1 /*
2  * Mesa 3-D graphics library
3  * Version:  6.5.3
4  *
5  * Copyright (C) 1999-2007  Brian Paul   All Rights Reserved.
6  * Copyright (c) 2008 VMware, Inc.
7  *
8  * Permission is hereby granted, free of charge, to any person obtaining a
9  * copy of this software and associated documentation files (the "Software"),
10  * to deal in the Software without restriction, including without limitation
11  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
12  * and/or sell copies of the Software, and to permit persons to whom the
13  * Software is furnished to do so, subject to the following conditions:
14  *
15  * The above copyright notice and this permission notice shall be included
16  * in all copies or substantial portions of the Software.
17  *
18  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
19  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
20  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
21  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
22  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
23  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
24  */
25 
26 
27 /**
28  * \file texcompress_s3tc.c
29  * GL_EXT_texture_compression_s3tc support.
30  */
31 
32 #ifndef USE_EXTERNAL_DXTN_LIB
33 #define USE_EXTERNAL_DXTN_LIB 1
34 #endif
35 
36 #include "glheader.h"
37 #include "imports.h"
38 #include "colormac.h"
39 #include "dlopen.h"
40 #include "image.h"
41 #include "macros.h"
42 #include "mfeatures.h"
43 #include "mtypes.h"
44 #include "texcompress.h"
45 #include "texcompress_s3tc.h"
46 #include "texstore.h"
47 #include "swrast/s_context.h"
48 
49 
50 #if FEATURE_texture_s3tc
51 
52 
53 #if defined(_WIN32) || defined(WIN32)
54 #define DXTN_LIBNAME "dxtn.dll"
55 #define RTLD_LAZY 0
56 #define RTLD_GLOBAL 0
57 #elif defined(__DJGPP__)
58 #define DXTN_LIBNAME "dxtn.dxe"
59 #else
60 #define DXTN_LIBNAME "libtxc_dxtn.so"
61 #endif
62 
63 #if FEATURE_EXT_texture_sRGB
64 /**
65  * Convert an 8-bit sRGB value from non-linear space to a
66  * linear RGB value in [0, 1].
67  * Implemented with a 256-entry lookup table.
68  */
69 static inline GLfloat
nonlinear_to_linear(GLubyte cs8)70 nonlinear_to_linear(GLubyte cs8)
71 {
72    static GLfloat table[256];
73    static GLboolean tableReady = GL_FALSE;
74    if (!tableReady) {
75       /* compute lookup table now */
76       GLuint i;
77       for (i = 0; i < 256; i++) {
78          const GLfloat cs = UBYTE_TO_FLOAT(i);
79          if (cs <= 0.04045) {
80             table[i] = cs / 12.92f;
81          }
82          else {
83             table[i] = (GLfloat) pow((cs + 0.055) / 1.055, 2.4);
84          }
85       }
86       tableReady = GL_TRUE;
87    }
88    return table[cs8];
89 }
90 #endif /* FEATURE_EXT_texture_sRGB */
91 
92 typedef void (*dxtFetchTexelFuncExt)( GLint srcRowstride, GLubyte *pixdata, GLint col, GLint row, GLvoid *texelOut );
93 
94 dxtFetchTexelFuncExt fetch_ext_rgb_dxt1 = NULL;
95 dxtFetchTexelFuncExt fetch_ext_rgba_dxt1 = NULL;
96 dxtFetchTexelFuncExt fetch_ext_rgba_dxt3 = NULL;
97 dxtFetchTexelFuncExt fetch_ext_rgba_dxt5 = NULL;
98 
99 typedef void (*dxtCompressTexFuncExt)(GLint srccomps, GLint width,
100                                       GLint height, const GLubyte *srcPixData,
101                                       GLenum destformat, GLubyte *dest,
102                                       GLint dstRowStride);
103 
104 static dxtCompressTexFuncExt ext_tx_compress_dxtn = NULL;
105 
106 static void *dxtlibhandle = NULL;
107 
108 
109 void
_mesa_init_texture_s3tc(struct gl_context * ctx)110 _mesa_init_texture_s3tc( struct gl_context *ctx )
111 {
112    /* called during context initialization */
113    ctx->Mesa_DXTn = GL_FALSE;
114 #if USE_EXTERNAL_DXTN_LIB
