src/mesa/main/texcompress.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  6.5.1
   4  *
   5  * Copyright (C) 1999-2006  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.c
  29  * Helper functions for texture compression.
  30  */
  31
  32
  33 #include "glheader.h"
  34 #include "imports.h"
  35 #include "colormac.h"
  36 #include "context.h"
  37 #include "formats.h"
  38 #include "mfeatures.h"
  39 #include "mtypes.h"
  40 #include "texcompress.h"
  41 #include "texcompress_fxt1.h"
  42 #include "texcompress_rgtc.h"
  43 #include "texcompress_s3tc.h"
  44 #include "texcompress_etc.h"
  45
  46
  47 /**
  48  * Get the GL base format of a specified GL compressed texture format
  49  *
  50  * From page 232 of the OpenGL 3.3 (Compatiblity Profile) spec:
  51  *
  52  *     "Compressed Internal Format      Base Internal Format    Type
  53  *     ---------------------------     --------------------    ---------
  54  *     COMPRESSED_ALPHA                ALPHA                   Generic
  55  *     COMPRESSED_LUMINANCE            LUMINANCE               Generic
  56  *     COMPRESSED_LUMINANCE_ALPHA      LUMINANCE_ALPHA         Generic
  57  *     COMPRESSED_INTENSITY            INTENSITY               Generic
  58  *     COMPRESSED_RED                  RED                     Generic
  59  *     COMPRESSED_RG                   RG                      Generic
  60  *     COMPRESSED_RGB                  RGB                     Generic
  61  *     COMPRESSED_RGBA                 RGBA                    Generic
  62  *     COMPRESSED_SRGB                 RGB                     Generic
  63  *     COMPRESSED_SRGB_ALPHA           RGBA                    Generic
  64  *     COMPRESSED_SLUMINANCE           LUMINANCE               Generic
  65  *     COMPRESSED_SLUMINANCE_ALPHA     LUMINANCE_ALPHA         Generic
  66  *     COMPRESSED_RED_RGTC1            RED                     Specific
  67  *     COMPRESSED_SIGNED_RED_RGTC1     RED                     Specific
  68  *     COMPRESSED_RG_RGTC2             RG                      Specific
  69  *     COMPRESSED_SIGNED_RG_RGTC2      RG                      Specific"
  70  *
  71  * \return
  72  * The base format of \c format if \c format is a compressed format (either
  73  * generic or specific.  Otherwise 0 is returned.
  74  */
  75 GLenum
  76 _mesa_gl_compressed_format_base_format(GLenum format)
  77 {
  78    switch (format) {
  79    case GL_COMPRESSED_RED:
  80    case GL_COMPRESSED_R11_EAC:
  81    case GL_COMPRESSED_RED_RGTC1:
  82    case GL_COMPRESSED_SIGNED_R11_EAC:
  83    case GL_COMPRESSED_SIGNED_RED_RGTC1:
  84       return GL_RED;
  85
  86    case GL_COMPRESSED_RG:
  87    case GL_COMPRESSED_RG11_EAC:
  88    case GL_COMPRESSED_RG_RGTC2:
  89    case GL_COMPRESSED_SIGNED_RG11_EAC:
  90    case GL_COMPRESSED_SIGNED_RG_RGTC2:
  91       return GL_RG;
  92
  93    case GL_COMPRESSED_RGB:
  94    case GL_COMPRESSED_SRGB:
  95    case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
  96    case GL_COMPRESSED_RGB_FXT1_3DFX:
  97    case GL_COMPRESSED_SRGB_S3TC_DXT1_EXT:
  98    case GL_ETC1_RGB8_OES:
  99    case GL_COMPRESSED_RGB8_ETC2:
 100    case GL_COMPRESSED_SRGB8_ETC2:
 101       return GL_RGB;
 102
 103    case GL_COMPRESSED_RGBA:
 104    case GL_COMPRESSED_SRGB_ALPHA:
 105    case GL_COMPRESSED_RGBA_BPTC_UNORM_ARB:
 106    case GL_COMPRESSED_SRGB_ALPHA_BPTC_UNORM_ARB:
 107    case GL_COMPRESSED_RGB_BPTC_SIGNED_FLOAT_ARB:
 108    case GL_COMPRESSED_RGB_BPTC_UNSIGNED_FLOAT_ARB:
 109    case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
