src/mesa/swrast/s_readpix.c

   1 /*
   2  * Mesa 3-D graphics library
   3  * Version:  7.0.3
   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 "main/glheader.h"
  27 #include "main/bufferobj.h"
  28 #include "main/colormac.h"
  29 #include "main/convolve.h"
  30 #include "main/context.h"
  31 #include "main/feedback.h"
  32 #include "main/formats.h"
  33 #include "main/image.h"
  34 #include "main/macros.h"
  35 #include "main/imports.h"
  36 #include "main/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->Format == MESA_FORMAT_Z16);
 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->Format == MESA_FORMAT_X8_Z24 ||
 123              rb->Format == MESA_FORMAT_S8_Z24 ||
 124              rb->Format == MESA_FORMAT_Z24_X8 ||
 125              rb->Format == MESA_FORMAT_Z24_S8);
 126       ASSERT(rb->DataType == GL_UNSIGNED_INT ||
 127              rb->DataType == GL_UNSIGNED_INT_24_8);
 128       for (j = 0; j < height; j++, y++) {
 129          GLuint *dest = (GLuint *)
 130             _mesa_image_address2d(packing, pixels, width, height,
 131                                   GL_DEPTH_COMPONENT, type, j, 0);
 132          GLint k;
 133          rb->GetRow(ctx, rb, width, x, y, dest);
 134          /* convert range from 24-bit to 32-bit */
 135          if (rb->Format == MESA_FORMAT_X8_Z24 ||
 136              rb->Format == MESA_FORMAT_S8_Z24) {
 137             for (k = 0; k < width; k++) {
 138                /* Note: put MSByte of 24-bit value into LSByte */
 139                dest[k] = (dest[k] << 8) | ((dest[k] >> 16) & 0xff);
 140             }
 141          }
 142          else {
 143             for (k = 0; k < width; k++) {
 144                /* Note: fill in LSByte by replication */
 145                dest[k] = dest[k] | ((dest[k] >> 8) & 0xff);
 146             }
 147          }
 148       }
 149    }
 150    else if (type == GL_UNSIGNED_INT && fb->Visual.depthBits == 32
 151             && !biasOrScale && !packing->SwapBytes) {
 152       /* Special case: directly read 32-bit unsigned depth values. */
 153       GLint j;
 154       ASSERT(rb->Format == MESA_FORMAT_Z32);
 155       ASSERT(rb->DataType == GL_UNSIGNED_INT);
 156       for (j = 0; j < height; j++, y++) {
 157          void *dest = _mesa_image_address2d(packing, pixels, width, height,
 158                                             GL_DEPTH_COMPONENT, type, j, 0);
 159          rb->GetRow(ctx, rb, width, x, y, dest);
 160       }
 161    }
 162    else {
 163       /* General case (slower) */
 164       GLint j;
 165       for (j = 0; j < height; j++, y++) {
 166          GLfloat depthValues[MAX_WIDTH];
 167          GLvoid *dest = _mesa_image_address2d(packing, pixels, width, height,
 168                                               GL_DEPTH_COMPONENT, type, j, 0);
 169          _swrast_read_depth_span_float(ctx, rb, width, x, y, depthValues);
 170          _mesa_pack_depth_span(ctx, width, dest, type, depthValues, packing);
 171       }
 172    }
 173 }
 174
 175
 176 /**
 177  * Read pixels for format=GL_STENCIL_INDEX.
