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/********************************************************************************
* *
* F S C o l o r Q u a n t i z a t i o n *
* *
*********************************************************************************
* Copyright (C) 1999,2022 by Jeroen van der Zijp. All Rights Reserved. *
*********************************************************************************
* This library is free software; you can redistribute it and/or modify *
* it under the terms of the GNU Lesser General Public License as published by *
* the Free Software Foundation; either version 3 of the License, or *
* (at your option) any later version. *
* *
* This library is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
* GNU Lesser General Public License for more details. *
* *
* You should have received a copy of the GNU Lesser General Public License *
* along with this program. If not, see <http://www.gnu.org/licenses/> *
********************************************************************************/
#include "xincs.h"
#include "fxver.h"
#include "fxdefs.h"
#include "fxmath.h"
#include "FXElement.h"
/*
Notes:
- The fxfsquantize is a floyd-steinberg dither. It is quite fast
but not as good as Heckbert's or Wu's.
*/
using namespace FX;
// Up to 256 colors: 3 bits R, 3 bits G, 2 bits B (RRRGGGBB)
#define REDMASK 0xe0
#define REDSHIFT 0
#define GREENMASK 0xe0
#define GREENSHIFT 3
#define BLUEMASK 0xc0
#define BLUESHIFT 6
/*******************************************************************************/
namespace FX {
extern FXbool fxfsquantize(FXuchar* dst,const FXColor* src,FXColor* colormap,FXint& actualcolors,FXint w,FXint h,FXint maxcolors);
// Floyd-Steinberg quantization full 32 bpp to less than or equal to maxcolors
FXbool fxfsquantize(FXuchar* dst,const FXColor* src,FXColor* colormap,FXint& actualcolors,FXint w,FXint h,FXint){
FXint i,j,val,r1,g1,b1,*cr,*cg,*cb,*nr,*ng,*nb,*p;
FXint *begin;
// Fill colormap
for(r1=i=0; r1<8; r1++){
for(g1=0; g1<8; g1++){
for(b1=0; b1<4; b1++){
((FXuchar*)(colormap+i))[0]=(b1*255+1)/3;
((FXuchar*)(colormap+i))[1]=(g1*255+3)/7;
((FXuchar*)(colormap+i))[2]=(r1*255+3)/7;
((FXuchar*)(colormap+i))[3]=255;
i++;
}
}
}
// Temporary storage
if(!allocElms(begin,w*2*3)) return false;
// Set up rows
cr=begin;
cg=cr+w;
cb=cg+w;
nr=cb+w;
ng=nr+w;
nb=ng+w;
// Get first line of picture
for(j=0; j<w; j++){
nr[j]=((const FXuchar*)(src+j))[2];
ng[j]=((const FXuchar*)(src+j))[1];
nb[j]=((const FXuchar*)(src+j))[0];
}
src+=w;
// Dither loop
for(i=0; i<h; i++){
// Swap lines
FXSWAP(cr,nr,p);
FXSWAP(cg,ng,p);
FXSWAP(cb,nb,p);
// Get next line
if(i!=h-1){
for(j=0; j<w; j++){
nr[j]=((const FXuchar*)(src+j))[2];
ng[j]=((const FXuchar*)(src+j))[1];
nb[j]=((const FXuchar*)(src+j))[0];
}
src+=w;
}
// Dither
for(j=0; j<w; j++){
r1=cr[j]; r1=FXCLAMP(0,r1,255);
g1=cg[j]; g1=FXCLAMP(0,g1,255);
b1=cb[j]; b1=FXCLAMP(0,b1,255);
// choose actual pixel value
val=(((r1&REDMASK)>>REDSHIFT)|((g1&GREENMASK)>>GREENSHIFT)|((b1&BLUEMASK)>>BLUESHIFT));
*dst++=val;
// compute color errors
r1-=((FXuchar*)(colormap+val))[2];
g1-=((FXuchar*)(colormap+val))[1];
b1-=((FXuchar*)(colormap+val))[0];
// Add fractions of errors to adjacent pixels
if(j!=w-1){ // Adjust RIGHT pixel
cr[j+1]+=(r1*7)/16;
cg[j+1]+=(g1*7)/16;
cb[j+1]+=(b1*7)/16;
}
if(i!=h-1){ // do BOTTOM pixel
nr[j]+=(r1*5)/16;
ng[j]+=(g1*5)/16;
nb[j]+=(b1*5)/16;
if(j>0){ // do BOTTOM LEFT pixel
nr[j-1]+=(r1*3)/16;
ng[j-1]+=(g1*3)/16;
nb[j-1]+=(b1*3)/16;
}
if(j!=w-1){ // do BOTTOM RIGHT pixel
nr[j+1]+=(r1)/16;
ng[j+1]+=(g1)/16;
nb[j+1]+=(b1)/16;
}
}
}
}
freeElms(begin);
actualcolors=256;
return true;
}
}
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