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stb_dxt: fix bug with constant color & varying alpha

This commit is contained in:
Sean Barrett 2018-01-29 05:17:07 -08:00
parent 76ec599c68
commit d808adb77f
2 changed files with 13 additions and 6 deletions
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13
stb_dxt.h
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@ -1,4 +1,4 @@
// stb_dxt.h - v1.07 - DXT1/DXT5 compressor - public domain
// stb_dxt.h - v1.08 - DXT1/DXT5 compressor - public domain
// original by fabian "ryg" giesen - ported to C by stb
// use '#define STB_DXT_IMPLEMENTATION' before including to create the implementation
//
@ -9,7 +9,8 @@
// and "high quality" using mode.
//
// version history:
// v1.07 - bc4; allow not using libc; add STB_DXT_STATIC
// v1.08 - (sbt) fix bug in dxt-with-alpha block
// v1.07 - (stb) bc4; allow not using libc; add STB_DXT_STATIC
// v1.06 - (stb) fix to known-broken 1.05
// v1.05 - (stb) support bc5/3dc (Arvids Kokins), use extern "C" in C++ (Pavel Krajcevski)
// v1.04 - (ryg) default to no rounding bias for lerped colors (as per S3TC/DX10 spec);
@ -649,6 +650,7 @@ static void stb__InitDXT()
void stb_compress_dxt_block(unsigned char *dest, const unsigned char *src, int alpha, int mode)
{
unsigned char *data[16][4];
static int init=1;
if (init) {
stb__InitDXT();
@ -656,8 +658,15 @@ void stb_compress_dxt_block(unsigned char *dest, const unsigned char *src, int a
}
if (alpha) {
int i;
stb__CompressAlphaBlock(dest,(unsigned char*) src+3, 4);
dest += 8;
// make a new copy of the data in which alpha is opaque,
// because code uses a fast test for color constancy
memcpy(data, src, 4*16);
for (i=0; i < 16; ++i)
data[i][3] = 255;
src = &data[0][0];
}
stb__CompressColorBlock(dest,(unsigned char*) src,mode);

6
stb_image.h
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@ -1,5 +1,5 @@
/* stb_image - v2.17 - public domain image loader - http://nothings.org/stb_image.h
no warranty implied; use at your own risk
/* stb_image - v2.17 - public domain image loader - http://nothings.org/stb
no warranty implied; use at your own risk
Do this:
#define STB_IMAGE_IMPLEMENTATION
@ -107,10 +107,8 @@ RECENT REVISION HISTORY:
// DOCUMENTATION
//
// Limitations:
// - no 16-bit-per-channel PNG
// - no 12-bit-per-channel JPEG
// - no JPEGs with arithmetic coding
// - no 1-bit BMP
// - GIF always returns *comp=4
//
// Basic usage (see HDR discussion below for HDR usage):