| 摘要 |
PURPOSE:To attain a color picture with high quality by compressing and mapping the saturation and lightness of an input color picture signal into the saturation and lightness of an output system in a prescribed function. CONSTITUTION:A compression ROM 10 applying compression and mapping consists of a RGB/Luv conversion section 11, a garadation (lightness) compression section 13, a saturation compression section 15, an Luv/R'G'B' conversion section 17. The RGB signal of each picture element is converted into the Luv by the conversion section 11 according to an equation I. Then the lightness is compressed. In taking the maximum and minimum values of the lightness of the input system of a hue as L4, L1 and those of the output system as L3, L2, then L, u, v are converted respectively into L'', u'' and v'' according to an equation II. Then the saturation is compressed. The lengths in the saturation of the region corresponding to the lightness LA are taken as l1, l2. In this case L'', u, V'' are converted into L', u', v' according to equation III. As a result, the input color picture signal having wide color reproducing range is subjected to compression and mapping in the natural form.
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