Attachment 57646 Details for Bug 46631 – readpix: Don't disable fast path for normalized types

[patch] readpix: Don't disable fast path for normalized types

0001-readpix-Don-t-disable-fast-path-for-normalized-types.patch (text/plain), 3.02 KB, created by Neil Roberts on 2012-02-25 17:44:51 UTC

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Creator: Neil Roberts

Created: 2012-02-25 17:44:51 UTC

Size: 3.02 KB

patch

obsolete

>From 9aa5e5829e58fddea5de453a8ec522002456ba43 Mon Sep 17 00:00:00 2001
>From: Neil Roberts <neil@linux.intel.com>
>Date: Sun, 26 Feb 2012 01:33:40 +0000
>Subject: [PATCH] readpix: Don't disable fast path for normalized types
>
>Mesa has a fast path for the generic fallback when using glReadPixels
>for RGBA data which uses memcpy. However it was really difficult to
>hit this case because it would not be used if any transferOps are
>enabled. Any type apart from floating point or non-normalized integer
>types (so any of the common types) would force enabling clamping so
>the fast path could not be used. This patch makes it ignore clamping
>when determining whether to use the fast path if the data type of the
>buffer is an unsigned normalized type because in that case clamping
>will not have any effect anyway.
>
>This patch additionally makes it explicitly ignore luminance types
>because in that case the conversion to and from RGB does not end up
>with exactly the same values.
>
>https://bugs.freedesktop.org/show_bug.cgi?id=46631
>---
> src/mesa/main/readpix.c |   32 +++++++++++++++++++++++++-------
> 1 files changed, 25 insertions(+), 7 deletions(-)
>
>diff --git a/src/mesa/main/readpix.c b/src/mesa/main/readpix.c
>index 0f429ab..dd438f9 100644
>--- a/src/mesa/main/readpix.c
>+++ b/src/mesa/main/readpix.c
>@@ -225,6 +225,26 @@ fast_read_rgba_pixels_memcpy( struct gl_context *ctx,
>                                              ctx->Pack.SwapBytes))
>       return GL_FALSE;
> 
>+   /* If the format is unsigned normalized then we can ignore clamping
>+      because the values are already in the range 0->1 so it won't
>+      have any effect anyway */
>+   if (_mesa_get_format_datatype (rb->Format) == GL_UNSIGNED_NORMALIZED)
>+      transferOps &= ~IMAGE_CLAMP_BIT;
>+
>+   if (transferOps)
>+      return GL_FALSE;
>+
>+   /* This can't handle luminance buffers because it would effectively
>+      need to multiply the luminance values by 3. The spec says it
>+      should convert to RGB by setting all of the components to the
>+      luminance value and then convert back to luminance by adding all
>+      of the components together. */
>+   switch (_mesa_get_format_base_format(rb->Format)) {
>+   case GL_LUMINANCE:
>+   case GL_LUMINANCE_ALPHA:
>+      return GL_FALSE;
>+   }
>+
>    dstStride = _mesa_image_row_stride(packing, width, format, type);
>    dst = (GLubyte *) _mesa_image_address2d(packing, pixels, width, height,
> 					   format, type, 0, 0);
>@@ -320,13 +340,11 @@ read_rgba_pixels( struct gl_context *ctx,
>       transferOps |= IMAGE_CLAMP_BIT;
>    }
> 
>-   if (!transferOps) {
>-      /* Try the optimized paths first. */
>-      if (fast_read_rgba_pixels_memcpy(ctx, x, y, width, height,
>-				       format, type, pixels, packing,
>-				       transferOps)) {
>-	 return;
>-      }
>+   /* Try the optimized paths first. */
>+   if (fast_read_rgba_pixels_memcpy(ctx, x, y, width, height,
>+                                    format, type, pixels, packing,
>+                                    transferOps)) {
>+      return;
>    }
> 
>    slow_read_rgba_pixels(ctx, x, y, width, height,
>-- 
>1.7.3.16.g9464b
>

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