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Transparent GIFs?
Posted: Wed Nov 15, 2017 20:02
by holographic
Hello, nice people.
I wanted to ask: am I doing something wrong or transparent animated GIFs don't show as transparent?
It looks like any transparent GIF I throw at it gets shown as without alpha channel and with a white background.
It looks like I can somehow get it to use the transparency when I put the layer blending mode that has the GIF in it to Displace with an Opacity of 100%.
Thanks for reading and have an extra nice day!
Re: Transparent GIFs?
Posted: Wed Nov 15, 2017 20:14
by Zoltán
Thanks for reporting this,
indeed it looks like this is broken, I created a ticket. (#10164)
Re: Transparent GIFs?
Posted: Wed Nov 15, 2017 21:54
by Arvol
Would an automask FX work in the meantime?
Re: Transparent GIFs?
Posted: Wed Nov 15, 2017 22:20
by Oaktown
If the alpha channel is showing up in the clip and you’re getting white instead of transparent, have you tried to set up to straight instead of pre-multiplied?
Re: Transparent GIFs?
Posted: Wed Nov 15, 2017 22:53
by Zoltán
Oaktown wrote:If the alpha channel is showing up in the clip and you’re getting white instead of transparent, have you tried to set up to straight instead of pre-multiplied?
It's not showing up, unfortunately.
Re: Transparent GIFs?
Posted: Wed Nov 15, 2017 23:10
by Oaktown
Then it may be best to replace the transparent layer with a chroma green until you can get it fixed.
Re: Transparent GIFs?
Posted: Thu Nov 16, 2017 07:46
by Oaktown
I remembered running into this a few years back so I did some research and it turns out GIF doesn’t support alpha:
http://whatis.techtarget.com/definition/transparent-GIF
So, in your case, the color white is the “transparency” which is why you don’t see an alpha channel. So either, you key the white or you can replace it with a chroma green (or blue) which is easier to key than white.
Re: Transparent GIFs?
Posted: Thu Nov 16, 2017 09:47
by Joris
turns out GIF doesn’t support alpha
Pretty sure it does and this is just a bug where we don't display the transparency correctly.
Re: Transparent GIFs?
Posted: Thu Nov 16, 2017 10:32
by Oaktown
Pretty sure it does and this is just a bug where we don't display the transparency correctly.
My understanding is that GIF is only 24-bit and the transparency is palette-based transparency so you have to define a background color that is the "transparency" and do background matting to replace the background color with alpha.
So, yes it works as "transparency" but it's not an alpha layer which would require an add'l 8-bit.
As far as I undesrtand, the quickest way to use a GIF with transparency besides keying the background color is to open it in photoshop, select all the images and export>render video. I'm attaching two clips (one GIF with white transparency and the same rendered with Photoshop in QuickTime Animation codec)
Re: Transparent GIFs?
Posted: Thu Nov 16, 2017 11:15
by Joris
Yes, you were referring specifically to an alpha channel.
To a less technically versed person, your post could be interpreted as transparency in gifs is not supported. I just wanted to make clear that that is not the case.