[lazarus] TGraphic Transparency

andrew johnson acjgenius at earthlink.net
Fri Mar 21 10:05:24 EST 2003

On Fri, 2003-03-21 at 01:35, Tony Maro wrote:
> On Thu, 2003-03-20 at 20:44, andrew johnson wrote:
> > 
> > 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
> 	I can see reason to have both transparencies applied before it's
> drawn.  I think this is logical.  Of course it's a judgment (that
> spelling doesn't look right, but that's what my spel cheker says) call
> barring previous Delphi work in this regard...

ok. see this is what I wasn't sure of, obviously in the case of it
having an existing transparency we should have a way of using it, but
what if they have trans. turned of? should we disable both the existing
and the by colour? or should it only affect by colour etc? i.e. what are
the long reaching implications of having two possible transp. types at
the same time or separate et al?

> >    b.) it doesn't
> 	Apply the graphic format's transparency still.
well the only reason this is a question is because of secondary
implications of the above... considerations of consistancy etc. not
really that big a deal, but for thoroughness should be mentioned.

> > 
> > 2.) how should it be handled on types which don't support it natively
> 	Obviously apply the transparency to the graphic as it's being drawn. 
> Well obvious to me, but I'm infamous for misunderstanding the question.

well the question here is _what_ transparency, i.e. how is this
transparency determined. If it is just a color is replaced like I think
I remember, how is that colour determined? where does that colour come
from? is it just a generic default? I don't think so because I remember
loading different bitmaps with different colours used and Delphi almost
always picked the right one. Anyway, like I say its been awhile since I
had use of this so I can't remember the ins and outs of how it worked,
so its hard to guess how it should work. 


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