Gifsicle

Gifsicle is a command-line tool for creating, editing, and getting information about GIF images and animations. Making a GIF animation with gifsicle is easy:

gifsicle --delay=10 --loop *.gif > anim.gif

• gifsicle anim.gif '#0' > firstframe.gif
• You can also edit animations by replacing, deleting, or inserting frames:
• gifsicle -b anim.gif --replace '#0' new.gif

• Batch mode for changing GIFs in place.
• Prints detailed information about GIFs, including comments.
• Control over interlacing, comments, looping, transparency...
• Creates well-behaved GIFs: removes redundant colors, only uses local color tables if it absolutely has to (local color tables waste space and can cause viewing artifacts), etc.
• It can shrink colormaps and change images to use the Web-safe palette (or any colormap you choose).
• Optimize your animations! This stores only the changed portion of each frame, and can radically shrink your GIFs. You can also use transparency to make them even smaller. Gifsicle's optimizer is pretty powerful, and usually reduces animations to within a couple bytes of the best commercial optimizers.
• Unoptimizing animations, which makes them easier to edit.
• A dumb name.

• Correct an optimization bug introduced in 1.76.
• Major improvements to color selection (important when reducing colormap size). Use gamma-corrected colors in selection and dithering; this makes image quality much better. Also, when reducing colors with dithering, prefer to select colors that dithering can't approximate.
• Add ordered dithering modes, which avoid animation artifacts. The default ordered dithering mode (`--dither=ordered`) is a novel mode that combines some of the visual advantages of error diffusion with the artifact avoidance of ordered dithering.
• Add halftone dithering (`--dither=halftone`).
• gifview: Improved cache memory management for better animations. Collect memory for old frames based on an explicit --memory-limit (default 40MB).
• gifview: Add `--fallback-delay` option, to specify a fallback delay for frames with delay 0.
• Fix `-O2` crashes introduced with `--resize` improvements.
• Improve `--careful` (fewer crashes).
• Improve `-O2`: again, don't refuse to optimize images with local color tables.
• Greatly improve `--dither` speed.
• Improve `--resize` behavior: avoid animation artifacts due to different rounding decisions. Also speed it up.
• Fix bug where `-O2` would refuse to optimize some images with local color tables, claiming that "more than 256 colors were required". What was really required is previous disposal.
• Fix crash bugs on some combinations of `--crop` and `--resize` (prevalent on images whose first frame didn't cover the whole logical screen).
• Avoid rounding errors in `--resize`.
• Report error when `-I` is combined with `-b`.
• Frame selections also apply in batch mode.
• Fix `--crop` bug introduced in version 1.68, visible in images containing local color tables.
• gifsicle: Alberto Nannini reported some images that are optimized beyond what Gifsicle can do. In fact, Gifsicle's GIF writer was limited enough that even when running without optimization, it seriously expanded the input images. Some improvements to Gifsicle's writing procedure avoid this problem; now `gifsicle IMAGE` will produce large results less often, and when it does generate larger results, they're larger by hundreds of bytes, not hundreds of thousands. However, due to restrictions in the current optimizer (and on my time), I was unable to improve `gifsicle -O3`'s handling of these images. The optimizer that produced the images must be doing something pretty clever. (Is it SuperGIF?)
• gifsicle: Frame specifications like "#2-0" are allowed; they insert frames in reverse order. Feature request from Leon Arnott. * gifview: Add --min-delay option.
• gifsicle: Add -Okeep-empty for Gerald Johanson.
• gifsicle: Several users (Kornel Lesiński and others) reported "bugs" with Gifsicle-optimized images and Mac programs like Safari. The bug was in Safari, but add --careful to work around it.
• Improve -O3 a bit (although for some images, the new -O3 is bigger than the old).