Commmonly used imagemagick commands
ImageMagick is an open source tool for editing and converting raster images created in 1987 by John Cristy.
I use ImageMagick on the command line for quick image edits such as cropping, resizing or rotating.
Use convert to create a new output file or mogrify to overwrite the input file.
Rotating
mogrify -rotate "90" file.png
Rotates an image by 90 degrees clockwise.
Cropping
convert -crop 640x480+50+100 +repage input.png output.png
Crops the image at X:50 Y:100 to a size of W: 640 H:480.+repage will prevent export of the cropped area.
convert -crop 3:2+50+100 +repage input.png output.png
Crops the image at X:50 Y:100 to a ratio of W: 3 H:2
convert -crop 3:2+50+100 +repage input.png output.png
Crops the image at X:50 Y:100 to a ratio of W: 3 H:2
Resizing
mogrify -geometry 50% file.png
Resizes the image down by half.
mogrify -geometry 1024x file.png
Resizes the image to a width of 1024px.
mogrify -geometry x800 file.png
Resizes the image to a height of 800px.
mogrify -geometry 800x800 file.png
Resizes the image to 800px at the longer side.
mogrify -density 72 -units pixelsperinch file.png
Changes the DPI of the image to 72.
Dithering
convert input.png -dither FloydSteinberg -colors 8 output.png
Dithers the image with 8 colors.
convert input.png -dither FloydSteinberg -remap colortable.gif output.png
Dithers the image using a colortable.
Tiling
montage * output.png
Tiles all images in folder.
montage * output.png -background "#000000"
Sets the background color the black.
PDF conversion
convert file.pdf -flatten output.png
Converts a pdf to.png
Image Sequencing
convert -delay 200 -loop 0 *.png output.gif
Creates an infinitely looping GIF with 2 seconds delay between each frame.
Information
identify file.png
Displays information on the file such as width and height.
Offline Documentation
To make the documentation available offline, install the imagemagick-6-doc package.