Gifsicle Man Page

NAME

gifsicle - manipulates GIF images and animations

SYNOPSIS

gifsicle [options, frames, and filenames]...

DESCRIPTION

gifsicle is a powerful command-line program for manipulating GIF image files. Extensive options let you control what exactly it does.

This man page assumes that you know what GIFs and GIF animations are. For a tutorial, you might try some of the resources listed on-line at webreference.com: http://www.webreference.com/authoring/graphics/animation.html

INTRODUCTION

Without options, gifsicle acts like a filter: you feed it a GIF on standard input, and it writes that GIF on standard output. That means these two commands do the same thing:

% gifsicle < in.gif > out.gif
% gifsicle < in.gif | gifsicle | gifsicle | gifsicle > out.gif

Well, that's not very interesting! Most times you'll tell gifsicle to alter its inputs by giving it command line options. The -i option, for example, tells it to interlace its input files:

% gifsicle -i < pic.gif > interlaced-pic.gif

This style doesn't work very well if you want to modify GIF files in place. For that, you should use the --batch option: with --batch, gifsicle will modify the files you specify instead of writing a new file to the standard output. To interlace all the GIFs in the current directory, you could say:

% gifsicle --batch -i *.gif

gifsicle is good at creating and manipulating GIF animations. The simplest way to create an animation is to give more than one input file, which gifsicle will combine to create a ``flipbook'' animation:

% gifsicle pic1.gif pic2.gif pic3.gif > animation.gif

Options like --delay, --loopcount, and --optimize will help you tune your animations; see their descriptions for more details.

The next sections index gifsicle's options and describe them in gory detail. New users may want to skip to the Examples section at the end.

CONCEPT INDEX

This index is meant to help you find options that do what you want. Concepts are on the left, relevant gifsicle options are on the right.

Animations, changing ...		frame selections, frame changes, etc.
disposal ...		--disposal
looping ...		--loopcount
portions of ...		frame selections
smaller ...		--optimize, --colors
speed ...		--delay
Background color ...		--background
Colors, changing ...		--change-color, --use-colormap, --dither, --transform-colormap
reducing number ...		--colors, --dither
Comments ...		--comment
Extensions ...		--extension, --app-extension, --extension-info
File size ...		--optimize, --unoptimize, --colors
Image transformations ...
cropping ...		--crop
flipping ...		--flip-*
resizing ...		--resize, --scale
rotating ...		--rotate-*
Grayscale ...		--use-colormap
Interlacing ...		--interlace
Positioning frames ...		--position
Screen, logical ...		--logical-screen
Selecting frames ...		frame selections (like #0)
Transparency ...		--transparent
Warnings ...		--no-warnings
Web-safe palette ...		--use-colormap

COMMAND LINE

gifsicle's command line consists of GIF input files and options. Most options start with a dash (-) or plus (+); frame selections, a kind of option, start with a number sign (#). Anything else is a GIF input file.

gifsicle reads and processes GIF input files in order. If no GIF input file is given, or you give the special filename `-', it reads from the standard input.

gifsicle exits with status 0 if there were no errors and status 1 otherwise.

OPTIONS

Every option has a long form, `--long-descriptive-name'. You don't need to type the whole long descriptive name, just enough to make it unambiguous.

Some options also have a short form, `-X'. You can combine short options if they don't take arguments: `-IIb' is the same as `-I -I -b'. But be careful with options that do take arguments: `-cblah' means `-c blah', not `-c -b -l -a -h'.

Many options also have a converse, `--no-option', which turns off the option. You can turn off a short option `-X' by saying `+X' instead.

Mode Options

Mode options tell gifsicle what kind of output to generate. There can be at most one mode option, which must precede any GIF inputs.

--merge, -m

Combine all GIF inputs into one file with multiple frames and write that file to the standard output. This is the default mode.

--batch, -b

Modify each GIF input in place by reading and writing to the same filename. (GIFs read from the standard input are written to the standard output.)

--explode, -e

Create an output GIF for each frame of each input file. The output GIFs are named `xxx.000', `xxx.001', and so on, where `xxx' is the name of the input file (or whatever you specified with `--output') and the numeric extension is the frame number.

