[Mesa-dev] [PATCH] mesa: fix GL_LUMINANCE handling in glGetTexImage

[Anuj Phogat]

On Thu, Mar 8, 2012 at 7:19 PM, Brian Paul <brianp at vmware.com> wrote:
> There are several cases in which we need to explicity "rebase" colors
> (ex: set G=B=0) when getting GL_LUMINANCE textures:
> 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
>
> Fixes https://bugs.freedesktop.org/show_bug.cgi?id=46679
>
> Also fixes the new piglit getteximage-luminance test.
> ---
>  src/mesa/main/texgetimage.c |   30 ++++++++++++++++++++++++++++--
>  1 files changed, 28 insertions(+), 2 deletions(-)
>
> diff --git a/src/mesa/main/texgetimage.c b/src/mesa/main/texgetimage.c
> index 44a828a..05b052a 100644
> --- a/src/mesa/main/texgetimage.c
> +++ b/src/mesa/main/texgetimage.c
> @@ -298,6 +298,8 @@ get_tex_rgba_uncompressed(struct gl_context *ctx, GLuint dimensions,
>     const gl_format texFormat =
>        _mesa_get_srgb_format_linear(texImage->TexFormat);
>     const GLuint width = texImage->Width;
> +   const GLenum destBaseFormat = _mesa_base_tex_format(ctx, format);
> +   GLenum rebaseFormat = GL_NONE;
>     GLuint height = texImage->Height;
>     GLuint depth = texImage->Depth;
>     GLuint img, row;
> @@ -318,6 +320,28 @@ get_tex_rgba_uncompressed(struct gl_context *ctx, GLuint dimensions,
>        height = 1;
>     }
>
> +   if (texImage->_BaseFormat == GL_LUMINANCE ||
> +       texImage->_BaseFormat == GL_INTENSITY ||
> +       texImage->_BaseFormat == GL_LUMINANCE_ALPHA) {
> +      /* If a luminance (or intensity) texture is read back as RGB(A), the
> +       * returned value should be (L,0,0,1), not (L,L,L,1).  Set rebaseFormat
> +       * here to get G=B=0.
> +       */
> +      rebaseFormat = texImage->_BaseFormat;
> +   }
> +   else if ((texImage->_BaseFormat == GL_RGBA ||
> +             texImage->_BaseFormat == GL_RGB) &&
> +            (destBaseFormat == GL_LUMINANCE ||
> +             destBaseFormat == GL_LUMINANCE_ALPHA ||
> +             destBaseFormat == GL_LUMINANCE_INTEGER_EXT ||
> +             destBaseFormat == GL_LUMINANCE_ALPHA_INTEGER_EXT)) {
> +      /* If we're reading back an RGB(A) texture as luminance then we need
> +       * to return L=tex(R).  Note, that's different from glReadPixels which
> +       * returns L=R+G+B.
> +       */
Brian, don't we need do handle the similar case for compressed textures?
i.e. _mesa_meta_GetTexImage()->decompress_texture_image() currently
uses _mesa_ReadPixels() to get the compressed texture data, which
returns  L=R+G+B. I haven't yet tested how NVIDIA/AMD handle compressed
textures in glGetTexImage().

> +      rebaseFormat = GL_LUMINANCE_ALPHA; /* this covers GL_LUMINANCE too */
> +   }
> +
>     for (img = 0; img < depth; img++) {
>        GLubyte *srcMap;
>        GLint rowstride;
> @@ -335,12 +359,14 @@ get_tex_rgba_uncompressed(struct gl_context *ctx, GLuint dimensions,
>
>             if (is_integer) {
>                _mesa_unpack_uint_rgba_row(texFormat, width, src, rgba_uint);
> -               _mesa_rebase_rgba_uint(width, rgba_uint, texImage->_BaseFormat);
> +               if (rebaseFormat)
> +                  _mesa_rebase_rgba_uint(width, rgba_uint, rebaseFormat);
>                _mesa_pack_rgba_span_int(ctx, width, rgba_uint,
>                                         format, type, dest);
>             } else {
>                _mesa_unpack_rgba_row(texFormat, width, src, rgba);
> -               _mesa_rebase_rgba_float(width, rgba, texImage->_BaseFormat);
> +               if (rebaseFormat)
> +                  _mesa_rebase_rgba_float(width, rgba, rebaseFormat);
>                _mesa_pack_rgba_span_float(ctx, width, (GLfloat (*)[4]) rgba,
>                                           format, type, dest,
>                                           &ctx->Pack, transferOps);
> --
> 1.7.3.4
>
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/mesa-dev