| 摘要 |
PROBLEM TO BE SOLVED: To suppress deterioration of gradational characteristics of reproduced images when a printing speed is made high in an image-forming apparatus with a thermal head. SOLUTION: A set printing mode is judged at a printing start. When a high- speed printing mode is set (S103: No), the presence/absence of a bias of a density distribution is judged on the basis of a standard deviationσof image data of the document (S103 and S104). If the density distribution is not biased (S104: No), and LUT1 of subtracting only the number of gray levels of an output image and carrying out a gray level transformation for an entire density region is selected (S105). When the density distribution is biased to a specific density region (104: Yes), at which of a low density region, a middle density region and a high density region the bias of the density distribution is located is judged, and LUTs 2-4 of subtracting the number of gray levers of the output image and favorably reproducing a gradation of the density region where the density distribution is biased are selected (S106-S111).
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