[FIXED] BUG: Alpha and WEBP

Post any defects you find in the released or beta versions of the ImageMagick software here. Include the ImageMagick version, OS, and any command-line required to reproduce the problem. Got a patch for a bug? Post it here.
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tc33
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[FIXED] BUG: Alpha and WEBP

Post by tc33 » 2013-02-13T15:52:59-07:00

Reference post: viewtopic.php?f=1&t=20836
magick wrote:Download the Webp library and use the cwebp and dwebp tools to convert your PNG to the Webp format. With these tools we're getting a black alpha channel. If you can get them to produce transparent Webp, let us know. We can then use these utilities to determine why alpha fails to work with ImageMagick.
Using IM 6.8.2.8 and libwebp 0.2.1, this appears to remain an issue. I am able to use cwebp from libwebp 0.2.1 to successfully convert a PNG with alpha to webp. Using IM, the image gets corrupted. Seems to work fine with input files that do not have an alpha channel. I also noticed the same behavior with GIFs that have alpha.

Another interesting point is that some image viewers can read the IM-generated file properly (in my case, Irfanview), but Chrome and the webp codec for windows cannot read the IM file properly; apparently they only render the alpha channel (?)

Source file (though any file with alpha seems to cause the problem): http://cssignet.free.fr/png-test-corpus ... dbe-c0.png

Thanks!

Edit: Confirmed/fixed in 6.8.3.0. Thank you!
Last edited by tc33 on 2013-02-19T15:17:36-07:00, edited 1 time in total.

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magick
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Re: BUG: Alpha and WEBP

Post by magick » 2013-02-14T05:21:38-07:00

We can reproduce the problem you posted and have a patch in ImageMagick 6.8.3-0 Beta available by sometime tomorrow. Thanks.

tc33
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Re: BUG: Alpha and WEBP

Post by tc33 » 2013-02-14T10:56:33-07:00

Thank you!

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