aboutsummaryrefslogtreecommitdiff
path: root/mesalib/src/mesa/main/texcompress.c
blob: 03e05d5ef7b02a8d0dbc16346a0f31f0623b676d (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
/*
 * Mesa 3-D graphics library
 * Version:  6.5.1
 *
 * Copyright (C) 1999-2006  Brian Paul   All Rights Reserved.
 * Copyright (c) 2008 VMware, Inc.
 *
 * 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.
 */


/**
 * \file texcompress.c
 * Helper functions for texture compression.
 */


#include "glheader.h"
#include "imports.h"
#include "colormac.h"
#include "formats.h"
#include "mfeatures.h"
#include "mtypes.h"
#include "texcompress.h"
#include "texcompress_fxt1.h"
#include "texcompress_rgtc.h"
#include "texcompress_s3tc.h"
#include "swrast/s_context.h"


/**
 * Get the GL base format of a specified GL compressed texture format
 *
 * From page 232 of the OpenGL 3.3 (Compatiblity Profile) spec:
 *
 *     "Compressed Internal Format      Base Internal Format    Type
 *     ---------------------------     --------------------    ---------
 *     COMPRESSED_ALPHA                ALPHA                   Generic
 *     COMPRESSED_LUMINANCE            LUMINANCE               Generic
 *     COMPRESSED_LUMINANCE_ALPHA      LUMINANCE_ALPHA         Generic
 *     COMPRESSED_INTENSITY            INTENSITY               Generic
 *     COMPRESSED_RED                  RED                     Generic
 *     COMPRESSED_RG                   RG                      Generic
 *     COMPRESSED_RGB                  RGB                     Generic
 *     COMPRESSED_RGBA                 RGBA                    Generic
 *     COMPRESSED_SRGB                 RGB                     Generic
 *     COMPRESSED_SRGB_ALPHA           RGBA                    Generic
 *     COMPRESSED_SLUMINANCE           LUMINANCE               Generic
 *     COMPRESSED_SLUMINANCE_ALPHA     LUMINANCE_ALPHA         Generic
 *     COMPRESSED_RED_RGTC1            RED                     Specific
 *     COMPRESSED_SIGNED_RED_RGTC1     RED                     Specific
 *     COMPRESSED_RG_RGTC2             RG                      Specific
 *     COMPRESSED_SIGNED_RG_RGTC2      RG                      Specific"
 *
 * \return
 * The base format of \c format if \c format is a compressed format (either
 * generic or specific.  Otherwise 0 is returned.
 */
GLenum
_mesa_gl_compressed_format_base_format(GLenum format)
{
   switch (format) {
   case GL_COMPRESSED_RED:
   case GL_COMPRESSED_RED_RGTC1:
   case GL_COMPRESSED_SIGNED_RED_RGTC1:
      return GL_RED;

   case GL_COMPRESSED_RG:
   case GL_COMPRESSED_RG_RGTC2:
   case GL_COMPRESSED_SIGNED_RG_RGTC2:
      return GL_RG;

   case GL_COMPRESSED_RGB:
   case GL_COMPRESSED_SRGB:
   case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
   case GL_COMPRESSED_RGB_FXT1_3DFX:
   case GL_COMPRESSED_SRGB_S3TC_DXT1_EXT:
      return GL_RGB;

   case GL_COMPRESSED_RGBA:
   case GL_COMPRESSED_SRGB_ALPHA:
   case GL_COMPRESSED_RGBA_BPTC_UNORM_ARB:
   case GL_COMPRESSED_SRGB_ALPHA_BPTC_UNORM_ARB:
   case GL_COMPRESSED_RGB_BPTC_SIGNED_FLOAT_ARB:
   case GL_COMPRESSED_RGB_BPTC_UNSIGNED_FLOAT_ARB:
   case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
   case GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
   case GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
   case GL_COMPRESSED_RGBA_FXT1_3DFX:
   case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT:
   case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT:
   case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT:
      return GL_RGBA;

   case GL_COMPRESSED_ALPHA:
      return GL_ALPHA;

   case GL_COMPRESSED_LUMINANCE:
   case GL_COMPRESSED_SLUMINANCE:
   case GL_COMPRESSED_LUMINANCE_LATC1_EXT:
   case GL_COMPRESSED_SIGNED_LUMINANCE_LATC1_EXT:
      return GL_LUMINANCE;