 178  */
 179 static void
 180 read_stencil_pixels( GLcontext *ctx,
 181                      GLint x, GLint y,
 182                      GLsizei width, GLsizei height,
 183                      GLenum type, GLvoid *pixels,
 184                      const struct gl_pixelstore_attrib *packing )
 185 {
 186    struct gl_framebuffer *fb = ctx->ReadBuffer;
 187    struct gl_renderbuffer *rb = fb->_StencilBuffer;
 188    GLint j;
 189
 190    if (!rb)
 191       return;
 192
 193    /* width should never be > MAX_WIDTH since we did clipping earlier */
 194    ASSERT(width <= MAX_WIDTH);
 195
 196    /* process image row by row */
 197    for (j=0;j<height;j++,y++) {
 198       GLvoid *dest;
 199       GLstencil stencil[MAX_WIDTH];
 200
 201       _swrast_read_stencil_span(ctx, rb, width, x, y, stencil);
 202
 203       dest = _mesa_image_address2d(packing, pixels, width, height,
 204                                    GL_STENCIL_INDEX, type, j, 0);
 205
 206       _mesa_pack_stencil_span(ctx, width, type, dest, stencil, packing);
 207    }
 208 }
 209
 210
 211
 212 /**
 213  * Optimized glReadPixels for particular pixel formats when pixel
 214  * scaling, biasing, mapping, etc. are disabled.
 215  * \return GL_TRUE if success, GL_FALSE if unable to do the readpixels
 216  */
 217 static GLboolean
 218 fast_read_rgba_pixels( GLcontext *ctx,
 219                        GLint x, GLint y,
 220                        GLsizei width, GLsizei height,
 221                        GLenum format, GLenum type,
 222                        GLvoid *pixels,
 223                        const struct gl_pixelstore_attrib *packing,
 224                        GLbitfield transferOps)
 225 {
 226    struct gl_renderbuffer *rb = ctx->ReadBuffer->_ColorReadBuffer;
 227
 228    if (!rb)
 229       return GL_FALSE;
 230
 231    ASSERT(rb->_BaseFormat == GL_RGBA || rb->_BaseFormat == GL_RGB);
 232
 233    /* clipping should have already been done */
 234    ASSERT(x + width <= (GLint) rb->Width);
 235    ASSERT(y + height <= (GLint) rb->Height);
 236
 237    /* check for things we can't handle here */
 238    if (transferOps ||
 239        packing->SwapBytes ||
 240        packing->LsbFirst) {
 241       return GL_FALSE;
 242    }
 243
 244    if (format == GL_RGBA && rb->DataType == type) {
 245       const GLint dstStride = _mesa_image_row_stride(packing, width,
 246                                                      format, type);
 247       GLubyte *dest
 248          = (GLubyte *) _mesa_image_address2d(packing, pixels, width, height,
 249                                              format, type, 0, 0);
 250       GLint row;
 251       ASSERT(rb->GetRow);
 252       for (row = 0; row < height; row++) {
 253          rb->GetRow(ctx, rb, width, x, y + row, dest);
 254          dest += dstStride;
 255       }
 256       return GL_TRUE;
 257    }
 258
 259    if (format == GL_RGB &&
 260        rb->DataType == GL_UNSIGNED_BYTE &&
 261        type == GL_UNSIGNED_BYTE) {
 262       const GLint dstStride = _mesa_image_row_stride(packing, width,
 263                                                      format, type);
 264       GLubyte *dest
 265          = (GLubyte *) _mesa_image_address2d(packing, pixels, width, height,
 266                                              format, type, 0, 0);
 267       GLint row;
 268       ASSERT(rb->GetRow);
 269       for (row = 0; row < height; row++) {
 270          GLubyte tempRow[MAX_WIDTH][4];
 271          GLint col;
 272          rb->GetRow(ctx, rb, width, x, y + row, tempRow);
 273          /* convert RGBA to RGB */
 274          for (col = 0; col < width; col++) {
 275             dest[col * 3 + 0] = tempRow[col][0];
 276             dest[col * 3 + 1] = tempRow[col][1];
 277             dest[col * 3 + 2] = tempRow[col][2];
 278          }
 279          dest += dstStride;
 280       }
 281       return GL_TRUE;
 282    }
 283
 284    /* not handled */
 285    return GL_FALSE;
 286 }
 287
 288
 289 /**
 290  * When we're using a low-precision color buffer (like 16-bit 5/6/5)
 291  * we have to adjust our color values a bit to pass conformance.
