Apparatus and methods for recompression of digital images
AssigneeBeamr Imaging Ltd
InventorsSharon Carmel, Dror Gill, Tamar Shoham
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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.
Claims23
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.
A computerized system of image recompression, comprising a processor operatively connected to a memory, the processor configured to:
- 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.
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:
- 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.
Dependencies are inferred from the claim text.