| 摘要 |
PROBLEM TO BE SOLVED: To attain quick and efficient print for draft print and pseudo gradation by converting a color representation system accurately to a degree through quick calculation. SOLUTION: RGB color representation system color image data are received in this method and the image data are divided into blocks of m×n picture elements consisting of plural color data (S100), and mean values Ra, Ga, Ba of parameters R, G, B are calculated in each block (S110). Color conversion processing is applied only to the mean values to obtain parameters Ca, Ma, Ya in the CMY color representation system (S120). Individual picture element color data are obtained by calculating parameters after conversion as C1=Ca+ΔR1, M1=Ma+ΔG1, and Y1=Ya+ΔB1 based on a difference (ΔR1,ΔG1,ΔB1) from the mean values Ra, Ga, Ba.
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