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

[Brian Paul]

On Mon, Sep 10, 2012 at 3:16 PM, Anuj Phogat <anuj.phogat at gmail.com> wrote:
> 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().

That's probably correct.  Can you take care of that?

-Brian