Image coding apparatus, image decoding apparatus, image display apparatus and image processing apparatus

• US 20050175251A1
• Filed: 02/08/2005
• Published: 08/11/2005
• Est. Priority Date: 02/09/2004
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Sanyo Electric Company Limited (Panasonic Holdings Corporation)
• Inventors: Okada, Shigeyuki, Taketa, Kazuhiko
• Granted Patent: US 8,005,309 B2
• Time in Patent Office: Days
• US Class Current: 382/248
• CPC Class Codes: H04N 19/126 Details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
• CPC Class Codes: H04N 19/127 Prioritisation of hardware or computational resources
• CPC Class Codes: H04N 19/156 Availability of hardware or computational resources, e.g. encoding based on power-saving criteria
• CPC Class Codes: H04N 19/162 User input
• CPC Class Codes: H04N 19/17 the unit being an image region, e.g. an object
• CPC Class Codes: H04N 19/184 the unit being bits, e.g. of the compressed video stream
• CPC Class Codes: H04N 19/1883 the unit relating to sub-band structure, e.g. hierarchical level, directional tree, e.g. low-high [LH], high-low [HL], high-high [HH]
• CPC Class Codes: H04N 19/63 using sub-band based transform, e.g. wavelets
• CPC Class Codes: H04N 19/647 using significance based coding, e.g. Embedded Zerotrees of Wavelets [EZW] or Set Partitioning in Hierarchical Trees [SPIHT]

Abstract

A wavelet transform unit performs a wavelet transform on original images and a quantization unit quantizes wavelet transform coefficients. A ROI selector selects a region of interest or regions of interest in the original image, and a ROI mask generator generates ROI masks with which the wavelet transform coefficients (which are also called ROI transform coefficients) corresponding to the regions of interest are specified. By referring to the ROI masks, a lower-bit zero substitution unit substitutes low-order bits of non-ROI transform coefficients with zeros. An entropy coding unit entropy-codes the wavelet transform coefficients sequentially from high-order bit-planes, after the substitution. A coded data generator turns coded data into streams together with parameters and then outputs coded images.

Claims

1. An image coding apparatus, including:

a transform unit which transforms an image to spatial frequency domain so as to generate transform coefficients, each of which corresponds to a pixel of the image;

a substitution unit which substitutes a predetermined number of low-order bits with zero values in a bit string of the transform coefficients corresponding to part of a region in the image; and

a coding unit which encodes a bit string of the transform coefficients for the entire image sequentially from high-order bits, after substitution by said substitution unit.

2. An image coding apparatus, including:

a transform unit which transforms an image to spatial frequency domain so as to generate transform coefficients each of which corresponds to a pixel of the image;

a substitution unit which substitutes with zero values a certain number of low-order bits according to a degree of priority defined for each of a plurality of regions in the image in a bit string of the transform coefficients corresponding to the each of the plurality of regions in the image; and

a coding unit which encodes bit strings of the transform coefficients for the entire image sequentially from high-order bits, after substitution by said substitution unit.

3. An image decoding apparatus, including:

a decoding unit which decodes an encoded image so as to acquire transform coefficients in spatial frequency domain;

a substitution unit which substitutes a predetermined number of low-order bits with zero values in a bit string of the transform coefficients corresponding to part of a region in the image; and

an inverse-transform unit which restores the image by subjecting a bit string of the transform coefficients for the entire image to an inverse transform after substitution by said substitution unit.

4. An image decoding apparatus, including:

a decoding unit which decodes an encoded image so as to acquire transform coefficients in spatial frequency domain;

a substitution unit which substitutes with zero values a number of low-order bits according to a degree of priority defined for each of a plurality of regions in the image in a bit string of the transform coefficients corresponding to the each of the plurality of regions in the image; and

an inverse-transform unit which restores the image by subjecting a bit string of the transform coefficients for the entire image to an inverse transform after substitution by said substitution unit.

5. An image coding method characterized in that in transform coefficients in spatial frequency domain of an image the transform coefficients corresponding to part of a region in the image are specified and a predetermined number of low-order bits are substituted with zero values in a bit string of the transform coefficients corresponding to the specified part of a region in the image and, thereafter, a bit string of the transform coefficients for the entire image is encoded, as a whole, sequentially from high-order bits.

6. An image decoding method characterized in that in transform coefficients in spatial frequency domain of an image obtained by decoding an encoded image the transform coefficients corresponding to part of a region in the image are specified and a predetermined number of low-order bits are substituted with zero values in a bit string of the transform coefficients corresponding to the specified part of a region in the image and, thereafter, a bit string of the transform coefficients for the entire image are inverse-transformed so as to restore an image.

7. An image coding method characterized in that in transform coefficients in spatial frequency domain of an image the transform coefficients corresponding to a plurality of regions in the image are specified and a certain number of low-order bits according to a degree of priority defined for each of the plurality of regions in the image are substituted with zero values in a bit string of the transform coefficients corresponding to the specified plurality of regions and, thereafter, a bit string of the transform coefficients for the entire image is encoded, as a whole, sequentially from high-order bits.

8. An image decoding method characterized in that in transform coefficients in spatial frequency domain of an image obtained by decoding an encoded image the transform coefficients corresponding to a plurality of regions in the image are specified and a certain number of low-order bits according to a degree of priority defined for each of the plurality of regions in the image are substituted by zero values in a bit string of the transform coefficients corresponding to the specified plurality of regions and, thereafter, a bit string of the transform coefficients for the entire image are inverse-transformed so as to restore an image.

