s_readpix.c

Mesa is an open-source implementation of the OpenGL specification - a system for rendering interacti

/*
 * 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 )
{
   SWcontext *swrast = SWRAST_CONTEXT(ctx);
   GLbitfield transferOps = ctx->_ImageTransferState;
   struct gl_framebuffer *fb = ctx->ReadBuffer;
   struct gl_renderbuffer *rb = fb->_ColorReadBuffer;

   if (!rb)
      return;

   if (type == GL_FLOAT && ((ctx->Color.ClampReadColor == GL_TRUE) ||
                            (ctx->Color.ClampReadColor == GL_FIXED_ONLY_ARB &&
                             rb->DataType != GL_FLOAT)))
      transferOps |= IMAGE_CLAMP_BIT;

   /* Try optimized path first */
   if (fast_read_rgba_pixels(ctx, x, y, width, height,
                             format, type, pixels, packing, transferOps)) {
      return; /* done! */
   }

   /* width should never be > MAX_WIDTH since we did clipping earlier */
   ASSERT(width <= MAX_WIDTH);

   if (ctx->Pixel.Convolution2DEnabled || ctx->Pixel.Separable2DEnabled) {
      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++) {
         if (fb->Visual.rgbMode) {
            _swrast_read_rgba_span(ctx, rb, width, x, y, GL_FLOAT, dest);
         }
         else {
            GLuint index[MAX_WIDTH];
            ASSERT(rb->DataType == GL_UNSIGNED_INT);
            rb->GetRow(ctx, rb, width, x, y, index);
            _mesa_apply_ci_transfer_ops(ctx,
                                        transferOps & IMAGE_SHIFT_OFFSET_BIT,
                                        width, index);
            _mesa_map_ci_to_rgba(ctx, width, index, (GLfloat (*)[4]) dest);
         }
         _mesa_apply_rgba_transfer_ops(ctx, 
                                      transferOps & IMAGE_PRE_CONVOLUTION_BITS,
                                      width, (GLfloat (*)[4]) dest);
         dest += width * 4;
      }

      /* do convolution */
      if (ctx->Pixel.Convolution2DEnabled) {
         _mesa_convolve_2d_image(ctx, &width, &height, tmpImage, convImage);
      }
      else {
         ASSERT(ctx->Pixel.Separable2DEnabled);
         _mesa_convolve_sep_image(ctx, &width, &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, width, height,
                                      format, type, row, 0);
         _mesa_pack_rgba_span_float(ctx, width, (GLfloat (*)[4]) src,
                                    format, type, dest, packing,
                                    transferOps & IMAGE_POST_CONVOLUTION_BITS);
         src += width * 4;
      }
      _mesa_free(convImage);
   }
   else {
      /* no convolution */
      const GLint dstStride
         = _mesa_image_row_stride(packing, width, format, type);
      GLfloat (*rgba)[4] = swrast->SpanArrays->attribs[FRAG_ATTRIB_COL0];
      GLint row;
      GLubyte *dst
         = (GLubyte *) _mesa_image_address2d(packing, pixels, width, height,
                                             format, type, 0, 0);

      /* make sure we don't apply 1D convolution */
      transferOps &= ~(IMAGE_CONVOLUTION_BIT |
                       IMAGE_POST_CONVOLUTION_SCALE_BIAS);

      for (row = 0; row < height; row++, y++) {

         /* Get float rgba pixels */
         if (fb->Visual.rgbMode) {
            _swrast_read_rgba_span(ctx, rb, width, x, y, GL_FLOAT, rgba);
         }
         else {
            /* read CI and convert to RGBA */
            GLuint index[MAX_WIDTH];
            ASSERT(rb->DataType == GL_UNSIGNED_INT);
            rb->GetRow(ctx, rb, width, x, y, index);
            _mesa_apply_ci_transfer_ops(ctx,
                                        transferOps & IMAGE_SHIFT_OFFSET_BIT,
                                        width, index);
            _mesa_map_ci_to_rgba(ctx, width, index, rgba);
         }

         /* apply fudge factor for shallow color buffers */
         if (fb->Visual.redBits < 8 ||
             fb->Visual.greenBits < 8 ||
             fb->Visual.blueBits < 8) {
            adjust_colors(ctx, width, rgba);
         }

