Halftone image down-sampling
Halftone color image down-sampling, performed on a color-channel-by-color-channel basis, with respect to which the selected, overall down-sampling ratio determines whether one or plural down-sampling stage(s) is(are) implemented. If B<(A−1), where A is the original pixel resolution, and B is the intended final resolution, then plural down-sampling steps are conducted. Otherwise, only a single down-sampling stage is involved. Each down-sampling stage involves looking at successive adjacent clusters containing four pixels arranged in row-and-column paired manners, and calculating new down-sampled pixel values based upon a special averaging strategy. In this strategy, if the population of white pixels in each group of four examined pixels is no more than 50-percent, the white pixel values are not included in the calculated average. If white pixels dominate the group, the non-white pixel values are not included in the calculated average.
Sharp Laboratories of America, Inc.
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Ching-Wei Jiaping
Chang Song