[Newbies] Fading a PNG
greenbes at puzzlingevidence.net
Mon Apr 23 07:32:08 UTC 2007
Following Bert's advice, I see that HaloMorph overrides #drawSubmorphsOn:
and calls its Canvas using asAlphaBlendingCanvas. That seems like a good
place to start.
I tried subclassing ImageMorph and adding this method:
^ super drawOn: (aCanvas asAlphaBlendingCanvas: alphaValue).
Unfortunately, it didn't display anything at all. I tried alpha values of
0.5 and 1.0. If I remove the alpha blending stuff, and simply call:
^ super drawOn: aCanvas.
it works like a normal ImageMorph, so at least I know it isn't broken
Any suggestions on how to get asAlphaBlendingCanvas to blend some alphas?
On 4/23/07, Steven Greenberg <greenbes at puzzlingevidence.net> wrote:
> Thanks for the pointer! I didn't try that code in the workspace, but if
> you enable "haloTransitions" using the Preferences browser then the halos
> fade in and out.
> On 4/22/07, Bert Freudenberg <bert at freudenbergs.de> wrote:
> > On Apr 23, 2007, at 0:44 , Steven Greenberg wrote:
> > > I have a PNG image that I'd like to display fading out. I tried
> > > the BitBlt method suggested by "Team RAR" to fade the image, but I
> > > can't make it work.
> > >
> > > The image loads properly from a file and displays fine as an
> > > ImageMorph. I have been able to use a TransformationMorph to
> > > rotate and scale it, and PNG transparency is working properly.
> > >
> > > Is the "Team RAR" BitBlt method the only way, or are there
> > > alternatives?
> > >
> > > I'm running a 3.9 image, and my display depth is set to 32 bits.
> > >
> > Normally you would just use an alpha-blending canvas. See HaloMorph
> > fadeIn/fadeOut and draw methods. To try those halos, enable this:
> > Preferences enable: #haloTransitions
> > Now when I tried then the halo icons do not actually show until alpha
> > is one. No idea why that is.
> > - Bert -
> > _______________________________________________
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