9. An image display apparatus including a display unit which displays, on a screen, moving images that differ in image quality for each of a plurality of regions set for the screen.

10. An image display apparatus according to claim 9, further including a specifying unit which specifies on the screen at least one of a region of interest and a non-region-of-interest, wherein the plurality of regions are set for the screen by specification of the at least one of a region of interest and a non-region-of-interest.

13. An image display apparatus according to claim 9, further including a decoding block which receives positional information on the plurality of regions, decodes a coded image by referring to the positional information and generates a decoded image differing in image quality for each of the plurality of regions,

wherein said display unit displays on the screen the decoded image generated by said decoding block.

14. An image display apparatus according to claim 9, further including a coding block which receives positional information on the plurality of regions, codes an original image by referring to the positional information and generates a coded image differing in image quality for each of the plurality of regions,

wherein said display unit displays, on the screen, an image that has been decoded based on the coded image.

11. An image display apparatus including a display unit which displays, on a screen, moving images that have a plurality of regions with different image qualities and an area of overlap in the regions.

12. An image display apparatus including a display unit which displays, on a screen, moving images that have a plurality of regions that are given different image qualities while visibility is retained.

15. An image display apparatus, including:

a selector which selects at least one of a region of interest and a non-region-of-interest for a screen on which moving images are displayed; and

a display unit which displays on the screen the moving images that differ in image quality for each of a plurality of regions set for the screen as a result of selecting the at least one of a region of interest and a non-region-of-interest.

16. An image display apparatus according to claim 15, wherein said selector sets a degree of priority for each of the plurality of regions and said display unit displays the plurality of regions with image qualities according to the degrees of priority.

17. An image display apparatus according to claim 16, wherein if an area of overlap exists among the plurality of regions, image quality in the area of overlap is determined based on a region having a higher degree of priority.

18. An image display apparatus, including:

a selector which selects a region of interest for a screen on which moving images are displayed; and

a display unit which displays the whole screen with a predetermined image quality in a state where the region of interest is not selected and which displays on the screen the region of interest with a higher image quality than that of other regions in a state where the region of interest is selected.

19. An image display apparatus according to claim 18, wherein when a plurality of regions of interest are selected, said display unit displays so that image quality differs for each of the plurality of regions of interest.

20. An image display apparatus according to claim 18, wherein said selector selects a region which changes with time as the region of interest.

21. An image display method characterized in that moving images which are given different image qualities for each of a plurality of regions set for a screen are displayed on the screen.

22. An image coding apparatus, including:

a transform unit which transforms an image to spatial frequency domain so as to generate transform coefficients each of which corresponds to a pixel of the image;

a scale-up unit which scales up a bit string of the transform coefficients corresponding to each of a plurality of regions in the image, by a bit number according to a degree of priority defined for each of the plurality of regions in the image; and

a coding unit which encodes the transform coefficients for the entire image sequentially from high-order bits, after upscaling by said scale-up unit.

23. An image coding apparatus, including:

a region selector which selects in an image a plurality of regions that differ in a degree of priority; and

a coding unit which encodes the image according to the degree of priority for each of the plurality of regions so as to generate a coded image including the plurality of regions that differ in image quality.

24. An image decoding apparatus, including:

a region selector which selects in an image a plurality of regions that differ in a degree of priority; and

an inverse transform unit which inverse-transforms an image that has been encoded according to respective degrees of priority in the plurality of regions and which restores an image including the plurality of regions that differ in image quality.

25. An image processing apparatus characterized in that it decodes moving image data in such a manner that a plurality of regions on a screen are given different image qualities and displayed and adjusts the image quality of the plurality of regions respectively in such a manner that a processing amount of entire decoding processing does not exceed a predetermined value.

26. An image processing apparatus, comprising:

a region specifying unit which specifies a region of interest for a screen; and

a decoding unit which decodes an image in such a manner that a region of interest and a normal region, which is an area other than the region of interest, are each given a different image quality.

27. An image processing apparatus according to claim 26, wherein said decoding unit adjusts the image quality of the region of interest and the normal region, respectively, in a manner such that a processing amount of entire decoding processing does not exceed a predetermined value.

28. An image processing apparatus according to claim 26, wherein said decoding unit raises the image quality of the region of interest whereas it lowers the image quality of the normal region.

29. An image processing apparatus according to claim 27, wherein said region specifying unit includes:

a decision unit which determines whether the processing amount of entire decoding processing exceeds the predetermined value or not when the image quality of the region of interest is raised; and

an image quality instruction unit which determines, according to a result of decision, whether increase in the image quality of the region of interest is permitted or not.

30. An image processing apparatus according to claim 27, wherein said region specifying unit includes:

an image quality instruction unit which raises the image quality of the region of interest; and

a decision unit which determines whether the processing amount of a decoding processing exceeds the predetermined value or not when the image quality of the region of interest is raised,

wherein said image quality instruction unit lowers the image quality of the normal region when said decision unit judges that the processing amount thereof exceeds the predetermined value.

31. An image processing unit according to claim 30, wherein when said decision unit judges that the processing amount thereof exceeds the predetermined value, said image quality instruction unit provides a display to warn a user that the image quality of the normal region will be lowered.

32. An image processing unit according to claim 30, wherein when said decision unit judges that the processing amount thereof exceeds the predetermined value, said image quality instruction unit inquires of a user whether the image quality of the region of interest is to be raised or not.