Error diffusion halftoning system
First Claim
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1. A method of selecting an intensity threshold in a halftoning system used to render respective pixels of an image on a display, said halftoning system providing respective accumulated errors, each based on at least one respective variance between a rendered intensity of a pixel and a quantized measured intensity of a corresponding pixel of a contone image to be displayed, each respective accumulated error subject to recalculation pixel-by-pixel, said method comprising the steps of:
- (a) selecting a first predetermined intensity threshold if either one of said accumulated errors of a current pixel and a neighboring pixel exceeds a first error threshold;
(b) selecting a second predetermined intensity threshold if said accumulated error of a pixel remotely neighboring said current pixel exceeds a second error threshold and said first predetermined intensity threshold is not selected;
(c) selecting a third predetermined intensity threshold if neither of said first and said second intensity thresholds are selected; and
(d) rendering a pixel of said image on a display based upon said selected predetermined intensity threshold.
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Abstract
Artifacts of error diffusion halftoning are reduced by selecting a halftone threshold for a current pixel on the basis of an accumulated halftone error for the pixel and its neighbors.
23 Citations
12 Claims
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1. A method of selecting an intensity threshold in a halftoning system used to render respective pixels of an image on a display, said halftoning system providing respective accumulated errors, each based on at least one respective variance between a rendered intensity of a pixel and a quantized measured intensity of a corresponding pixel of a contone image to be displayed, each respective accumulated error subject to recalculation pixel-by-pixel, said method comprising the steps of:
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(a) selecting a first predetermined intensity threshold if either one of said accumulated errors of a current pixel and a neighboring pixel exceeds a first error threshold; (b) selecting a second predetermined intensity threshold if said accumulated error of a pixel remotely neighboring said current pixel exceeds a second error threshold and said first predetermined intensity threshold is not selected; (c) selecting a third predetermined intensity threshold if neither of said first and said second intensity thresholds are selected; and (d) rendering a pixel of said image on a display based upon said selected predetermined intensity threshold. - View Dependent Claims (2, 3, 4)
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5. An error diffusion halftone image display method providing respective accumulated errors, each based on at least one respective variance between a rendered intensity of a pixel and a quantized measured intensity of a corresponding pixel of a contone image to be displayed, each respective accumulated error subject to recalculation pixel-by-pixel, said method comprising the steps of:
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(a) determining an intensity of a current pixel in an image; (b) augmenting said intensity of said current pixel with a current pixel accumulated error; (c) selecting a first predetermined intensity threshold if either one of said current pixel accumulated error and an immediate neighboring pixel accumulated error is less than a first error threshold; (d) selecting a second predetermined intensity threshold if a remote neighboring pixel accumulated error is less than a second error threshold and said first error threshold is not selected; (e) selecting a third predetermined intensity threshold if a more remote neighboring pixel accumulated error is less than a third error threshold and neither of said first and said second error thresholds are selected; (f) selecting a fourth predetermined intensity threshold if one of said first, said second, and said third predetermined intensity thresholds is not selected; (g) displaying said current pixel with one of a first displayed intensity if said augmented intensity of said current pixel exceeds said selected predetermined intensity threshold and otherwise displaying said current pixel with a second displayed intensity; and (h) assigning an error between said displayed intensity and said augmented intensity of said current pixel to at least one pixel neighboring said current pixel. - View Dependent Claims (6, 7, 8, 9, 10, 11, 12)
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Specification