Modified source engine (2017) developed by valve and leaked in 2020. Not for commercial purporses
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//========= Copyright Valve Corporation, All rights reserved. ============//
//
// Purpose:
//
// $NoKeywords: $
//
//=============================================================================//
#include <quantize.h>
#include <minmax.h>
#define N_EXTRAVALUES 1
#define N_DIMENSIONS (3+N_EXTRAVALUES)
#define PIXEL(x,y,c) Image[4*((x)+((Width*(y))))+c]
static uint8 Weights[]={5,7,4,8};
static int ExtraValueXForms[3*N_EXTRAVALUES]={
76,151,28,
};
#define MAX_QUANTIZE_IMAGE_WIDTH 4096
void ColorQuantize(uint8 const *Image,
int Width,
int Height,
int flags, int ncolors,
uint8 *out_pixels,
uint8 *out_palette,
int firstcolor)
{
int Error[MAX_QUANTIZE_IMAGE_WIDTH+1][3][2];
struct Sample *s=AllocSamples(Width*Height,N_DIMENSIONS);
int x,y,c;
for(y=0;y<Height;y++)
for(x=0;x<Width;x++)
{
for(c=0;c<3;c++)
NthSample(s,y*Width+x,N_DIMENSIONS)->Value[c]=PIXEL(x,y,c);
// now, let's generate extra values to quantize on
for(int i=0;i<N_EXTRAVALUES;i++)
{
int val1=0;
for(c=0;c<3;c++)
val1+=PIXEL(x,y,c)*ExtraValueXForms[i*3+c];
val1>>=8;
NthSample(s,y*Width+x,N_DIMENSIONS)->Value[c]=(uint8)
(min(255,max(0,val1)));
}
}
struct QuantizedValue *q=Quantize(s,Width*Height,N_DIMENSIONS,
ncolors,Weights,firstcolor);
delete[] s;
memset(out_palette,0x55,768);
for(int p=0;p<256;p++)
{
struct QuantizedValue *v=FindQNode(q,p);
if (v)
for(c=0;c<3;c++)
out_palette[p*3+c]=v->Mean[c];
}
memset(Error,0,sizeof(Error));
for(y=0;y<Height;y++)
{
int ErrorUse=y & 1;
int ErrorUpdate=ErrorUse^1;
for(x=0;x<Width;x++)
{
uint8 samp[3];
for(c=0;c<3;c++)
{
int tryc=PIXEL(x,y,c);
if (! (flags & QUANTFLAGS_NODITHER))
{
tryc+=Error[x][c][ErrorUse];
Error[x][c][ErrorUse]=0;
}
samp[c]=(uint8) min(255,max(0,tryc));
}
struct QuantizedValue *f=FindMatch(samp,3,Weights,q);
out_pixels[Width*y+x]=(uint8) (f->value);
if (! (flags & QUANTFLAGS_NODITHER))
for(int i=0;i<3;i++)
{
int newerr=samp[i]-f->Mean[i];
int orthog_error=(newerr*3)/8;
Error[x+1][i][ErrorUse]+=orthog_error;
Error[x][i][ErrorUpdate]=orthog_error;
Error[x+1][i][ErrorUpdate]=newerr-2*orthog_error;
}
}
}
if (q) FreeQuantization(q);
}