No pages metadata for animated gif

[jaubourg]

Maybe I'm doing something wrong but whenever I load an animated gif and do operations on it, I always end up with the first frame transformed and that's it.

In order to determine if this was due to something deep into our code, I looked more closely into the metadata reported by sharp for animated gifs.

From what I understand from the docs, an animated image is supposed to give a pages value that is a number.

If I input an animated monkey found online, I end up with a metadata.pages that's undefined and sharp only acts on the first frame.

Is this by design? Am I missing something?

Also, I saw outputting animated webp was supported but is outputting apng supported too? Could be nice to have a clear support grid somewhere in the docs where this kind of things would be listed. But I know how difficult and time-consuming writing docs can be ;)

[lovell]

Bonjour, it looks like sharp needs to expose libvips' n property on the input so a caller can request all frames (with GIF you have to decode all the frames to find out the frame count and dimensions).

At the command line i see:

$ vipsheader -a small-animated-hear-see-speak-no-evil-moving-monkey.gif | grep page
$ vipsheader -a small-animated-hear-see-speak-no-evil-moving-monkey.gif[n=-1] | grep page
page-height: 157

So it looks like libvips itself also needs to expose the GIF page count too.

[jaubourg]

I dunno if this is related but I see not pages metadata for the following apng and animated webp image:

• https://upload.wikimedia.org/wikipedia/commons/1/14/Animated_PNG_example_bouncing_beach_ball.png
• https://mathiasbynens.be/demo/animated-webp-supported.webp

[jaubourg]

I also get a Error: webp2vips: unable to read pixels when I try and do any action on the webp above except getting metadata. Metadata show it's 400x400 though.

[lovell]

The forthcoming libvips v8.8.0 will add support for animated WebP.

libpng does not support animated PNG.

[jaubourg]

Ah that makes sense now. Thanks @lovell :)

[lovell]

Commit 9cc06c8 expose libvips' n parameter as the pages input option to select how many pages to load. This will be in v0.22.0.

[lovell]

v0.22.0 now available.

[RaboliotLeGris]

Salutations!

I think it's related to this issue.

I'm using sharp 0.22.1 and I'm trying to extract the number of pages of a GIF to determine if it's a animated one. But each time the metadata doesn't contains the pages attribute.

I've tried with several GIF picked on the web and also with the one that Jaubourd provides.

Here is a small standalone that show the issue.

wget http://www.netanimations.net/small-animated-hear-see-speak-no-evil-moving-monkey.gif
node -e "require('sharp')('small-animated-hear-see-speak-no-evil-moving-monkey.gif').metadata().then((meta) => console.log(meta, meta.pages))"

Am I missing something ? :)

[lovell]

It looks like libvips 8.8.0 is required for the pages property - see libvips/libvips@2968bee

[tomgallagher]

Hi Lovell, hope you're well.

Am I right in saying animated gif input to animated webp output will be possible in the near-ish future?

[lovell]

@tomgallagher libvips v8.8.0 supports this.

[tomgallagher]

And lipvips v8.8.0 may be included in Sharp 0.23.0?

[lovell]

@tomgallagher Yes, that's the plan.

[tomgallagher]

Great. Thanks.

[tomgallagher]

@lovell If the Sharp API need to change to accommodate libvips v8.8.0, I can help with the documentation if that's plausible and time-saving.