source: trunk/sys/TinyGL/src/image_util.c @ 186

#include "zgl.h"

/*
 * image conversion
 */

void gl_convertRGB_to_5R6G5B(unsigned short *pixmap,unsigned char *rgb,
                             int xsize,int ysize)
{
  int i,n;
  unsigned char *p;

  p=rgb;
  n=xsize*ysize;
  for(i=0;i<n;i++) {
    pixmap[i]=((p[0]&0xF8)<<8) | ((p[1]&0xFC)<<3) | ((p[2]&0xF8)>>3); 
    p+=3;
  }
}

void gl_convertRGB_to_8A8R8G8B(unsigned int *pixmap, unsigned char *rgb,
                               int xsize, int ysize)
{
    int i,n;
    unsigned char *p;
    
    p=rgb;
    n=xsize*ysize;
    for(i=0;i<n;i++) {
        pixmap[i]=(((unsigned int)p[0])<<16) | 
            (((unsigned int)p[1])<<8) | 
            (((unsigned int)p[2])); 
        p+=3;
    }
}

/*
 * linear interpolation with xf,yf normalized to 2^16
 */

#define INTERP_NORM_BITS  16
#define INTERP_NORM       (1 << INTERP_NORM_BITS)

static inline int interpolate(int v00,int v01,int v10,int xf,int yf)
{
  return v00+(((v01-v00)*xf + (v10-v00)*yf) >> INTERP_NORM_BITS);
}


/* 
 * TODO: more accurate resampling 
 */

void gl_resizeImage(unsigned char *dest,int xsize_dest,int ysize_dest,
                    unsigned char *src,int xsize_src,int ysize_src)
{
  unsigned char *pix,*pix_src;
  float x1,y1,x1inc,y1inc;
  int xi,yi,j,xf,yf,x,y;

  pix=dest;
  pix_src=src;
  
  x1inc=(float) (xsize_src - 1) / (float) (xsize_dest - 1);
  y1inc=(float) (ysize_src - 1) / (float) (ysize_dest - 1);

  y1=0;
  for(y=0;y<ysize_dest;y++) {
    x1=0;
    for(x=0;x<xsize_dest;x++) {
      xi=(int) x1;
      yi=(int) y1;
      xf=(int) ((x1 - floor(x1)) * INTERP_NORM);
      yf=(int) ((y1 - floor(y1)) * INTERP_NORM);
      
      if ((xf+yf) <= INTERP_NORM) {
        for(j=0;j<3;j++) {
          pix[j]=interpolate(pix_src[(yi*xsize_src+xi)*3+j],
                             pix_src[(yi*xsize_src+xi+1)*3+j],
                             pix_src[((yi+1)*xsize_src+xi)*3+j],
                             xf,yf);
        }
      } else {
        xf=INTERP_NORM - xf;
        yf=INTERP_NORM - yf;
        for(j=0;j<3;j++) {
          pix[j]=interpolate(pix_src[((yi+1)*xsize_src+xi+1)*3+j],
                             pix_src[((yi+1)*xsize_src+xi)*3+j],
                             pix_src[(yi*xsize_src+xi+1)*3+j],
                             xf,yf);
        }
      }
      
      pix+=3;
      x1+=x1inc;
    }
    y1+=y1inc;
  }
}

#define FRAC_BITS 16

/* resizing with no interlating nor nearest pixel */

void gl_resizeImageNoInterpolate(unsigned char *dest,int xsize_dest,int ysize_dest,
                                 unsigned char *src,int xsize_src,int ysize_src)
{
  unsigned char *pix,*pix_src,*pix1;
  int x1,y1,x1inc,y1inc;
  int xi,yi,x,y;

  pix=dest;
  pix_src=src;
  
  x1inc=(int)((float) ((xsize_src)<<FRAC_BITS) / (float) (xsize_dest));
  y1inc=(int)((float) ((ysize_src)<<FRAC_BITS) / (float) (ysize_dest));

  y1=0;
  for(y=0;y<ysize_dest;y++) {
    x1=0;
    for(x=0;x<xsize_dest;x++) {
      xi=x1 >> FRAC_BITS;
      yi=y1 >> FRAC_BITS;
      pix1=pix_src+(yi*xsize_src+xi)*3;

      pix[0]=pix1[0];
      pix[1]=pix1[1];
      pix[2]=pix1[2];

      pix+=3;
      x1+=x1inc;
    }
    y1+=y1inc;
  }
}