Re: [Mesa3d-users] problem with display

[Brian P. <bri...@tu...>]

Jonathan Richard wrote:
> 
> 
> On 10/9/07, *Brian Paul* <bri...@tu... 
> <mailto:bri...@tu...>> wrote:
> 
>     Jonathan Richard wrote:
>      > Hi, I use mesa3d for 16 bits offscreen rendering and it seems to be
>      > working well. Unfortunately I also need to display a 3d model on the
>      > screen. However since I linked with the opengl32.dll 16 bits per
>      > channel version, the color that are displayed are not the right ones.
>      > How does the conversion from 16 bits to 8 bits is performed? What
>     can
>      > I do to get the right 8 bits colors? thanks
> 
>     If Mesa's compiled for deep (16/32-bit) color channels and it sees that
>     you're rendering into a shallower renderbuffer it should down-convert
>     the color as needed.  This would take place in src/mesa/swrast/s_span.c
>     in the convert_color_type() function.
> 
>     Perhaps you can use your debugger to see if that function is getting
>     called.
> 
>     -Brian
> 
>  
> Hi Brian, I forget to say that I'm developping on ms windows. Does it 
> change your answer? You should get a look at this message wrote by Karl 
> Schultz:
>  
> "The current GDI driver expects only 8 bit per channel data from Mesa.  
> You would have to modify the GDI driver to convert the 16 bit per 
> channel image generated by Mesa to 8 bit per channel, keeping the upper 
> 8 bits.  This should not be too hard to do.  If you look in 
> drivers/windows/gdi, I think most of the code is in wmesa.c.  There is 
> probably a call to a BitBlt function.  Just before that call, you would 
> walk through the source pixel array and convert it in place to 8 bits 
> per channel.
> Hopefully there is a data structure someplace where you can determine 
> the component size and decide when it is appropriate to do this."
>  
> Is he right?

He was right, as of about 6-12 months ago.  At some point I added the 
convert_color_type() code to handle the situation you describe.  Karl 
may not be aware of it.

-Brian