ImageMagick

ImageMagick is a suite of commandline tools for manipulating images. It's often called the "swiss army knife" of image tools. It is free software.

Links

• http://www.imagemagick.org/

• usage tutorial

General

Imagemagick provides a number of commandline tools, none of which are named imagemagick, but rather:

• convert: create/modify an image and save as a new file
• mogrify: makes changes to an image "in-place" (replacing the original -- use with caution!)
• montage: automated "poster" maker that creates a "thumbnail" image of a number of images (in a grid with variable spacing and options like showing the filename)
• identify: display information about an image
• display: show an image in a window (may not work on OS X, use the "open" command instead)

How to check if ImageMagick is installed

Type the name of one of the above commands in a terminal/shell, such as:

convert

Installing ImageMagick

In Linux, ImageMagick should either already be installed, or is available via whatever package manager the distribution supports. In Debian/Ubuntu:

sudo apt-get install imagemagick

On Mac OSX, packages often exist for specific OS X version (searching for "imagemagick OSX" should bring up some packages that have been pre-compiled for the particular version of OSX you have) As of early 2013, this link seems to be up to date. Package management projects, such as port, may also work. Compiling from source is also possible when Development tools are installed.

Seeing what version of ImageMagick you have

Use the --version option with an ImageMagick command.

convert --version

Creating new images (without changing any originals)

Use convert. Convert always produces a new output file, generally you give the output file at the end of the command.

convert original.png -resize 160x120 icon.png

Modifying images "in-place" (changing the originals)

Use mogrify. Mogrify supports the same options as convert, only it modifies it's input, replacing the original (so you need to be careful with it).

Mogrify can be used with a wildcard to modify many files at once.

mogrify -resize 320x240 *.JPG

Getting Information about an Image

identify original.png

Displaying an image

display foo.png

Cutting

Cutting out a particular rectangle from an image

The format of the crop option is: WIDTHxHEIGHT+LEFT+TOP

For instance, to extract a 256 pixel square from an image 500 pixels from the left, at the top (0):

convert FILE0058.JPG -crop 256x256+500+0 tile.jpg

Cuting an image up into tiles or strips / "Cookie Cutting"

The crop command, when not given a specific position to cut out, will repeat as many times as it can, "cookie-cutter style", producing a series of images.

convert original.png -crop 64x64 tile%04d.png
convert original.png -crop 64x strip%04d.png
convert original.png -crop x64 bar%04d.png

Transforming

Converting/Changing image formats

convert original.png new.jpg
convert original.png -quality 1 lo.jpg

Resizing images

convert -resize 640x640 FILE0058.JPG work.png
convert -resize 640x640! FILE0058.JPG work.png

Assembling

Creating an animated gif from multiple images

convert tile*.png slide.gif
convert -delay 5 -dispose background -page +0+0 tile*.png slide.gif

Overlaying/Combining 2 images into a new image

Use composite. Composite is both a command-line tool on its own, and also it's available via the "-composite" option of convert. Note that the order of things is different depending on which way you use.

Creating a "contact sheet" / table of images

Use montage.

Drawing

TODO: check circle parameters (radius one number only?!)

convert -size 300x300 xc:lightgray -fill black -draw 'rectangle 0,0 150,150' rect.gif
convert -size 300x300 xc:lightgray -fill black -draw 'circle 150,150 50,40' circle.gif

Finding more examples of drawing with ImageMagick

http://www.imagemagick.org/Usage/draw/#primitives