 110    case GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
 111    case GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
 112    case GL_COMPRESSED_RGBA_FXT1_3DFX:
 113    case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT:
 114    case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT:
 115    case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT:
 116    case GL_COMPRESSED_RGBA8_ETC2_EAC:
 117    case GL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC:
 118    case GL_COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2:
 119    case GL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2:
 120       return GL_RGBA;
 121
 122    case GL_COMPRESSED_ALPHA:
 123       return GL_ALPHA;
 124
 125    case GL_COMPRESSED_LUMINANCE:
 126    case GL_COMPRESSED_SLUMINANCE:
 127    case GL_COMPRESSED_LUMINANCE_LATC1_EXT:
 128    case GL_COMPRESSED_SIGNED_LUMINANCE_LATC1_EXT:
 129       return GL_LUMINANCE;
 130
 131    case GL_COMPRESSED_LUMINANCE_ALPHA:
 132    case GL_COMPRESSED_SLUMINANCE_ALPHA:
 133    case GL_COMPRESSED_LUMINANCE_ALPHA_LATC2_EXT:
 134    case GL_COMPRESSED_SIGNED_LUMINANCE_ALPHA_LATC2_EXT:
 135    case GL_COMPRESSED_LUMINANCE_ALPHA_3DC_ATI:
 136       return GL_LUMINANCE_ALPHA;
 137
 138    case GL_COMPRESSED_INTENSITY:
 139       return GL_INTENSITY;
 140
 141    default:
 142       return 0;
 143    }
 144 }
 145
 146 /**
 147  * Return list of (and count of) all specific texture compression
 148  * formats that are supported.
 149  *
 150  * Some formats are \b not returned by this function.  The
 151  * \c GL_COMPRESSED_TEXTURE_FORMATS query only returns formats that are
 152  * "suitable for general-purpose usage."  All texture compression extensions
 153  * have taken this to mean either linear RGB or linear RGBA.
 154  *
 155  * The GL_ARB_texture_compress_rgtc spec says:
 156  *
 157  *    "19) Should the GL_NUM_COMPRESSED_TEXTURE_FORMATS and
 158  *        GL_COMPRESSED_TEXTURE_FORMATS queries return the RGTC formats?
 159  *
 160  *        RESOLVED:  No.
 161  *
 162  *        The OpenGL 2.1 specification says "The only values returned
 163  *        by this query [GL_COMPRESSED_TEXTURE_FORMATS"] are those
 164  *        corresponding to formats suitable for general-purpose usage.
 165  *        The renderer will not enumerate formats with restrictions that
 166  *        need to be specifically understood prior to use."
 167  *
 168  *        Compressed textures with just red or red-green components are
 169  *        not general-purpose so should not be returned by these queries
 170  *        because they have restrictions.
 171  *
 172  *        Applications that seek to use the RGTC formats should do so
 173  *        by looking for this extension's name in the string returned by
 174  *        glGetString(GL_EXTENSIONS) rather than
 175  *        what GL_NUM_COMPRESSED_TEXTURE_FORMATS and
 176  *        GL_COMPRESSED_TEXTURE_FORMATS return."
 177  *
 178  * There is nearly identical wording in the GL_EXT_texture_compression_rgtc
 179  * spec.
 180  *
 181  * The GL_EXT_texture_rRGB spec says:
 182  *
 183  *    "22) Should the new COMPRESSED_SRGB_* formats be listed in an
 184  *        implementation's GL_COMPRESSED_TEXTURE_FORMATS list?
 185  *
 186  *        RESOLVED:  No.  Section 3.8.1 says formats listed by
 187  *        GL_COMPRESSED_TEXTURE_FORMATS are "suitable for general-purpose
 188  *        usage."  The non-linear distribution of red, green, and
 189  *        blue for these sRGB compressed formats makes them not really
 190  *        general-purpose."
