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 "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_COMPONENT24);
 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             /* Note: put MSByte of 24-bit value into LSByte */
 133             dest[k] = (dest[k] << 8) | ((dest[k] >> 16) & 0xff);
 134          }
 135       }
 136    }
 137    else if (type == GL_UNSIGNED_INT && fb->Visual.depthBits == 32
 138             && !biasOrScale && !packing->SwapBytes) {
 139       /* Special case: directly read 32-bit unsigned depth values. */
 140       GLint j;
 141       ASSERT(rb->InternalFormat == GL_DEPTH_COMPONENT32);
 142       ASSERT(rb->DataType == GL_UNSIGNED_INT);
 143       for (j = 0; j < height; j++, y++) {
 144          void *dest = _mesa_image_address2d(packing, pixels, width, height,
 145                                             GL_DEPTH_COMPONENT, type, j, 0);
 146          rb->GetRow(ctx, rb, width, x, y, dest);
 147       }
 148    }
 149    else {
 150       /* General case (slower) */
 151       GLint j;
 152       for (j = 0; j < height; j++, y++) {
 153          GLfloat depthValues[MAX_WIDTH];
 154          GLvoid *dest = _mesa_image_address2d(packing, pixels, width, height,
 155                                               GL_DEPTH_COMPONENT, type, j, 0);
 156          _swrast_read_depth_span_float(ctx, rb, width, x, y, depthValues);
 157          _mesa_pack_depth_span(ctx, width, dest, type, depthValues, packing);
 158       }
 159    }
 160 }
 161
 162
 163 /**
 164  * Read pixels for format=GL_STENCIL_INDEX.
 165  */
 166 static void
 167 read_stencil_pixels( GLcontext *ctx,
 168                      GLint x, GLint y,
 169                      GLsizei width, GLsizei height,
 170                      GLenum type, GLvoid *pixels,
 171                      const struct gl_pixelstore_attrib *packing )
 172 {
 173    struct gl_framebuffer *fb = ctx->ReadBuffer;
 174    struct gl_renderbuffer *rb = fb->_StencilBuffer;
 175    GLint j;
 176
 177    if (!rb)
 178       return;
 179
 180    /* width should never be > MAX_WIDTH since we did clipping earlier */
 181    ASSERT(width <= MAX_WIDTH);
 182
 183    /* process image row by row */
 184    for (j=0;j<height;j++,y++) {
 185       GLvoid *dest;
 186       GLstencil stencil[MAX_WIDTH];
 187
 188       _swrast_read_stencil_span(ctx, rb, width, x, y, stencil);
 189
 190       dest = _mesa_image_address2d(packing, pixels, width, height,
 191                                    GL_STENCIL_INDEX, type, j, 0);
 192
 193       _mesa_pack_stencil_span(ctx, width, type, dest, stencil, packing);
 194    }
 195 }
 196
 197
 198
 199 /**
 200  * Optimized glReadPixels for particular pixel formats when pixel
 201  * scaling, biasing, mapping, etc. are disabled.
 202  * \return GL_TRUE if success, GL_FALSE if unable to do the readpixels
 203  */
 204 static GLboolean
 205 fast_read_rgba_pixels( GLcontext *ctx,
 206                        GLint x, GLint y,
 207                        GLsizei width, GLsizei height,
 208                        GLenum format, GLenum type,
 209                        GLvoid *pixels,
 210                        const struct gl_pixelstore_attrib *packing,
 211                        GLbitfield transferOps)
 212 {
 213    struct gl_renderbuffer *rb = ctx->ReadBuffer->_ColorReadBuffer;
 214
 215    if (!rb)
 216       return GL_FALSE;
 217
 218    ASSERT(rb->_BaseFormat == GL_RGBA || rb->_BaseFormat == GL_RGB);
 219
 220    /* clipping should have already been done */
 221    ASSERT(x + width <= (GLint) rb->Width);
 222    ASSERT(y + height <= (GLint) rb->Height);