--explode-by-name, -E

Same as --explode, but write named frames to files `xxx.name' instead of `xxx.frame-number'.

General Options

General options control what information gifsicle prints and where it writes its output. The info options and --verbose can be turned off with `--no-X'.

--color-info

Like --info, but also print information about input files' colormaps. --cinfo is a synonym for --color-info.

--extension-info

Like --info, but also print any unrecognized GIF extensions in a hexdump(1)-like format. --xinfo is a synonym for --extension-info.

--help, -h

Print usage information and exit.

--info, -I

Print a human-readable description of each input GIF to the standard output, or whatever file you specify with -o. This option suppresses normal output. (If you give two --info or -I options, the description will be printed on standard error and output will occur as usual.)

-o file

--output file

Send output to file. The special filename `-' means the standard output.

--verbose, -v

Print progress information (files read and written) to standard error.

--no-warnings, -w

Suppresses all warning messages.

--version

Print the version number and some short non-warranty information and exit.

Frame Selections

A frame selection tells gifsicle which frames to use from the current input file. They are useful only for animations, as non-animated GIFs only have one frame. Here are the legal forms for frame specifications.

#num

Select frame num. (The first frame is `#0'. Negative numbers count backwards from the last frame, which is `#-1'.)

#num1-num2

Select frames num1 through num2.

#num1-

Select frames num1 through the last frame.

#name

Select the frame named name.

For example,

gifsicle happy.gif

will use all of `happy.gif's frames, while

gifsicle happy.gif #0

will only use the first.

What gifsicle does with the selected frames depends on the current mode. In merge mode, only the selected frames are merged into the output GIF. In batch mode, only the selected frames are modified; other frames remain unchanged. In explode mode, only the selected frames are exploded into output GIFs.

Frame Change Options

Frame change options insert new frames into an animation or replace or delete frames that already exist. Some things -- for example, changing one frame in an animation -- are difficult to express with frame selection, but easy with frame changes.

--delete frames [frames...]

Delete frames from the input GIF.

--insert-before frame other-GIFs

Insert other-GIFs before frame in the input GIF.

--append other-GIFs

Append other-GIFs to the input GIF.

--replace frames other-GIFs

Replace frames from the input GIF with other-GIFs.

--done

Complete the current set of frame changes.

The frames arguments are frame selections (see above). These arguments always refer to frames from the original input GIF. So, if `in.gif' has 3 frames and `other.gif' has one, this command

gifsicle in.gif --delete #0 --replace #2 other.gif

will produce an output animation with 2 frames: `in.gif' frame 1, then `other.gif'.

The other-GIFs arguments are any number of GIF input files and frame selections. These images are combined in merge mode and added to the input GIF. The other-GIFs last until the next frame change option, so this command replaces the first frame of `in.gif' with the merge of `a.gif' and `b.gif':

gifsicle -b in.gif --replace #0 a.gif b.gif

This command, however, replaces the first frame of `in.gif' with `a.gif' and then processes `b.gif' separately:

gifsicle -b in.gif --replace #0 a.gif --done b.gif

Warning: You shouldn't use both frame selections and frame changes on the same input GIF.

Image Options

Image options modify input images (by changing their interlacing, transparency, and cropping, for example). Each image option stays in effect until the next image option in the same category. They have three forms: `--X', `--no-X', and `--same-X'. The default is `--same-X', which means that X's value is copied from each input. The converse, `--no-X', erases X; for instance, --no-interlace turns interlacing off, while --no-comments strips comments. Only the `--X' form is generally described.

-B color

--background color

Set the output GIF's background to color. The argument can have the same forms as in the --transparent option below.

--crop x1,y1-x2,y2

--crop x1,y1+widthxheight

Crop the following frames to a smaller rectangular area. The top-left corner of this rectangle is (x1,y1); you can give either the lower-right corner, (x2,y2), or the width and height of the rectangle. If width or height is negative, gifsicle will make the image's width or height smaller by that amount. For example, --crop 2,2+-4x-4 will shave 2 pixels off each side of the image.

--flip-horizontal

--flip-vertical

Flip the following frames horizontally or vertically.

