Authors:
Tefen Lin
and
Jie Wang
Affiliation:
University of Massachusetts, United States
Keyword(s):
Error diffusion, Floyd-Steinberg dither, Serpentine Floyd-Steinberg, Block error diffusion, Sub-block error diffusion.
Related
Ontology
Subjects/Areas/Topics:
Applications and Services
;
Computer Vision, Visualization and Computer Graphics
;
Digital Image Processing
;
Entertainment Imaging Applications
;
Image and Video Analysis
;
Image Enhancement and Restoration
;
Image Formation and Preprocessing
Abstract:
In mosaic art images made from bricks, tiles, or counted cross-stitch patterns, artists would need to divide the original image into small parts of reasonable sizes and shapes and represent the colors of each part using just one “closest” color selected from a given color palette. Using standard methods to automate this process, the resulting mosaic image may contain undesirable visual artifacts of patches and color bandings. Error-diffusion dithering algorithms have been used to reduce such artifacts. We observe that image parsing directions are critical for diffusing errors, and we present a new error-diffusion scheme called “Four-Way Block dithering” (FWB) to correct certain artifacts caused by existing methods, including the directional and latticed appearance produced by Floyd and Steinberg’s dithering (FSD). FWB divides the input image into blocks of equal size with each block consisting of four sub-blocks such that the size of each sub-block is suitable for an underlying er
ror-diffusion algorithm. Scanning the blocks from left to right and from top to bottom, for each block being scanned, FWB starts from the center of the block and diffuses errors along four directions on each sub-block. We show that FWB can better retain the original structure and reduce unstructured artifacts. We also show that FWB dithering produces much better peak signal-to-noise ratios on mosaic images over those generated by FSD.
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