 191  *
 192  * The GL_EXT_texture_compression_latc spec says:
 193  *
 194  *    "16) Should the GL_NUM_COMPRESSED_TEXTURE_FORMATS and
 195  *        GL_COMPRESSED_TEXTURE_FORMATS queries return the LATC formats?
 196  *
 197  *        RESOLVED:  No.
 198  *
 199  *        The OpenGL 2.1 specification says "The only values returned
 200  *        by this query [GL_COMPRESSED_TEXTURE_FORMATS"] are those
 201  *        corresponding to formats suitable for general-purpose usage.
 202  *        The renderer will not enumerate formats with restrictions that
 203  *        need to be specifically understood prior to use."
 204  *
 205  *        Historically, OpenGL implementation have advertised the RGB and
 206  *        RGBA versions of the S3TC extensions compressed format tokens
 207  *        through this mechanism.
 208  *
 209  *        The specification is not sufficiently clear about what "suitable
 210  *        for general-purpose usage" means.  Historically that seems to mean
 211  *        unsigned RGB or unsigned RGBA.  The DXT1 format supporting alpha
 212  *        (GL_COMPRESSED_RGBA_S3TC_DXT1_EXT) is not exposed in the list (at
 213  *        least for NVIDIA drivers) because the alpha is always 1.0 expect
 214  *        when it is 0.0 when RGB is required to be black.  NVIDIA's even
 215  *        limits itself to true linear RGB or RGBA formats, specifically
 216  *        not including EXT_texture_sRGB's sRGB S3TC compressed formats.
 217  *
 218  *        Adding luminance and luminance-alpha texture formats (and
 219  *        certainly signed versions of luminance and luminance-alpha
 220  *        formats!) invites potential comptaibility problems with old
 221  *        applications using this mechanism since old applications are
 222  *        unlikely to expect non-RGB or non-RGBA formats to be advertised
 223  *        through this mechanism.  However no specific misinteractions
 224  *        with old applications is known.
 225  *
 226  *        Applications that seek to use the LATC formats should do so
 227  *        by looking for this extension's name in the string returned by
 228  *        glGetString(GL_EXTENSIONS) rather than
 229  *        what GL_NUM_COMPRESSED_TEXTURE_FORMATS and
 230  *        GL_COMPRESSED_TEXTURE_FORMATS return."
 231  *
 232  * There is no formal spec for GL_ATI_texture_compression_3dc.  Since the
 233  * formats added by this extension are luminance-alpha formats, it is
 234  * reasonable to expect them to follow the same rules as
 235  * GL_EXT_texture_compression_latc.  At the very least, Catalyst 11.6 does not
 236  * expose the 3dc formats through this mechanism.
 237  *
 238  * \param ctx  the GL context
 239  * \param formats  the resulting format list (may be NULL).
 240  *
 241  * \return number of formats.
 242  */
 243 GLuint
 244 _mesa_get_compressed_formats(struct gl_context *ctx, GLint *formats)
 245 {
 246    GLuint n = 0;
 247    if (ctx->Extensions.TDFX_texture_compression_FXT1) {
 248       if (formats) {
 249          formats[n++] = GL_COMPRESSED_RGB_FXT1_3DFX;
