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txc_fetch_dxtn.c
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/*
* libtxc_dxtn
* Version: 0.1
*
* Copyright (C) 2004 Roland Scheidegger All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included
* in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
* OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
* AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
#include <stdio.h>
#include "txc_dxtn.h"
#define EXP5TO8R(packedcol) \
((((packedcol) >> 8) & 0xf8) | (((packedcol) >> 13) & 0x7))
#define EXP6TO8G(packedcol) \
((((packedcol) >> 3) & 0xfc) | (((packedcol) >> 9) & 0x3))
#define EXP5TO8B(packedcol) \
((((packedcol) << 3) & 0xf8) | (((packedcol) >> 2) & 0x7))
#define EXP4TO8(col) \
((col) | ((col) << 4))
/* inefficient. To be efficient, it would be necessary to decode 16 pixels at once */
static void dxt135_decode_imageblock ( const GLubyte *img_block_src,
GLint i, GLint j, GLuint dxt_type, GLvoid *texel ) {
GLchan *rgba = (GLchan *) texel;
const GLushort color0 = img_block_src[0] | (img_block_src[1] << 8);
const GLushort color1 = img_block_src[2] | (img_block_src[3] << 8);
const GLuint bits = img_block_src[4] | (img_block_src[5] << 8) |
(img_block_src[6] << 16) | (img_block_src[7] << 24);
/* What about big/little endian? */
GLubyte bit_pos = 2 * (j * 4 + i) ;
GLubyte code = (GLubyte) ((bits >> bit_pos) & 3);
rgba[ACOMP] = CHAN_MAX;
switch (code) {
case 0:
rgba[RCOMP] = UBYTE_TO_CHAN( EXP5TO8R(color0) );
rgba[GCOMP] = UBYTE_TO_CHAN( EXP6TO8G(color0) );
rgba[BCOMP] = UBYTE_TO_CHAN( EXP5TO8B(color0) );
break;
case 1:
rgba[RCOMP] = UBYTE_TO_CHAN( EXP5TO8R(color1) );
rgba[GCOMP] = UBYTE_TO_CHAN( EXP6TO8G(color1) );
rgba[BCOMP] = UBYTE_TO_CHAN( EXP5TO8B(color1) );
break;
case 2:
if (color0 > color1) {
rgba[RCOMP] = UBYTE_TO_CHAN( ((EXP5TO8R(color0) * 2 + EXP5TO8R(color1)) / 3) );
rgba[GCOMP] = UBYTE_TO_CHAN( ((EXP6TO8G(color0) * 2 + EXP6TO8G(color1)) / 3) );
rgba[BCOMP] = UBYTE_TO_CHAN( ((EXP5TO8B(color0) * 2 + EXP5TO8B(color1)) / 3) );
}
else {
rgba[RCOMP] = UBYTE_TO_CHAN( ((EXP5TO8R(color0) + EXP5TO8R(color1)) / 2) );
rgba[GCOMP] = UBYTE_TO_CHAN( ((EXP6TO8G(color0) + EXP6TO8G(color1)) / 2) );
rgba[BCOMP] = UBYTE_TO_CHAN( ((EXP5TO8B(color0) + EXP5TO8B(color1)) / 2) );
}
break;
case 3:
if ((dxt_type > 1) || (color0 > color1)) {
rgba[RCOMP] = UBYTE_TO_CHAN( ((EXP5TO8R(color0) + EXP5TO8R(color1) * 2) / 3) );
rgba[GCOMP] = UBYTE_TO_CHAN( ((EXP6TO8G(color0) + EXP6TO8G(color1) * 2) / 3) );
rgba[BCOMP] = UBYTE_TO_CHAN( ((EXP5TO8B(color0) + EXP5TO8B(color1) * 2) / 3) );
}
else {
rgba[RCOMP] = 0;
rgba[GCOMP] = 0;
rgba[BCOMP] = 0;
if (dxt_type == 1) rgba[ACOMP] = UBYTE_TO_CHAN(0);
}
break;
default:
/* CANNOT happen (I hope) */
break;
}
}
void fetch_2d_texel_rgb_dxt1(GLint srcRowStride, const GLubyte *pixdata,
GLint i, GLint j, GLvoid *texel)
{
/* Extract the (i,j) pixel from pixdata and return it
* in texel[RCOMP], texel[GCOMP], texel[BCOMP], texel[ACOMP].
*/
const GLubyte *blksrc = (pixdata + ((srcRowStride + 3) / 4 * (j / 4) + (i / 4)) * 8);
dxt135_decode_imageblock(blksrc, (i&3), (j&3), 0, texel);
}
void fetch_2d_texel_rgba_dxt1(GLint srcRowStride, const GLubyte *pixdata,
GLint i, GLint j, GLvoid *texel)
{
/* Extract the (i,j) pixel from pixdata and return it
* in texel[RCOMP], texel[GCOMP], texel[BCOMP], texel[ACOMP].
*/
const GLubyte *blksrc = (pixdata + ((srcRowStride + 3) / 4 * (j / 4) + (i / 4)) * 8);
dxt135_decode_imageblock(blksrc, (i&3), (j&3), 1, texel);
}
void fetch_2d_texel_rgba_dxt3(GLint srcRowStride, const GLubyte *pixdata,
GLint i, GLint j, GLvoid *texel) {
/* Extract the (i,j) pixel from pixdata and return it
* in texel[RCOMP], texel[GCOMP], texel[BCOMP], texel[ACOMP].
