From: Eli Zaretskii <eliz@gnu.org>
To: Alan Third <alan@idiocy.org>
Cc: larsi@gnus.org, 44120@debbugs.gnu.org
Subject: bug#44120: 28.0.50; Animated GIFs sometimes leave "trails"
Date: Thu, 22 Oct 2020 15:54:29 +0300 [thread overview]
Message-ID: <835z72mnei.fsf@gnu.org> (raw)
In-Reply-To: <20201021200842.GB47992@breton.holly.idiocy.org> (message from Alan Third on Wed, 21 Oct 2020 21:08:42 +0100)
> Date: Wed, 21 Oct 2020 21:08:42 +0100
> From: Alan Third <alan@idiocy.org>
> Cc: 44120@debbugs.gnu.org
>
> >From image.c:
>
> /* From gif89a spec: 1 = "keep in place", 2 = "restore
> to background". Treat any other value like 2. */
>
> >From the gif89a spec:
>
> iv) Disposal Method - Indicates the way in which the graphic is to
> be treated after being displayed.
>
> Values : 0 - No disposal specified. The decoder is
> not required to take any action.
> 1 - Do not dispose. The graphic is to be left
> in place.
> 2 - Restore to background color. The area used by the
> graphic must be restored to the background color.
> 3 - Restore to previous. The decoder is required to
> restore the area overwritten by the graphic with
> what was there prior to rendering the graphic.
> 4-7 - To be defined.
>
> That gif uses a disposal value of 3 quite a lot.
>
> It looks like when a block is updated with a disposal value of 3 we
> should hang onto the previous contents and then restore them in, I
> guess, the next frame.
FTR, the image renders correctly on MS-Windows when
w32-use-native-image-API is non-nil, so this indeed seems like a
problem with our GIF code.
next prev parent reply other threads:[~2020-10-22 12:54 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-21 19:17 bug#44120: 28.0.50; Animated GIFs sometimes leave "trails" Lars Ingebrigtsen
2020-10-21 20:08 ` Alan Third
2020-10-22 12:01 ` Lars Ingebrigtsen
2020-10-22 12:14 ` Alan Third
2020-10-22 12:54 ` Eli Zaretskii [this message]
2020-10-21 20:37 ` Stefan Kangas
2020-10-22 12:02 ` Lars Ingebrigtsen
2022-04-10 15:13 ` Lars Ingebrigtsen
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