[Mesa-dev] [PATCH] mesa: set clamp bit in glGetTexImage for GL_UNSIGNED_NORMALIZED

[Ian Romanick]

On 01/26/2012 06:40 AM, Brian Paul wrote:
> On Tue, Jan 24, 2012 at 10:58 PM, Anuj Phogat<anuj.phogat at gmail.com>  wrote:
>> Color clamping should be enabled in glGetTexImage if texture dataType is
>> GL_UNSIGNED_NORMALIZED and format is GL_LUMINANCE or GL_LUMINANCE_ALPHA
>>
>> Fixes 2 Intel oglconform test cases: pxconv-gettex and pxtrans-gettex
>> https://bugs.freedesktop.org/show_bug.cgi?id=40864
>>
>> NOTE: This is a candidate for the 8.0 branch
>>
>> Signed-off-by: Anuj Phogat<anuj.phogat at gmail.com>
>> ---
>>   src/mesa/main/texgetimage.c |    7 ++++++-
>>   1 files changed, 6 insertions(+), 1 deletions(-)
>>
>> diff --git a/src/mesa/main/texgetimage.c b/src/mesa/main/texgetimage.c
>> index 8c85c1e..f89b868 100644
>> --- a/src/mesa/main/texgetimage.c
>> +++ b/src/mesa/main/texgetimage.c
>> @@ -415,7 +415,12 @@ get_tex_rgba(struct gl_context *ctx, GLuint dimensions,
>>           transferOps |= IMAGE_CLAMP_BIT;
>>        }
>>     }
>> -
>> +   else if ((format == GL_LUMINANCE ||
>> +            format == GL_LUMINANCE_ALPHA)&&
>> +            dataType == GL_UNSIGNED_NORMALIZED) {
>> +      transferOps |= IMAGE_CLAMP_BIT;
>> +   }
>> +
>>     if (_mesa_is_format_compressed(texImage->TexFormat)) {
>>        get_tex_rgba_compressed(ctx, dimensions, format, type,
>>                                pixels, texImage, transferOps);
>> --
>
> This looks OK.  However, we need to add more comments here.  I had to
> do some digging to recall why luminance and lum/alpha are special.
> The reason is if the source image is RGB, the returned luminance is
> R+G+B and we need to clamp the sum to [0,1].

When Anuj and I discussed this patch, I had another concern, but I'm not 
sure it matters.  If dataType is GL_SIGNED_NORMALIZED, it seems like the 
value should clamp to [-1,1].  We don't currently have a way to do that. 
  Does that seem right to you?

> Would you please add a comment about that?  Thanks.

Good idea.