 223
 224    /* check for things we can't handle here */
 225    if (transferOps ||
 226        packing->SwapBytes ||
 227        packing->LsbFirst) {
 228       return GL_FALSE;
 229    }
 230
 231    if (format == GL_RGBA && rb->DataType == type) {
 232       const GLint dstStride = _mesa_image_row_stride(packing, width,
 233                                                      format, type);
 234       GLubyte *dest
 235          = (GLubyte *) _mesa_image_address2d(packing, pixels, width, height,
 236                                              format, type, 0, 0);
 237       GLint row;
 238       ASSERT(rb->GetRow);
 239       for (row = 0; row < height; row++) {
 240          rb->GetRow(ctx, rb, width, x, y + row, dest);
 241          dest += dstStride;
 242       }
 243       return GL_TRUE;
 244    }
 245
 246    if (format == GL_RGB &&
 247        rb->DataType == GL_UNSIGNED_BYTE &&
 248        type == GL_UNSIGNED_BYTE) {
 249       const GLint dstStride = _mesa_image_row_stride(packing, width,
 250                                                      format, type);
 251       GLubyte *dest
 252          = (GLubyte *) _mesa_image_address2d(packing, pixels, width, height,
 253                                              format, type, 0, 0);
 254       GLint row;
 255       ASSERT(rb->GetRow);
 256       for (row = 0; row < height; row++) {
 257          GLubyte tempRow[MAX_WIDTH][4];
 258          GLint col;
 259          rb->GetRow(ctx, rb, width, x, y + row, tempRow);
 260          /* convert RGBA to RGB */
 261          for (col = 0; col < width; col++) {
 262             dest[col * 3 + 0] = tempRow[col][0];
 263             dest[col * 3 + 1] = tempRow[col][1];
 264             dest[col * 3 + 2] = tempRow[col][2];
 265          }
 266          dest += dstStride;
 267       }
 268       return GL_TRUE;
 269    }
 270
 271    /* not handled */
 272    return GL_FALSE;
 273 }
 274
 275
 276 /**
 277  * When we're using a low-precision color buffer (like 16-bit 5/6/5)
 278  * we have to adjust our color values a bit to pass conformance.
 279  * The problem is when a 5 or 6-bit color value is convert to an 8-bit
 280  * value and then a floating point value, the floating point values don't
 281  * increment uniformly as the 5 or 6-bit value is incremented.
 282  *
 283  * This function adjusts floating point values to compensate.
 284  */
 285 static void
 286 adjust_colors(GLcontext *ctx, GLuint n, GLfloat rgba[][4])
 287 {
 288    const GLuint rShift = 8 - ctx->Visual.redBits;
 289    const GLuint gShift = 8 - ctx->Visual.greenBits;
 290    const GLuint bShift = 8 - ctx->Visual.blueBits;
 291    const GLfloat rScale = 1.0F / (GLfloat) ((1 << ctx->Visual.redBits  ) - 1);
 292    const GLfloat gScale = 1.0F / (GLfloat) ((1 << ctx->Visual.greenBits) - 1);
 293    const GLfloat bScale = 1.0F / (GLfloat) ((1 << ctx->Visual.blueBits ) - 1);
 294    GLuint i;
 295    for (i = 0; i < n; i++) {
 296       GLint r, g, b;
 297       /* convert float back to ubyte */
 298       CLAMPED_FLOAT_TO_UBYTE(r, rgba[i][RCOMP]);
 299       CLAMPED_FLOAT_TO_UBYTE(g, rgba[i][GCOMP]);
 300       CLAMPED_FLOAT_TO_UBYTE(b, rgba[i][BCOMP]);
 301       /* using only the N most significant bits of the ubyte value, convert to
 302        * float in [0,1].
 303        */
 304       rgba[i][RCOMP] = (GLfloat) (r >> rShift) * rScale;
 305       rgba[i][GCOMP] = (GLfloat) (g >> gShift) * gScale;
 306       rgba[i][BCOMP] = (GLfloat) (b >> bShift) * bScale;
 307    }
 308 }
 309
 310
 311
 312 /*
 313  * Read R, G, B, A, RGB, L, or LA pixels.