 250          formats[n++] = GL_COMPRESSED_RGBA_FXT1_3DFX;
 251       }
 252       else {
 253          n += 2;
 254       }
 255    }
 256
 257    if (ctx->Extensions.EXT_texture_compression_s3tc) {
 258       if (formats) {
 259          formats[n++] = GL_COMPRESSED_RGB_S3TC_DXT1_EXT;
 260          formats[n++] = GL_COMPRESSED_RGBA_S3TC_DXT3_EXT;
 261          formats[n++] = GL_COMPRESSED_RGBA_S3TC_DXT5_EXT;
 262       }
 263       else {
 264          n += 3;
 265       }
 266    }
 267    if (ctx->Extensions.S3_s3tc) {
 268       if (formats) {
 269          formats[n++] = GL_RGB_S3TC;
 270          formats[n++] = GL_RGB4_S3TC;
 271          formats[n++] = GL_RGBA_S3TC;
 272          formats[n++] = GL_RGBA4_S3TC;
 273       }
 274       else {
 275          n += 4;
 276       }
 277    }
 278
 279    if (ctx->Extensions.OES_compressed_ETC1_RGB8_texture) {
 280       if (formats) {
 281          formats[n++] = GL_ETC1_RGB8_OES;
 282       }
 283       else {
 284          n += 1;
 285       }
 286    }
 287
 288    if (ctx->API == API_OPENGLES) {
 289       if (formats) {
 290          formats[n++] = GL_PALETTE4_RGB8_OES;
 291          formats[n++] = GL_PALETTE4_RGBA8_OES;
 292          formats[n++] = GL_PALETTE4_R5_G6_B5_OES;
 293          formats[n++] = GL_PALETTE4_RGBA4_OES;
 294          formats[n++] = GL_PALETTE4_RGB5_A1_OES;
 295          formats[n++] = GL_PALETTE8_RGB8_OES;
 296          formats[n++] = GL_PALETTE8_RGBA8_OES;
 297          formats[n++] = GL_PALETTE8_R5_G6_B5_OES;
 298          formats[n++] = GL_PALETTE8_RGBA4_OES;
 299          formats[n++] = GL_PALETTE8_RGB5_A1_OES;
 300       }
 301       else {
 302          n += 10;
 303       }
 304    }
 305
 306    if (_mesa_is_gles3(ctx)) {
 307       if (formats) {
 308          formats[n++] = GL_COMPRESSED_RGB8_ETC2;
 309          formats[n++] = GL_COMPRESSED_SRGB8_ETC2;
 310          formats[n++] = GL_COMPRESSED_RGBA8_ETC2_EAC;
 311          formats[n++] = GL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC;
 312          formats[n++] = GL_COMPRESSED_R11_EAC;
 313          formats[n++] = GL_COMPRESSED_RG11_EAC;
 314          formats[n++] = GL_COMPRESSED_SIGNED_R11_EAC;
 315          formats[n++] = GL_COMPRESSED_SIGNED_RG11_EAC;
 316          formats[n++] = GL_COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2;
 317          formats[n++] = GL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2;
 318       }
 319       else {
 320          n += 10;
 321       }
 322    }
 323    return n;
 324 }
 325
 326
 327 /**
 328  * Convert a compressed MESA_FORMAT_x to a GLenum.
 329  */
 330 gl_format
 331 _mesa_glenum_to_compressed_format(GLenum format)
 332 {
 333    switch (format) {
 334    case GL_COMPRESSED_RGB_FXT1_3DFX:
 335       return MESA_FORMAT_RGB_FXT1;
 336    case GL_COMPRESSED_RGBA_FXT1_3DFX:
 337       return MESA_FORMAT_RGBA_FXT1;
 338
 339    case GL_COMPRESSED_RGB_S3TC_DXT1_EXT:
 340    case GL_RGB_S3TC:
 341       return MESA_FORMAT_RGB_DXT1;
 342    case GL_COMPRESSED_RGBA_S3TC_DXT1_EXT:
 343    case GL_RGB4_S3TC:
 344       return MESA_FORMAT_RGBA_DXT1;
