src/mesa/swrast/s_readpix.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  6.5.2
   4  *
   5  * Copyright (C) 1999-2006  Brian Paul   All Rights Reserved.
   6  *
   7  * Permission is hereby granted, free of charge, to any person obtaining a
   8  * copy of this software and associated documentation files (the "Software"),
   9  * to deal in the Software without restriction, including without limitation
  10  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
  11  * and/or sell copies of the Software, and to permit persons to whom the
  12  * Software is furnished to do so, subject to the following conditions:
  13  *
  14  * The above copyright notice and this permission notice shall be included
  15  * in all copies or substantial portions of the Software.
  16  *
  17  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  18  * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  20  * BRIAN PAUL BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
  21  * AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
  22  * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
  23  */
  24
  25
  26 #include "glheader.h"
  27 #include "bufferobj.h"
  28 #include "colormac.h"
  29 #include "convolve.h"
  30 #include "context.h"
  31 #include "feedback.h"
  32 #include "image.h"
  33 #include "macros.h"
  34 #include "imports.h"
  35 #include "pixel.h"
  36 #include "state.h"
  37
  38 #include "s_context.h"
  39 #include "s_depth.h"
  40 #include "s_span.h"
  41 #include "s_stencil.h"
  42
  43
  44 /*
  45  * Read a block of color index pixels.
  46  */
  47 static void
  48 read_index_pixels( GLcontext *ctx,
  49                    GLint x, GLint y,
  50                    GLsizei width, GLsizei height,
  51                    GLenum type, GLvoid *pixels,
  52                    const struct gl_pixelstore_attrib *packing )
  53 {
  54    struct gl_renderbuffer *rb = ctx->ReadBuffer->_ColorReadBuffer;
  55    GLint i;
  56
  57    ASSERT(rb);
  58
  59    /* width should never be > MAX_WIDTH since we did clipping earlier */
  60    ASSERT(width <= MAX_WIDTH);
  61
  62    /* process image row by row */
  63    for (i = 0; i < height; i++) {
  64       GLuint index[MAX_WIDTH];
  65       GLvoid *dest;
  66       ASSERT(rb->DataType == GL_UNSIGNED_INT);
  67       rb->GetRow(ctx, rb, width, x, y + i, index);
  68
  69       dest = _mesa_image_address2d(packing, pixels, width, height,
  70                                    GL_COLOR_INDEX, type, i, 0);
  71
  72       _mesa_pack_index_span(ctx, width, type, dest, index,
  73                             &ctx->Pack, ctx->_ImageTransferState);
  74    }
  75 }
  76
  77
  78
  79 /**
  80  * Read pixels for format=GL_DEPTH_COMPONENT.
  81  */
  82 static void
  83 read_depth_pixels( GLcontext *ctx,
  84                    GLint x, GLint y,
  85                    GLsizei width, GLsizei height,
  86                    GLenum type, GLvoid *pixels,
  87                    const struct gl_pixelstore_attrib *packing )
  88 {
  89    struct gl_framebuffer *fb = ctx->ReadBuffer;
  90    struct gl_renderbuffer *rb = fb->_DepthBuffer;
  91    const GLboolean biasOrScale
  92       = ctx->Pixel.DepthScale != 1.0 || ctx->Pixel.DepthBias != 0.0;
  93
  94    /* clipping should have been done already */
  95    ASSERT(x >= 0);
  96    ASSERT(y >= 0);
  97    ASSERT(x + width <= rb->Width);
  98    ASSERT(y + height <= rb->Height);
  99    /* width should never be > MAX_WIDTH since we did clipping earlier */
 100    ASSERT(width <= MAX_WIDTH);
 101
 102    ASSERT(rb);
 103
 104    if (type == GL_UNSIGNED_SHORT && fb->Visual.depthBits == 16
 105        && !biasOrScale && !packing->SwapBytes) {
