[Mesa-dev] [PATCH 2/4] ReadPixels: Force ALPHA to 1 while rebasing RGBA values for GL_RGB format

[Carl Worth]

When performing a ReadPixels operation, we may be reading from a buffer that
stores alpha values, but that is actually representing a buffer with no alpha
channel. In this case, while rebasing the values, touch up all alpha values
read to 1.0.

This commit fixes the following piglit (sub) tests:

	ARB_texture_float/fbo-colormask-formats
		GL_RBG16F_ARB
	EXT_texture_snorm/fbo-colormask-formats
		GL_RGB16_SNORM
		GL_RGB8_SNORM
		GL_RGB_SNORM

It likely improves the results of other tests as well, but a PASS remains
elusive due to additional bugs.
---
 src/mesa/main/pack.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/mesa/main/pack.c b/src/mesa/main/pack.c
index d6a97b3..e00ae63 100644
--- a/src/mesa/main/pack.c
+++ b/src/mesa/main/pack.c
@@ -6022,6 +6022,11 @@ _mesa_rebase_rgba_float(GLuint n, GLfloat rgba[][4], GLenum baseFormat)
          rgba[i][BCOMP] = 0.0F;
       }
       break;
+   case GL_RGB:
+      for (i = 0; i < n; i++) {
+         rgba[i][ACOMP] = 1.0F;
+      }
+      break;
    default:
       /* no-op */
       ;
@@ -6060,6 +6065,11 @@ _mesa_rebase_rgba_uint(GLuint n, GLuint rgba[][4], GLenum baseFormat)
          rgba[i][BCOMP] = 0;
       }
       break;
+   case GL_RGB:
+      for (i = 0; i < n; i++) {
+         rgba[i][ACOMP] = 1;
+      }
+      break;
    default:
       /* no-op */
       ;
-- 
1.7.10.4