Hello @deftomat,

I hadn't realized that GIF loop == 1 actually meant play twice (ie. rewind once).

I think the gif-loop metadata item should keep the GIF meaning (otherwise the name is confusing and it could break old code), but I agree that we need a new loop tag with a single defined meaning that the imagemagick, libwebp and giflib loaders and savers all respect.

So how about:

• gif-loop is simply the value in a GIF file. We tag this as deprecated, but still set it in the loaders for compatibility.
• loop has webp meaning, ie. 0 == forever, 1 == play once, 2 == play twice, etc.

For reference, giflib: 0 == forever, 1 == play twice, 2 == play 3 times, etc. IM uses the same convention as webp.

What do you think?

Handy for testing:

#!/usr/bin/python3

import sys
import pyvips

im = pyvips.Image.new_from_file(sys.argv[1], n=-1, access="sequential")
im = im.copy()
im.set("gif-loop", int(sys.argv[3]))
im.write_to_file(sys.argv[2])

Then:

$ ./set-loop.py ~/pics/dancing-banana.webp x.gif 1
$

Hi. Yes, it sounds good. I will update it.

@jcupitt I'm not exactly sure how we want to deprecate gif-loop. I understand that gifload.c will fill loop and gif-loop properties but what about magicksave.c? Which option should have the priority? User can forgot to update both options. Unfortunately, there is no gif-loop setter so I cannot update both gif-loop and loop when one of them change.

ping @jcupitt 🙂

Hiya, sorry for not responding. I think the savers should all do this:

1. If "loop" is set, use that, and don't look for "gif-loop". It has the webp meaning, so 0 == forever, 1 == play once, 2 == play twice etc.
2. Only if "loop" is not set, check "gif-loop". This has the gif meaning, so 0 == forever, 1 == play twice, 2 == play three times etc.

libvips has a deprecation system for header fields, so we can add "gif-loop" to that and it'll vanish from all interfaces, though it'll still work if you use it explicitly.

@jcupitt
Sorry for keeping this PR open for so long.

I add loop field with the correct (webp) meaning to both webp and gif.

Also, I add .editorconfig as it could help contributors. Config will force supported editors to use tabs instead of spaces and stops them from removing the trailing spaces. I was fighting with my editor as I had a massive amount of changes after each save 😞

OK, let's merge. I can see a couple of tiny things, but I'll zap them in another patch.

Thank you very much for working on this, @deftomat !

I added some other file types to .editorconfig, adjusted some formatting, and added "gif-loop" to the list of deprecated (and hidden) metadata fields.

AWESOME, thanks 👍

Is there an automated way how to format files in this project? Because I always forgot to put spaces into IFs 😞

I keep meaning to write an indent file, but I'm too lazy :(