 314  */
 315 static void
 316 read_rgba_pixels( GLcontext *ctx,
 317                   GLint x, GLint y,
 318                   GLsizei width, GLsizei height,
 319                   GLenum format, GLenum type, GLvoid *pixels,
 320                   const struct gl_pixelstore_attrib *packing )
 321 {
 322    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 323    GLbitfield transferOps = ctx->_ImageTransferState;
 324    struct gl_framebuffer *fb = ctx->ReadBuffer;
 325    struct gl_renderbuffer *rb = fb->_ColorReadBuffer;
 326
 327    if (!rb)
 328       return;
 329
 330    if (type == GL_FLOAT && ((ctx->Color.ClampReadColor == GL_TRUE) ||
 331                             (ctx->Color.ClampReadColor == GL_FIXED_ONLY_ARB &&
 332                              rb->DataType != GL_FLOAT)))
 333       transferOps |= IMAGE_CLAMP_BIT;
 334
 335    /* Try optimized path first */
 336    if (fast_read_rgba_pixels(ctx, x, y, width, height,
 337                              format, type, pixels, packing, transferOps)) {
 338       return; /* done! */
 339    }
 340
 341    /* width should never be > MAX_WIDTH since we did clipping earlier */
 342    ASSERT(width <= MAX_WIDTH);
 343
 344    if (ctx->Pixel.Convolution2DEnabled || ctx->Pixel.Separable2DEnabled) {
 345       GLfloat *dest, *src, *tmpImage, *convImage;
 346       GLint row;
 347
 348       tmpImage = (GLfloat *) _mesa_malloc(width * height * 4 * sizeof(GLfloat));
 349       if (!tmpImage) {
 350          _mesa_error(ctx, GL_OUT_OF_MEMORY, "glReadPixels");
 351          return;
 352       }
 353       convImage = (GLfloat *) _mesa_malloc(width * height * 4 * sizeof(GLfloat));
 354       if (!convImage) {
 355          _mesa_free(tmpImage);
 356          _mesa_error(ctx, GL_OUT_OF_MEMORY, "glReadPixels");
 357          return;
 358       }
 359
 360       /* read full RGBA, FLOAT image */
 361       dest = tmpImage;
 362       for (row = 0; row < height; row++, y++) {
 363          if (fb->Visual.rgbMode) {
 364             _swrast_read_rgba_span(ctx, rb, width, x, y, GL_FLOAT, dest);
 365          }
 366          else {
 367             GLuint index[MAX_WIDTH];
 368             ASSERT(rb->DataType == GL_UNSIGNED_INT);
 369             rb->GetRow(ctx, rb, width, x, y, index);
 370             _mesa_apply_ci_transfer_ops(ctx,
 371                                         transferOps & IMAGE_SHIFT_OFFSET_BIT,
 372                                         width, index);
 373             _mesa_map_ci_to_rgba(ctx, width, index, (GLfloat (*)[4]) dest);
 374          }
 375          _mesa_apply_rgba_transfer_ops(ctx,
 376                                       transferOps & IMAGE_PRE_CONVOLUTION_BITS,
 377                                       width, (GLfloat (*)[4]) dest);
 378          dest += width * 4;
 379       }
 380
 381       /* do convolution */
 382       if (ctx->Pixel.Convolution2DEnabled) {
 383          _mesa_convolve_2d_image(ctx, &width, &height, tmpImage, convImage);
 384       }
 385       else {
 386          ASSERT(ctx->Pixel.Separable2DEnabled);
 387          _mesa_convolve_sep_image(ctx, &width, &height, tmpImage, convImage);
 388       }
 389       _mesa_free(tmpImage);
 390
 391       /* finish transfer ops and pack the resulting image */
 392       src = convImage;
 393       for (row = 0; row < height; row++) {
 394          GLvoid *dest;
 395          dest = _mesa_image_address2d(packing, pixels, width, height,
 396                                       format, type, row, 0);
 397          _mesa_pack_rgba_span_float(ctx, width, (GLfloat (*)[4]) src,
 398                                     format, type, dest, packing,
 399                                     transferOps & IMAGE_POST_CONVOLUTION_BITS);
 400          src += width * 4;
 401       }
 402       _mesa_free(convImage);
 403    }
 404    else {
 405       /* no convolution */
 406       const GLint dstStride
 407          = _mesa_image_row_stride(packing, width, format, type);
 408       GLfloat (*rgba)[4] = swrast->SpanArrays->attribs[FRAG_ATTRIB_COL0];
 409       GLint row;
 410       GLubyte *dst
 411          = (GLubyte *) _mesa_image_address2d(packing, pixels, width, height,
 412                                              format, type, 0, 0);
 413
 414       /* make sure we don't apply 1D convolution */
 415       transferOps &= ~(IMAGE_CONVOLUTION_BIT |
 416                        IMAGE_POST_CONVOLUTION_SCALE_BIAS);
 417
 418       for (row = 0; row < height; row++, y++) {
 419
 420          /* Get float rgba pixels */
 421          if (fb->Visual.rgbMode) {
 422             _swrast_read_rgba_span(ctx, rb, width, x, y, GL_FLOAT, rgba);
 423          }
 424          else {
 425             /* read CI and convert to RGBA */
 426             GLuint index[MAX_WIDTH];
 427             ASSERT(rb->DataType == GL_UNSIGNED_INT);
 428             rb->GetRow(ctx, rb, width, x, y, index);
 429             _mesa_apply_ci_transfer_ops(ctx,
 430                                         transferOps & IMAGE_SHIFT_OFFSET_BIT,
 431                                         width, index);
 432             _mesa_map_ci_to_rgba(ctx, width, index, rgba);
 433          }
 434
 435          /* apply fudge factor for shallow color buffers */
 436          if (fb->Visual.redBits < 8 ||
 437              fb->Visual.greenBits < 8 ||
 438              fb->Visual.blueBits < 8) {
 439             adjust_colors(ctx, width, rgba);
 440          }
 441
 442          /* pack the row of RGBA pixels into user's buffer */
 443          _mesa_pack_rgba_span_float(ctx, width, rgba, format, type, dst,
 444                                     packing, transferOps);
 445
 446          dst += dstStride;
 447       }
 448    }
 449 }
 450
 451
 452 /**
 453  * Read combined depth/stencil values.