 345    case GL_COMPRESSED_RGBA_S3TC_DXT3_EXT:
 346    case GL_RGBA_S3TC:
 347       return MESA_FORMAT_RGBA_DXT3;
 348    case GL_COMPRESSED_RGBA_S3TC_DXT5_EXT:
 349    case GL_RGBA4_S3TC:
 350       return MESA_FORMAT_RGBA_DXT5;
 351
 352    case GL_COMPRESSED_SRGB_S3TC_DXT1_EXT:
 353       return MESA_FORMAT_SRGB_DXT1;
 354    case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT:
 355       return MESA_FORMAT_SRGBA_DXT1;
 356    case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT:
 357       return MESA_FORMAT_SRGBA_DXT3;
 358    case GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT:
 359       return MESA_FORMAT_SRGBA_DXT5;
 360
 361    case GL_COMPRESSED_RED_RGTC1:
 362       return MESA_FORMAT_RED_RGTC1;
 363    case GL_COMPRESSED_SIGNED_RED_RGTC1:
 364       return MESA_FORMAT_SIGNED_RED_RGTC1;
 365    case GL_COMPRESSED_RG_RGTC2:
 366       return MESA_FORMAT_RG_RGTC2;
 367    case GL_COMPRESSED_SIGNED_RG_RGTC2:
 368       return MESA_FORMAT_SIGNED_RG_RGTC2;
 369
 370    case GL_COMPRESSED_LUMINANCE_LATC1_EXT:
 371       return MESA_FORMAT_L_LATC1;
 372    case GL_COMPRESSED_SIGNED_LUMINANCE_LATC1_EXT:
 373       return MESA_FORMAT_SIGNED_L_LATC1;
 374    case GL_COMPRESSED_LUMINANCE_ALPHA_LATC2_EXT:
 375    case GL_COMPRESSED_LUMINANCE_ALPHA_3DC_ATI:
 376       return MESA_FORMAT_LA_LATC2;
 377    case GL_COMPRESSED_SIGNED_LUMINANCE_ALPHA_LATC2_EXT:
 378       return MESA_FORMAT_SIGNED_LA_LATC2;
 379
 380    case GL_ETC1_RGB8_OES:
 381       return MESA_FORMAT_ETC1_RGB8;
 382    case GL_COMPRESSED_RGB8_ETC2:
 383       return MESA_FORMAT_ETC2_RGB8;
 384    case GL_COMPRESSED_SRGB8_ETC2:
 385       return MESA_FORMAT_ETC2_SRGB8;
 386    case GL_COMPRESSED_RGBA8_ETC2_EAC:
 387       return MESA_FORMAT_ETC2_RGBA8_EAC;
 388    case GL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC:
 389       return MESA_FORMAT_ETC2_SRGB8_ALPHA8_EAC;
 390    case GL_COMPRESSED_R11_EAC:
 391       return MESA_FORMAT_ETC2_R11_EAC;
 392    case GL_COMPRESSED_RG11_EAC:
 393       return MESA_FORMAT_ETC2_RG11_EAC;
 394    case GL_COMPRESSED_SIGNED_R11_EAC:
 395       return MESA_FORMAT_ETC2_SIGNED_R11_EAC;
 396    case GL_COMPRESSED_SIGNED_RG11_EAC:
 397       return MESA_FORMAT_ETC2_SIGNED_RG11_EAC;
 398    case GL_COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2:
 399       return MESA_FORMAT_ETC2_RGB8_PUNCHTHROUGH_ALPHA1;
 400    case GL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2:
 401       return MESA_FORMAT_ETC2_SRGB8_PUNCHTHROUGH_ALPHA1;
 402
 403    default:
 404       return MESA_FORMAT_NONE;
 405    }
 406 }
 407
 408
 409 /**
 410  * Given a compressed MESA_FORMAT_x value, return the corresponding
 411  * GLenum for that format.
 412  * This is needed for glGetTexLevelParameter(GL_TEXTURE_INTERNAL_FORMAT)
 413  * which must return the specific texture format used when the user might
 414  * have originally specified a generic compressed format in their
 415  * glTexImage2D() call.
 416  * For non-compressed textures, we always return the user-specified
 417  * internal format unchanged.
