s_readpix.c

winNT技术操作系统,国外开放的原代码和LIUX一样

         for (row=0; row<readHeight; row++) {
            rb->GetRow(ctx, rb, readWidth, srcX, srcY, dest);
            dest += rowLength * 4;
            srcY++;
         }
         return GL_TRUE;
      }
      else {
         /* can't do this format/type combination */
         return GL_FALSE;
      }
   }
}



/*
 * Read R, G, B, A, RGB, L, or LA pixels.
 */
static void
read_rgba_pixels( GLcontext *ctx,
                  GLint x, GLint y,
                  GLsizei width, GLsizei height,
                  GLenum format, GLenum type, GLvoid *pixels,
                  const struct gl_pixelstore_attrib *packing )
{
   struct gl_renderbuffer *rb = ctx->ReadBuffer->_ColorReadBuffer;
   GLint readWidth;

   if (!rb) {
      /* No readbuffer is OK with GL_EXT_framebuffer_object */
      return;
   }

   /* do error checking on pixel type, format was already checked by caller */
   switch (type) {
      case GL_UNSIGNED_BYTE:
      case GL_BYTE:
      case GL_UNSIGNED_SHORT:
      case GL_SHORT:
      case GL_UNSIGNED_INT:
      case GL_INT:
      case GL_FLOAT:
      case GL_UNSIGNED_BYTE_3_3_2:
      case GL_UNSIGNED_BYTE_2_3_3_REV:
      case GL_UNSIGNED_SHORT_5_6_5:
      case GL_UNSIGNED_SHORT_5_6_5_REV:
      case GL_UNSIGNED_SHORT_4_4_4_4:
      case GL_UNSIGNED_SHORT_4_4_4_4_REV:
      case GL_UNSIGNED_SHORT_5_5_5_1:
      case GL_UNSIGNED_SHORT_1_5_5_5_REV:
      case GL_UNSIGNED_INT_8_8_8_8:
      case GL_UNSIGNED_INT_8_8_8_8_REV:
      case GL_UNSIGNED_INT_10_10_10_2:
      case GL_UNSIGNED_INT_2_10_10_10_REV:
         /* valid pixel type */
         break;
      case GL_HALF_FLOAT_ARB:
         if (!ctx->Extensions.ARB_half_float_pixel) {
            _mesa_error( ctx, GL_INVALID_ENUM, "glReadPixels(type)" );
            return;
         }
         break;
      default:
         _mesa_error( ctx, GL_INVALID_ENUM, "glReadPixels(type)" );
         return;
   }

   if (!_mesa_is_legal_format_and_type(ctx, format, type) ||
       format == GL_INTENSITY) {
      _mesa_error(ctx, GL_INVALID_OPERATION, "glReadPixels(format or type)");
      return;
   }

   _swrast_use_read_buffer(ctx);

   /* Try optimized path first */
   if (read_fast_rgba_pixels( ctx, x, y, width, height,
                              format, type, pixels, packing )) {

      _swrast_use_draw_buffer(ctx);
      return; /* done! */
   }

   /* XXX: width should never be > MAX_WIDTH since we did clipping earlier */
   readWidth = (width > MAX_WIDTH) ? MAX_WIDTH : width;


   if (ctx->Pixel.Convolution2DEnabled || ctx->Pixel.Separable2DEnabled) {
      const GLuint transferOps = ctx->_ImageTransferState;
      GLfloat *dest, *src, *tmpImage, *convImage;
      GLint row;

      tmpImage = (GLfloat *) _mesa_malloc(width * height * 4 * sizeof(GLfloat));
      if (!tmpImage) {
         _mesa_error(ctx, GL_OUT_OF_MEMORY, "glReadPixels");
         return;
      }
      convImage = (GLfloat *) _mesa_malloc(width * height * 4 * sizeof(GLfloat));
      if (!convImage) {
         _mesa_free(tmpImage);
         _mesa_error(ctx, GL_OUT_OF_MEMORY, "glReadPixels");
         return;
      }

      /* read full RGBA, FLOAT image */
      dest = tmpImage;
      for (row = 0; row < height; row++, y++) {
         GLchan rgba[MAX_WIDTH][4];
         if (ctx->Visual.rgbMode) {
            _swrast_read_rgba_span(ctx, rb, readWidth, x, y, rgba);
         }
         else {
            GLuint index[MAX_WIDTH];
            ASSERT(rb->DataType == GL_UNSIGNED_INT);
            rb->GetRow(ctx, rb, readWidth, x, y, index);
            if (ctx->Pixel.IndexShift != 0 || ctx->Pixel.IndexOffset !=0 ) {
               _mesa_map_ci(ctx, readWidth, index);
            }
            _mesa_map_ci_to_rgba_chan(ctx, readWidth, index, rgba);
         }
         _mesa_pack_rgba_span_chan(ctx, readWidth, (const GLchan (*)[4]) rgba,
                              GL_RGBA, GL_FLOAT, dest, &ctx->DefaultPacking,
                              transferOps & IMAGE_PRE_CONVOLUTION_BITS);
         dest += width * 4;
      }

      /* do convolution */
      if (ctx->Pixel.Convolution2DEnabled) {
         _mesa_convolve_2d_image(ctx, &readWidth, &height, tmpImage, convImage);
      }
      else {
         ASSERT(ctx->Pixel.Separable2DEnabled);
         _mesa_convolve_sep_image(ctx, &readWidth, &height, tmpImage, convImage);
      }
      _mesa_free(tmpImage);