 292  * The problem is when a 5 or 6-bit color value is convert to an 8-bit
 293  * value and then a floating point value, the floating point values don't
 294  * increment uniformly as the 5 or 6-bit value is incremented.
 295  *
 296  * This function adjusts floating point values to compensate.
 297  */
 298 static void
 299 adjust_colors(GLcontext *ctx, GLuint n, GLfloat rgba[][4])
 300 {
 301    const GLuint rShift = 8 - ctx->Visual.redBits;
 302    const GLuint gShift = 8 - ctx->Visual.greenBits;
 303    const GLuint bShift = 8 - ctx->Visual.blueBits;
 304    const GLfloat rScale = 1.0F / (GLfloat) ((1 << ctx->Visual.redBits  ) - 1);
 305    const GLfloat gScale = 1.0F / (GLfloat) ((1 << ctx->Visual.greenBits) - 1);
 306    const GLfloat bScale = 1.0F / (GLfloat) ((1 << ctx->Visual.blueBits ) - 1);
 307    GLuint i;
 308    for (i = 0; i < n; i++) {
 309       GLint r, g, b;
 310       /* convert float back to ubyte */
 311       CLAMPED_FLOAT_TO_UBYTE(r, rgba[i][RCOMP]);
 312       CLAMPED_FLOAT_TO_UBYTE(g, rgba[i][GCOMP]);
 313       CLAMPED_FLOAT_TO_UBYTE(b, rgba[i][BCOMP]);
 314       /* using only the N most significant bits of the ubyte value, convert to
 315        * float in [0,1].
 316        */
 317       rgba[i][RCOMP] = (GLfloat) (r >> rShift) * rScale;
 318       rgba[i][GCOMP] = (GLfloat) (g >> gShift) * gScale;
 319       rgba[i][BCOMP] = (GLfloat) (b >> bShift) * bScale;
 320    }
 321 }
 322
 323
 324
 325 /*
 326  * Read R, G, B, A, RGB, L, or LA pixels.
 327  */
 328 static void
 329 read_rgba_pixels( GLcontext *ctx,
 330                   GLint x, GLint y,
 331                   GLsizei width, GLsizei height,
 332                   GLenum format, GLenum type, GLvoid *pixels,
 333                   const struct gl_pixelstore_attrib *packing )
 334 {
 335    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 336    GLbitfield transferOps = ctx->_ImageTransferState;
 337    struct gl_framebuffer *fb = ctx->ReadBuffer;
 338    struct gl_renderbuffer *rb = fb->_ColorReadBuffer;
 339
 340    if (!rb)
 341       return;
 342
 343    if (type == GL_FLOAT && ((ctx->Color.ClampReadColor == GL_TRUE) ||
 344                             (ctx->Color.ClampReadColor == GL_FIXED_ONLY_ARB &&
 345                              rb->DataType != GL_FLOAT)))
 346       transferOps |= IMAGE_CLAMP_BIT;
 347
 348    /* Try optimized path first */
 349    if (fast_read_rgba_pixels(ctx, x, y, width, height,
 350                              format, type, pixels, packing, transferOps)) {
 351       return; /* done! */
 352    }
 353
 354    /* width should never be > MAX_WIDTH since we did clipping earlier */
 355    ASSERT(width <= MAX_WIDTH);
 356
 357    if (ctx->Pixel.Convolution2DEnabled || ctx->Pixel.Separable2DEnabled) {
 358       GLfloat *dest, *src, *tmpImage, *convImage;
 359       GLint row;
 360
 361       tmpImage = (GLfloat *) _mesa_malloc(width * height * 4 * sizeof(GLfloat));
 362       if (!tmpImage) {
 363          _mesa_error(ctx, GL_OUT_OF_MEMORY, "glReadPixels");
 364          return;
 365       }
 366       convImage = (GLfloat *) _mesa_malloc(width * height * 4 * sizeof(GLfloat));
 367       if (!convImage) {
 368          _mesa_free(tmpImage);
 369          _mesa_error(ctx, GL_OUT_OF_MEMORY, "glReadPixels");
 370          return;
 371       }
 372
 373       /* read full RGBA, FLOAT image */
 374       dest = tmpImage;
 375       for (row = 0; row < height; row++, y++) {
 376          if (fb->Visual.rgbMode) {
 377             _swrast_read_rgba_span(ctx, rb, width, x, y, GL_FLOAT, dest);
 378          }
 379          else {
 380             GLuint index[MAX_WIDTH];