 106       /* Special case: directly read 16-bit unsigned depth values. */
 107       GLint j;
 108       ASSERT(rb->InternalFormat == GL_DEPTH_COMPONENT16);
 109       ASSERT(rb->DataType == GL_UNSIGNED_SHORT);
 110       for (j = 0; j < height; j++, y++) {
 111          void *dest =_mesa_image_address2d(packing, pixels, width, height,
 112                                            GL_DEPTH_COMPONENT, type, j, 0);
 113          rb->GetRow(ctx, rb, width, x, y, dest);
 114       }
 115    }
 116    else if (type == GL_UNSIGNED_INT && fb->Visual.depthBits == 24
 117             && !biasOrScale && !packing->SwapBytes) {
 118       /* Special case: directly read 24-bit unsigned depth values. */
 119       GLint j;
 120       ASSERT(rb->InternalFormat == GL_DEPTH_COMPONENT32);
 121       ASSERT(rb->DataType == GL_UNSIGNED_INT);
 122       for (j = 0; j < height; j++, y++) {
 123          GLuint *dest = (GLuint *)
 124             _mesa_image_address2d(packing, pixels, width, height,
 125                                   GL_DEPTH_COMPONENT, type, j, 0);
 126          GLint k;
 127          rb->GetRow(ctx, rb, width, x, y, dest);
 128          /* convert range from 24-bit to 32-bit */
 129          for (k = 0; k < width; k++) {
 130             dest[k] = (dest[k] << 8) | (dest[k] >> 24);
 131          }
 132       }
 133    }
 134    else if (type == GL_UNSIGNED_INT && fb->Visual.depthBits == 32
 135             && !biasOrScale && !packing->SwapBytes) {
 136       /* Special case: directly read 32-bit unsigned depth values. */
 137       GLint j;
 138       ASSERT(rb->InternalFormat == GL_DEPTH_COMPONENT32);
 139       ASSERT(rb->DataType == GL_UNSIGNED_INT);
 140       for (j = 0; j < height; j++, y++) {
 141          void *dest = _mesa_image_address2d(packing, pixels, width, height,
 142                                             GL_DEPTH_COMPONENT, type, j, 0);
 143          rb->GetRow(ctx, rb, width, x, y, dest);
 144       }
 145    }
 146    else {
 147       /* General case (slower) */
 148       GLint j;
 149       for (j = 0; j < height; j++, y++) {
 150          GLfloat depthValues[MAX_WIDTH];
 151          GLvoid *dest = _mesa_image_address2d(packing, pixels, width, height,
 152                                               GL_DEPTH_COMPONENT, type, j, 0);
 153          _swrast_read_depth_span_float(ctx, rb, width, x, y, depthValues);
 154          _mesa_pack_depth_span(ctx, width, dest, type, depthValues, packing);
 155       }
 156    }
 157 }
 158
 159
 160 /**
 161  * Read pixels for format=GL_STENCIL_INDEX.
 162  */
 163 static void
 164 read_stencil_pixels( GLcontext *ctx,
 165                      GLint x, GLint y,
 166                      GLsizei width, GLsizei height,
 167                      GLenum type, GLvoid *pixels,
 168                      const struct gl_pixelstore_attrib *packing )
 169 {
 170    struct gl_framebuffer *fb = ctx->ReadBuffer;
 171    struct gl_renderbuffer *rb = fb->_StencilBuffer;
 172    GLint j;
 173
 174    ASSERT(rb);
 175
 176    /* width should never be > MAX_WIDTH since we did clipping earlier */
 177    ASSERT(width <= MAX_WIDTH);
 178
 179    /* process image row by row */
 180    for (j=0;j<height;j++,y++) {
 181       GLvoid *dest;
 182       GLstencil stencil[MAX_WIDTH];
 183
 184       _swrast_read_stencil_span(ctx, rb, width, x, y, stencil);
 185
 186       dest = _mesa_image_address2d(packing, pixels, width, height,
 187                                    GL_STENCIL_INDEX, type, j, 0);
 188
 189       _mesa_pack_stencil_span(ctx, width, type, dest, stencil, packing);
 190    }
 191 }
 192
 193
 194
 195 /**
 196  * Optimized glReadPixels for particular pixel formats when pixel
 197  * scaling, biasing, mapping, etc. are disabled.
