[AD] ALLEGRO_PIXEL_FORMAT_LUMINANCE_8

[Peter Wang <novalazy@xxxxxxxxxx>]

On Sun, 22 Apr 2012 17:05:50 +0200, Elias Pschernig <elias.pschernig@xxxxxxxxxx> wrote:
> On Sun, 22 Apr 2012 23:46:30 +1000
> Peter Wang <novalazy@xxxxxxxxxx> wrote:
> 
> > Hi,
> > 
> > I didn't want to step on any toes so I thought I'd ask before
> > committing this patch.
> > 
> > BTW, with this patch all the tests pass again with or without FBOs,
> > except for the indexed bitmap tests.  The images are now shades of red
> > due to r15529.  I'm not sure if the tests should be adjusted or what.
> > 
> 
> I only was avoiding GL_LUMINANCE because we don't have it in an
> ALLEGRO_OPENGL_3_0 | ALLEGRO_OPENGL_FORWARD_COMPATIBLE (not sure why
> that are two different flags) context. I don't know how important that
> forward compatible flag is though. I guess certain extensions won't be
> available without it.

What should we do about ALLEGRO_PIXEL_FORMAT_LUMINANCE_8, since
GL_LUMINANCE is deprecated.

It only exists so we have a single channel format suitable for indexed
images.  Maybe it is simplest to rename the pixel format, and to say
that it is not defined how the single channel is mapped to the G,B,A
channels?

[1] says "Luminance and intensity are not considered color-renderable.
Therefore, you cannot bind textures of this format to a FBO."
That means, if using OpenGL <= 2 and GL_LUMINANCE, we also need to not
use an FBO to render to those bitmaps, yes?  Maybe it is already doing
that.

Peter

[1]: http://www.opengl.org/wiki/Image_Format#Special_color_formats