 454  * We'll have already done error checking to be sure the expected
 455  * depth and stencil buffers really exist.
 456  */
 457 static void
 458 read_depth_stencil_pixels(GLcontext *ctx,
 459                           GLint x, GLint y,
 460                           GLsizei width, GLsizei height,
 461                           GLenum type, GLvoid *pixels,
 462                           const struct gl_pixelstore_attrib *packing )
 463 {
 464    const GLboolean scaleOrBias
 465       = ctx->Pixel.DepthScale != 1.0 || ctx->Pixel.DepthBias != 0.0;
 466    const GLboolean stencilTransfer = ctx->Pixel.IndexShift
 467       || ctx->Pixel.IndexOffset || ctx->Pixel.MapStencilFlag;
 468    struct gl_renderbuffer *depthRb, *stencilRb;
 469
 470    depthRb = ctx->ReadBuffer->_DepthBuffer;
 471    stencilRb = ctx->ReadBuffer->_StencilBuffer;
 472
 473    if (!depthRb || !stencilRb)
 474       return;
 475
 476    depthRb = ctx->ReadBuffer->Attachment[BUFFER_DEPTH].Renderbuffer;
 477    stencilRb = ctx->ReadBuffer->Attachment[BUFFER_STENCIL].Renderbuffer;
 478
 479    if (depthRb->_BaseFormat == GL_DEPTH_STENCIL_EXT &&
 480        stencilRb->_BaseFormat == GL_DEPTH_STENCIL_EXT &&
 481        depthRb == stencilRb &&
 482        !scaleOrBias &&
 483        !stencilTransfer) {
 484       /* This is the ideal case.
 485        * Reading GL_DEPTH_STENCIL pixels from combined depth/stencil buffer.
 486        * Plus, no pixel transfer ops to worry about!
 487        */
 488       GLint i;
 489       GLint dstStride = _mesa_image_row_stride(packing, width,
 490                                                GL_DEPTH_STENCIL_EXT, type);
 491       GLubyte *dst = (GLubyte *) _mesa_image_address2d(packing, pixels,
 492                                                        width, height,
 493                                                        GL_DEPTH_STENCIL_EXT,
 494                                                        type, 0, 0);
 495       for (i = 0; i < height; i++) {
 496          depthRb->GetRow(ctx, depthRb, width, x, y + i, dst);
 497          dst += dstStride;
 498       }
 499    }
 500    else {
 501       /* Reading GL_DEPTH_STENCIL pixels from separate depth/stencil buffers,
 502        * or we need pixel transfer.
 503        */
 504       GLint i;
 505       depthRb = ctx->ReadBuffer->_DepthBuffer;
 506       stencilRb = ctx->ReadBuffer->_StencilBuffer;
 507
 508       for (i = 0; i < height; i++) {
 509          GLstencil stencilVals[MAX_WIDTH];
 510
 511          GLuint *depthStencilDst = (GLuint *)
 512             _mesa_image_address2d(packing, pixels, width, height,
 513                                   GL_DEPTH_STENCIL_EXT, type, i, 0);
 514
 515          _swrast_read_stencil_span(ctx, stencilRb, width,
 516                                    x, y + i, stencilVals);
 517
 518          if (!scaleOrBias && !stencilTransfer
 519              && ctx->ReadBuffer->Visual.depthBits == 24) {
 520             /* ideal case */
 521             GLuint zVals[MAX_WIDTH]; /* 24-bit values! */
 522             GLint j;
 523             ASSERT(depthRb->DataType == GL_UNSIGNED_INT);
 524             /* note, we've already been clipped */
 525             depthRb->GetRow(ctx, depthRb, width, x, y + i, zVals);
 526             for (j = 0; j < width; j++) {
 527                depthStencilDst[j] = (zVals[j] << 8) | (stencilVals[j] & 0xff);
 528             }
 529          }
 530          else {
 531             /* general case */
 532             GLfloat depthVals[MAX_WIDTH];
 533             _swrast_read_depth_span_float(ctx, depthRb, width, x, y + i,
 534                                           depthVals);
 535             _mesa_pack_depth_stencil_span(ctx, width, depthStencilDst,
 536                                           depthVals, stencilVals, packing);
 537          }
 538       }
 539    }
 540 }
 541
 542
 543
 544 /**
 545  * Software fallback routine for ctx->Driver.ReadPixels().