 381             ASSERT(rb->DataType == GL_UNSIGNED_INT);
 382             rb->GetRow(ctx, rb, width, x, y, index);
 383             _mesa_apply_ci_transfer_ops(ctx,
 384                                         transferOps & IMAGE_SHIFT_OFFSET_BIT,
 385                                         width, index);
 386             _mesa_map_ci_to_rgba(ctx, width, index, (GLfloat (*)[4]) dest);
 387          }
 388          _mesa_apply_rgba_transfer_ops(ctx,
 389                                       transferOps & IMAGE_PRE_CONVOLUTION_BITS,
 390                                       width, (GLfloat (*)[4]) dest);
 391          dest += width * 4;
 392       }
 393
 394       /* do convolution */
 395       if (ctx->Pixel.Convolution2DEnabled) {
 396          _mesa_convolve_2d_image(ctx, &width, &height, tmpImage, convImage);
 397       }
 398       else {
 399          ASSERT(ctx->Pixel.Separable2DEnabled);
 400          _mesa_convolve_sep_image(ctx, &width, &height, tmpImage, convImage);
 401       }
 402       _mesa_free(tmpImage);
 403
 404       /* finish transfer ops and pack the resulting image */
 405       src = convImage;
 406       for (row = 0; row < height; row++) {
 407          GLvoid *dest;
 408          dest = _mesa_image_address2d(packing, pixels, width, height,
 409                                       format, type, row, 0);
 410          _mesa_pack_rgba_span_float(ctx, width, (GLfloat (*)[4]) src,
 411                                     format, type, dest, packing,
 412                                     transferOps & IMAGE_POST_CONVOLUTION_BITS);
 413          src += width * 4;
 414       }
 415       _mesa_free(convImage);
 416    }
 417    else {
 418       /* no convolution */
 419       const GLint dstStride
 420          = _mesa_image_row_stride(packing, width, format, type);
 421       GLfloat (*rgba)[4] = swrast->SpanArrays->attribs[FRAG_ATTRIB_COL0];
 422       GLint row;
 423       GLubyte *dst
 424          = (GLubyte *) _mesa_image_address2d(packing, pixels, width, height,
 425                                              format, type, 0, 0);
 426
 427       /* make sure we don't apply 1D convolution */
 428       transferOps &= ~(IMAGE_CONVOLUTION_BIT |
 429                        IMAGE_POST_CONVOLUTION_SCALE_BIAS);
 430
 431       for (row = 0; row < height; row++, y++) {
 432
 433          /* Get float rgba pixels */
 434          if (fb->Visual.rgbMode) {
 435             _swrast_read_rgba_span(ctx, rb, width, x, y, GL_FLOAT, rgba);
 436          }
 437          else {
 438             /* read CI and convert to RGBA */
 439             GLuint index[MAX_WIDTH];
 440             ASSERT(rb->DataType == GL_UNSIGNED_INT);
 441             rb->GetRow(ctx, rb, width, x, y, index);
 442             _mesa_apply_ci_transfer_ops(ctx,
 443                                         transferOps & IMAGE_SHIFT_OFFSET_BIT,
 444                                         width, index);
 445             _mesa_map_ci_to_rgba(ctx, width, index, rgba);
 446          }
 447
 448          /* apply fudge factor for shallow color buffers */
 449          if (fb->Visual.redBits < 8 ||
 450              fb->Visual.greenBits < 8 ||
 451              fb->Visual.blueBits < 8) {
 452             adjust_colors(ctx, width, rgba);
 453          }
 454
 455          /* pack the row of RGBA pixels into user's buffer */
 456          _mesa_pack_rgba_span_float(ctx, width, rgba, format, type, dst,
 457                                     packing, transferOps);
 458
 459          dst += dstStride;
 460       }
 461    }
 462 }
 463
 464
 465 /**
 466  * Read combined depth/stencil values.