   case GL_COMPRESSED_LUMINANCE_ALPHA:
   case GL_COMPRESSED_SLUMINANCE_ALPHA:
   case GL_COMPRESSED_LUMINANCE_ALPHA_LATC2_EXT:
   case GL_COMPRESSED_SIGNED_LUMINANCE_ALPHA_LATC2_EXT:
   case GL_COMPRESSED_LUMINANCE_ALPHA_3DC_ATI:
      return GL_LUMINANCE_ALPHA;

   case GL_COMPRESSED_INTENSITY:
      return GL_INTENSITY;

   default:
      return 0;
   }
}

/**
 * Return list of (and count of) all specific texture compression
 * formats that are supported.
 *
 * Some formats are \b not returned by this function.  The
 * \c GL_COMPRESSED_TEXTURE_FORMATS query only returns formats that are
 * "suitable for general-purpose usage."  All texture compression extensions
 * have taken this to mean either linear RGB or linear RGBA.
 *
 * The GL_ARB_texture_compress_rgtc spec says:
 *
 *    "19) Should the GL_NUM_COMPRESSED_TEXTURE_FORMATS and
 *        GL_COMPRESSED_TEXTURE_FORMATS queries return the RGTC formats?
 *
 *        RESOLVED:  No.
 *
 *        The OpenGL 2.1 specification says "The only values returned
 *        by this query [GL_COMPRESSED_TEXTURE_FORMATS"] are those
 *        corresponding to formats suitable for general-purpose usage.
 *        The renderer will not enumerate formats with restrictions that
 *        need to be specifically understood prior to use."
 *
 *        Compressed textures with just red or red-green components are
 *        not general-purpose so should not be returned by these queries
 *        because they have restrictions.
 *
 *        Applications that seek to use the RGTC formats should do so
 *        by looking for this extension's name in the string returned by
 *        glGetString(GL_EXTENSIONS) rather than
 *        what GL_NUM_COMPRESSED_TEXTURE_FORMATS and
 *        GL_COMPRESSED_TEXTURE_FORMATS return."
 *
 * There is nearly identical wording in the GL_EXT_texture_compression_rgtc
 * spec.
 *
 * The GL_EXT_texture_rRGB spec says:
 *
 *    "22) Should the new COMPRESSED_SRGB_* formats be listed in an
 *        implementation's GL_COMPRESSED_TEXTURE_FORMATS list?
 *
 *        RESOLVED:  No.  Section 3.8.1 says formats listed by
 *        GL_COMPRESSED_TEXTURE_FORMATS are "suitable for general-purpose
 *        usage."  The non-linear distribution of red, green, and
 *        blue for these sRGB compressed formats makes them not really
 *        general-purpose."
 *
 * The GL_EXT_texture_compression_latc spec says:
 *
 *    "16) Should the GL_NUM_COMPRESSED_TEXTURE_FORMATS and
 *        GL_COMPRESSED_TEXTURE_FORMATS queries return the LATC formats?
 *
 *        RESOLVED:  No.
 *
 *        The OpenGL 2.1 specification says "The only values returned
 *        by this query [GL_COMPRESSED_TEXTURE_FORMATS"] are those
 *        corresponding to formats suitable for general-purpose usage.
 *        The renderer will not enumerate formats with restrictions that
 *        need to be specifically understood prior to use."
 *
 *        Historically, OpenGL implementation have advertised the RGB and
 *        RGBA versions of the S3TC extensions compressed format tokens
 *        through this mechanism.
 *
 *        The specification is not sufficiently clear about what "suitable
 *        for general-purpose usage" means.  Historically that seems to mean
 *        unsigned RGB or unsigned RGBA.  The DXT1 format supporting alpha
 *        (GL_COMPRESSED_RGBA_S3TC_DXT1_EXT) is not exposed in the list (at
 *        least for NVIDIA drivers) because the alpha is always 1.0 expect
 *        when it is 0.0 when RGB is required to be black.  NVIDIA's even
 *        limits itself to true linear RGB or RGBA formats, specifically
 *        not including EXT_texture_sRGB's sRGB S3TC compressed formats.
 *
 *        Adding luminance and luminance-alpha texture formats (and
 *        certainly signed versions of luminance and luminance-alpha
 *        formats!) invites potential comptaibility problems with old
 *        applications using this mechanism since old applications are
 *        unlikely to expect non-RGB or non-RGBA formats to be advertised
 *        through this mechanism.  However no specific misinteractions
 *        with old applications is known.
 *
 *        Applications that seek to use the LATC formats should do so
 *        by looking for this extension's name in the string returned by
 *        glGetString(GL_EXTENSIONS) rather than
 *        what GL_NUM_COMPRESSED_TEXTURE_FORMATS and
 *        GL_COMPRESSED_TEXTURE_FORMATS return."
 *
 * There is no formal spec for GL_ATI_texture_compression_3dc.  Since the
 * formats added by this extension are luminance-alpha formats, it is
 * reasonable to expect them to follow the same rules as
 * GL_EXT_texture_compression_latc.  At the very least, Catalyst 11.6 does not
 * expose the 3dc formats through this mechanism.
 *
 * \param ctx  the GL context
 * \param formats  the resulting format list (may be NULL).
 *
 * \return number of formats.
 */
GLuint
_mesa_get_compressed_formats(struct gl_context *ctx, GLint *formats)
{
   GLuint n = 0;
   if (ctx->Extensions.TDFX_texture_compression_FXT1) {
      if (formats) {
         formats[n++] = GL_COMPRESSED_RGB_FXT1_3DFX;
         formats[n++] = GL_COMPRESSED_RGBA_FXT1_3DFX;
      }
      else {
         n += 2;
      }
   }

