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US 6,324,305 B1Granted
Method and apparatus for segmenting a composite image into mixed raster content planes
AssigneeXerox Corporation
InventorsThomas M. Holladay, Robert R. Buckley, R. Victor Klassen, Norman W. Zeck, Peter A. Crean
Life of this patent
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Abstract
An improved technique for compressing a color or gray scale pixel map representing a document using an MRC format including a method of segmenting an original pixel map into two planes, and then compressing the data or each plane in an efficient manner. The image is segmented such that pixels that compress well under a lossy compression technique are placed on one plane and pixels that must be compressed losslessly are placed on another plane. Lossy compression is then applied to the lossy pixel plane while lossless compression is applied to the lossless pixel plane.
Claims25
A method of processing digital image data that is composed of multiple superimposed separations, comprising:
- a) dividing the image data into separations, wherein each separation is composed of light intensity signals in respective discrete locations, each of said light intensity signals having a value which indicates a magnitude of a light intensity of the image data in said separation at said discrete location;
- b) partitioning each separation by creating a lossless signal plane and a lossy signal plane, said partitioning including, in stated order, the steps of:
- 1) selecting a number of consecutive discrete locations in said separation, said selected locations having respective light intensity values having magnitudes that lie within a pre-determined range;
- 2) calculating an average value for the light intensity values;
- and
- 3) replacing the values of signals in each of said consecutive discrete locations with said calculated average light intensity value;
- c) generating a selector map which indicates, for each discrete location in each of said separations, whether a light intensity signal previously located thereon has been placed on said lossless signal plane or on said lossy signal plane;
- and
- d) for at least one separation, separately compressing said lossless signal plane and said lossy signal plane in a manner suitable for compressing a type of data contained thereon, wherein said lossy signal plane is composed of a lossy subset of light intensity signals placed in discrete locations that correspond to discrete locations of lossy light intensity signals in said separation, and wherein the signals present in discrete locations on said lossless plane that correspond to discrete locations of lossless light intensity signals in said separation are ignored.
6 more elements
An apparatus for processing digital image data that is composed of multiple superimposed separations, comprising:
- a) means for dividing the image data into separations, wherein each separation is composed of light intensity signals in respective discrete locations, each of said light intensity signals having a value which indicates a magnitude of a light intensity of the image data in said separation at said discrete location;
- b) means for partitioning each separation by creating a lossless signal plane and a lossy signal plane, said partitioning including means for:
- 1) selecting a number of consecutive discrete locations in said separation, said selected locations having respective signals, and said signals having respective light intensity values, said values having respective magnitudes that lie within a pre-determined range;
- 2) calculating an average value for said selected light intensity values in the selected locations;
- and
- 3) replacing the values of the signals in each of said consecutive discrete locations with said calculated average light intensity value;
- c) means for generating a selector map which indicates, for each discrete location in each of said separations, whether a light intensity signal previously located thereon has been placed on said lossless signal plane or on said lossy signal plane;
- and
- d) for at least one separation, means for separately compressing said lossless signal plane and said lossy signal plane in a manner suitable for compressing a type of data contained thereon, wherein said lossy signal plane is composed of a lossy subset of light intensity signals placed in discrete locations that correspond to discrete locations of lossy light intensity signals in said separation, and wherein the signals present in discrete locations on said lossless plane that correspond to discrete locations of lossless light intensity signals in said separation are ignored.
6 more elements
An apparatus for processing digital image data that is composed of multiple superimposed separations, comprising:
- a) a divider which divides the image data into separations, wherein each separation is composed of light intensity signals in respective discrete locations, each of said light intensity signals having a respective light intensity value which indicates a magnitude of a light intensity of the image data in said separation at said discrete location;
- b) a partitioner which partitions each separation by creating a lossless signal plane and a lossy signal plane, said partitioner further comprising:
- 1) a run length counter which counts a number of consecutive discrete locations in said separation for which said signals have equal light intensity magnitudes;
- and
- 2) a designator which places said signals in said lossy signal plane when said counted number of consecutive discrete locations is less than a pre-determined value, and places signals not designated for said lossy signal plane in said lossless signal plane;
- c) a selector map generator which generates a selector map that indicates for each discrete location in each of said separations, whether light intensity signals previously located thereon have been placed on said lossless signal plane or on said lossy signal plane;
- and
- d) for at least one separation, a plurality of data compressors which separately compress said lossless signal plane and said lossy signal plane in a manner suitable for compressing a type of data contained thereon, said lossy signal plane is composed of a lossy subset of light intensity signals placed in discrete locations that correspond to discrete locations of lossy light intensity signals in said separation, and wherein the signals present in discrete locations on said lossless plane, that correspond to discrete locations of lossless light intensity signals in said separation, are ignored.
5 more elements
A programmable storage device readable by a machine, tangibly embodying a program of instructions having method steps, the method steps comprising:
- a) dividing the image data into separations, wherein each separation is composed of light intensity signals in respective discrete locations, each of said light intensity signals having a value which indicates a magnitude of a light intensity of the image data in said separation at said discrete location;
- b) partitioning each separation by creating a lossless signal plane and a lossy signal plane, said partitioning including, in stated order, the steps of:
- 1) selecting a number of consecutive discrete locations in said separation, said selected locations having respective signals, and said signals having respective light intensity magnitudes that lie within a pre-determined range;
- 2) calculating an average value for the light intensity values;
- and
- 3) replacing the values of signals in each of said consecutive discrete locations with said calculated average light intensity value;
- c) generating a selector map which indicates, for each discrete location in each of said separations, whether a light intensity signal previously located thereon has been placed on said lossless signal plane or on said lossy signal plane;
- and
- d) for at least one separation, separately compressing said lossless signal planes and said lossy signal planes in a manner suitable for compressing a type of data contained thereon, wherein said lossy signal plane is composed of a lossy subset of light intensity signals placed in discrete locations that correspond to discrete locations of lossy light intensity signals in said separation, and wherein signals present in discrete locations on said lossless plane, that correspond to discrete locations of lossless light intensity signals in said separation, are ignored.
6 more elements
Dependencies are inferred from the claim text.