 467  * We'll have already done error checking to be sure the expected
 468  * depth and stencil buffers really exist.
 469  */
 470 static void
 471 read_depth_stencil_pixels(GLcontext *ctx,
 472                           GLint x, GLint y,
 473                           GLsizei width, GLsizei height,
 474                           GLenum type, GLvoid *pixels,
 475                           const struct gl_pixelstore_attrib *packing )
 476 {
 477    const GLboolean scaleOrBias
 478       = ctx->Pixel.DepthScale != 1.0 || ctx->Pixel.DepthBias != 0.0;
 479    const GLboolean stencilTransfer = ctx->Pixel.IndexShift
 480       || ctx->Pixel.IndexOffset || ctx->Pixel.MapStencilFlag;
 481    struct gl_renderbuffer *depthRb, *stencilRb;
 482
 483    depthRb = ctx->ReadBuffer->_DepthBuffer;
 484    stencilRb = ctx->ReadBuffer->_StencilBuffer;
 485
 486    if (!depthRb || !stencilRb)
 487       return;
 488
 489    depthRb = ctx->ReadBuffer->Attachment[BUFFER_DEPTH].Renderbuffer;
 490    stencilRb = ctx->ReadBuffer->Attachment[BUFFER_STENCIL].Renderbuffer;
 491
 492    if (depthRb->_BaseFormat == GL_DEPTH_STENCIL_EXT &&
 493        stencilRb->_BaseFormat == GL_DEPTH_STENCIL_EXT &&
 494        depthRb == stencilRb &&
 495        !scaleOrBias &&
 496        !stencilTransfer) {
 497       /* This is the ideal case.
 498        * Reading GL_DEPTH_STENCIL pixels from combined depth/stencil buffer.
 499        * Plus, no pixel transfer ops to worry about!
 500        */
 501       GLint i;
 502       GLint dstStride = _mesa_image_row_stride(packing, width,
 503                                                GL_DEPTH_STENCIL_EXT, type);
 504       GLubyte *dst = (GLubyte *) _mesa_image_address2d(packing, pixels,
 505                                                        width, height,
 506                                                        GL_DEPTH_STENCIL_EXT,
 507                                                        type, 0, 0);
 508       for (i = 0; i < height; i++) {
 509          depthRb->GetRow(ctx, depthRb, width, x, y + i, dst);
 510          dst += dstStride;
 511       }
 512    }
 513    else {
 514       /* Reading GL_DEPTH_STENCIL pixels from separate depth/stencil buffers,
 515        * or we need pixel transfer.