 546  * By time we get here, all error checking will have been done.
 547  */
 548 void
 549 _swrast_ReadPixels( GLcontext *ctx,
 550                     GLint x, GLint y, GLsizei width, GLsizei height,
 551                     GLenum format, GLenum type,
 552                     const struct gl_pixelstore_attrib *packing,
 553                     GLvoid *pixels )
 554 {
 555    SWcontext *swrast = SWRAST_CONTEXT(ctx);
 556    struct gl_pixelstore_attrib clippedPacking = *packing;
 557
 558    /* Need to do RENDER_START before clipping or anything else since this
 559     * is where a driver may grab the hw lock and get an updated window
 560     * size.
 561     */
 562    RENDER_START(swrast, ctx);
 563
 564    if (ctx->NewState)
 565       _mesa_update_state(ctx);
 566
 567    if (swrast->NewState)
 568       _swrast_validate_derived( ctx );
 569
 570    /* Do all needed clipping here, so that we can forget about it later */
 571    if (!_mesa_clip_readpixels(ctx, &x, &y, &width, &height, &clippedPacking)) {
 572       /* The ReadPixels region is totally outside the window bounds */
 573       goto end;
 574    }
 575
 576    if (clippedPacking.BufferObj->Name) {
 577       /* pack into PBO */
 578       GLubyte *buf;
 579       if (!_mesa_validate_pbo_access(2, &clippedPacking, width, height, 1,
 580                                      format, type, pixels)) {
 581          _mesa_error(ctx, GL_INVALID_OPERATION,
 582                      "glReadPixels(invalid PBO access)");
 583          goto end;
 584       }
 585       buf = (GLubyte *) ctx->Driver.MapBuffer(ctx, GL_PIXEL_PACK_BUFFER_EXT,
 586                                               GL_WRITE_ONLY_ARB,
 587                                               clippedPacking.BufferObj);
 588       if (!buf) {
 589          /* buffer is already mapped - that's an error */
 590          _mesa_error(ctx, GL_INVALID_OPERATION, "glReadPixels(PBO is mapped)");
 591          goto end;
 592       }
 593       pixels = ADD_POINTERS(buf, pixels);
 594    }
 595
 596    switch (format) {
 597       case GL_COLOR_INDEX:
 598          read_index_pixels(ctx, x, y, width, height, type, pixels,
 599                            &clippedPacking);
 600          break;
 601       case GL_STENCIL_INDEX:
 602          read_stencil_pixels(ctx, x, y, width, height, type, pixels,
 603                              &clippedPacking);
 604          break;
 605       case GL_DEPTH_COMPONENT:
 606          read_depth_pixels(ctx, x, y, width, height, type, pixels,
 607                            &clippedPacking);
 608          break;
 609       case GL_RED:
 610       case GL_GREEN:
 611       case GL_BLUE:
 612       case GL_ALPHA:
 613       case GL_RGB:
 614       case GL_LUMINANCE:
 615       case GL_LUMINANCE_ALPHA:
 616       case GL_RGBA:
 617       case GL_BGR:
 618       case GL_BGRA:
 619       case GL_ABGR_EXT:
 620          read_rgba_pixels(ctx, x, y, width, height,
 621                           format, type, pixels, &clippedPacking);
 622          break;
 623       case GL_DEPTH_STENCIL_EXT:
 624          read_depth_stencil_pixels(ctx, x, y, width, height,
 625                                    type, pixels, &clippedPacking);
 626          break;
 627       default:
 628          _mesa_problem(ctx, "unexpected format in _swrast_ReadPixels");
 629          /* don't return yet, clean-up */
 630    }
 631
 632
 633 end:
 634    RENDER_FINISH(swrast, ctx);
 635
 636    if (clippedPacking.BufferObj->Name) {
 637       /* done with PBO so unmap it now */
 638       ctx->Driver.UnmapBuffer(ctx, GL_PIXEL_PACK_BUFFER_EXT,
 639                               clippedPacking.BufferObj);
 640    }
 641 }