      /* finish transfer ops and pack the resulting image */
      src = convImage;
      for (row = 0; row < height; row++) {
         GLvoid *dest;
         dest = _mesa_image_address2d(packing, pixels, readWidth, height,
                                      format, type, row, 0);
         _mesa_pack_rgba_span_float(ctx, readWidth,
                                    (const GLfloat (*)[4]) src,
                                    format, type, dest, packing,
                                    transferOps & IMAGE_POST_CONVOLUTION_BITS);
         src += readWidth * 4;
      }
   }
   else {
      /* no convolution */
      GLint row;
      for (row = 0; row < height; row++, y++) {
         GLchan rgba[MAX_WIDTH][4];
         GLvoid *dst;
         if (ctx->Visual.rgbMode) {
            _swrast_read_rgba_span(ctx, rb, readWidth, x, y, rgba);
         }
         else {
            GLuint index[MAX_WIDTH];
            ASSERT(rb->DataType == GL_UNSIGNED_INT);
            rb->GetRow(ctx, rb, readWidth, x, y, index);
            if (ctx->Pixel.IndexShift != 0 || ctx->Pixel.IndexOffset != 0) {
               _mesa_map_ci(ctx, readWidth, index);
            }
            _mesa_map_ci_to_rgba_chan(ctx, readWidth, index, rgba);
         }
         dst = _mesa_image_address2d(packing, pixels, width, height,
                                     format, type, row, 0);
         if (ctx->Visual.redBits < CHAN_BITS ||
             ctx->Visual.greenBits < CHAN_BITS ||
             ctx->Visual.blueBits < CHAN_BITS) {
            /* Requantize the color values into floating point and go from
             * there.  This fixes conformance failures with 16-bit color
             * buffers, for example.
             */
            DEFMARRAY(GLfloat, rgbaf, MAX_WIDTH, 4);  /* mac 32k limitation */
            CHECKARRAY(rgbaf, return);  /* mac 32k limitation */
            _mesa_chan_to_float_span(ctx, readWidth,
                                     (CONST GLchan (*)[4]) rgba, rgbaf);
            _mesa_pack_rgba_span_float(ctx, readWidth,
                                       (CONST GLfloat (*)[4]) rgbaf,
                                       format, type, dst, packing,
                                       ctx->_ImageTransferState);
            UNDEFARRAY(rgbaf);  /* mac 32k limitation */
         }
         else {
            /* GLubytes are fine */
            _mesa_pack_rgba_span_chan(ctx, readWidth, (CONST GLchan (*)[4]) rgba,
                                 format, type, dst, packing,
                                 ctx->_ImageTransferState);
         }
      }
   }

   _swrast_use_draw_buffer(ctx);
}


/**
 * Software fallback routine for ctx->Driver.ReadPixels().
 * We wind up using the swrast->ReadSpan() routines to do the job.
 */
void
_swrast_ReadPixels( GLcontext *ctx,
		    GLint x, GLint y, GLsizei width, GLsizei height,
		    GLenum format, GLenum type,
		    const struct gl_pixelstore_attrib *packing,
		    GLvoid *pixels )
{
   SWcontext *swrast = SWRAST_CONTEXT(ctx);
   struct gl_pixelstore_attrib clippedPacking;

   if (swrast->NewState)
      _swrast_validate_derived( ctx );

   /* Do all needed clipping here, so that we can forget about it later */
   clippedPacking = *packing;
   if (clippedPacking.RowLength == 0) {
      clippedPacking.RowLength = width;
   }
   if (!_mesa_clip_readpixels(ctx, &x, &y, &width, &height,
                              &clippedPacking.SkipPixels,
                              &clippedPacking.SkipRows)) {
      /* The ReadPixels region is totally outside the window bounds */
      return;
   }

   if (clippedPacking.BufferObj->Name) {
      /* pack into PBO */
      GLubyte *buf;
      if (!_mesa_validate_pbo_access(2, &clippedPacking, width, height, 1,
                                     format, type, pixels)) {
         _mesa_error(ctx, GL_INVALID_OPERATION,
                     "glReadPixels(invalid PBO access)");
         return;
      }
      buf = (GLubyte *) ctx->Driver.MapBuffer(ctx, GL_PIXEL_PACK_BUFFER_EXT,
                                              GL_WRITE_ONLY_ARB,
                                              clippedPacking.BufferObj);
      if (!buf) {
         /* buffer is already mapped - that's an error */
         _mesa_error(ctx, GL_INVALID_OPERATION, "glReadPixels(PBO is mapped)");
         return;
      }
      pixels = ADD_POINTERS(buf, pixels);
   }

   RENDER_START(swrast, ctx);

   switch (format) {
      case GL_COLOR_INDEX:
         read_index_pixels(ctx, x, y, width, height, type, pixels,
                           &clippedPacking);
	 break;
      case GL_STENCIL_INDEX:
	 read_stencil_pixels(ctx, x,y, width,height, type, pixels,
                             &clippedPacking);
         break;
      case GL_DEPTH_COMPONENT:
	 read_depth_pixels(ctx, x, y, width, height, type, pixels,
                           &clippedPacking);
	 break;
      case GL_RED:
      case GL_GREEN:
      case GL_BLUE:
      case GL_ALPHA:
      case GL_RGB:
      case GL_LUMINANCE:
      case GL_LUMINANCE_ALPHA:
      case GL_RGBA:
      case GL_BGR:
      case GL_BGRA:
      case GL_ABGR_EXT:
         read_rgba_pixels(ctx, x, y, width, height,
                          format, type, pixels, &clippedPacking);
	 break;
      default:
	 _mesa_error( ctx, GL_INVALID_ENUM, "glReadPixels(format)" );
         /* don't return yet, clean-up */
   }

   RENDER_FINISH(swrast, ctx);

   if (clippedPacking.BufferObj->Name) {
      /* done with PBO so unmap it now */
      ctx->Driver.UnmapBuffer(ctx, GL_PIXEL_PACK_BUFFER_EXT,
                              clippedPacking.BufferObj);
   }
}