Apparatus and methods for recompression of digital images
First Claim
Patent Images
1. A computerized method of image recompression, comprising:
- compressing each individual block in at least one image plane of an image to be re-compressed, including;
JPEG-coding said individual block, using a global quantization matrix, thereby obtaining a proposed output block of integers; and
for at least one individual region in the at least one image plane;
generating a regional compression parameter defining a region-specific level of compression which guarantees no more than a controlled amount of perceptual degradation of said individual region;
generating a regional quantization matrix from said regional compression parameter; and
for at least one particular block in said individual region, determining whether at least one entry in the proposed output block of integers JPEG-coded from said particular block would have been zero if said JPEG-coding step applied to said particular block had used said regional quantization matrix rather than said global quantization matrix, and if so, zeroing said at least one entry.
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Abstract
A system and method for generating a second reduced size digital image from a first digital image, the method including iteratively compressing the first digital image to an extent determined by a quality measure comprising at least a blockiness measure quantifying added artifactual edges along coding block boundaries of the second image and/or use of a quantization matrix generated by computing a weighted average of the quantization matrix of the first digital image and a scaled second quantization matrix.
57 Citations
23 Claims
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1. A computerized method of image recompression, comprising:
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compressing each individual block in at least one image plane of an image to be re-compressed, including; JPEG-coding said individual block, using a global quantization matrix, thereby obtaining a proposed output block of integers; and for at least one individual region in the at least one image plane; generating a regional compression parameter defining a region-specific level of compression which guarantees no more than a controlled amount of perceptual degradation of said individual region; generating a regional quantization matrix from said regional compression parameter; and for at least one particular block in said individual region, determining whether at least one entry in the proposed output block of integers JPEG-coded from said particular block would have been zero if said JPEG-coding step applied to said particular block had used said regional quantization matrix rather than said global quantization matrix, and if so, zeroing said at least one entry. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A computerized system of image recompression, comprising a processor operatively connected to a memory, the processor configured to:
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compress each individual block in at least one image plane of an image to be re-compressed, including; JPEG-code said individual block, using a global quantization matrix, thereby obtaining a proposed output block of integers; and for at least one individual region in the at least one image plane; generate a regional compression parameter defining a region-specific level of compression which guarantees no more than a controlled amount of perceptual degradation of said individual region; generate a regional quantization matrix from said regional compression parameter; and for at least one particular block in said individual region, determine whether at least one entry in the proposed output block of integers JPEG-coded from said particular block would have been zero if said JPEG-coding step applied to said particular block had used said regional quantization matrix rather than said global quantization matrix, and if so, zero said at least one entry. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A non-transitory computer readable storage medium tangibly embodying a program of instructions executable by a computer to perform a method of image recompression, comprising the steps:
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compressing each individual block in at least one image plane of an image to be re-compressed, including; JPEG-coding said individual block, using a global quantization matrix, thereby obtaining a proposed output block of integers; and for at least one individual region in the at least one image plane; generating a regional compression parameter defining a region-specific level of compression which guarantees no more than a controlled amount of perceptual degradation of said individual region; generating a regional quantization matrix from said regional compression parameter; and for at least one particular block in said individual region, determining whether at least one entry in the proposed output block of integers JPEG-coded from said particular block would have been zero if said JPEG-coding step applied to said particular block had used said regional quantization matrix rather than said global quantization matrix, and if so, zeroing said at least one entry.
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Specification