-i

--interlace

Turn interlacing on.

-S widthxheight

--logical-screen widthxheight

Set the output logical screen to widthxheight. --no-logical-screen sets the output logical screen to the size of the largest output frame, while --same-logical-screen sets the output logical screen to the largest input logical screen. --screen is a synonym for --logical-screen.

-p x,y

--position x,y

Set the following frames' positions to (x,y). --no-position means --position 0,0. Normally, --position x,y places every succeeding frame exactly at x,y. However, if an entire animation is input, x,y is treated as the position for the animation.

--rotate-90

--rotate-180

--rotate-270

Rotate the following frames by 90, 180, or 270 degrees. --no-rotate turns off any rotation.

-t color

--transparent color

Make color transparent in the following frames. Color can be a colormap index (0-255), a hexadecimal color specification (like #FF00FF for magenta), or slash- or comma-separated red, green and blue values (each between 0 and 255).

Extension Options

Extension options add non-visual information to the output GIF. This includes names, comments, and generic extensions.

-x app-name extension

--app-extension app-name extension

Add an application extension named app-name and with the value extension to the output GIF.

-c text

--comment text

Add a comment, text, to the output GIF. The comment will be placed before the next frame in the stream.

--no-comments and --same-comments affect all the images following, and apply only to input GIF comments, not ones added with --comment.

--extension number extension

Add an extension numbered number and with the value extension to the output GIF. Number can be in decimal, octal, hex, or it can be a single character like `n', whose ASCII value is used.

--no-extensions (or +x) and --same-extensions affect all the images following, and apply only to input GIF extensions.

-n text

--name text

Set the next frame's name to text. This name is stored as an extension in the output GIF.

--no-names and --same-names affect all the images following. They apply only to input GIF names, not ones added with --name.

Animation Options

Animation options are image options applying only to GIF animations. Most of them act like image options, and have the same three forms (see above).

-d time

--delay time

Set the delay between frames to time in hundredths of a second.

-D method

--disposal method

Set the disposal method for the following frames to method. Method can be a number between 0 and 7 (although only 0 through 3 are generally meaningful), or one of these names: none, asis, background (or bg), previous. --no-disposal means --disposal=none.

-l[count]

--loopcount[=count]

Set the Netscape loop extension to count. Count is an integer, or forever to loop endlessly. The default is forever. --no-loopcount turns off looping.

-O[level]

--optimize[=level]

Optimize output GIF animations for space. Level determines how much optimization is done. There are currently two levels:

-O1

Stores only the changed portion of each image. This is the default.

-O2

Also uses transparency to shrink the file further.

There is no --same-optimize option.

-U

--unoptimize

Unoptimize GIF animations into an easy-to-edit form.

GIF animations are often optimized (see --optimize) to make them smaller and faster to load, which unfortunately makes them difficult to edit. --unoptimize changes optimized input GIFs into unoptimized GIFs, where each frame is a faithful representation of what a user would see at that point in the animation.

There is no --same-unoptimize option.

Whole-GIF Options

Whole-GIF options effect entire GIFs as they are read or written. They can be turned off with `--no-option'.

--change-color color1 color2

Change color1 to color2 in the following input GIFs. (The color arguments have the same forms as in the -t option.) You can change multiple colors by giving the option multiple times. Color changes don't interfere with one another, so you can safely swap two colors with `--change-color color1 color2 --change-color color2 color1'. They all take effect as an input GIF is read. --no-change-color cancels all color changes.

-k num

--colors num

Reduce the number of distinct colors in each output GIF to num or less. Num must be between 2 and 256. This can be used to shrink output GIFs or eliminate any local color tables.

Unless you give --use-colormap, an adaptive group of colors is chosen from the existing color table. You can affect this process with the --color-method option. Gifsicle may need to add an additional color (making num+1 in all) if there is transparency in the image.

--color-method method

Determine how a smaller colormap is chosen. There are three choices: diversity, the default, is xv(1)'s diversity algorithm, which uses a strict subset of the existing colors. blend-diversity is a modification of this: some color values are blended from a group of the existing colors. median-cut is the median cut algorithm described by Heckbert. --method is a synonym for --color-method.