115    if (!dxtlibhandle) {
116       dxtlibhandle = _mesa_dlopen(DXTN_LIBNAME, 0);
117       if (!dxtlibhandle) {
118 	 _mesa_warning(ctx, "couldn't open " DXTN_LIBNAME ", software DXTn "
119 	    "compression/decompression unavailable");
120       }
121       else {
122          /* the fetch functions are not per context! Might be problematic... */
123          fetch_ext_rgb_dxt1 = (dxtFetchTexelFuncExt)
124             _mesa_dlsym(dxtlibhandle, "fetch_2d_texel_rgb_dxt1");
125          fetch_ext_rgba_dxt1 = (dxtFetchTexelFuncExt)
126             _mesa_dlsym(dxtlibhandle, "fetch_2d_texel_rgba_dxt1");
127          fetch_ext_rgba_dxt3 = (dxtFetchTexelFuncExt)
128             _mesa_dlsym(dxtlibhandle, "fetch_2d_texel_rgba_dxt3");
129          fetch_ext_rgba_dxt5 = (dxtFetchTexelFuncExt)
130             _mesa_dlsym(dxtlibhandle, "fetch_2d_texel_rgba_dxt5");
131          ext_tx_compress_dxtn = (dxtCompressTexFuncExt)
132             _mesa_dlsym(dxtlibhandle, "tx_compress_dxtn");
133 
134          if (!fetch_ext_rgb_dxt1 ||
135              !fetch_ext_rgba_dxt1 ||
136              !fetch_ext_rgba_dxt3 ||
137              !fetch_ext_rgba_dxt5 ||
138              !ext_tx_compress_dxtn) {
139 	    _mesa_warning(ctx, "couldn't reference all symbols in "
140 	       DXTN_LIBNAME ", software DXTn compression/decompression "
141 	       "unavailable");
142             fetch_ext_rgb_dxt1 = NULL;
143             fetch_ext_rgba_dxt1 = NULL;
144             fetch_ext_rgba_dxt3 = NULL;
145             fetch_ext_rgba_dxt5 = NULL;
146             ext_tx_compress_dxtn = NULL;
147             _mesa_dlclose(dxtlibhandle);
148             dxtlibhandle = NULL;
149          }
150       }
151    }
152    if (dxtlibhandle) {
153       ctx->Mesa_DXTn = GL_TRUE;
154    }
155 #else
156    (void) ctx;
157 #endif
158 }
159 
160 /**
161  * Store user's image in rgb_dxt1 format.
162  */
163 GLboolean
_mesa_texstore_rgb_dxt1(TEXSTORE_PARAMS)164 _mesa_texstore_rgb_dxt1(TEXSTORE_PARAMS)
165 {
166    const GLubyte *pixels;
167    GLubyte *dst;
168    const GLubyte *tempImage = NULL;
169 
170    ASSERT(dstFormat == MESA_FORMAT_RGB_DXT1 ||
171           dstFormat == MESA_FORMAT_SRGB_DXT1);
172 
173    if (srcFormat != GL_RGB ||
174        srcType != GL_UNSIGNED_BYTE ||
175        ctx->_ImageTransferState ||
176        srcPacking->RowLength != srcWidth ||
177        srcPacking->SwapBytes) {
178       /* convert image to RGB/GLubyte */
179       tempImage = _mesa_make_temp_ubyte_image(ctx, dims,
180                                              baseInternalFormat,
181                                              _mesa_get_format_base_format(dstFormat),
182                                              srcWidth, srcHeight, srcDepth,
183                                              srcFormat, srcType, srcAddr,
184                                              srcPacking);
185       if (!tempImage)
186          return GL_FALSE; /* out of memory */
187       pixels = tempImage;
188       srcFormat = GL_RGB;
189    }
190    else {
191       pixels = _mesa_image_address2d(srcPacking, srcAddr, srcWidth, srcHeight,
192                                      srcFormat, srcType, 0, 0);
193    }
194 
195    dst = dstSlices[0];
196 
197    if (ext_tx_compress_dxtn) {
198       (*ext_tx_compress_dxtn)(3, srcWidth, srcHeight, pixels,
199                               GL_COMPRESSED_RGB_S3TC_DXT1_EXT,
200                               dst, dstRowStride);
201    }
202    else {
203       _mesa_warning(ctx, "external dxt library not available: texstore_rgb_dxt1");
204    }
205 
206    if (tempImage)
207       free((void *) tempImage);
208 
209    return GL_TRUE;
210 }
211 
212 
213 /**
214  * Store user's image in rgba_dxt1 format.
