--crop-transparency only seems to trim the bottom and right transparency

[scheibo]

When I try to use gifsicle --crop-transparency 218.gif -o cropped.gif on the following image I get a new gif which is trimmed but which only seems to have had the transparency removed from the bottom and right of the image:

• Before:
• After:

However, if I use https://ezgif.com/ with the "trim transparent pixels around the image" option and select "Crop with: Gifsicle" I get the properly cropped image that I would expect:

• Ezgif:

I understand this project has no association with https://ezgif.com/, but the fact that they claim to be using Gifsicle in this instance makes me believe that I should be able to achieve the same results and that I must simply be "holding it wrong". Am I missing something basic? If it helps: I'm using Gifsicle 1.93 and I've tried the command on both Ubuntu Linux and on macOS Catalina.

Thanks!

[scheibo]

I reached out the ezgif.com and they explained that they actually have the same issue and that the workaround was to call Gifsicle 4 times as a workaround: crop-transparency, rotate-90, crop-transparency, rotate-90 etc. Hopefully any other user that stumbles across this bug via Google can benefit from this clever workaround as well (though obviously actually fixing Gifsicle to make this workaround unnecessary is still desirable)!

$ gifsicle --crop-transparency input.gif -o output.gif
$ gifsicle --rotate-90 -b output.gif
$ gifsicle --crop-transparency -b output.gif
$ gifsicle --rotate-90 -b output.gif
$ gifsicle --crop-transparency -b output.gif
$ gifsicle --rotate-90 -b output.gif
$ gifsicle --crop-transparency -b output.gif
$ gifsicle --rotate-90 -b output.gif

[TPS]

If bottom & right cropping works correctly, wouldn't just

$ gifsicle --crop-transparency input.gif -o output.gif
$ gifsicle --rotate-180 -b output.gif
$ gifsicle --crop-transparency -b output.gif
$ gifsicle --rotate-180 -b output.gif

be enough?

[scheibo]

Ahah yes, oops! diff seems to report it gives the same result. Which is great for cutting the workaround in half, but its disappointing a workaround is needed in the first place.

[TPS]

I think EZGIF should've figured out that workaround, too. Maybe they've got someone to help contribute a fix back here?

[scheibo]

ezgif actually is already using 180, I had just somehow managed to interpret it incorrectly despite it being quite explicit: https://twitter.com/ezgif_com/status/1417713291410001921