Exporting transparent PNGs (again)
Chris Carroll-Davis
asgg35 at dsl.pipex.com
Tue Jul 4 11:06:41 EDT 2006
Hello again.
Well, I've made some progress! I can now stick an image on a card
and use that image to make an alpha channel for a second image.
Hurrah. Trouble is it is S--L--O--W! It takes over 10 seconds to
process a tiny 50-pixel square image!!! The utility I'm making needs
to export about 3000 - much larger - graphics!
The problem is that ImageData uses 4 bytes per pixel (even if it is a
8-bit greyscale image) but AlphaData only uses 1 byte per pixel, so I
have to strip the data out in a repeat loop that is huge; even for
moderately sized graphics! I started with a 300 x 300 graphic, but
of course for AlphaData that is 300x300 bytes = 90,000 repeats.
Yuk! There must be a better way
Is there any lightning fast way of manipulating the binary data
without resorting to a repeat loop?
Help!
Chris
On 4 Jul 2006, at 12:54, Chris Carroll-Davis wrote:
> Hello again folks.
>
> I recently posted a question about Rev's weird behaviour when
> exporting transparent PNGs from fields with Japanese text. No-one
> (understandably) was able to offer any help so, as is often the
> case, I think I'll be looking for a workaround...
>
> ... Exporting non-transparent PNGs works fine so, in theory, should
> I not be able to export the image (perhaps to clipboard or
> variable) then apply this to a graphic as an alpha channel? Then
> export the resulting image as transparent PNG?
>
> So... two questions:
> 1) Does the above workaround solution sound feasible?
> 2) How the devil do I do it???!!
>
> I've had a few half-hearted attempts at using the alphadata
> property, but I can't get it to work at all! Can anyone point me
> to some example stacks that use this property that I can dissect?
>
> I'd be grateful for any suggestions!!
>
>
> Chris
>
>
> _______________________________________________
> use-revolution mailing list
> use-revolution at lists.runrev.com
> Please visit this url to subscribe, unsubscribe and manage your
> subscription preferences:
> http://lists.runrev.com/mailman/listinfo/use-revolution
More information about the use-livecode
mailing list