mesa: Fix GL_LUMINANCE handling for textures in glGetTexImage

We need to rebase colors (ex: set G=B=0) when getting GL_LUMINANCE
textures in following cases:
1. If the luminance texture is actually stored as rgba
2. If getting a luminance texture, but returning rgba
3. If getting an rgba texture, but returning luminance

A similar fix was pushed by Brian Paul for uncompressed textures
in commit: f5d0ced.
Fixes https://bugs.freedesktop.org/show_bug.cgi?id=47220

Observed no regressions in piglit and ogles2conform due to this fix.
This patch will cause failures in intel oglconform pxconv-gettex,
pxstore-gettex and pxtrans-gettex test cases. The cause of failures
is a bug in test cases. Expected luminance value is calculted
incorrectly in test cases: L = R+G+B.

V2: Set G = 0 when getting a RG texture but returning luminance.

Note: This is a candidate for stable branches.

Signed-off-by: Anuj Phogat <[email protected]>
Reviewed-by: Ian Romanick <[email protected]>

1 files changed, 14 insertions, 3 deletions

diff --git a/src/mesa/drivers/common/meta.c b/src/mesa/drivers/common/meta.c
index 08bd899f861..d5e8af3c0a6 100644
--- a/src/mesa/drivers/common/meta.c
+++ b/src/mesa/drivers/common/meta.c
@@ -3685,6 +3685,7 @@ decompress_texture_image(struct gl_context *ctx,
    /* read pixels from renderbuffer */
    {
       GLenum baseTexFormat = texImage->_BaseFormat;
+      GLenum destBaseFormat = _mesa_base_tex_format(ctx, destFormat);
 
       /* The pixel transfer state will be set to default values at this point
        * (see MESA_META_PIXEL_TRANSFER) so pixel transfer ops are effectively
@@ -3693,9 +3694,19 @@ decompress_texture_image(struct gl_context *ctx,
        * returned as red and two-channel texture values are returned as
        * red/alpha.
        */
-      if (baseTexFormat == GL_LUMINANCE ||
-          baseTexFormat == GL_LUMINANCE_ALPHA ||
-          baseTexFormat == GL_INTENSITY) {
+      if ((baseTexFormat == GL_LUMINANCE ||
+           baseTexFormat == GL_LUMINANCE_ALPHA ||
+           baseTexFormat == GL_INTENSITY) ||
+          /* If we're reading back an RGB(A) texture (using glGetTexImage) as
+	   * luminance then we need to return L=tex(R).
+	   */
+          ((baseTexFormat == GL_RGBA ||
+            baseTexFormat == GL_RGB  ||
+            baseTexFormat == GL_RG) &&
+          (destBaseFormat == GL_LUMINANCE ||
+           destBaseFormat == GL_LUMINANCE_ALPHA ||
+           destBaseFormat == GL_LUMINANCE_INTEGER_EXT ||
+           destBaseFormat == GL_LUMINANCE_ALPHA_INTEGER_EXT))) {
          /* Green and blue must be zero */
          _mesa_PixelTransferf(GL_GREEN_SCALE, 0.0f);
          _mesa_PixelTransferf(GL_BLUE_SCALE, 0.0f);