[lazarus] TGraphic Transparency

Solerman Kaplon solerman at wonder.com.br
Fri Mar 21 08:30:03 EST 2003

Hi Andrew,

It's annoying to see that the delphi TGraphic can get displayed right on 
a TImage, so will be nice if the Lazarus one correct this, eg: for 
display right an PNG with an alpha channel. Maybe you can get some info 
on this on g32.org, they have an excelente TImage replacement that 
supports full 32 bits images at pixel level, althow porting it will may 
be to much hard for a first version...

just my two cents,


andrew johnson wrote:
> I would like to get TGraphic Transparency working, and since it only
> affects display, and that is always handled by StretchBlt in the long
> run, I was hoping to add it there. 
> However since png's, and other more advanced graphic types can have an
> existing transparency for instance, I would like to get the general
> opinion on exactly how this should be handled. With XPM's/BMP's for
> instance, I believe it is simply whatever is the current brush color is
> replaced with a transparent mask, but I am not positive as it has been
> awhile since I used this feature myself. 
> So anyway, essentially I have the following questions before I finish
> and commit:
> 1.) How should transparency be handled with graphic types that support
> it natively when
>    a.) the current graphic has such a channel
>    b.) it doesn't
> 2.) how should it be handled on types which don't support it natively
> Andrew
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