   if (ctx->Extensions.EXT_texture_compression_s3tc) {
      if (formats) {
         formats[n++] = GL_COMPRESSED_RGB_S3TC_DXT1_EXT;
         formats[n++] = GL_COMPRESSED_RGBA_S3TC_DXT3_EXT;
         formats[n++] = GL_COMPRESSED_RGBA_S3TC_DXT5_EXT;
      }
      else {
         n += 3;
      }
   }
   if (ctx->Extensions.S3_s3tc) {
      if (formats) {
         formats[n++] = GL_RGB_S3TC;
         formats[n++] = GL_RGB4_S3TC;
         formats[n++] = GL_RGBA_S3TC;
         formats[n++] = GL_RGBA4_S3TC;
      }
      else {
         n += 4;
      }
   }

#if FEATURE_ES1
   if (ctx->API == API_OPENGLES) {
      if (formats) {
	 formats[n++] = GL_PALETTE4_RGB8_OES;
	 formats[n++] = GL_PALETTE4_RGBA8_OES;
	 formats[n++] = GL_PALETTE4_R5_G6_B5_OES;
	 formats[n++] = GL_PALETTE4_RGBA4_OES;
	 formats[n++] = GL_PALETTE4_RGB5_A1_OES;
	 formats[n++] = GL_PALETTE8_RGB8_OES;
	 formats[n++] = GL_PALETTE8_RGBA8_OES;
	 formats[n++] = GL_PALETTE8_R5_G6_B5_OES;
	 formats[n++] = GL_PALETTE8_RGBA4_OES;
	 formats[n++] = GL_PALETTE8_RGB5_A1_OES;
      }
      else {
	 n += 10;
      }
   }
#endif

   return n;
}


/**
 * Convert a compressed MESA_FORMAT_x to a GLenum.
 */
gl_format
_mesa_glenum_to_compressed_format(GLenum format)
{
   switch (format) {
   case GL_COMPRESSED_RGB_FXT1_3DFX:
      return MESA_FORMAT_RGB_FXT1;
   case GL_COMPRESSED_RGBA_FXT1_3DFX:
      return MESA_FORMAT_RGBA_FXT1;

   case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
   case GL_RGB_S3TC:
      return MESA_FORMAT_RGB_DXT1;
   case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
   case GL_RGB4_S3TC:
      return MESA_FORMAT_RGBA_DXT1;
   case GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
   case GL_RGBA_S3TC:
      return MESA_FORMAT_RGBA_DXT3;
   case GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
   case GL_RGBA4_S3TC:
      return MESA_FORMAT_RGBA_DXT5;

   case GL_COMPRESSED_SRGB_S3TC_DXT1_EXT:
      return MESA_FORMAT_SRGB_DXT1;
   case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT:
      return MESA_FORMAT_SRGBA_DXT1;
   case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT:
      return MESA_FORMAT_SRGBA_DXT3;
   case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT:
      return MESA_FORMAT_SRGBA_DXT5;