215  */
216 GLboolean
_mesa_texstore_rgba_dxt1(TEXSTORE_PARAMS)217 _mesa_texstore_rgba_dxt1(TEXSTORE_PARAMS)
218 {
219    const GLubyte *pixels;
220    GLubyte *dst;
221    const GLubyte *tempImage = NULL;
222 
223    ASSERT(dstFormat == MESA_FORMAT_RGBA_DXT1 ||
224           dstFormat == MESA_FORMAT_SRGBA_DXT1);
225 
226    if (srcFormat != GL_RGBA ||
227        srcType != GL_UNSIGNED_BYTE ||
228        ctx->_ImageTransferState ||
229        srcPacking->RowLength != srcWidth ||
230        srcPacking->SwapBytes) {
231       /* convert image to RGBA/GLubyte */
232       tempImage = _mesa_make_temp_ubyte_image(ctx, dims,
233                                              baseInternalFormat,
234                                              _mesa_get_format_base_format(dstFormat),
235                                              srcWidth, srcHeight, srcDepth,
236                                              srcFormat, srcType, srcAddr,
237                                              srcPacking);
238       if (!tempImage)
239          return GL_FALSE; /* out of memory */
240       pixels = tempImage;
241       srcFormat = GL_RGBA;
242    }
243    else {
244       pixels = _mesa_image_address2d(srcPacking, srcAddr, srcWidth, srcHeight,
245                                      srcFormat, srcType, 0, 0);
246    }
247 
248    dst = dstSlices[0];
249 
250    if (ext_tx_compress_dxtn) {
251       (*ext_tx_compress_dxtn)(4, srcWidth, srcHeight, pixels,
252                               GL_COMPRESSED_RGBA_S3TC_DXT1_EXT,
253                               dst, dstRowStride);
254    }
255    else {
256       _mesa_warning(ctx, "external dxt library not available: texstore_rgba_dxt1");
257    }
258 
259    if (tempImage)
260       free((void*) tempImage);
261 
262    return GL_TRUE;
263 }
264 
265 
266 /**
267  * Store user's image in rgba_dxt3 format.
268  */
269 GLboolean
_mesa_texstore_rgba_dxt3(TEXSTORE_PARAMS)270 _mesa_texstore_rgba_dxt3(TEXSTORE_PARAMS)
271 {
272    const GLubyte *pixels;
273    GLubyte *dst;
274    const GLubyte *tempImage = NULL;
275 
276    ASSERT(dstFormat == MESA_FORMAT_RGBA_DXT3 ||
277           dstFormat == MESA_FORMAT_SRGBA_DXT3);
278 
279    if (srcFormat != GL_RGBA ||
280        srcType != GL_UNSIGNED_BYTE ||
281        ctx->_ImageTransferState ||
282        srcPacking->RowLength != srcWidth ||
283        srcPacking->SwapBytes) {
284       /* convert image to RGBA/GLubyte */
285       tempImage = _mesa_make_temp_ubyte_image(ctx, dims,
286                                              baseInternalFormat,
287                                              _mesa_get_format_base_format(dstFormat),
288                                              srcWidth, srcHeight, srcDepth,
289                                              srcFormat, srcType, srcAddr,
290                                              srcPacking);
291       if (!tempImage)
292          return GL_FALSE; /* out of memory */
293       pixels = tempImage;
294    }
295    else {
296       pixels = _mesa_image_address2d(srcPacking, srcAddr, srcWidth, srcHeight,
297                                      srcFormat, srcType, 0, 0);
298    }
299 
300    dst = dstSlices[0];
301 
302    if (ext_tx_compress_dxtn) {
303       (*ext_tx_compress_dxtn)(4, srcWidth, srcHeight, pixels,
304                               GL_COMPRESSED_RGBA_S3TC_DXT3_EXT,
305                               dst, dstRowStride);
306    }
307    else {
308       _mesa_warning(ctx, "external dxt library not available: texstore_rgba_dxt3");
309    }
310 
311    if (tempImage)
312       free((void *) tempImage);
313 
314    return GL_TRUE;
315 }
316 
317 
318 /**
319  * Store user's image in rgba_dxt5 format.