*/
GLchan *rgba = (GLchan *) texel;
const GLubyte *blksrc = (pixdata + ((srcRowStride + 3) / 4 * (j / 4) + (i / 4)) * 16);
#if 0
/* Simple 32bit version. */
/* that's pretty brain-dead for a single pixel, isn't it? */
const GLubyte bit_pos = 4 * ((j&3) * 4 + (i&3));
const GLuint alpha_low = blksrc[0] | (blksrc[1] << 8) | (blksrc[2] << 16) | (blksrc[3] << 24);
const GLuint alpha_high = blksrc[4] | (blksrc[5] << 8) | (blksrc[6] << 16) | (blksrc[7] << 24);
dxt135_decode_imageblock(blksrc + 8, (i&3), (j&3), 2, texel);
if (bit_pos < 32)
rgba[ACOMP] = UBYTE_TO_CHAN( (GLubyte)(EXP4TO8((alpha_low >> bit_pos) & 15)) );
else
rgba[ACOMP] = UBYTE_TO_CHAN( (GLubyte)(EXP4TO8((alpha_high >> (bit_pos - 32)) & 15)) );
#endif
#if 1
/* TODO test this! */
const GLubyte anibble = (blksrc[((j&3) * 4 + (i&3)) / 2] >> (4 * (i&1))) & 0xf;
dxt135_decode_imageblock(blksrc + 8, (i&3), (j&3), 2, texel);
rgba[ACOMP] = UBYTE_TO_CHAN( (GLubyte)(EXP4TO8(anibble)) );
#endif
}
void fetch_2d_texel_rgba_dxt5(GLint srcRowStride, const GLubyte *pixdata,
GLint i, GLint j, GLvoid *texel) {
/* Extract the (i,j) pixel from pixdata and return it
* in texel[RCOMP], texel[GCOMP], texel[BCOMP], texel[ACOMP].
*/
GLchan *rgba = (GLchan *) texel;
const GLubyte *blksrc = (pixdata + ((srcRowStride + 3) / 4 * (j / 4) + (i / 4)) * 16);
const GLubyte alpha0 = blksrc[0];
const GLubyte alpha1 = blksrc[1];
#if 0
const GLubyte bit_pos = 3 * ((j&3) * 4 + (i&3));
/* simple 32bit version */
const GLuint bits_low = blksrc[2] | (blksrc[3] << 8) | (blksrc[4] << 16) | (blksrc[5] << 24);
const GLuint bits_high = blksrc[6] | (blksrc[7] << 8);
GLubyte code;
if (bit_pos < 30)
code = (GLubyte) ((bits_low >> bit_pos) & 7);
else if (bit_pos == 30)
code = (GLubyte) ((bits_low >> 30) & 3) | ((bits_high << 2) & 4);
else
code = (GLubyte) ((bits_high >> (bit_pos - 32)) & 7);
#endif
#if 1
/* TODO test this! */
const GLubyte bit_pos = ((j&3) * 4 + (i&3)) * 3;
const GLubyte acodelow = blksrc[2 + bit_pos / 8];
const GLubyte acodehigh = blksrc[3 + bit_pos / 8];
const GLubyte code = (acodelow >> (bit_pos & 0x7) |
(acodehigh << (8 - (bit_pos & 0x7)))) & 0x7;
#endif
dxt135_decode_imageblock(blksrc + 8, (i&3), (j&3), 2, texel);
#if 0
if (alpha0 > alpha1) {
switch (code) {
case 0:
rgba[ACOMP] = UBYTE_TO_CHAN( alpha0 );
break;
case 1:
rgba[ACOMP] = UBYTE_TO_CHAN( alpha1 );
break;
case 2:
case 3:
case 4:
case 5:
case 6:
case 7:
rgba[ACOMP] = UBYTE_TO_CHAN( ((alpha0 * (8 - code) + (alpha1 * (code - 1))) / 7) );
break;
}
}
else {
switch (code) {
case 0:
rgba[ACOMP] = UBYTE_TO_CHAN( alpha0 );
break;
case 1:
rgba[ACOMP] = UBYTE_TO_CHAN( alpha1 );
break;
case 2:
case 3:
case 4:
case 5:
rgba[ACOMP] = UBYTE_TO_CHAN( ((alpha0 * (6 - code) + (alpha1 * (code - 1))) / 5) );
break;
case 6:
rgba[ACOMP] = 0;
break;
case 7:
rgba[ACOMP] = CHAN_MAX;
break;
}
}
#endif
/* not sure. Which version is faster? */
#if 1
/* TODO test this */
if (code == 0)
rgba[ACOMP] = UBYTE_TO_CHAN( alpha0 );
else if (code == 1)
rgba[ACOMP] = UBYTE_TO_CHAN( alpha1 );
else if (alpha0 > alpha1)
rgba[ACOMP] = UBYTE_TO_CHAN( ((alpha0 * (8 - code) + (alpha1 * (code - 1))) / 7) );
else if (code < 6)
rgba[ACOMP] = UBYTE_TO_CHAN( ((alpha0 * (6 - code) + (alpha1 * (code - 1))) / 5) );
else if (code == 6)
rgba[ACOMP] = 0;
else
rgba[ACOMP] = CHAN_MAX;
#endif
}