 418  */
 419 GLenum
 420 _mesa_compressed_format_to_glenum(struct gl_context *ctx, gl_format mesaFormat)
 421 {
 422    switch (mesaFormat) {
 423    case MESA_FORMAT_RGB_FXT1:
 424       return GL_COMPRESSED_RGB_FXT1_3DFX;
 425    case MESA_FORMAT_RGBA_FXT1:
 426       return GL_COMPRESSED_RGBA_FXT1_3DFX;
 427    case MESA_FORMAT_RGB_DXT1:
 428       return GL_COMPRESSED_RGB_S3TC_DXT1_EXT;
 429    case MESA_FORMAT_RGBA_DXT1:
 430       return GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
 431    case MESA_FORMAT_RGBA_DXT3:
 432       return GL_COMPRESSED_RGBA_S3TC_DXT3_EXT;
 433    case MESA_FORMAT_RGBA_DXT5:
 434       return GL_COMPRESSED_RGBA_S3TC_DXT5_EXT;
 435    case MESA_FORMAT_SRGB_DXT1:
 436       return GL_COMPRESSED_SRGB_S3TC_DXT1_EXT;
 437    case MESA_FORMAT_SRGBA_DXT1:
 438       return GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT1_EXT;
 439    case MESA_FORMAT_SRGBA_DXT3:
 440       return GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT3_EXT;
 441    case MESA_FORMAT_SRGBA_DXT5:
 442       return GL_COMPRESSED_SRGB_ALPHA_S3TC_DXT5_EXT;
 443    case MESA_FORMAT_RED_RGTC1:
 444       return GL_COMPRESSED_RED_RGTC1;
 445    case MESA_FORMAT_SIGNED_RED_RGTC1:
 446       return GL_COMPRESSED_SIGNED_RED_RGTC1;
 447    case MESA_FORMAT_RG_RGTC2:
 448       return GL_COMPRESSED_RG_RGTC2;
 449    case MESA_FORMAT_SIGNED_RG_RGTC2:
 450       return GL_COMPRESSED_SIGNED_RG_RGTC2;
 451
 452    case MESA_FORMAT_L_LATC1:
 453       return GL_COMPRESSED_LUMINANCE_LATC1_EXT;
 454    case MESA_FORMAT_SIGNED_L_LATC1:
 455       return GL_COMPRESSED_SIGNED_LUMINANCE_LATC1_EXT;
 456    case MESA_FORMAT_LA_LATC2:
 457       return GL_COMPRESSED_LUMINANCE_ALPHA_LATC2_EXT;
 458    case MESA_FORMAT_SIGNED_LA_LATC2:
 459       return GL_COMPRESSED_SIGNED_LUMINANCE_ALPHA_LATC2_EXT;
 460
 461    case MESA_FORMAT_ETC1_RGB8:
 462       return GL_ETC1_RGB8_OES;
 463    case MESA_FORMAT_ETC2_RGB8:
 464       return GL_COMPRESSED_RGB8_ETC2;
 465    case MESA_FORMAT_ETC2_SRGB8:
 466       return GL_COMPRESSED_SRGB8_ETC2;
 467    case MESA_FORMAT_ETC2_RGBA8_EAC:
 468       return GL_COMPRESSED_RGBA8_ETC2_EAC;
 469    case MESA_FORMAT_ETC2_SRGB8_ALPHA8_EAC:
 470       return GL_COMPRESSED_SRGB8_ALPHA8_ETC2_EAC;
 471    case MESA_FORMAT_ETC2_R11_EAC:
 472       return GL_COMPRESSED_R11_EAC;
 473    case MESA_FORMAT_ETC2_RG11_EAC:
 474       return GL_COMPRESSED_RG11_EAC;
 475    case MESA_FORMAT_ETC2_SIGNED_R11_EAC:
 476       return GL_COMPRESSED_SIGNED_R11_EAC;
 477    case MESA_FORMAT_ETC2_SIGNED_RG11_EAC:
 478       return GL_COMPRESSED_SIGNED_RG11_EAC;
 479    case MESA_FORMAT_ETC2_RGB8_PUNCHTHROUGH_ALPHA1:
 480       return GL_COMPRESSED_RGB8_PUNCHTHROUGH_ALPHA1_ETC2;
 481    case MESA_FORMAT_ETC2_SRGB8_PUNCHTHROUGH_ALPHA1:
 482       return GL_COMPRESSED_SRGB8_PUNCHTHROUGH_ALPHA1_ETC2;
 483
 484    default:
 485       _mesa_problem(ctx, "Unexpected mesa texture format in"
 486                     " _mesa_compressed_format_to_glenum()");
 487       return 0;
 488    }
 489 }
 490
 491
 492 /*
 493  * Return the address of the pixel at (col, row, img) in a
 494  * compressed texture image.
