Streak compensation in compressed image paths
AssigneeXerox Corporation
InventorsEdgar Bernal, Robert Paul Loce
Life of this patent
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Abstract
In accordance with the present disclosure, there is provided a method for compensating tones on a compressed digital image data. The method comprises generating the compressed digital image from an input digital image data using a wavelet-based compression method; recovering a low resolution version of the input digital image data from the compressed digital image data by partially decompressing the compressed digital image; applying compensating tone reproduction curves (TRC) to the low resolution version of the input digital image data to generate a compensated low resolution image; re-compressing the image using the compensated low resolution image; and, subsequently decompressing all of the compensated pixel arrays to produce decompressed compensated image data.
Claims14
A method for compensating tones for performing streak compensation on a compressed digital image data, comprising:
- generating a compressed digital image from an input digital image data using a wavelet-based compression method;
- recovering a low resolution version of the input digital image data from the compressed digital image data by partially decompressing the compressed digital image;
- applying spatially varying compensating tone reproduction curves (TRC) to the low resolution version of the input digital image data to generate a streak compensated low resolution image;
- subsequently decompressing all of the compensated pixel arrays to produce decompressed compensated image data;
- wherein the partial decompression utilizes reversed multiple wavelet decomposition steps, and a number of reversed decomposition steps yields a low resolution image at the resolution of a desired streak compensation;
- wherein the number of reversed decomposition steps is based on the spatial resolution of the available TRCs;
- and,
- wherein the number of reversed steps combines the compressed digital image data from lowest frequency wavelet sub bands to form the partially decompressed compressed digital image
- performing recompression to the streak compensated low resolution image and combining the recompressed streak compensated low resolution image with remaining sub-bands to form a streak compensated compressed digital image.
In a printing system for processing document images, apparatus for performing streak compensation on compressed digital image data being operable to:
- generate a compressed digital image from an input digital image data using a wavelet-based compression method;
- recover a low resolution version of the input digital image data from the compressed digital image data by partially decompressing the compressed digital image;
- apply spatially varying compensating tone reproduction curves (TRC) to the low resolution version of the input digital image data to generate a streak compensated low resolution image;
- subsequently decompress all of the input digital image data to produce decompressed compensated image data;
- wherein said compressed digital image data is lossy wavelet encoded image data;
- wherein the partial decompression utilizes reversal of multiple wavelet decomposition steps, and a number of reversed steps yields a low resolution image at the resolution of a desired streak compensation;
- wherein the number of reversed steps is based on the resolution of the available TRCs;
- wherein the number of reversed steps is based on (NL-T);
- wherein the number of reversed steps combines the compressed digital image data from lowest frequency sub bands to form the partially decompressed digital image;
- and,
- wherein each successive decomposition step of the sub band has generally half of the horizontal and half of the vertical resolution of the previous step.
A method for performing streak compensation on a compressed digital image data, the method comprising:
- identifying a type compression applied to the image;
- directing the compressed digital image data to a streak compensation module suitable for performing streak compensation on the type of compressed digital image data;
- performing streak compensation using the compressed digital image data using the suitable streak compensation module;
- wherein performing steak compensation includes applying spatially varying compensating tone reproduction curves;
- wherein said type of compressed digital image data is run-length encoding;
- decoding a run-length encoded stream to recover a full resolution image data;
- applying a compensation to the data to obtain a spatially uniform data stream;
- wherein the data source provides line art image data and the compressed data type is run-length encoding;
- and,
- wherein the identifying is performed by recognizing page description language commands.
Dependencies are inferred from the claim text.