Method and apparatus for automatically determining a quantization factor value that produces a desired average compression ratio of an image sequence using JPEG compression
AssigneeSiemens Medical Systems, Inc.
InventorPing Hua
Life of this patent
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Abstract
A sequence of angiographic images is made up of frames of data. A sample sequence, made up of a number of such frames, is compressed using a lower value of the quantization factor and the resulting average compression ratio is determined. The same sample sequence is also compressed using a higher value for the quantization factor and another average compression ratio is determined. The value of the quantization factor corresponding to a desired average compression ratio of the entire sequence can then be determined by linear interpolation.
Claims8
A method for automatically determining, for a desired average compression ratio C, and within a predetermined range of quantization values, an appropriate value for a quantization factor Q for use in JPEG compression of image data from a sequence of angiographic images made up of frames of video data, comprising the following steps:
- sampling N frames of video data from the sequence;
- determining, using a low value quantization factor Q that is within said predetermined range and that is assumed to be less than said appropriate value, a lower average compression ratio for the sampled N frames of video data;
- determining, using a high value quantization factor Q that is within said predetermined range and that is assumed to be greater than said appropriate value, a higher average compression ratio for the sampled N frames of video data;
- and
- determining said appropriate value by linear interpolation.
A method for automatically determining, for a desired average compression ratio C, and within a predetermined range of quantization values, an appropriate value for a quantization factor Q for use in JPEG compression of image data of a type wherein, within a predetermined domain that includes said range, average compression ratio varies linearly with respect to quantization factor, comprising the following steps:
- extracting a sample from said image data;
- determining, using a low value quantization factor Q that is within said predetermined range and that is assumed to be less than said appropriate value, a lower average compression ratio for the sample;
- determining, using a high value quantization factor Q that is within said predetermined range and that is assumed to be greater than said appropriate value, a higher average compression ratio for the sample;
- and
- determining said appropriate value by linear interpolation.
A computer-based angiography system that automatically determines, for a desired average compression ratio C, and within a predetermined range of quantization values, an appropriate value for a quantization factor Q for use in JPEG compression of image data from a sequence of angiographic images made up of frames of video data, comprising the following steps:
- means for sampling N frames of video data from the sequence;
- means for determining, using a low value guantization factor Q that is within said predetermined range and that is assumed to be less than said appropriate value, a lower average compression ratio for the sampled N frames of video data;
- means for determining, using a high value quantization factor Q that is within said predetermined range and that is assumed to be greater than said appropriate value, a higher average compression ratio for the sampled N frames of video data;
- and
- means for determining said appropriate value by linear interpolation.
A method for automatically determining, for a desired average compression ratio C, and within a predetermined range of quantization values, an appropriate value for a parameter for use in JPEG compression of image data of a type wherein, within a predetermined domain that includes said range, average compression ratio varies linearly with respect to said parameter, comprising the following steps:
- extracting a sample from said image data;
- determining, using a low value of said parameter that is within said predetermined range and that is assumed to be less than said appropriate value, a lower average compression ratio for the sample;
- determining, using a high value of said parameter that is within said predetermined range and that is assumed to be greater than said appropriate value, a higher average compression ratio for the sample;
- and
- determining said appropriate value by linear interpolation.
Dependencies are inferred from the claim text.