image/gif: local color table transparency is not respected

[gopherbot]

by andybons:

go version devel +125bf33c1905 Sat Sep 21 17:53:44 2013 +1000 darwin/amd64

Attached is the repro case with the example output as well.

I’ll follow up with more information on the gif that could be causing it, but other
animated gifs seem to work fine.

Attachments:

1. test.gif (420174 bytes)
2. test.go (389 bytes)
3. test1.gif (419790 bytes)

[gopherbot]

Comment 1 by andybons:

It seems it may be an issue with the decoder.

Attachments:

1. 18th_frame.jpg (10681 bytes)
2. test.go (448 bytes)

[minux]

Comment 2:

$ gifsicle test.gif '#18' > test-18.gif
the resulting looks exactly like the 18th_frame.jpg you posted, so perhaps
the problem is not Go's image/gif.

[nigeltao]

Comment 3:

As another data point, gif2png shows a similar thing (frame 18 looks similar to your
18th_frame.jpg, and doesn't look like any previous frames) but test.p18 is mostly
transparent, not mostly opaque black.

[nigeltao]

Comment 4:

I think the 18th frame actually does look like that (albeit transparent instead of
opaque black). I'd normally close this issue as WorkingAsIntended, but I'll leave it
open for the local color table transparency thing.
I've attached the test.p18 file generated by gif2png.

Labels changed: added priority-later, removed priority-triage.

Status changed to Accepted.

Attachments:

1. test.p18 (5853 bytes)

[nigeltao]

Comment 5:

I have mailed out https://golang.org/cl/13829043/ but we are currently in the
1.2 code freeze. This will land after 1.2 is released.

[rsc]

Comment 6:

Labels changed: added go1.3maybe.

[rsc]

Comment 7:

Labels changed: added release-none, removed go1.3maybe.

[rsc]

Comment 8:

Labels changed: added repo-main.

[nigeltao]

Comment 9:

This issue was closed by revision ff6b922.

Status changed to Fixed.

[gopherbot]

Comment 10 by dan.pupius:

Nice, thanks!