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#include <stdlib.h>
#include <stdio.h>
static int mul8bit(int a, int b)
{
int t = a * b + 128;
return((t + (t >> 8)) >> 8);
}
static int lerp13(int a, int b)
{
#if 0
return(a + mul8bit(b - a, 0x55));
#else
return((2 * a + b) / 3);
#endif
}
static void prepare_opt_table(unsigned char *tab,
const unsigned char *expand, int size)
{
int i, mn, mx, bestE, minE, maxE, e;
for(i = 0; i < 256; ++i)
{
bestE = 256 * 100;
for(mn = 0; mn < size; ++mn)
{
for(mx = 0; mx < size; ++mx)
{
minE = expand[mn];
maxE = expand[mx];
e = abs(lerp13(maxE, minE) - i) * 100;
e += abs(mx - mn) * 3;
if(e < bestE)
{
tab[i * 2 + 0] = mx;
tab[i * 2 + 1] = mn;
bestE = e;
}
}
}
}
}
#if 0
int main(void)
{
FILE *fp;
int i, v;
unsigned char expand5[32];
unsigned char expand6[64];
unsigned char quantRB[256 + 16];
unsigned char quantG[256 + 16];
unsigned char omatch5[256][2];
unsigned char omatch6[256][2];
fp = fopen("dxt_tables.h", "w");
fprintf(fp,
"#ifndef DXT_TABLES_H\n"
"#define DXT_TABLES_H\n\n");
for(i = 0; i < 32; ++i)
expand5[i] = (i << 3) | (i >> 2);
for(i = 0; i < 64; ++i)
expand6[i] = (i << 2) | (i >> 4);
for(i = 0; i < 256 + 16; ++i)
{
v = i - 8;
if(v < 0) v = 0;
if(v > 255) v = 255;
quantRB[i] = expand5[mul8bit(v, 31)];
quantG[i] = expand6[mul8bit(v, 63)];
}
fprintf(fp,
"static const unsigned char quantRB[256 + 16] =\n"
"{");
for(i = 0; i < 256 + 16; ++i)
{
if(i % 8 == 0) fprintf(fp, "\n ");
fprintf(fp, "0x%02x, ", quantRB[i]);
}
fprintf(fp, "\n};\n\n");
fprintf(fp,
"static const unsigned char quantG[256 + 16] =\n"
"{");
for(i = 0; i < 256 + 16; ++i)
{
if(i % 8 == 0) fprintf(fp, "\n ");
fprintf(fp, "0x%02x, ", quantG[i]);
}
fprintf(fp, "\n};\n\n");
prepare_opt_table(&omatch5[0][0], expand5, 32);
prepare_opt_table(&omatch6[0][0], expand6, 64);
fprintf(fp,
"static const unsigned char omatch5[256][2] =\n"
"{");
for(i = 0; i < 256; ++i)
{
if(i % 4 == 0) fprintf(fp, "\n ");
fprintf(fp, "{0x%02x, 0x%02x}, ", omatch5[i][0], omatch5[i][1]);
}
fprintf(fp, "\n};\n\n");
fprintf(fp,
"static const unsigned char omatch6[256][2] =\n"
"{");
for(i = 0; i < 256; ++i)
{
if(i % 4 == 0) fprintf(fp, "\n ");
fprintf(fp, "{0x%02x, 0x%02x}, ", omatch6[i][0], omatch6[i][1]);
}
fprintf(fp, "\n};\n\n");
fprintf(fp, "#endif\n");
fclose(fp);
return(0);
}
#endif
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