   case GL_COMPRESSED_RED_RGTC1:
      return MESA_FORMAT_RED_RGTC1;
   case GL_COMPRESSED_SIGNED_RED_RGTC1:
      return MESA_FORMAT_SIGNED_RED_RGTC1;
   case GL_COMPRESSED_RG_RGTC2:
      return MESA_FORMAT_RG_RGTC2;
   case GL_COMPRESSED_SIGNED_RG_RGTC2:
      return MESA_FORMAT_SIGNED_RG_RGTC2;

   case GL_COMPRESSED_LUMINANCE_LATC1_EXT:
      return MESA_FORMAT_L_LATC1;
   case GL_COMPRESSED_SIGNED_LUMINANCE_LATC1_EXT:
      return MESA_FORMAT_SIGNED_L_LATC1;
   case GL_COMPRESSED_LUMINANCE_ALPHA_LATC2_EXT:
   case GL_COMPRESSED_LUMINANCE_ALPHA_3DC_ATI:
      return MESA_FORMAT_LA_LATC2;
   case GL_COMPRESSED_SIGNED_LUMINANCE_ALPHA_LATC2_EXT:
      return MESA_FORMAT_SIGNED_LA_LATC2;

   default:
      return MESA_FORMAT_NONE;
   }
}


/**
 * Given a compressed MESA_FORMAT_x value, return the corresponding
 * GLenum for that format.
 * This is needed for glGetTexLevelParameter(GL_TEXTURE_INTERNAL_FORMAT)
 * which must return the specific texture format used when the user might
 * have originally specified a generic compressed format in their
 * glTexImage2D() call.
 * For non-compressed textures, we always return the user-specified
 * internal format unchanged.
 */
GLenum
_mesa_compressed_format_to_glenum(struct gl_context *ctx, GLuint mesaFormat)
{
   switch (mesaFormat) {
#if FEATURE_texture_fxt1
   case MESA_FORMAT_RGB_FXT1:
      return GL_COMPRESSED_RGB_FXT1_3DFX;
   case MESA_FORMAT_RGBA_FXT1:
      return GL_COMPRESSED_RGBA_FXT1_3DFX;
#endif
#if FEATURE_texture_s3tc
   case MESA_FORMAT_RGB_DXT1:
      return GL_COMPRESSED_RGB_S3TC_DXT1_EXT;
   case MESA_FORMAT_RGBA_DXT1:
      return GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
   case MESA_FORMAT_RGBA_DXT3:
      return GL_COMPRESSED_RGBA_S3TC_DXT3_EXT;
   case MESA_FORMAT_RGBA_DXT5:
      return GL_COMPRESSED_RGBA_S3TC_DXT5_EXT;
#if FEATURE_EXT_texture_sRGB
   case MESA_FORMAT_SRGB_DXT1:
      return GL_COMPRESSED_SRGB_S3TC_DXT1_EXT;
   case MESA_FORMAT_SRGBA_DXT1:
      return GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT;
   case MESA_FORMAT_SRGBA_DXT3:
      return GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT;
   case MESA_FORMAT_SRGBA_DXT5:
      return GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT;
#endif
#endif

   case MESA_FORMAT_RED_RGTC1:
      return GL_COMPRESSED_RED_RGTC1;
   case MESA_FORMAT_SIGNED_RED_RGTC1:
      return GL_COMPRESSED_SIGNED_RED_RGTC1;
   case MESA_FORMAT_RG_RGTC2:
      return GL_COMPRESSED_RG_RGTC2;
   case MESA_FORMAT_SIGNED_RG_RGTC2:
      return GL_COMPRESSED_SIGNED_RG_RGTC2;

   case MESA_FORMAT_L_LATC1:
      return GL_COMPRESSED_LUMINANCE_LATC1_EXT;
   case MESA_FORMAT_SIGNED_L_LATC1:
      return GL_COMPRESSED_SIGNED_LUMINANCE_LATC1_EXT;
   case MESA_FORMAT_LA_LATC2:
      return GL_COMPRESSED_LUMINANCE_ALPHA_LATC2_EXT;
   case MESA_FORMAT_SIGNED_LA_LATC2:
      return GL_COMPRESSED_SIGNED_LUMINANCE_ALPHA_LATC2_EXT;

   default:
      _mesa_problem(ctx, "Unexpected mesa texture format in"
                    " _mesa_compressed_format_to_glenum()");
      return 0;
   }
}


