[fpc-devel] Correlation between TFPColor and RGB values (possible inconsistencies)

[Mattias Gaertner]

On Wed, 17 Feb 2010 04:39:26 -0300
Luiz Americo Pereira Camara <luizmed at oi.com.br> wrote:

> Mattias Gaertner escreveu:
> > On Tue, 16 Feb 2010 17:15:37 -0300
> > Luiz Americo Pereira Camara <luizmed at oi.com.br> wrote:
> >
> >   
> >> or
> >>
> >> colGray be redefined as colGray       : TFPColor = (Red: $8080; Green: 
> >> $8080; Blue: $8080; Alpha: alphaOpaque) ??
> >>     
> >
> > Yes, although this rarely makes a difference.
> >   
> 
> It does.
> See below.
> 
> >  
> >   
> >> This info will help to fix http://bugs.freepascal.org/view.php?id=15793
> >>     
> >
> > IMO the bug report is misleading. Converting a TFPColor to RGB looses
> > bits. 
> 
> The bug is not about converting to RGB. See the attached example in 
> bugreport.
> 
>   SetCol := colGray;
>   Img.Colors[0,0] := SetCol;
>   GetCol := Img.Colors[0,0];
> 
>   SetCol <> GetCol

That's exactly what my long response explained. 
Why do you expect that the 48bit color constants can be assigned to
24bit images without loss? Is this somewhere wrongly documented?


Mattias