 198  */
 199 static GLboolean
 200 fast_read_rgba_pixels( GLcontext *ctx,
 201                        GLint x, GLint y,
 202                        GLsizei width, GLsizei height,
 203                        GLenum format, GLenum type,
 204                        GLvoid *pixels,
 205                        const struct gl_pixelstore_attrib *packing,
 206                        GLbitfield transferOps)
 207 {
 208    struct gl_renderbuffer *rb = ctx->ReadBuffer->_ColorReadBuffer;
 209
 210    ASSERT(rb->_BaseFormat == GL_RGBA || rb->_BaseFormat == GL_RGB);
 211
 212    /* clipping should have already been done */
 213    ASSERT(x + width <= rb->Width);
 214    ASSERT(y + height <= rb->Height);
 215
 216    /* check for things we can't handle here */
 217    if (transferOps ||
 218        packing->SwapBytes ||
 219        packing->LsbFirst) {
 220       return GL_FALSE;
 221    }
 222
 223    if (format == GL_RGBA && rb->DataType == type) {
 224       const GLint dstStride = _mesa_image_row_stride(packing, width,
 225                                                      format, type);
 226       GLubyte *dest = _mesa_image_address2d(packing, pixels, width, height,
 227                                             format, type, 0, 0);
 228       GLint row;
 229       ASSERT(rb->GetRow);
 230       for (row = 0; row < height; row++) {
 231          rb->GetRow(ctx, rb, width, x, y + row, dest);
 232          dest += dstStride;
 233       }
 234       return GL_TRUE;
 235    }
 236
 237    if (format == GL_RGB &&
 238        rb->DataType == GL_UNSIGNED_BYTE &&
 239        type == GL_UNSIGNED_BYTE) {
 240       const GLint dstStride = _mesa_image_row_stride(packing, width,
 241                                                      format, type);
 242       GLubyte *dest = _mesa_image_address2d(packing, pixels, width, height,
 243                                             format, type, 0, 0);
 244       GLint row;
 245       ASSERT(rb->GetRow);
 246       for (row = 0; row < height; row++) {
 247          GLubyte tempRow[MAX_WIDTH][4];
 248          GLint col;
 249          rb->GetRow(ctx, rb, width, x, y + row, tempRow);
 250          /* convert RGBA to RGB */
 251          for (col = 0; col < width; col++) {
 252             dest[col * 3 + 0] = tempRow[col][0];
 253             dest[col * 3 + 1] = tempRow[col][1];
 254             dest[col * 3 + 2] = tempRow[col][2];
 255          }
 256          dest += dstStride;
 257       }
 258       return GL_TRUE;
 259    }
 260
 261    /* not handled */
 262    return GL_FALSE;
 263 }
 264
 265
 266 /**
 267  * When we're using a low-precision color buffer (like 16-bit 5/6/5)
 268  * we have to adjust our color values a bit to pass conformance.
 269  * The problem is when a 5 or 6-bit color value is convert to an 8-bit
 270  * value and then a floating point value, the floating point values don't
 271  * increment uniformly as the 5 or 6-bit value is incremented.
 272  *
 273  * This function adjusts floating point values to compensate.
 274  */
 275 static void
 276 adjust_colors(GLcontext *ctx, GLuint n, GLfloat rgba[][4])
 277 {
 278    const GLuint rShift = 8 - ctx->Visual.redBits;
 279    const GLuint gShift = 8 - ctx->Visual.greenBits;
 280    const GLuint bShift = 8 - ctx->Visual.blueBits;
 281    const GLfloat rScale = 1.0F / (GLfloat) ((1 << ctx->Visual.redBits  ) - 1);
 282    const GLfloat gScale = 1.0F / (GLfloat) ((1 << ctx->Visual.greenBits) - 1);
 283    const GLfloat bScale = 1.0F / (GLfloat) ((1 << ctx->Visual.blueBits ) - 1);
 284    GLuint i;
 285    for (i = 0; i < n; i++) {
 286       GLint r, g, b;
 287       /* convert float back to ubyte */
 288       CLAMPED_FLOAT_TO_UBYTE(r, rgba[i][RCOMP]);
 289       CLAMPED_FLOAT_TO_UBYTE(g, rgba[i][GCOMP]);
 290       CLAMPED_FLOAT_TO_UBYTE(b, rgba[i][BCOMP]);
 291       /* using only the N most significant bits of the ubyte value, convert to
 292        * float in [0,1].
 293        */
 294       rgba[i][RCOMP] = (GLfloat) (r >> rShift) * rScale;
 295       rgba[i][GCOMP] = (GLfloat) (g >> gShift) * gScale;
 296       rgba[i][BCOMP] = (GLfloat) (b >> bShift) * bScale;
 297    }
 298 }
 299
 300
 301
 302 /*
 303  * Read R, G, B, A, RGB, L, or LA pixels.
 304  */
 305 static void
 306 read_rgba_pixels( GLcontext *ctx,
 307                   GLint x, GLint y,
 308                   GLsizei width, GLsizei height,
 309                   GLenum format, GLenum type, GLvoid *pixels,
 310                   const struct gl_pixelstore_attrib *packing )
 311 {
 312    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 313    GLbitfield transferOps = ctx->_ImageTransferState;
 314    struct gl_framebuffer *fb = ctx->ReadBuffer;
 315    struct gl_renderbuffer *rb = fb->_ColorReadBuffer;
 316
 317    ASSERT(rb);
 318
 319    if (type == GL_FLOAT && ((ctx->Color.ClampReadColor == GL_TRUE) ||
 320                             (ctx->Color.ClampReadColor == GL_FIXED_ONLY_ARB &&
 321                              rb->DataType != GL_FLOAT)))
 322       transferOps |= IMAGE_CLAMP_BIT;
 323
 324    /* Try optimized path first */
 325    if (fast_read_rgba_pixels(ctx, x, y, width, height,
 326                              format, type, pixels, packing, transferOps)) {
 327       return; /* done! */
 328    }
 329
 330    /* width should never be > MAX_WIDTH since we did clipping earlier */
 331    ASSERT(width <= MAX_WIDTH);
 332
 333    if (ctx->Pixel.Convolution2DEnabled || ctx->Pixel.Separable2DEnabled) {
 334       GLfloat *dest, *src, *tmpImage, *convImage;
 335       GLint row;
 336
 337       tmpImage = (GLfloat *) _mesa_malloc(width * height * 4 * sizeof(GLfloat));
 338       if (!tmpImage) {
 339          _mesa_error(ctx, GL_OUT_OF_MEMORY, "glReadPixels");
 340          return;
 341       }
 342       convImage = (GLfloat *) _mesa_malloc(width * height * 4 * sizeof(GLfloat));
 343       if (!convImage) {
 344          _mesa_free(tmpImage);
 345          _mesa_error(ctx, GL_OUT_OF_MEMORY, "glReadPixels");
 346          return;
 347       }
 348
 349       /* read full RGBA, FLOAT image */
 350       dest = tmpImage;
 351       for (row = 0; row < height; row++, y++) {
 352          if (fb->Visual.rgbMode) {
 353             _swrast_read_rgba_span(ctx, rb, width, x, y, GL_FLOAT, dest);
 354          }
 355          else {
 356             GLuint index[MAX_WIDTH];
 357             ASSERT(rb->DataType == GL_UNSIGNED_INT);
 358             rb->GetRow(ctx, rb, width, x, y, index);
 359             _mesa_apply_ci_transfer_ops(ctx,
 360                                         transferOps & IMAGE_SHIFT_OFFSET_BIT,
 361                                         width, index);
 362             _mesa_map_ci_to_rgba(ctx, width, index, (GLfloat (*)[4]) dest);
 363          }
 364          _mesa_apply_rgba_transfer_ops(ctx,
 365                                       transferOps & IMAGE_PRE_CONVOLUTION_BITS,
 366                                       width, (GLfloat (*)[4]) dest);
 367          dest += width * 4;
 368       }
 369
 370       /* do convolution */
 371       if (ctx->Pixel.Convolution2DEnabled) {
 372          _mesa_convolve_2d_image(ctx, &width, &height, tmpImage, convImage);
 373       }
 374       else {
 375          ASSERT(ctx->Pixel.Separable2DEnabled);
 376          _mesa_convolve_sep_image(ctx, &width, &height, tmpImage, convImage);
 377       }
 378       _mesa_free(tmpImage);
 379
 380       /* finish transfer ops and pack the resulting image */
 381       src = convImage;
 382       for (row = 0; row < height; row++) {
 383          GLvoid *dest;
 384          dest = _mesa_image_address2d(packing, pixels, width, height,
 385                                       format, type, row, 0);
 386          _mesa_pack_rgba_span_float(ctx, width, (GLfloat (*)[4]) src,
 387                                     format, type, dest, packing,
 388                                     transferOps & IMAGE_POST_CONVOLUTION_BITS);
 389          src += width * 4;
 390       }
 391       _mesa_free(convImage);
 392    }
 393    else {
 394       /* no convolution */
 395       const GLint dstStride
 396          = _mesa_image_row_stride(packing, width, format, type);
 397       GLfloat (*rgba)[4] = swrast->SpanArrays->color.sz4.rgba;
 398       GLint row;
 399       GLubyte *dst = _mesa_image_address2d(packing, pixels, width, height,
 400                                            format, type, 0, 0);
 401
 402       for (row = 0; row < height; row++, y++) {
 403
 404          /* Get float rgba pixels */
 405          if (fb->Visual.rgbMode) {
 406             _swrast_read_rgba_span(ctx, rb, width, x, y, GL_FLOAT, rgba);
 407          }
 408          else {
 409             /* read CI and convert to RGBA */
 410             GLuint index[MAX_WIDTH];
 411             ASSERT(rb->DataType == GL_UNSIGNED_INT);
 412             rb->GetRow(ctx, rb, width, x, y, index);
 413             _mesa_apply_ci_transfer_ops(ctx,
 414                                         transferOps & IMAGE_SHIFT_OFFSET_BIT,
 415                                         width, index);
 416             _mesa_map_ci_to_rgba(ctx, width, index, rgba);
 417          }
 418
 419          /* apply fudge factor for shallow color buffers */
 420          if (fb->Visual.redBits < 8 ||
 421              fb->Visual.greenBits < 8 ||
 422              fb->Visual.blueBits < 8) {
 423             adjust_colors(ctx, width, rgba);
 424          }
 425
 426          /* pack the row of RGBA pixels into user's buffer */
 427          _mesa_pack_rgba_span_float(ctx, width, rgba, format, type, dst,
 428                                     packing, transferOps);
 429
 430          dst += dstStride;
 431       }
 432    }
 433 }
 434
 435
 436 /**
 437  * Read combined depth/stencil values.
 438  * We'll have already done error checking to be sure the expected
 439  * depth and stencil buffers really exist.
 440  */
 441 static void
 442 read_depth_stencil_pixels(GLcontext *ctx,
 443                           GLint x, GLint y,
 444                           GLsizei width, GLsizei height,
 445                           GLenum type, GLvoid *pixels,
 446                           const struct gl_pixelstore_attrib *packing )
 447 {
 448    const GLboolean scaleOrBias
 449       = ctx->Pixel.DepthScale != 1.0 || ctx->Pixel.DepthBias != 0.0;
 450    const GLboolean stencilTransfer = ctx->Pixel.IndexShift
 451       || ctx->Pixel.IndexOffset || ctx->Pixel.MapStencilFlag;
 452    struct gl_renderbuffer *depthRb, *stencilRb;
 453
 454    depthRb = ctx->ReadBuffer->_DepthBuffer;
 455    stencilRb = ctx->ReadBuffer->_StencilBuffer;
 456
 457    ASSERT(depthRb);
 458    ASSERT(stencilRb);
 459
 460    depthRb = ctx->ReadBuffer->Attachment[BUFFER_DEPTH].Renderbuffer;
 461    stencilRb = ctx->ReadBuffer->Attachment[BUFFER_STENCIL].Renderbuffer;
 462
 463    if (depthRb->_BaseFormat == GL_DEPTH_STENCIL_EXT &&
 464        stencilRb->_BaseFormat == GL_DEPTH_STENCIL_EXT &&
 465        depthRb == stencilRb &&
 466        !scaleOrBias &&
 467        !stencilTransfer) {
 468       /* This is the ideal case.
 469        * Reading GL_DEPTH_STENCIL pixels from combined depth/stencil buffer.
 470        * Plus, no pixel transfer ops to worry about!
 471        */
 472       GLint i;
 473       GLint dstStride = _mesa_image_row_stride(packing, width,
 474                                                GL_DEPTH_STENCIL_EXT, type);
 475       GLubyte *dst = (GLubyte *) _mesa_image_address2d(packing, pixels,
 476                                                        width, height,
 477                                                        GL_DEPTH_STENCIL_EXT,
 478                                                        type, 0, 0);
 479       for (i = 0; i < height; i++) {
 480          depthRb->GetRow(ctx, depthRb, width, x, y + i, dst);
 481          dst += dstStride;
 482       }
 483    }
 484    else {
 485       /* Reading GL_DEPTH_STENCIL pixels from separate depth/stencil buffers,
 486        * or we need pixel transfer.
 487        */
 488       GLint i;
 489       depthRb = ctx->ReadBuffer->_DepthBuffer;
 490       stencilRb = ctx->ReadBuffer->_StencilBuffer;
 491
 492       for (i = 0; i < height; i++) {
 493          GLstencil stencilVals[MAX_WIDTH];
 494
 495          GLuint *depthStencilDst = (GLuint *)
 496             _mesa_image_address2d(packing, pixels, width, height,
 497                                   GL_DEPTH_STENCIL_EXT, type, i, 0);
 498
 499          _swrast_read_stencil_span(ctx, stencilRb, width,
 500                                    x, y + i, stencilVals);
 501
 502          if (!scaleOrBias && !stencilTransfer
 503              && ctx->ReadBuffer->Visual.depthBits == 24) {
 504             /* ideal case */
 505             GLuint zVals[MAX_WIDTH]; /* 24-bit values! */
 506             GLint j;
 507             ASSERT(depthRb->DataType == GL_UNSIGNED_INT);
 508             /* note, we've already been clipped */
 509             depthRb->GetRow(ctx, depthRb, width, x, y + i, zVals);
 510             for (j = 0; j < width; j++) {
 511                depthStencilDst[j] = (zVals[j] << 8) | (stencilVals[j] & 0xff);
 512             }
 513          }
 514          else {
 515             /* general case */
 516             GLfloat depthVals[MAX_WIDTH];
 517             _swrast_read_depth_span_float(ctx, depthRb, width, x, y + i,
 518                                           depthVals);
 519             _mesa_pack_depth_stencil_span(ctx, width, depthStencilDst,
 520                                           depthVals, stencilVals, packing);
 521          }
 522       }
 523    }
 524 }
 525
 526
 527
 528 /**
 529  * Software fallback routine for ctx->Driver.ReadPixels().
 530  * By time we get here, all error checking will have been done.
 531  */
 532 void
 533 _swrast_ReadPixels( GLcontext *ctx,
 534                     GLint x, GLint y, GLsizei width, GLsizei height,
 535                     GLenum format, GLenum type,
 536                     const struct gl_pixelstore_attrib *packing,
 537                     GLvoid *pixels )
 538 {
 539    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 540    struct gl_pixelstore_attrib clippedPacking = *packing;
 541
 542    /* Need to do RENDER_START before clipping or anything else since this
 543     * is where a driver may grab the hw lock and get an updated window
 544     * size.
 545     */
 546    RENDER_START(swrast, ctx);
 547
 548    if (ctx->NewState)
 549       _mesa_update_state(ctx);
 550
 551    if (swrast->NewState)
 552       _swrast_validate_derived( ctx );
 553
 554    /* Do all needed clipping here, so that we can forget about it later */
 555    if (!_mesa_clip_readpixels(ctx, &x, &y, &width, &height, &clippedPacking)) {
 556       /* The ReadPixels region is totally outside the window bounds */
 557       goto end;
 558    }
 559
 560    if (clippedPacking.BufferObj->Name) {
 561       /* pack into PBO */
 562       GLubyte *buf;
 563       if (!_mesa_validate_pbo_access(2, &clippedPacking, width, height, 1,
 564                                      format, type, pixels)) {
 565          _mesa_error(ctx, GL_INVALID_OPERATION,
 566                      "glReadPixels(invalid PBO access)");
 567          goto end;
 568       }
 569       buf = (GLubyte *) ctx->Driver.MapBuffer(ctx, GL_PIXEL_PACK_BUFFER_EXT,
 570                                               GL_WRITE_ONLY_ARB,
 571                                               clippedPacking.BufferObj);
 572       if (!buf) {
 573          /* buffer is already mapped - that's an error */
 574          _mesa_error(ctx, GL_INVALID_OPERATION, "glReadPixels(PBO is mapped)");
 575          goto end;
 576       }
 577       pixels = ADD_POINTERS(buf, pixels);
 578    }
 579
 580    switch (format) {
 581       case GL_COLOR_INDEX:
 582          read_index_pixels(ctx, x, y, width, height, type, pixels,
 583                            &clippedPacking);
 584          break;
 585       case GL_STENCIL_INDEX:
 586          read_stencil_pixels(ctx, x, y, width, height, type, pixels,
 587                              &clippedPacking);
 588          break;
 589       case GL_DEPTH_COMPONENT:
 590          read_depth_pixels(ctx, x, y, width, height, type, pixels,
 591                            &clippedPacking);
 592          break;
 593       case GL_RED:
 594       case GL_GREEN:
 595       case GL_BLUE:
 596       case GL_ALPHA:
 597       case GL_RGB:
 598       case GL_LUMINANCE:
 599       case GL_LUMINANCE_ALPHA:
 600       case GL_RGBA:
 601       case GL_BGR:
 602       case GL_BGRA:
 603       case GL_ABGR_EXT:
 604          read_rgba_pixels(ctx, x, y, width, height,
 605                           format, type, pixels, &clippedPacking);
 606          break;
 607       case GL_DEPTH_STENCIL_EXT:
 608          read_depth_stencil_pixels(ctx, x, y, width, height,
 609                                    type, pixels, &clippedPacking);
 610          break;
 611       default:
 612          _mesa_problem(ctx, "unexpected format in _swrast_ReadPixels");
 613          /* don't return yet, clean-up */
 614    }
 615
 616
 617 end:
 618    RENDER_FINISH(swrast, ctx);
 619
 620    if (clippedPacking.BufferObj->Name) {
 621       /* done with PBO so unmap it now */
 622       ctx->Driver.UnmapBuffer(ctx, GL_PIXEL_PACK_BUFFER_EXT,
 623                               clippedPacking.BufferObj);
 624    }
 625 }