buttery generates continuous GIF loops.
$ buttery homer.gifSee buttery -help for more options.
https://github.com/mcandre/buttery/releases
$ go install github.com/mcandre/buttery/cmd/buttery@latesthttps://pkg.go.dev/github.com/mcandre/buttery
FreeBSD
(None)
For more information on developing buttery itself, see DEVELOPMENT.md.
buttery -check <GIF> can act as a linter for basic GIF file format integrity. In the event of a corrupt GIF file, the program emits a brief message and exits non-zero.
buttery -getFrames <GIF> reports the frame count. This is useful for planning edits, particularly towards the far end of the original animation sequence.
-stitch Mirror is the primary transition smoothing option, and the default buttery behavior.
Mirror twists the GIF timeline around like a Mobius strip, so that it arrives naturally back at the start. This is useful for smoothing GIF's that present misaligned images at the extreme ends of the loop.
We can diagram logically how Mirror works, by examining its effect on the frame sequence. With the notation:
real frame sequence (successive sequence repeated during infinite loop playback...)
1 2 3 (1 2 3 ...)
Each restart of the loop has a jarring visual jump from frame 3 to its successor frame 1.
1 2 3 2 (1 2 3 2 ...)
Of course, running the buttery editor yourself is the best way to appreciate how it works.
By mirroring the sequence backward in time, we remove the biggest visual jump. The overall visual effect is that of a sailor rowing back and forth in place. The Mirror transition often dramatically improves the smoothness of a GIF loop.
However, some motion may still appear awkward with mirroring, such as sharp, quick motions towards the extreme ends of the loop, or motions that appear to defy physical entropy. For this reason, we provide alternative transitions and other editing tools, described below.
The transisions -stitch FlipH or -stitch FlipV disguise jarring misalignment, by reflecting the frames horizontally or vertically.
With the notation:
R: An original "right" frameL: A frame reflected horizontally "leftward"U: A original "upright" frameD: A frame reflected vertically "downward"
FlipH:
R R R (R R R ...)
FlipV:
U U U (U U U ...)
FlipH:
R R R L L L (R R R L L L ...)
FlipV:
U U U D D D (U U U D D D ...)
The FlipH/FlipV transitions are snappy, with an effect like rebounding a tennis ball across a net.
The -stitch None transition applies no particular transition at all between animation cycles. In art, sometimes less is more.
Animation smoothing takes a long time. We recommend pre-cutting your source assets to the desired subsequence. Every frame removed from the input GIF makes the buttery editing process faster.
Often, animations appear to accelerate when frame are removed. This is not always a bad thing; sometimes a fast animation helps to smooth over more subtle details.
The -trimStart <n> / -trimEnd <n> options drop n frames from the start and/or end of the original sequence. Zero indicates no trimming.
For brevity, we will now assume the None transition and elide the successive sequence repetitions.
1 2 3 4 5
With -trimStart 1:
2 3 4 5
With -trimEnd 1:
1 2 3 4
With -trimStart 1 and -trimEnd 1:
2 3 4
For convenience, we provide a similar option -trimEdges <n>. This drops n frames from both sides of the original sequence. Zero indicates no trimming.
1 2 3 4 5
With -trimEdges 1:
2 3 4
The -window <n> option truncates the original sequence to a fixed frame count. This is helpful for cutting down long animations. Zero indicates no truncation.
1 2 3 4 5
With -window 3:
1 2 3
With -window 3 and -trimStart 1:
2 3 4
The -shift <offset> option performs a circular, leftward shift on the original sequence. This is useful for fine tuning how the GIF's very first cycle presents, before entering successive loops.
Zero is the neutral shift. A negative offset indicates rightward shift.
1 2 3
With -shift 1:
2 3 1
With -shift -1:
3 1 2
The -speed <factor> option adjusts animation speed. Speed is expressed as a factor relative to the original GIF frame delay. We recommend using magnitudes between 0.2 (slow) and 2.0 (fast).
1 = 1.0 is the neutral speed factor.
Zero speed factor acts as -window 1, freezing the sequence to a single frame.
Negative speed factors like -1, -2, -0.2, etc., navigate the original sequence in reverse order, from back to front.
We can diagram this in terms of the frame delays, expressed in centiseconds. That is, 4cs indicates 4 centisec = 4/100 sec between advancing to the next frame.
4cs 6cs 8cs
With -speed 2:
2cs 3cs 4cs
With -speed 0.5:
8cs 12cs 16cs
With -speed -1:
8cs 6cs 4cs
GIFs have some further quirks worth noting, regarding animation speed.
The lowest delay value is zero, though in GIF format speak, that indicates a reset to a default 1 sec delay, which is slow.
In theory, the fastest GIF delay is 1 centisec. However, this equates to an FPS frame rate higher than most computer systems can handle. In practice, the fastest GIF delay is 2 centisec, nearly 60 FPS. Unfortunately, some GIF rendering engines such as Google Chrome, may also treat 1 centisec as a reset to default 1 sec delay, which is slow. In order to ensure wide compatibility with many different GIF viewing applications, buttery enforces a lower bound of 2 centisec for frame delays.
Frame delays are sensitive to high speed factors. Even most factors like 3.0 and higher, may produce a stuttery or blurred effect.
Short, single digit frame delays are even more sensitive to speed factors. This is due to inherent limitations in delay integer precision. As a result, many different values of factors can yield animations with identical animation speeds.
Note that some GIF's are already using the quickest delay setting possible, about 2cs. In that case, a speed factor greater than or equal to 1, may not have the desired effect.
- ffmpeg edits and converts videos
- gifenc.sh converts numerous video formats to animated GIF's
- ImageMagick converts between multimedia formats, including GIF and WEBP
- karp for conveniently browsing files and directories
- mkvtools edits MKV videos
- VLC plays numerous multimedia formats
- webm supports audio in animation loops
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