

24. The method of claim 14, wherein the inverse switching of the current image format of the first region comprises inversely switching the current image format to the determined image format when the determined image format and the current image format of the first region are different from each other.

28. A computer readable recording medium having recorded thereon a computer program for executing the method of claim 13.

25. An apparatus for coding an image, the apparatus comprising:

a region format mode determiner which determines an image format and a coding mode of each of regions of the image;

a region format switch which determines whether a current image format of a first region from among the regions of the image is to be switched, based on the determined image format, and switching the current image format to the determined image format, based on a result of the determining of whether the current image format of the first region is to be switched;

a region coder which codes the first region, based on the determined image format and coding mode; and

a processor which controls operations of the region format mode determiner, the region format switch, and the region coder.

26. An apparatus for decoding an image, the apparatus comprising:

a bit stream parser which parses image format information, coding mode information, and code image data in units of regions of a coded image, from a bit stream containing the coded image;

a region format mode determiner which determines an image format and a decoding mode of a first region, based on the image format information and the coding mode information that are parsed in units of the regions of the coded image;

a region decoder which decodes coded image data of the first region, based on the determined image format and decoding mode;

a region format inverse switch which determines whether a current image format of the first region is to be inversely switched, based on the determined image format, and inversely switching the current image format to the determined image format, based on a result of the determining of whether the current image format of the first region is to be inversely switched; and

a processor which controls operations of the bit stream parser, the region format mode determiner, the region decoder, and the region format switch.