golgotha/i4/quantize/dither_quantize.cc

/********************************************************************** <BR>
  This file is part of Crack dot Com's free source code release of
  Golgotha. <a href="http://www.crack.com/golgotha_release"> <BR> for
  information about compiling & licensing issues visit this URL</a> 
  <PRE> If that doesn't help, contact Jonathan Clark at 
  golgotha_source@usa.net (Subject should have "GOLG" in it) 
***********************************************************************/

#include "image/image.hh"
#include "error/error.hh"
#include "memory/malloc.hh"
#include "image/context.hh"
#include <memory.h>

inline void argb_split(w32 c, int &a, int &r, int &g, int &b)
{
  a=(c&0xff000000)>>24;
  r=(c&0xff0000)>>16;
  g=(c&0xff00)>>8;
  b=(c&0xff)>>0;
}

inline w32 pack_argb(int a, int r, int g, int b)
{
  return (a<<24) | (r<<16) | (g<<8) | b;
}

void i4_dither_quantize(i4_image_class *source, i4_image_class *dest)
{
  int w=source->width(), h=source->height(), x,y;

  I4_ASSERT(source && dest && w==dest->width() && h==dest->height(), "source size !=dest");
  
  int size=(w+1)*(h+1)*4;
  w32 *er_im=(w32 *)i4_malloc(size,"");
  memset(er_im, 0, size);
  w32 *cur_er=er_im;

  i4_draw_context_class context(0,0, w-1, h-1);
  for (y=0; y<h; y++)
  {
    for (x=0; x<w; x++, cur_er++)
    {
      w32 c=source->get_pixel(x,y, context);
      int r,g,b,a, ea,er,eg,eb;

      argb_split(c, a,r,g,b);
      argb_split(*cur_er, ea, er, eg,eb);

      ea-=127; er-=127; eg-=127; eb-=127;

      a+=ea; if (a<0) a=0; if (a>255) a=255;
      r+=er; if (r<0) r=0; if (r>255) r=255;
      g+=eg; if (g<0) g=0; if (g>255) g=255;
      b+=eb; if (b<0) b=0; if (b>255) b=255;
     

      dest->put_pixel(x,y, pack_argb(a,r,g,b), context);
      w32 d=dest->get_pixel(x,y, context);      // see what the differance is
      argb_split(d, ea, er, eg, eb);

      ea-=a;
      er-=r;
      eg-=g;
      eb-=b;

      cur_er[1]+=pack_argb( (ea/4)+127, (er/4)+127, (eg/4)+127, (eb/4)+127);
      cur_er[w+1]+=pack_argb( (ea/2)+127, (er/2)+127, (eg/2)+127, (eb/2)+127);
      cur_er[w+1+1]+=pack_argb( (ea/4)+127, (er/4)+127, (eg/4)+127, (eb/4)+127);   
    }

    cur_er++;
  }

  i4_free(er_im);
}