 495  * \param col, row, img - image position (3D), should be a multiple of the
 496  *                        format's block size.
 497  * \param format - compressed image format
 498  * \param width - image width (stride) in pixels
 499  * \param image - the image address
 500  * \return address of pixel at (row, col, img)
 501  */
 502 GLubyte *
 503 _mesa_compressed_image_address(GLint col, GLint row, GLint img,
 504                                gl_format mesaFormat,
 505                                GLsizei width, const GLubyte *image)
 506 {
 507    /* XXX only 2D images implemented, not 3D */
 508    const GLuint blockSize = _mesa_get_format_bytes(mesaFormat);
 509    GLuint bw, bh;
 510    GLint offset;
 511
 512    _mesa_get_format_block_size(mesaFormat, &bw, &bh);
 513
 514    ASSERT(col % bw == 0);
 515    ASSERT(row % bh == 0);
 516
 517    offset = ((width + bw - 1) / bw) * (row / bh) + col / bw;
 518    offset *= blockSize;
 519
 520    return (GLubyte *) image + offset;
 521 }
 522
 523
 524 /**
 525  * Return a texel-fetch function for the given format, or NULL if
 526  * invalid format.
 527  */
 528 compressed_fetch_func
 529 _mesa_get_compressed_fetch_func(gl_format format)
 530 {
 531    switch (format) {
 532    case MESA_FORMAT_RGB_DXT1:
 533    case MESA_FORMAT_RGBA_DXT1:
 534    case MESA_FORMAT_RGBA_DXT3:
 535    case MESA_FORMAT_RGBA_DXT5:
 536    case MESA_FORMAT_SRGB_DXT1:
 537    case MESA_FORMAT_SRGBA_DXT1:
 538    case MESA_FORMAT_SRGBA_DXT3:
 539    case MESA_FORMAT_SRGBA_DXT5:
 540       return _mesa_get_dxt_fetch_func(format);
 541    case MESA_FORMAT_RGB_FXT1:
 542    case MESA_FORMAT_RGBA_FXT1:
 543       return _mesa_get_fxt_fetch_func(format);
 544    case MESA_FORMAT_RED_RGTC1:
 545    case MESA_FORMAT_L_LATC1:
 546    case MESA_FORMAT_SIGNED_RED_RGTC1:
 547    case MESA_FORMAT_SIGNED_L_LATC1:
 548    case MESA_FORMAT_RG_RGTC2:
 549    case MESA_FORMAT_LA_LATC2:
 550    case MESA_FORMAT_SIGNED_RG_RGTC2:
 551    case MESA_FORMAT_SIGNED_LA_LATC2:
 552       return _mesa_get_compressed_rgtc_func(format);
 553    case MESA_FORMAT_ETC1_RGB8:
 554       return _mesa_get_etc_fetch_func(format);
 555    default:
 556       return NULL;
 557    }
 558 }
 559
 560
 561 /**
 562  * Decompress a compressed texture image, returning a GL_RGBA/GL_FLOAT image.
 563  * \param srcRowStride  stride in bytes between rows of blocks in the
 564  *                      compressed source image.
 565  */
 566 void
 567 _mesa_decompress_image(gl_format format, GLuint width, GLuint height,
 568                        const GLubyte *src, GLint srcRowStride,
 569                        GLfloat *dest)
 570 {
 571    compressed_fetch_func fetch;
 572    GLuint i, j;
 573    GLuint bytes, bw, bh;
 574    GLint stride;
 575
 576    bytes = _mesa_get_format_bytes(format);
 577    _mesa_get_format_block_size(format, &bw, &bh);
 578
 579    fetch = _mesa_get_compressed_fetch_func(format);
 580    if (!fetch) {
 581       _mesa_problem(NULL, "Unexpected format in _mesa_decompress_image()");
 582       return;
 583    }
 584
 585    stride = srcRowStride * bh / bytes;
 586
 587    for (j = 0; j < height; j++) {
 588       for (i = 0; i < width; i++) {
 589          fetch(src, NULL, stride, i, j, 0, dest);
 590          dest += 4;
 591       }
 592    }
 593 }