320  */
321 GLboolean
_mesa_texstore_rgba_dxt5(TEXSTORE_PARAMS)322 _mesa_texstore_rgba_dxt5(TEXSTORE_PARAMS)
323 {
324    const GLubyte *pixels;
325    GLubyte *dst;
326    const GLubyte *tempImage = NULL;
327 
328    ASSERT(dstFormat == MESA_FORMAT_RGBA_DXT5 ||
329           dstFormat == MESA_FORMAT_SRGBA_DXT5);
330 
331    if (srcFormat != GL_RGBA ||
332        srcType != GL_UNSIGNED_BYTE ||
333        ctx->_ImageTransferState ||
334        srcPacking->RowLength != srcWidth ||
335        srcPacking->SwapBytes) {
336       /* convert image to RGBA/GLubyte */
337       tempImage = _mesa_make_temp_ubyte_image(ctx, dims,
338                                              baseInternalFormat,
339                                    	     _mesa_get_format_base_format(dstFormat),
340                                              srcWidth, srcHeight, srcDepth,
341                                              srcFormat, srcType, srcAddr,
342                                              srcPacking);
343       if (!tempImage)
344          return GL_FALSE; /* out of memory */
345       pixels = tempImage;
346    }
347    else {
348       pixels = _mesa_image_address2d(srcPacking, srcAddr, srcWidth, srcHeight,
349                                      srcFormat, srcType, 0, 0);
350    }
351 
352    dst = dstSlices[0];
353 
354    if (ext_tx_compress_dxtn) {
355       (*ext_tx_compress_dxtn)(4, srcWidth, srcHeight, pixels,
356                               GL_COMPRESSED_RGBA_S3TC_DXT5_EXT,
357                               dst, dstRowStride);
358    }
359    else {
360       _mesa_warning(ctx, "external dxt library not available: texstore_rgba_dxt5");
361    }
362 
363    if (tempImage)
364       free((void *) tempImage);
365 
366    return GL_TRUE;
367 }
368 
369 
370 static void
fetch_texel_2d_rgb_dxt1(const struct swrast_texture_image * texImage,GLint i,GLint j,GLint k,GLubyte * texel)371 fetch_texel_2d_rgb_dxt1(const struct swrast_texture_image *texImage,
372                         GLint i, GLint j, GLint k, GLubyte *texel)
373 {
374    (void) k;
375    if (fetch_ext_rgb_dxt1) {
376       GLint sliceOffset = k ? texImage->ImageOffsets[k] / 2 : 0;
377       fetch_ext_rgb_dxt1(texImage->RowStride,
378                          texImage->Map + sliceOffset, i, j, texel);
379    }
380    else
381       _mesa_debug(NULL, "attempted to decode s3tc texture without library available: fetch_texel_2d_rgb_dxt1");
382 }
383 
384 
385 void
_mesa_fetch_texel_rgb_dxt1(const struct swrast_texture_image * texImage,GLint i,GLint j,GLint k,GLfloat * texel)386 _mesa_fetch_texel_rgb_dxt1(const struct swrast_texture_image *texImage,
387                            GLint i, GLint j, GLint k, GLfloat *texel)
388 {
389    /* just sample as GLubyte and convert to float here */
390    GLubyte rgba[4];
391    fetch_texel_2d_rgb_dxt1(texImage, i, j, k, rgba);
392    texel[RCOMP] = UBYTE_TO_FLOAT(rgba[RCOMP]);
393    texel[GCOMP] = UBYTE_TO_FLOAT(rgba[GCOMP]);
394    texel[BCOMP] = UBYTE_TO_FLOAT(rgba[BCOMP]);
395    texel[ACOMP] = UBYTE_TO_FLOAT(rgba[ACOMP]);
396 }
397 
398 
399 static void
fetch_texel_2d_rgba_dxt1(const struct swrast_texture_image * texImage,GLint i,GLint j,GLint k,GLubyte * texel)400 fetch_texel_2d_rgba_dxt1(const struct swrast_texture_image *texImage,