 516        */
 517       GLint i;
 518       depthRb = ctx->ReadBuffer->_DepthBuffer;
 519       stencilRb = ctx->ReadBuffer->_StencilBuffer;
 520
 521       for (i = 0; i < height; i++) {
 522          GLstencil stencilVals[MAX_WIDTH];
 523
 524          GLuint *depthStencilDst = (GLuint *)
 525             _mesa_image_address2d(packing, pixels, width, height,
 526                                   GL_DEPTH_STENCIL_EXT, type, i, 0);
 527
 528          _swrast_read_stencil_span(ctx, stencilRb, width,
 529                                    x, y + i, stencilVals);
 530
 531          if (!scaleOrBias && !stencilTransfer
 532              && ctx->ReadBuffer->Visual.depthBits == 24) {
 533             /* ideal case */
 534             GLuint zVals[MAX_WIDTH]; /* 24-bit values! */
 535             GLint j;
 536             ASSERT(depthRb->DataType == GL_UNSIGNED_INT);
 537             /* note, we've already been clipped */
 538             depthRb->GetRow(ctx, depthRb, width, x, y + i, zVals);
 539             for (j = 0; j < width; j++) {
 540                depthStencilDst[j] = (zVals[j] << 8) | (stencilVals[j] & 0xff);
 541             }
 542          }
 543          else {
 544             /* general case */
 545             GLfloat depthVals[MAX_WIDTH];
 546             _swrast_read_depth_span_float(ctx, depthRb, width, x, y + i,
 547                                           depthVals);
 548             _mesa_pack_depth_stencil_span(ctx, width, depthStencilDst,
 549                                           depthVals, stencilVals, packing);
 550          }
 551       }
 552    }
 553 }
 554
 555
 556
 557 /**
 558  * Software fallback routine for ctx->Driver.ReadPixels().
 559  * By time we get here, all error checking will have been done.
 560  */
 561 void
 562 _swrast_ReadPixels( GLcontext *ctx,
 563                     GLint x, GLint y, GLsizei width, GLsizei height,
 564                     GLenum format, GLenum type,
 565                     const struct gl_pixelstore_attrib *packing,
 566                     GLvoid *pixels )
 567 {
 568    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 569    struct gl_pixelstore_attrib clippedPacking = *packing;
 570
 571    if (ctx->NewState)
 572       _mesa_update_state(ctx);
 573
 574    /* Need to do swrast_render_start() before clipping or anything else
 575     * since this is where a driver may grab the hw lock and get an updated
 576     * window size.
 577     */
 578    swrast_render_start(ctx);
 579
 580    if (swrast->NewState)
 581       _swrast_validate_derived( ctx );
 582
 583    /* Do all needed clipping here, so that we can forget about it later */
 584    if (!_mesa_clip_readpixels(ctx, &x, &y, &width, &height, &clippedPacking)) {
 585       /* The ReadPixels region is totally outside the window bounds */
 586       swrast_render_finish(ctx);
 587       return;
 588    }
 589
 590    pixels = _mesa_map_pbo_dest(ctx, &clippedPacking, pixels);
 591    if (!pixels)
 592       return;
 593
 594    switch (format) {
 595       case GL_COLOR_INDEX:
 596          read_index_pixels(ctx, x, y, width, height, type, pixels,
 597                            &clippedPacking);
 598          break;
 599       case GL_STENCIL_INDEX:
 600          read_stencil_pixels(ctx, x, y, width, height, type, pixels,
 601                              &clippedPacking);
 602          break;
 603       case GL_DEPTH_COMPONENT:
 604          read_depth_pixels(ctx, x, y, width, height, type, pixels,
 605                            &clippedPacking);
 606          break;
 607       case GL_RED:
 608       case GL_GREEN:
 609       case GL_BLUE:
 610       case GL_ALPHA:
 611       case GL_RGB:
 612       case GL_LUMINANCE:
 613       case GL_LUMINANCE_ALPHA:
 614       case GL_RGBA:
 615       case GL_BGR:
 616       case GL_BGRA:
 617       case GL_ABGR_EXT:
 618          read_rgba_pixels(ctx, x, y, width, height,
 619                           format, type, pixels, &clippedPacking);
 620          break;
 621       case GL_DEPTH_STENCIL_EXT:
 622          read_depth_stencil_pixels(ctx, x, y, width, height,
 623                                    type, pixels, &clippedPacking);
 624          break;
 625       default:
 626          _mesa_problem(ctx, "unexpected format in _swrast_ReadPixels");
 627          /* don't return yet, clean-up */
 628    }
 629
 630    swrast_render_finish(ctx);
 631
 632    _mesa_unmap_pbo_dest(ctx, &clippedPacking);
 633 }