/*
 * Return the address of the pixel at (col, row, img) in a
 * compressed texture image.
 * \param col, row, img - image position (3D), should be a multiple of the
 *                        format's block size.
 * \param format - compressed image format
 * \param width - image width (stride) in pixels
 * \param image - the image address
 * \return address of pixel at (row, col, img)
 */
GLubyte *
_mesa_compressed_image_address(GLint col, GLint row, GLint img,
                               gl_format mesaFormat,
                               GLsizei width, const GLubyte *image)
{
   /* XXX only 2D images implemented, not 3D */
   const GLuint blockSize = _mesa_get_format_bytes(mesaFormat);
   GLuint bw, bh;
   GLint offset;

   _mesa_get_format_block_size(mesaFormat, &bw, &bh);

   ASSERT(col % bw == 0);
   ASSERT(row % bh == 0);

   offset = ((width + bw - 1) / bw) * (row / bh) + col / bw;
   offset *= blockSize;

   return (GLubyte *) image + offset;
}


/**
 * Decompress a compressed texture image, returning a GL_RGBA/GL_FLOAT image.
 */
void
_mesa_decompress_image(gl_format format, GLuint width, GLuint height,
                       const GLubyte *src, GLint srcRowStride,
                       GLfloat *dest)
{
   void (*fetch)(const struct swrast_texture_image *texImage,
                 GLint i, GLint j, GLint k, GLfloat *texel);
   struct swrast_texture_image texImage;  /* dummy teximage */
   GLuint i, j;

   /* setup dummy texture image info */
   memset(&texImage, 0, sizeof(texImage));
   texImage.Base.Data = (void *) src;
   texImage.Base.RowStride = srcRowStride;

   switch (format) {
   /* DXT formats */
   case MESA_FORMAT_RGB_DXT1:
      fetch = _mesa_fetch_texel_2d_f_rgb_dxt1;
      break;
   case MESA_FORMAT_RGBA_DXT1:
      fetch = _mesa_fetch_texel_2d_f_rgba_dxt1;
      break;
   case MESA_FORMAT_RGBA_DXT3:
      fetch = _mesa_fetch_texel_2d_f_rgba_dxt3;
      break;
   case MESA_FORMAT_RGBA_DXT5:
      fetch = _mesa_fetch_texel_2d_f_rgba_dxt5;
      break;

   /* FXT1 formats */
   case MESA_FORMAT_RGB_FXT1:
      fetch = _mesa_fetch_texel_2d_f_rgb_fxt1;
      break;
   case MESA_FORMAT_RGBA_FXT1:
      fetch = _mesa_fetch_texel_2d_f_rgba_fxt1;
      break;

   /* Red/RG formats */
   case MESA_FORMAT_RED_RGTC1:
      fetch = _mesa_fetch_texel_2d_f_red_rgtc1;
      break;
   case MESA_FORMAT_SIGNED_RED_RGTC1:
      fetch = _mesa_fetch_texel_2d_f_signed_red_rgtc1;
      break;
   case MESA_FORMAT_RG_RGTC2:
      fetch = _mesa_fetch_texel_2d_f_rg_rgtc2;
      break;
   case MESA_FORMAT_SIGNED_RG_RGTC2:
      fetch = _mesa_fetch_texel_2d_f_signed_rg_rgtc2;
      break;

   /* L/LA formats */
   case MESA_FORMAT_L_LATC1:
      fetch = _mesa_fetch_texel_2d_f_l_latc1;
      break;
   case MESA_FORMAT_SIGNED_L_LATC1:
      fetch = _mesa_fetch_texel_2d_f_signed_l_latc1;
      break;
   case MESA_FORMAT_LA_LATC2:
      fetch = _mesa_fetch_texel_2d_f_la_latc2;
      break;
   case MESA_FORMAT_SIGNED_LA_LATC2:
      fetch = _mesa_fetch_texel_2d_f_signed_la_latc2;
      break;

   default:
      _mesa_problem(NULL, "Unexpected format in _mesa_decompress_image()");
      return;
   }

   for (j = 0; j < height; j++) {
      for (i = 0; i < width; i++) {
         fetch(&texImage, i, j, 0, dest);
         dest += 4;
      }
   }
}