| 摘要 |
This invention detects an area where image quality greatly changes upon resolution conversion. For this purpose, a block segmentation unit extracts a tile having Tw×Th pixels from a buffer, and stores the tile in a tile buffer. A two-colors ratio calculating unit counts the number of times the number of colors included in a surrounding pixel group positioned near a pixel of interest becomes two during raster scanning of the tile buffer, and calculates a two-colors ratio Cr. A continuous pixel ratio calculating unit calculates, as a run ratio Rr, a ratio at which pixels having the same color continue during scanning of the tile buffer. A difference calculating unit calculates a resolution conversion error Dt when an image of the tile is converted to ½ the resolution. A determination unit determines based on Cr, Rr, and Dt whether a tile of interest is suitable for resolution conversion.
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