Transparency and PNG format

Thomas McGrath III 3mcgrath at
Wed Nov 30 09:57:48 EST 2005


PNGs support transparency as well as not. They are IMO the best for  
lossless compression. GIFs are good for animation.

I use PNGs all of the time. I use Photoshop (not elements) and when I  
save a png I delete my background and make sure the BG is transparent  
(with little checker boxes in PS) But If I 'flatten' the image it  
takes away the transparency and instead if I flatten visible layers  
(Do not include the BG) then delete the BG it always works perfectly.  
That is the way I do it. I am not sure about GC since I don't use  
that anymore.

This is not a limitation but rather a feature of PNGs that you can do  
both. Rev respects which ever way you saved the file.


On Nov 29, 2005, at 5:05 PM, graham samuel wrote:

> Folks, I've got a number of small GIFs in an app, representing  
> human figures - therefore not rectangular. I managed to give each  
> one a transparent background and RR honours this when I import the  
> GIFs as images (i.e. the background information on the card shows  
> up around the shape of the figure).
> I've now started to using PNGs rather than GIFS, and I can give  
> them transparent backgrounds in exactly the same way as the GIFs  
> (GraphicConverter on the Mac is really good for this - a lot  
> simpler than Photoshop Elements... but I digress). However when I  
> import a PNG as an image, the transparency disappears and the  
> figure therefore appears in a white rectangle. I can fix this with  
> inks, but only on the Mac, and this app is destined for PC users  
> mostly.
> I've looked at the docs, but I can't see a way of telling RR to use  
> the transparency in a PNG. I see a bit about Alpha Channels, but I  
> don't know if I'm using an Alpha Channel or not, and anyway I can't  
> understand how RR deals with them. I can of course convert all my  
> PNGs to GIFs, but is this the only solution? (This leads me to ask  
> if is there any disadvantage to using GIFs over PNGs - I kind of  
> thought there was, but I'm no longer sure why).
> Can anyone clarify this for me?
> Graham
> ----------------------------------------
> Graham Samuel / The Living Fossil Co. / UK and France
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