Higher order error diffusion of digital halftoning
AssigneeSharp Laboratories of America, Inc.
InventorWilliam Ho Chang
Life of this patent
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Abstract
In the error diffusion technique for digital halftoning the output color for a first pixel is selected by comparing an adjusted input color signal to a boundary separating output colors in a pallette for a display device. The error or difference between the selected output color and the input color signal is determined and portions of that difference are added to the input color signals for neighboring pixels diffusing the error throughout the area neighboring the first pixel. Error diffusion can create artifacts in the image as rendered by the display device. Error diffusion artifacts are reduced or eliminated by a higher order error diffusion method where the boundary separating output colors in the device's pallette is adjusted as a function of the error in a previous pixel.
Claims5
A method of error diffusion for digital halftoning comprising:
- (a) disassociating an input image into a plurality of input signals representing a color of each of a plurality of input image pixels;
- (b) altering said input signal for a subject pixel with a diffusion function of an error signal for another pixel;
- (c) modifying said diffusion function of said error signal with a transformation function;
- (d) altering said modified diffusion function with a boundary adjustment function;
- (e) adjusting a color space boundary in a color pallette for an output device by said diffusion function as modified by said transformation function and said boundary adjustment function;
- and
- (f) selecting an output color from said color pallette for said subject pixel by comparing said altered input signal for said subject pixel to said adjusted color space boundary.
Dependencies are inferred from the claim text.