[Newbies] Fading a PNG

[Bert Freudenberg]

Try drawing something other than an image. I have a hunch the alpha- 
bitblt is wrong ...

Btw, which platform are you on? Which VM?

- Bert -

On Apr 23, 2007, at 9:32 , Steven Greenberg wrote:

> 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:
>
>     drawOn: aCanvas
>         ^ 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 someplace else.
>
> 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.
>
>     Thanks,
>     Steve
>
>
>
>
> 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 -