-f

--dither

This option only matters if the colormap was changed. With --dither on, Floyd-Steinberg error diffusion is used to approximate any colors that were removed. This looks better, but makes bigger files and can cause animation artifacts, so it is off by default.

--resize widthxheight

Resize the output GIF to widthxheight. Resizing happens after all input frames have been combined and before optimization.

--scale Xfactor[xYfactor]

Scale the output GIF's width and height by Xfactor and Yfactor. If Yfactor is not given, it defaults to Xfactor. Scaling happens after all input frames have been combined and before optimization.

--transform-colormap command

Command should be a shell command that reads from standard input and writes to standard output. Each colormap in the output GIF is translated into text colormap format (see --use-colormap below) and piped to the command. The output that command generates (which should also be in text colormap format) will be used as the colormap instead.

--use-colormap colormap

Set the image's colormap to colormap. Colormap can be web for the 216-color ``Web-safe palette''; gray for grayscale; bw for black-and-white; or the name of a file. That file should either be a text file (the format is described below) or a GIF file, whose global colormap will be used. If --colors=N is also given, an N-sized subset of colormap will be used.

Text colormap files have a very simple format:

# each non-comment line represents one color, "red green blue"
# each component should be between 0 and 255
0 0 0            # like this
255 255 255

EXAMPLES

Here are a bunch of examples showing how gifsicle is commonly used.

First, let's create an animation, `anim.gif':

% gifsicle a.gif b.gif c.gif d.gif > anim.gif

This animation will move very quickly: since we didn't specify a delay, a browser will cycle through the frames as fast as it can. Let's slow it down and pause .5 seconds between frames, using the --delay option.

% gifsicle --delay 50 a.gif b.gif c.gif d.gif > anim.gif

If we also want the GIF to loop three times, we can use --loopcount:

% gifsicle -d 50 --loop=3 a.gif b.gif c.gif d.gif > anim.gif

(Rather than type --delay again, we used its short form, -d. Many options have short forms; you can see them by running `gifsicle --help'. We also abbreviated --loopcount to --loop, which is OK since no other option starts with `loop'.)

To explode `anim.gif' into its component frames:

% gifsicle --explode anim.gif
% ls anim.gif*
anim.gif      anim.gif.000  anim.gif.001  anim.gif.002  anim.gif.003

To optimize `anim.gif':

% gifsicle -b -O2 anim.gif

To change the second frame of `anim.gif' to `x.gif':

% gifsicle -b --unoptimize -O2 anim.gif --replace #1 x.gif

--unoptimize is used since `anim.gif' was optimized in the last step. Editing individual frames in optimized GIFs is dangerous without --unoptimize; frames following the changed frame could be corrupted by the change. Of course, this might be what you want.

Note that --unoptimize and --optimize can be on simultaneously. --unoptimize affects input GIF files, while --optimize affects output GIF files.

To print information about the first and fourth frames of `anim.gif':

% gifsicle -I #0 #3 < anim.gif
(information printed)

To make black the transparent color in all the GIFs in the current directory, and also print information about each:

% gifsicle -bII --trans #000000 *.gif
(information printed)

Giving -I twice forces normal output to occur. With only one -I, the GIFs would not have changed on disk.

To change `anim.gif' to use a 64-color subset of the Web-safe palette:

% gifsicle -b --colors=64 --use-col=web anim.gif

To make a dithered black-and-white version of `anim.gif':

% gifsicle --dither --use-col=bw anim.gif > anim-bw.gif

BUGS

Please email suggestions, additions, patches and bugs to eddietwo@lcs.mit.edu.

AUTHORS

Eddie Kohler <eddietwo@lcs.mit.edu>
http://www.pdos.lcs.mit.edu/~eddietwo/
He wrote it.

Anne Dudfield <anne@lvld.hp.com>
http://www.frii.com/~annied/
She named it.

Hans Dinsen-Hansen <dino@danbbs.dk>
http://www.danbbs.dk/~dino/
Adaptive tree method for GIF writing.

http://www.lcdf.org/~eddietwo/gifsicle/
Back to The gifsicle home page.