Segmentation method and system for multiple raster content (MRC) representation of documents

1. A method for separating an image signal into a set of image planes in accordance with a control signal, the method comprising the operations of:

receiving the control signal and producing a threshold selector signal, via a selector module based on the control signal;

receiving the selector signal and producing a decision signal, via an edge processing module;

receiving the image signal and the decision signal, and outputting an initial foreground signal and an initial background signal, via a foreground/background separation module, a representation of the current pixel of the image signal being included in at least one of the initial foreground signal and the initial background signal in accordance with the decision signal; and

sub-sampling, by a programmable amount, the initial foreground signal and the initial background signal while ignoring undefined pixels.

2. The method of claim 1 , further comprising:

filling undefined pixels in the initial foreground and initial background signals with values computed so as to substantially prevent artifacts and to facilitate good compression ratio, using a cleanup module; and

outputting a final foreground signal and a final background signal.

3. The method of claim 2 , wherein the operation of filling comprises:

extending content of defined pixels in each of the initial foreground and initial background signals to neighboring undefined pixels by filling neighboring undefined pixels with diluted foreground and background values, respectively, using a dilate module;

averaging non-zero content of the diluted foreground and background values over minimum coded unit blocks and outputting averaged block values, using a block average module; and

filling any remaining undefined pixels with the averaged block values, using a fill module.

4. A system for separating an image signal into a set of image planes in accordance with a control signal, the system comprising:

a selector module receiving the control signal and producing a threshold selector signal based on the control signal;

an edge processing module receiving the selector signal and producing a decision signal;

a foreground/background separation module receiving the image signal and the decision signal, and outputting an initial foreground signal and an initial background signal, a representation of the current pixel of the image signal being included in at least one of the initial foreground signal and the initial background signal in accordance with the decision signal; and

a sub-sampling module sub-sampling, by a programmable amount, the initial foreground signal and the initial background signal and ignoring undefined pixels.

5. The system of claim 4 , further comprising:

a cleanup module comprising the sub-sampling module, the cleanup module receiving the initial foreground signal and the initial background signal, filling undefined pixels in the initial foreground and initial background signals with values computed to substantially prevent compression ringing artifacts, and to facilitate good compression ratio and outputting a final foreground signal and a final background signal.

6. The system of claim 5 , wherein the cleanup module further comprises:

a dilate module extending content of defined pixels in each of the initial foreground and initial background signals to neighboring undefined pixels by filling neighboring undefined pixels with diluted foreground and background values, respectively;

a block average module averaging non-zero content of the diluted foreground and background values over minimum coded unit blocks and outputting averaged block values; and

a fill module filling any remaining undefined pixels with the averaged block values.

7. An article of manufacture comprising:

a machine usable medium having program code embedded therein, the program code being used for separating an image signal into a set of image planes in accordance with a control signal, the program code comprising:

machine readable code to receive and process the control signal, and produce a threshold selector signal based on the control signal;

machine readable code to receive the selector signal and produce a decision signal;

machine readable code to receive and process the image signal and the decision signal, and output an initial foreground signal and an initial background signal, a representation of the current pixel of the image signal being included in at least one of the initial foreground signal and the initial background signal in accordance with the decision signal; and

machine readable code to sub-sample, by a programmable amount, the initial foreground signal and the initial background signal while ignoring undefined pixels.

8. The article of manufacture of claim 7 wherein the machine readable code further comprises:

machine readable code to receive the initial foreground signal and the initial background signal;

machine readable code to fill undefined pixels in the initial foreground and initial background signals with values computed so as to substantially prevent artifacts and to facilitate good compression ratio; and

a machine readable coded to output a final foreground signal and a final background signal.

9. The article of manufacture of claim 8 , wherein the machine readable code to fill undefined pixels comprises:

machine readable code to extend content of defined pixels in each of the initial foreground and initial background signals to neighboring undefined pixels by filling neighboring undefined pixels with diluted foreground and background values, respectively;

machine readable code to average non-zero content of the diluted foreground and background values over minimum coded unit blocks and to output averaged block values; and

machine readable code to fill any remaining undefined pixels with the averaged block values.

10. A system for separating an image signal into a set of image planes in accordance with a control signal, the system comprising:

means for receiving the control signal and producing a threshold selector signal, via a selector module based on the control signal;

means for receiving the selector signal and producing a decision signal, via an edge processing module; and

means for receiving the image signal and the decision signal, and outputting an initial foreground signal and an initial background signal, via a foreground/background separation module, a representation of the current pixel of the image signal being included in at least one of the initial foreground signal and the initial background signal in accordance with the decision signal; and

means for sub-sampling, by a programmable amount, the initial foreground signal and the initial background signal and ignoring undefined pixels.

11. The system of claim 10 , further comprising:

means for filling undefined pixels in the initial foreground and initial background signals with values computed so as to substantially prevent artifacts and to facilitate good compression ratio, using a cleanup module; and

means for outputting a final foreground signal a final background signal.

12. The system of claim 11 , wherein the means for filling comprises:

means for extending content of defined pixels in each of the initial foreground and initial background signals to neighboring undefined pixels by filling neighboring undefined pixels with diluted foreground and background values, respectively, using a dilate module;

means for averaging non-zero content of the diluted foreground and background values over minimum coded unit blocks and outputting averaged block values, using a block average module; and

means for filling any remaining undefined pixels with the averaged block values, using a fill module.