Re: rgb to yuv240p conversion

[Justin Schoeman <justin@xxxxxxxxxxxxxxxxxxxx>]

Jeroen Vreeken wrote:
> 
> Hi,
> 
> I am looking for a piece of code (or just documentation) to convert an
> bgr24 image to yuv240p.
> I have found some stuff but the result is terrible, overflows and black and
> white images...
> 
> Jeroen
> 
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Try this one (from Rene Muller):

void rgb_yuv(int w, int h, unsigned char *rgb, unsigned char *buf) {
   register int i,j; char *off = buf+w*h, *off2 = buf+w*h+w*h/4;
   for(j=0; j<h; j++) {
      for(i=0; i<w; i++) {
         int b = *rgb++;
         int g = *rgb++;
         int r = *rgb++;
         int y,cb,cr;
         y  =  (0.257 * r) + (0.504 * g) + (0.098 * b) + 16;
         cr =  (0.439 * r) - (0.368 * g) - (0.071 * b) + 128;
         cb = -(0.148 * r) - (0.291 * g) + (0.439 * b) + 128;
         if(y<0) y = 0; if(y>255) y = 255;
         if(cb<0) cb = 0; if(cb>255) cb = 255;
         if(cr<0) cr = 0; if(cr>255) cr = 255;
         *buf++ = y;
         if(j&1&&i&1)
            *off++ = cr;
         if(j&1&&i&1)
            *off2++ = cb;
      }
   }
}