| 摘要 |
N rasters of multi-valued data indicating a halftone image is input to a buffer and a pixel of interest to be quantized is quantized for the input multi-valued data. Furthermore, error of a quantized pixel is distributed to peripheral pre-quantization pixels including pre-quantization pixels in a raster of pixels quantized before the quantized pixel, and error distributed with respect to the pixel of interest is added to the multi-valued data for which quantization is yet to be processed. And the quantizing and distributing and adding of error are repeated while moving the pixel of interest in a column direction, and, when processing of N pixels has been completed in regard to the column direction, equivalent processing is repeated while moving the pixel of interest in a raster direction, thereby quantizing the multi-valued data of the N rasters.
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