Subversion Repositories mb-jpeg

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