401                          GLint i, GLint j, GLint k, GLubyte *texel)
402 {
403    (void) k;
404    if (fetch_ext_rgba_dxt1) {
405       GLint sliceOffset = k ? texImage->ImageOffsets[k] / 2 : 0;
406       fetch_ext_rgba_dxt1(texImage->RowStride,
407                           texImage->Map + sliceOffset, i, j, texel);
408    }
409    else
410       _mesa_debug(NULL, "attempted to decode s3tc texture without library available: fetch_texel_2d_rgba_dxt1\n");
411 }
412 
413 
414 void
_mesa_fetch_texel_rgba_dxt1(const struct swrast_texture_image * texImage,GLint i,GLint j,GLint k,GLfloat * texel)415 _mesa_fetch_texel_rgba_dxt1(const struct swrast_texture_image *texImage,
416                             GLint i, GLint j, GLint k, GLfloat *texel)
417 {
418    /* just sample as GLubyte and convert to float here */
419    GLubyte rgba[4];
420    fetch_texel_2d_rgba_dxt1(texImage, i, j, k, rgba);
421    texel[RCOMP] = UBYTE_TO_FLOAT(rgba[RCOMP]);
422    texel[GCOMP] = UBYTE_TO_FLOAT(rgba[GCOMP]);
423    texel[BCOMP] = UBYTE_TO_FLOAT(rgba[BCOMP]);
424    texel[ACOMP] = UBYTE_TO_FLOAT(rgba[ACOMP]);
425 }
426 
427 
428 static void
fetch_texel_2d_rgba_dxt3(const struct swrast_texture_image * texImage,GLint i,GLint j,GLint k,GLubyte * texel)429 fetch_texel_2d_rgba_dxt3(const struct swrast_texture_image *texImage,
430                          GLint i, GLint j, GLint k, GLubyte *texel)
431 {
432    (void) k;
433    if (fetch_ext_rgba_dxt3) {
434       GLint sliceOffset = k ? texImage->ImageOffsets[k] : 0;
435       fetch_ext_rgba_dxt3(texImage->RowStride,
436                           texImage->Map + sliceOffset, i, j, texel);
437    }
438    else
439       _mesa_debug(NULL, "attempted to decode s3tc texture without library available: fetch_texel_2d_rgba_dxt3\n");
440 }
441 
442 
443 void
_mesa_fetch_texel_rgba_dxt3(const struct swrast_texture_image * texImage,GLint i,GLint j,GLint k,GLfloat * texel)444 _mesa_fetch_texel_rgba_dxt3(const struct swrast_texture_image *texImage,
445                             GLint i, GLint j, GLint k, GLfloat *texel)
446 {
447    /* just sample as GLubyte and convert to float here */
448    GLubyte rgba[4];
449    fetch_texel_2d_rgba_dxt3(texImage, i, j, k, rgba);
450    texel[RCOMP] = UBYTE_TO_FLOAT(rgba[RCOMP]);
451    texel[GCOMP] = UBYTE_TO_FLOAT(rgba[GCOMP]);
452    texel[BCOMP] = UBYTE_TO_FLOAT(rgba[BCOMP]);
453    texel[ACOMP] = UBYTE_TO_FLOAT(rgba[ACOMP]);
454 }
455 
456 
457 static void
fetch_texel_2d_rgba_dxt5(const struct swrast_texture_image * texImage,GLint i,GLint j,GLint k,GLubyte * texel)458 fetch_texel_2d_rgba_dxt5(const struct swrast_texture_image *texImage,
459                          GLint i, GLint j, GLint k, GLubyte *texel)
460 {
461    (void) k;
462    if (fetch_ext_rgba_dxt5) {
463       GLint sliceOffset = k ? texImage->ImageOffsets[k] : 0;
464       fetch_ext_rgba_dxt5(texImage->RowStride,
465                           texImage->Map + sliceOffset, i, j, texel);
466    }
467    else
468       _mesa_debug(NULL, "attempted to decode s3tc texture without library available: fetch_texel_2d_rgba_dxt5\n");
469 }
470 
471 
472 void
_mesa_fetch_texel_rgba_dxt5(const struct swrast_texture_image * texImage,GLint i,GLint j,GLint k,GLfloat * texel)473 _mesa_fetch_texel_rgba_dxt5(const struct swrast_texture_image *texImage,
