Re: [Gnash-commit] Renderer transparency

[Bastiaan Jacques]

On Fri, 29 Aug 2008, Benjamin Wolsey wrote:

> > revno: 9648
> > committer: Benjamin Wolsey <address@hidden>
> > branch nick: trunk
> > timestamp: Thu 2008-08-28 21:59:28 +0200
> > message:
> >   Convert VP6A video to image::ImageRGBA. This only succeeds with SwScale,
> >   not with older versions of ffmpeg.
> >
> >   Make renderers accept but ignore RGBA data. It is easy to get agg to render
> >   the RGBA images, slightly harder to get it to handle both RGB and RGBA, and
> >   so far I don't see how to get it to handle transparency correctly.
>
> Can anyone sort out renderer transparency handling? There are now lots
> of occasions when transparency is needed and displaying it either isn't
> implemented or often looks rubbish. At the moment, most of the code for
> reading and using transparent images is there in the core, but the
> renderers can't handle it.

I can probably do that.

> With video, RGBA images will display if, in
> render_handler_agg::drawVideoFrame(), you change line 453,
>
>    typedef agg::pixfmt_rgb24_pre baseformat;
>
> to
>
>    typedef agg::pixfmt_rgba32_pre baseformat;
>
> But they are solid, and obviously it ruins display of rgb images. I
> can't be sure that the transparency information is read correctly by
> ffmpeg, but I can be sure that changing the alpha element makes no
> difference to the display.
>
> Display of transparent bitmap characters (e.g. dynamically loaded PNG)
> is still waiting to be corrected too. This works but is faulty. Again,
> it might be the way the alpha data is read and not the fault of the
> renderer (though I don't think so), but until someone familiar with the
> renderer code looks at it, I won't know. I assumed that being able to
> load PNG images directly, as is possible since a couple of weeks ago,
> would make testing and debugging easier.

You can also just write a small method that writes out your RGBA data to
XPM or similarly simple image form to test that the data is correct.

> There are various open bug items related to this.
>
> It is necessary to have a version of ffmpeg with swscale for decoding
> VP6A video to RGBA.

I take it you don't want to convert this to RGB24 for efficiency reasons?

> I can provide useful SWFs for testing, ming source code and videos if
> anyone is interested in doing it. It would be very good to have it for
> the next release.

That would be very useful.

Bastiaan