| 摘要 |
PROBLEM TO BE SOLVED: To make banding or the like inconspicuous, and also, to prevent a line structure from being visually recognized when converting from high-gradation image data to low-gradation image data. SOLUTION: High-gradation input image data are quantized by using a threshold matrix as a line screen (a step 100). It is judged whether or not a target pixel is a specific pixel, to which error diffusion processing is applied by judging whether or not the density of the target pixel is in the range of prescribed density in which the line structure of the line can be easily recognized visually (a step 102). When the target pixel is the specific pixel, the error diffusion processing is executed to the pixel (a step 104). When the error diffusion processing is executed, the threshold of the threshold matrix is corrected corresponding to neighboring pixels in which quantization errors are diffused (a step 106). It is judged whether or not the processing is executed to all the pixels (a step 108). When the processing is executed to all the pixels, this routine is terminated. COPYRIGHT: (C)2007,JPO&INPIT
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