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quickwayne |
/*-----------------------------------------*/
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/* File : color.c, utilities for jfif view */
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/* Author : Pierre Guerrier, march 1998 */
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/*-----------------------------------------*/
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#include <stdlib.h>
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#include <stdio.h>
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/* Ensure number is >=0 and <=255 */
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#define Saturate(n) ((n) > 0 ? ((n) < 255 ? (n) : 255) : 0)
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/*------------------------------------------------------------*/
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/* internal color conversion utility */
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/*
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static unsigned char
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get_comp(int n, int i, int j)
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{
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int ip = i >> comp[n].VDIV; / * get coordinates in n-th comp pixels * /
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int jp = j >> comp[n].HDIV; / * within the MCU * /
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return MCU_buff[comp[n].IDX+comp[n].HS*(ip>>3)+(jp>>3)]->block[ip&7][jp&7];
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/ * this is the right block in MCU, and this right sample * /
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}
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*/
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/* and alternate macro, a little faster */
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/*
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#define get_comp(t,n,i,j) { int ip = i >> comp[n].VDIV; \
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int jp = j >> comp[n].HDIV; \
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t = MCU_buff[comp[n].IDX+comp[n].HS*(ip>>3)+(jp>>3) ]->block[ip&7][jp& 7]; \
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}
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*/
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/*---------------------------------------*/
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/* rules for color conversion: */
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/* r = y +1.402 v */
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/* g = y -0.34414u -0.71414v */
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/* b = y +1.772 u */
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/* Approximations: 1.402 # 7/5 = 1.400 */
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/* .71414 # 357/500 = 0.714 */
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/* .34414 # 43/125 = 0.344 */
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/* 1.772 = 443/250 */
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/*---------------------------------------*/
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/* Approximations: 1.402 # 359/256 = 1.40234 */
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/* .71414 # 183/256 = 0.71484 */
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/* .34414 # 11/32 = 0.34375 */
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/* 1.772 # 227/128 = 1.7734 */
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/*----------------------------------*/
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void
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color_conversion(void)
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{
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int i, j;
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unsigned char y,cb,cr;
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signed char rcb, rcr;
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long r,g,b;
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long offset;
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for (i = 0; i < MCU_sy; i++) /* pixel rows */
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{
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int ip_0 = i >> comp[0].VDIV;
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int ip_1 = i >> comp[1].VDIV;
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int ip_2 = i >> comp[2].VDIV;
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int inv_ndx_0 = comp[0].IDX + comp[0].HS * (ip_0 >> 3);
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int inv_ndx_1 = comp[1].IDX + comp[1].HS * (ip_1 >> 3);
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int inv_ndx_2 = comp[2].IDX + comp[2].HS * (ip_2 >> 3);
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int ip_0_lsbs = ip_0 & 7;
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int ip_1_lsbs = ip_1 & 7;
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int ip_2_lsbs = ip_2 & 7;
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int i_times_MCU_sx = i * MCU_sx;
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for (j = 0; j < MCU_sx; j++) /* pixel columns */
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{
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int jp_0 = j >> comp[0].HDIV;
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int jp_1 = j >> comp[1].HDIV;
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int jp_2 = j >> comp[2].HDIV;
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y = MCU_buff[inv_ndx_0 + (jp_0 >> 3)]->block[ip_0_lsbs][jp_0 & 7];
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cb = MCU_buff[inv_ndx_1 + (jp_1 >> 3)]->block[ip_1_lsbs][jp_1 & 7];
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cr = MCU_buff[inv_ndx_2 + (jp_2 >> 3)]->block[ip_2_lsbs][jp_2 & 7];
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rcb = cb - 128;
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rcr = cr - 128;
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r = y + ((359 * rcr) >> 8);
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g = y - ((11 * rcb) >> 5) - ((183 * rcr) >> 8);
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b = y + ((227 * rcb) >> 7);
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offset = 3 * (i_times_MCU_sx + j);
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ColorBuffer[offset + 2] = Saturate(r);
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ColorBuffer[offset + 1] = Saturate(g);
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ColorBuffer[offset + 0] = Saturate(b);
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/* note that this is SunRaster color ordering */
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}
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}
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}
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