         /* pack the row of RGBA pixels into user's buffer */
         _mesa_pack_rgba_span_float(ctx, width, rgba, format, type, dst,
                                    packing, transferOps);

         dst += dstStride;
      }
   }
}


/**
 * Read combined depth/stencil values.
 * We'll have already done error checking to be sure the expected
 * depth and stencil buffers really exist.
 */
static void
read_depth_stencil_pixels(GLcontext *ctx,
                          GLint x, GLint y,
                          GLsizei width, GLsizei height,
                          GLenum type, GLvoid *pixels,
                          const struct gl_pixelstore_attrib *packing )
{
   const GLboolean scaleOrBias
      = ctx->Pixel.DepthScale != 1.0 || ctx->Pixel.DepthBias != 0.0;
   const GLboolean stencilTransfer = ctx->Pixel.IndexShift
      || ctx->Pixel.IndexOffset || ctx->Pixel.MapStencilFlag;
   struct gl_renderbuffer *depthRb, *stencilRb;

   depthRb = ctx->ReadBuffer->_DepthBuffer;
   stencilRb = ctx->ReadBuffer->_StencilBuffer;

   if (!depthRb || !stencilRb)
      return;

   depthRb = ctx->ReadBuffer->Attachment[BUFFER_DEPTH].Renderbuffer;
   stencilRb = ctx->ReadBuffer->Attachment[BUFFER_STENCIL].Renderbuffer;

   if (depthRb->_BaseFormat == GL_DEPTH_STENCIL_EXT &&
       stencilRb->_BaseFormat == GL_DEPTH_STENCIL_EXT &&
       depthRb == stencilRb &&
       !scaleOrBias &&
       !stencilTransfer) {
      /* This is the ideal case.
       * Reading GL_DEPTH_STENCIL pixels from combined depth/stencil buffer.
       * Plus, no pixel transfer ops to worry about!
       */
      GLint i;
      GLint dstStride = _mesa_image_row_stride(packing, width,
                                               GL_DEPTH_STENCIL_EXT, type);
      GLubyte *dst = (GLubyte *) _mesa_image_address2d(packing, pixels,
                                                       width, height,
                                                       GL_DEPTH_STENCIL_EXT,
                                                       type, 0, 0);
      for (i = 0; i < height; i++) {
         depthRb->GetRow(ctx, depthRb, width, x, y + i, dst);
         dst += dstStride;
      }
   }
   else {
      /* Reading GL_DEPTH_STENCIL pixels from separate depth/stencil buffers,
       * or we need pixel transfer.
       */
      GLint i;
      depthRb = ctx->ReadBuffer->_DepthBuffer;
      stencilRb = ctx->ReadBuffer->_StencilBuffer;

      for (i = 0; i < height; i++) {
         GLstencil stencilVals[MAX_WIDTH];

         GLuint *depthStencilDst = (GLuint *)
            _mesa_image_address2d(packing, pixels, width, height,
                                  GL_DEPTH_STENCIL_EXT, type, i, 0);

         _swrast_read_stencil_span(ctx, stencilRb, width,
                                   x, y + i, stencilVals);

         if (!scaleOrBias && !stencilTransfer
             && ctx->ReadBuffer->Visual.depthBits == 24) {
            /* ideal case */
            GLuint zVals[MAX_WIDTH]; /* 24-bit values! */
            GLint j;
            ASSERT(depthRb->DataType == GL_UNSIGNED_INT);
            /* note, we've already been clipped */
            depthRb->GetRow(ctx, depthRb, width, x, y + i, zVals);
            for (j = 0; j < width; j++) {
               depthStencilDst[j] = (zVals[j] << 8) | (stencilVals[j] & 0xff);
            }
         }
         else {
            /* general case */
            GLfloat depthVals[MAX_WIDTH];
            _swrast_read_depth_span_float(ctx, depthRb, width, x, y + i,
                                          depthVals);
            _mesa_pack_depth_stencil_span(ctx, width, depthStencilDst,
                                          depthVals, stencilVals, packing);
         }
      }
   }
}



/**
 * Software fallback routine for ctx->Driver.ReadPixels().
 * By time we get here, all error checking will have been done.
 */
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 = *packing;

   /* Need to do RENDER_START before clipping or anything else since this
    * is where a driver may grab the hw lock and get an updated window
    * size.
    */
   RENDER_START(swrast, ctx);

   if (ctx->NewState)
      _mesa_update_state(ctx);

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

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

   pixels = _mesa_map_readpix_pbo(ctx, &clippedPacking, pixels);
   if (!pixels)
      return;
  
   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;
      case GL_DEPTH_STENCIL_EXT:
         read_depth_stencil_pixels(ctx, x, y, width, height,
                                   type, pixels, &clippedPacking);
         break;
      default:
	 _mesa_problem(ctx, "unexpected format in _swrast_ReadPixels");
         /* don't return yet, clean-up */
   }

   RENDER_FINISH(swrast, ctx);

   _mesa_unmap_readpix_pbo(ctx, &clippedPacking);
}