474                             GLint i, GLint j, GLint k, GLfloat *texel)
475 {
476    /* just sample as GLubyte and convert to float here */
477    GLubyte rgba[4];
478    fetch_texel_2d_rgba_dxt5(texImage, i, j, k, rgba);
479    texel[RCOMP] = UBYTE_TO_FLOAT(rgba[RCOMP]);
480    texel[GCOMP] = UBYTE_TO_FLOAT(rgba[GCOMP]);
481    texel[BCOMP] = UBYTE_TO_FLOAT(rgba[BCOMP]);
482    texel[ACOMP] = UBYTE_TO_FLOAT(rgba[ACOMP]);
483 }
484 
485 #if FEATURE_EXT_texture_sRGB
486 void
_mesa_fetch_texel_srgb_dxt1(const struct swrast_texture_image * texImage,GLint i,GLint j,GLint k,GLfloat * texel)487 _mesa_fetch_texel_srgb_dxt1(const struct swrast_texture_image *texImage,
488                             GLint i, GLint j, GLint k, GLfloat *texel)
489 {
490    /* just sample as GLubyte and convert to float here */
491    GLubyte rgba[4];
492    fetch_texel_2d_rgb_dxt1(texImage, i, j, k, rgba);
493    texel[RCOMP] = nonlinear_to_linear(rgba[RCOMP]);
494    texel[GCOMP] = nonlinear_to_linear(rgba[GCOMP]);
495    texel[BCOMP] = nonlinear_to_linear(rgba[BCOMP]);
496    texel[ACOMP] = UBYTE_TO_FLOAT(rgba[ACOMP]);
497 }
498 
499 void
_mesa_fetch_texel_srgba_dxt1(const struct swrast_texture_image * texImage,GLint i,GLint j,GLint k,GLfloat * texel)500 _mesa_fetch_texel_srgba_dxt1(const struct swrast_texture_image *texImage,
501                              GLint i, GLint j, GLint k, GLfloat *texel)
502 {
503    /* just sample as GLubyte and convert to float here */
504    GLubyte rgba[4];
505    fetch_texel_2d_rgba_dxt1(texImage, i, j, k, rgba);
506    texel[RCOMP] = nonlinear_to_linear(rgba[RCOMP]);
507    texel[GCOMP] = nonlinear_to_linear(rgba[GCOMP]);
508    texel[BCOMP] = nonlinear_to_linear(rgba[BCOMP]);
509    texel[ACOMP] = UBYTE_TO_FLOAT(rgba[ACOMP]);
510 }
511 
512 void
_mesa_fetch_texel_srgba_dxt3(const struct swrast_texture_image * texImage,GLint i,GLint j,GLint k,GLfloat * texel)513 _mesa_fetch_texel_srgba_dxt3(const struct swrast_texture_image *texImage,
514                              GLint i, GLint j, GLint k, GLfloat *texel)
515 {
516    /* just sample as GLubyte and convert to float here */
517    GLubyte rgba[4];
518    fetch_texel_2d_rgba_dxt3(texImage, i, j, k, rgba);
519    texel[RCOMP] = nonlinear_to_linear(rgba[RCOMP]);
520    texel[GCOMP] = nonlinear_to_linear(rgba[GCOMP]);
521    texel[BCOMP] = nonlinear_to_linear(rgba[BCOMP]);
522    texel[ACOMP] = UBYTE_TO_FLOAT(rgba[ACOMP]);
523 }
524 
525 void
_mesa_fetch_texel_srgba_dxt5(const struct swrast_texture_image * texImage,GLint i,GLint j,GLint k,GLfloat * texel)526 _mesa_fetch_texel_srgba_dxt5(const struct swrast_texture_image *texImage,
527                              GLint i, GLint j, GLint k, GLfloat *texel)
528 {
529    /* just sample as GLubyte and convert to float here */
530    GLubyte rgba[4];
531    fetch_texel_2d_rgba_dxt5(texImage, i, j, k, rgba);
532    texel[RCOMP] = nonlinear_to_linear(rgba[RCOMP]);
533    texel[GCOMP] = nonlinear_to_linear(rgba[GCOMP]);
534    texel[BCOMP] = nonlinear_to_linear(rgba[BCOMP]);
535    texel[ACOMP] = UBYTE_TO_FLOAT(rgba[ACOMP]);
536 }
537 #endif /* FEATURE_EXT_texture_sRGB */
538 
539 
540 #endif /* FEATURE_texture_s3tc */
541