Apparatus and methods for re-compression having a monotonic relationship between extent of compression and quality of compressed image
First Claim
1. A computerized method for generating a quantization matrix usable for independent disjoint block-level recompression of an image, the image generated by independent disjoint block level compression of a precursor image using at least one first quantization matrix, the method comprising:
- providing a second quantization matrix;
updating, using a processor, the second quantization matrix to provide a monotonic relationship between a compression extent and a compression quality when performing independent disjoint block-level recompression of the image using the second quantization matrix, including, for at least one (row, column) position, performing the following, giving rise to the quantization matrix;
calculating a ratio between values located at the position in the first quantization matrix and in the second quantization matrix;
calculating a rounding of the ratio;
calculating a rounding error, being a difference between the ratio and the rounding; and
if the rounding error fulfills an unacceptability criterion, decreasing, using the processor, the value at the position in the second quantization matrix.
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Accused Products
Abstract
A computerized method for independent disjoint block-level recompression of a first image generated by independent coding of disjoint blocks in a precursor image, the first image having at least one first quantization matrix associated therewith, the method comprising performing at least one independent disjoint block-level compression operation, using a processor on the first image, thereby to generate a re-compressed second image including generating a new quantization matrix and using the new quantization matrix for the independent disjoint block-level compression, including computing a rounding error created by the quantization process utilizing the new quantization matrix and, if needed, adjusting at least one value of the new quantization matrix to reduce a rounding error created by the quantization process utilizing the new quantization matrix.
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Citations
24 Claims
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1. A computerized method for generating a quantization matrix usable for independent disjoint block-level recompression of an image, the image generated by independent disjoint block level compression of a precursor image using at least one first quantization matrix, the method comprising:
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providing a second quantization matrix; updating, using a processor, the second quantization matrix to provide a monotonic relationship between a compression extent and a compression quality when performing independent disjoint block-level recompression of the image using the second quantization matrix, including, for at least one (row, column) position, performing the following, giving rise to the quantization matrix; calculating a ratio between values located at the position in the first quantization matrix and in the second quantization matrix; calculating a rounding of the ratio; calculating a rounding error, being a difference between the ratio and the rounding; and if the rounding error fulfills an unacceptability criterion, decreasing, using the processor, the value at the position in the second quantization matrix. - View Dependent Claims (2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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5. A computerized system for generating a quantization matrix usable for independent disjoint block-level recompression of an image, the image generated by independent disjoint block level compression of a precursor image using at least one first quantization matrix, the system comprising a processor configured to:
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receive a second quantization matrix; update the second quantization matrix to provide a monotonic relationship between a compression extent and a compression quality when performing independent disjoint block-level recompression of the image using the second quantization matrix, including, for at least one (row, column) position, performing the following, giving rise to the quantization matrix; calculating a ratio between values located at the position in the first quantization matrix and in the second quantization matrix; calculating a rounding of the ratio; calculating a rounding error, being a difference between the ratio and the rounding; and if the rounding error fulfills an unacceptability criterion, decreasing the value at the position in said second quantization matrix. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification