src/mesa/swrast/s_readpix.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  6.5.3
   4  *
   5  * Copyright (C) 1999-2007  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    if (!rb)
  58       return;
  59
  60    /* width should never be > MAX_WIDTH since we did clipping earlier */
  61    ASSERT(width <= MAX_WIDTH);
  62
  63    /* process image row by row */
  64    for (i = 0; i < height; i++) {
  65       GLuint index[MAX_WIDTH];
  66       GLvoid *dest;
  67       ASSERT(rb->DataType == GL_UNSIGNED_INT);
  68       rb->GetRow(ctx, rb, width, x, y + i, index);
  69
  70       dest = _mesa_image_address2d(packing, pixels, width, height,
  71                                    GL_COLOR_INDEX, type, i, 0);
  72
  73       _mesa_pack_index_span(ctx, width, type, dest, index,
  74                             &ctx->Pack, ctx->_ImageTransferState);
  75    }
  76 }
  77
  78
  79
  80 /**
  81  * Read pixels for format=GL_DEPTH_COMPONENT.
  82  */
  83 static void
  84 read_depth_pixels( GLcontext *ctx,
  85                    GLint x, GLint y,
  86                    GLsizei width, GLsizei height,
  87                    GLenum type, GLvoid *pixels,
  88                    const struct gl_pixelstore_attrib *packing )
  89 {
  90    struct gl_framebuffer *fb = ctx->ReadBuffer;
  91    struct gl_renderbuffer *rb = fb->_DepthBuffer;
  92    const GLboolean biasOrScale
  93       = ctx->Pixel.DepthScale != 1.0 || ctx->Pixel.DepthBias != 0.0;
  94
  95    if (!rb)
  96       return;
  97
  98    /* clipping should have been done already */
  99    ASSERT(x >= 0);
 100    ASSERT(y >= 0);
 101    ASSERT(x + width <= (GLint) rb->Width);
 102    ASSERT(y + height <= (GLint) rb->Height);
 103    /* width should never be > MAX_WIDTH since we did clipping earlier */
 104    ASSERT(width <= MAX_WIDTH);
 105
 106    if (type == GL_UNSIGNED_SHORT && fb->Visual.depthBits == 16
 107        && !biasOrScale && !packing->SwapBytes) {
 108       /* Special case: directly read 16-bit unsigned depth values. */
 109       GLint j;
 110       ASSERT(rb->InternalFormat == GL_DEPTH_COMPONENT16);
 111       ASSERT(rb->DataType == GL_UNSIGNED_SHORT);
 112       for (j = 0; j < height; j++, y++) {
 113          void *dest =_mesa_image_address2d(packing, pixels, width, height,
 114                                            GL_DEPTH_COMPONENT, type, j, 0);
 115          rb->GetRow(ctx, rb, width, x, y, dest);
 116       }
 117    }
 118    else if (type == GL_UNSIGNED_INT && fb->Visual.depthBits == 24
 119             && !biasOrScale && !packing->SwapBytes) {
 120       /* Special case: directly read 24-bit unsigned depth values. */
 121       GLint j;
 122       ASSERT(rb->InternalFormat == GL_DEPTH_COMPONENT32);
 123       ASSERT(rb->DataType == GL_UNSIGNED_INT);
 124       for (j = 0; j < height; j++, y++) {
 125          GLuint *dest = (GLuint *)
 126             _mesa_image_address2d(packing, pixels, width, height,
 127                                   GL_DEPTH_COMPONENT, type, j, 0);
 128          GLint k;
 129          rb->GetRow(ctx, rb, width, x, y, dest);
 130          /* convert range from 24-bit to 32-bit */
 131          for (k = 0; k < width; k++) {
 132             dest[k] = (dest[k] << 8) | (dest[k] >> 24);
 133          }
 134       }
 135    }
 136    else if (type == GL_UNSIGNED_INT && fb->Visual.depthBits == 32
 137             && !biasOrScale && !packing->SwapBytes) {
 138       /* Special case: directly read 32-bit unsigned depth values. */
 139       GLint j;
 140       ASSERT(rb->InternalFormat == GL_DEPTH_COMPONENT32);
 141       ASSERT(rb->DataType == GL_UNSIGNED_INT);
 142       for (j = 0; j < height; j++, y++) {
 143          void *dest = _mesa_image_address2d(packing, pixels, width, height,
 144                                             GL_DEPTH_COMPONENT, type, j, 0);
 145          rb->GetRow(ctx, rb, width, x, y, dest);
 146       }
 147    }
 148    else {
 149       /* General case (slower) */
 150       GLint j;
 151       for (j = 0; j < height; j++, y++) {
 152          GLfloat depthValues[MAX_WIDTH];
 153          GLvoid *dest = _mesa_image_address2d(packing, pixels, width, height,
 154                                               GL_DEPTH_COMPONENT, type, j, 0);
 155          _swrast_read_depth_span_float(ctx, rb, width, x, y, depthValues);
 156          _mesa_pack_depth_span(ctx, width, dest, type, depthValues, packing);
 157       }
 158    }
 159 }
 160
 161
 162 /**
 163  * Read pixels for format=GL_STENCIL_INDEX.
 164  */
 165 static void
 166 read_stencil_pixels( GLcontext *ctx,
 167                      GLint x, GLint y,
 168                      GLsizei width, GLsizei height,
 169                      GLenum type, GLvoid *pixels,
 170                      const struct gl_pixelstore_attrib *packing )
 171 {
 172    struct gl_framebuffer *fb = ctx->ReadBuffer;
 173    struct gl_renderbuffer *rb = fb->_StencilBuffer;
 174    GLint j;
 175
 176    if (!rb)
 177       return;
 178
 179    /* width should never be > MAX_WIDTH since we did clipping earlier */
 180    ASSERT(width <= MAX_WIDTH);
 181
 182    /* process image row by row */
 183    for (j=0;j<height;j++,y++) {
 184       GLvoid *dest;
 185       GLstencil stencil[MAX_WIDTH];
 186
 187       _swrast_read_stencil_span(ctx, rb, width, x, y, stencil);
 188
 189       dest = _mesa_image_address2d(packing, pixels, width, height,
 190                                    GL_STENCIL_INDEX, type, j, 0);
 191
 192       _mesa_pack_stencil_span(ctx, width, type, dest, stencil, packing);
 193    }
 194 }
 195
 196
 197
 198 /**
 199  * Optimized glReadPixels for particular pixel formats when pixel
 200  * scaling, biasing, mapping, etc. are disabled.
 201  * \return GL_TRUE if success, GL_FALSE if unable to do the readpixels
 202  */
 203 static GLboolean
 204 fast_read_rgba_pixels( GLcontext *ctx,
 205                        GLint x, GLint y,
 206                        GLsizei width, GLsizei height,
 207                        GLenum format, GLenum type,
 208                        GLvoid *pixels,
 209                        const struct gl_pixelstore_attrib *packing,
 210                        GLbitfield transferOps)
 211 {
 212    struct gl_renderbuffer *rb = ctx->ReadBuffer->_ColorReadBuffer;
 213
 214    if (!rb)
 215       return GL_FALSE;
 216
 217    ASSERT(rb->_BaseFormat == GL_RGBA || rb->_BaseFormat == GL_RGB);
 218
 219    /* clipping should have already been done */
 220    ASSERT(x + width <= (GLint) rb->Width);
 221    ASSERT(y + height <= (GLint) rb->Height);
 222
 223    /* check for things we can't handle here */
 224    if (transferOps ||
 225        packing->SwapBytes ||
 226        packing->LsbFirst) {
 227       return GL_FALSE;
 228    }
 229
 230    if (format == GL_RGBA && rb->DataType == type) {
 231       const GLint dstStride = _mesa_image_row_stride(packing, width,
 232                                                      format, type);
 233       GLubyte *dest
 234          = (GLubyte *) _mesa_image_address2d(packing, pixels, width, height,
 235                                              format, type, 0, 0);
 236       GLint row;
 237       ASSERT(rb->GetRow);
 238       for (row = 0; row < height; row++) {
 239          rb->GetRow(ctx, rb, width, x, y + row, dest);
 240          dest += dstStride;
 241       }
 242       return GL_TRUE;
 243    }
 244
 245    if (format == GL_RGB &&
 246        rb->DataType == GL_UNSIGNED_BYTE &&
 247        type == GL_UNSIGNED_BYTE) {
 248       const GLint dstStride = _mesa_image_row_stride(packing, width,
 249                                                      format, type);
 250       GLubyte *dest
 251          = (GLubyte *) _mesa_image_address2d(packing, pixels, width, height,
 252                                              format, type, 0, 0);
 253       GLint row;
 254       ASSERT(rb->GetRow);
 255       for (row = 0; row < height; row++) {
 256          GLubyte tempRow[MAX_WIDTH][4];
 257          GLint col;
 258          rb->GetRow(ctx, rb, width, x, y + row, tempRow);
 259          /* convert RGBA to RGB */
 260          for (col = 0; col < width; col++) {
 261             dest[col * 3 + 0] = tempRow[col][0];
 262             dest[col * 3 + 1] = tempRow[col][1];
 263             dest[col * 3 + 2] = tempRow[col][2];
 264          }
 265          dest += dstStride;
 266       }
 267       return GL_TRUE;
 268    }
 269
 270    /* not handled */
 271    return GL_FALSE;
 272 }
 273
 274
 275 /**
 276  * When we're using a low-precision color buffer (like 16-bit 5/6/5)
 277  * we have to adjust our color values a bit to pass conformance.
 278  * The problem is when a 5 or 6-bit color value is convert to an 8-bit
 279  * value and then a floating point value, the floating point values don't
 280  * increment uniformly as the 5 or 6-bit value is incremented.
 281  *
 282  * This function adjusts floating point values to compensate.
 283  */
 284 static void
 285 adjust_colors(GLcontext *ctx, GLuint n, GLfloat rgba[][4])
 286 {
 287    const GLuint rShift = 8 - ctx->Visual.redBits;
 288    const GLuint gShift = 8 - ctx->Visual.greenBits;
 289    const GLuint bShift = 8 - ctx->Visual.blueBits;
 290    const GLfloat rScale = 1.0F / (GLfloat) ((1 << ctx->Visual.redBits  ) - 1);
 291    const GLfloat gScale = 1.0F / (GLfloat) ((1 << ctx->Visual.greenBits) - 1);
 292    const GLfloat bScale = 1.0F / (GLfloat) ((1 << ctx->Visual.blueBits ) - 1);
 293    GLuint i;
 294    for (i = 0; i < n; i++) {
 295       GLint r, g, b;
 296       /* convert float back to ubyte */
 297       CLAMPED_FLOAT_TO_UBYTE(r, rgba[i][RCOMP]);
 298       CLAMPED_FLOAT_TO_UBYTE(g, rgba[i][GCOMP]);
 299       CLAMPED_FLOAT_TO_UBYTE(b, rgba[i][BCOMP]);
 300       /* using only the N most significant bits of the ubyte value, convert to
 301        * float in [0,1].
 302        */
 303       rgba[i][RCOMP] = (GLfloat) (r >> rShift) * rScale;
 304       rgba[i][GCOMP] = (GLfloat) (g >> gShift) * gScale;
 305       rgba[i][BCOMP] = (GLfloat) (b >> bShift) * bScale;
 306    }
 307 }
 308
 309
 310
 311 /*
 312  * Read R, G, B, A, RGB, L, or LA pixels.
 313  */
 314 static void
 315 read_rgba_pixels( GLcontext *ctx,
 316                   GLint x, GLint y,
 317                   GLsizei width, GLsizei height,
 318                   GLenum format, GLenum type, GLvoid *pixels,
 319                   const struct gl_pixelstore_attrib *packing )
 320 {
 321    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 322    GLbitfield transferOps = ctx->_ImageTransferState;
 323    struct gl_framebuffer *fb = ctx->ReadBuffer;
 324    struct gl_renderbuffer *rb = fb->_ColorReadBuffer;
 325
 326    if (!rb)
 327       return;
 328
 329    if (type == GL_FLOAT && ((ctx->Color.ClampReadColor == GL_TRUE) ||
 330                             (ctx->Color.ClampReadColor == GL_FIXED_ONLY_ARB &&
 331                              rb->DataType != GL_FLOAT)))
 332       transferOps |= IMAGE_CLAMP_BIT;
 333
 334    /* Try optimized path first */
 335    if (fast_read_rgba_pixels(ctx, x, y, width, height,
 336                              format, type, pixels, packing, transferOps)) {
 337       return; /* done! */
 338    }
 339
 340    /* width should never be > MAX_WIDTH since we did clipping earlier */
 341    ASSERT(width <= MAX_WIDTH);
 342
 343    if (ctx->Pixel.Convolution2DEnabled || ctx->Pixel.Separable2DEnabled) {
 344       GLfloat *dest, *src, *tmpImage, *convImage;
 345       GLint row;
 346
 347       tmpImage = (GLfloat *) _mesa_malloc(width * height * 4 * sizeof(GLfloat));
 348       if (!tmpImage) {
 349          _mesa_error(ctx, GL_OUT_OF_MEMORY, "glReadPixels");
 350          return;
 351       }
 352       convImage = (GLfloat *) _mesa_malloc(width * height * 4 * sizeof(GLfloat));
 353       if (!convImage) {
 354          _mesa_free(tmpImage);
 355          _mesa_error(ctx, GL_OUT_OF_MEMORY, "glReadPixels");
 356          return;
 357       }
 358
 359       /* read full RGBA, FLOAT image */
 360       dest = tmpImage;
 361       for (row = 0; row < height; row++, y++) {
 362          if (fb->Visual.rgbMode) {
 363             _swrast_read_rgba_span(ctx, rb, width, x, y, GL_FLOAT, dest);
 364          }
 365          else {
 366             GLuint index[MAX_WIDTH];
 367             ASSERT(rb->DataType == GL_UNSIGNED_INT);
 368             rb->GetRow(ctx, rb, width, x, y, index);
 369             _mesa_apply_ci_transfer_ops(ctx,
 370                                         transferOps & IMAGE_SHIFT_OFFSET_BIT,
 371                                         width, index);
 372             _mesa_map_ci_to_rgba(ctx, width, index, (GLfloat (*)[4]) dest);
 373          }
 374          _mesa_apply_rgba_transfer_ops(ctx,
 375                                       transferOps & IMAGE_PRE_CONVOLUTION_BITS,
 376                                       width, (GLfloat (*)[4]) dest);
 377          dest += width * 4;
 378       }
 379
 380       /* do convolution */
 381       if (ctx->Pixel.Convolution2DEnabled) {
 382          _mesa_convolve_2d_image(ctx, &width, &height, tmpImage, convImage);
 383       }
 384       else {
 385          ASSERT(ctx->Pixel.Separable2DEnabled);
 386          _mesa_convolve_sep_image(ctx, &width, &height, tmpImage, convImage);
 387       }
 388       _mesa_free(tmpImage);
 389
 390       /* finish transfer ops and pack the resulting image */
 391       src = convImage;
 392       for (row = 0; row < height; row++) {
 393          GLvoid *dest;
 394          dest = _mesa_image_address2d(packing, pixels, width, height,
 395                                       format, type, row, 0);
 396          _mesa_pack_rgba_span_float(ctx, width, (GLfloat (*)[4]) src,
 397                                     format, type, dest, packing,
 398                                     transferOps & IMAGE_POST_CONVOLUTION_BITS);
 399          src += width * 4;
 400       }
 401       _mesa_free(convImage);
 402    }
 403    else {
 404       /* no convolution */
 405       const GLint dstStride
 406          = _mesa_image_row_stride(packing, width, format, type);
 407       GLfloat (*rgba)[4] = swrast->SpanArrays->attribs[FRAG_ATTRIB_COL0];
 408       GLint row;
 409       GLubyte *dst
 410          = (GLubyte *) _mesa_image_address2d(packing, pixels, width, height,
 411                                              format, type, 0, 0);
 412
 413       for (row = 0; row < height; row++, y++) {
 414
 415          /* Get float rgba pixels */
 416          if (fb->Visual.rgbMode) {
 417             _swrast_read_rgba_span(ctx, rb, width, x, y, GL_FLOAT, rgba);
 418          }
 419          else {
 420             /* read CI and convert to RGBA */
 421             GLuint index[MAX_WIDTH];
 422             ASSERT(rb->DataType == GL_UNSIGNED_INT);
 423             rb->GetRow(ctx, rb, width, x, y, index);
 424             _mesa_apply_ci_transfer_ops(ctx,
 425                                         transferOps & IMAGE_SHIFT_OFFSET_BIT,
 426                                         width, index);
 427             _mesa_map_ci_to_rgba(ctx, width, index, rgba);
 428          }
 429
 430          /* apply fudge factor for shallow color buffers */
 431          if (fb->Visual.redBits < 8 ||
 432              fb->Visual.greenBits < 8 ||
 433              fb->Visual.blueBits < 8) {
 434             adjust_colors(ctx, width, rgba);
 435          }
 436
 437          /* pack the row of RGBA pixels into user's buffer */
 438          _mesa_pack_rgba_span_float(ctx, width, rgba, format, type, dst,
 439                                     packing, transferOps);
 440
 441          dst += dstStride;
 442       }
 443    }
 444 }
 445
 446
 447 /**
 448  * Read combined depth/stencil values.
 449  * We'll have already done error checking to be sure the expected
 450  * depth and stencil buffers really exist.
 451  */
 452 static void
 453 read_depth_stencil_pixels(GLcontext *ctx,
 454                           GLint x, GLint y,
 455                           GLsizei width, GLsizei height,
 456                           GLenum type, GLvoid *pixels,
 457                           const struct gl_pixelstore_attrib *packing )
 458 {
 459    const GLboolean scaleOrBias
 460       = ctx->Pixel.DepthScale != 1.0 || ctx->Pixel.DepthBias != 0.0;
 461    const GLboolean stencilTransfer = ctx->Pixel.IndexShift
 462       || ctx->Pixel.IndexOffset || ctx->Pixel.MapStencilFlag;
 463    struct gl_renderbuffer *depthRb, *stencilRb;
 464
 465    depthRb = ctx->ReadBuffer->_DepthBuffer;
 466    stencilRb = ctx->ReadBuffer->_StencilBuffer;
 467
 468    if (!depthRb || !stencilRb)
 469       return;
 470
 471    depthRb = ctx->ReadBuffer->Attachment[BUFFER_DEPTH].Renderbuffer;
 472    stencilRb = ctx->ReadBuffer->Attachment[BUFFER_STENCIL].Renderbuffer;
 473
 474    if (depthRb->_BaseFormat == GL_DEPTH_STENCIL_EXT &&
 475        stencilRb->_BaseFormat == GL_DEPTH_STENCIL_EXT &&
 476        depthRb == stencilRb &&
 477        !scaleOrBias &&
 478        !stencilTransfer) {
 479       /* This is the ideal case.
 480        * Reading GL_DEPTH_STENCIL pixels from combined depth/stencil buffer.
 481        * Plus, no pixel transfer ops to worry about!
 482        */
 483       GLint i;
 484       GLint dstStride = _mesa_image_row_stride(packing, width,
 485                                                GL_DEPTH_STENCIL_EXT, type);
 486       GLubyte *dst = (GLubyte *) _mesa_image_address2d(packing, pixels,
 487                                                        width, height,
 488                                                        GL_DEPTH_STENCIL_EXT,
 489                                                        type, 0, 0);
 490       for (i = 0; i < height; i++) {
 491          depthRb->GetRow(ctx, depthRb, width, x, y + i, dst);
 492          dst += dstStride;
 493       }
 494    }
 495    else {
 496       /* Reading GL_DEPTH_STENCIL pixels from separate depth/stencil buffers,
 497        * or we need pixel transfer.
 498        */
 499       GLint i;
 500       depthRb = ctx->ReadBuffer->_DepthBuffer;
 501       stencilRb = ctx->ReadBuffer->_StencilBuffer;
 502
 503       for (i = 0; i < height; i++) {
 504          GLstencil stencilVals[MAX_WIDTH];
 505
 506          GLuint *depthStencilDst = (GLuint *)
 507             _mesa_image_address2d(packing, pixels, width, height,
 508                                   GL_DEPTH_STENCIL_EXT, type, i, 0);
 509
 510          _swrast_read_stencil_span(ctx, stencilRb, width,
 511                                    x, y + i, stencilVals);
 512
 513          if (!scaleOrBias && !stencilTransfer
 514              && ctx->ReadBuffer->Visual.depthBits == 24) {
 515             /* ideal case */
 516             GLuint zVals[MAX_WIDTH]; /* 24-bit values! */
 517             GLint j;
 518             ASSERT(depthRb->DataType == GL_UNSIGNED_INT);
 519             /* note, we've already been clipped */
 520             depthRb->GetRow(ctx, depthRb, width, x, y + i, zVals);
 521             for (j = 0; j < width; j++) {
 522                depthStencilDst[j] = (zVals[j] << 8) | (stencilVals[j] & 0xff);
 523             }
 524          }
 525          else {
 526             /* general case */
 527             GLfloat depthVals[MAX_WIDTH];
 528             _swrast_read_depth_span_float(ctx, depthRb, width, x, y + i,
 529                                           depthVals);
 530             _mesa_pack_depth_stencil_span(ctx, width, depthStencilDst,
 531                                           depthVals, stencilVals, packing);
 532          }
 533       }
 534    }
 535 }
 536
 537
 538
 539 /**
 540  * Software fallback routine for ctx->Driver.ReadPixels().
 541  * By time we get here, all error checking will have been done.
 542  */
 543 void
 544 _swrast_ReadPixels( GLcontext *ctx,
 545                     GLint x, GLint y, GLsizei width, GLsizei height,
 546                     GLenum format, GLenum type,
 547                     const struct gl_pixelstore_attrib *packing,
 548                     GLvoid *pixels )
 549 {
 550    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 551    struct gl_pixelstore_attrib clippedPacking = *packing;
 552
 553    /* Need to do RENDER_START before clipping or anything else since this
 554     * is where a driver may grab the hw lock and get an updated window
 555     * size.
 556     */
 557    RENDER_START(swrast, ctx);
 558
 559    if (ctx->NewState)
 560       _mesa_update_state(ctx);
 561
 562    if (swrast->NewState)
 563       _swrast_validate_derived( ctx );
 564
 565    /* Do all needed clipping here, so that we can forget about it later */
 566    if (!_mesa_clip_readpixels(ctx, &x, &y, &width, &height, &clippedPacking)) {
 567       /* The ReadPixels region is totally outside the window bounds */
 568       goto end;
 569    }
 570
 571    if (clippedPacking.BufferObj->Name) {
 572       /* pack into PBO */
 573       GLubyte *buf;
 574       if (!_mesa_validate_pbo_access(2, &clippedPacking, width, height, 1,
 575                                      format, type, pixels)) {
 576          _mesa_error(ctx, GL_INVALID_OPERATION,
 577                      "glReadPixels(invalid PBO access)");
 578          goto end;
 579       }
 580       buf = (GLubyte *) ctx->Driver.MapBuffer(ctx, GL_PIXEL_PACK_BUFFER_EXT,
 581                                               GL_WRITE_ONLY_ARB,
 582                                               clippedPacking.BufferObj);
 583       if (!buf) {
 584          /* buffer is already mapped - that's an error */
 585          _mesa_error(ctx, GL_INVALID_OPERATION, "glReadPixels(PBO is mapped)");
 586          goto end;
 587       }
 588       pixels = ADD_POINTERS(buf, pixels);
 589    }
 590
 591    switch (format) {
 592       case GL_COLOR_INDEX:
 593          read_index_pixels(ctx, x, y, width, height, type, pixels,
 594                            &clippedPacking);
 595          break;
 596       case GL_STENCIL_INDEX:
 597          read_stencil_pixels(ctx, x, y, width, height, type, pixels,
 598                              &clippedPacking);
 599          break;
 600       case GL_DEPTH_COMPONENT:
 601          read_depth_pixels(ctx, x, y, width, height, type, pixels,
 602                            &clippedPacking);
 603          break;
 604       case GL_RED:
 605       case GL_GREEN:
 606       case GL_BLUE:
 607       case GL_ALPHA:
 608       case GL_RGB:
 609       case GL_LUMINANCE:
 610       case GL_LUMINANCE_ALPHA:
 611       case GL_RGBA:
 612       case GL_BGR:
 613       case GL_BGRA:
 614       case GL_ABGR_EXT:
 615          read_rgba_pixels(ctx, x, y, width, height,
 616                           format, type, pixels, &clippedPacking);
 617          break;
 618       case GL_DEPTH_STENCIL_EXT:
 619          read_depth_stencil_pixels(ctx, x, y, width, height,
 620                                    type, pixels, &clippedPacking);
 621          break;
 622       default:
 623          _mesa_problem(ctx, "unexpected format in _swrast_ReadPixels");
 624          /* don't return yet, clean-up */
 625    }
 626
 627
 628 end:
 629    RENDER_FINISH(swrast, ctx);
 630
 631    if (clippedPacking.BufferObj->Name) {
 632       /* done with PBO so unmap it now */
 633       ctx->Driver.UnmapBuffer(ctx, GL_PIXEL_PACK_BUFFER_EXT,
 634                               clippedPacking.BufferObj);
 635    }
 636 }