Modify Image from Linux Terminal

ImageMagick is a command-line software suite to edit bitmap images. In addition to basic operations like convert, resize, rotate, flip, mirror, it can also apply effects and draw text, lines, polygons, and so on.

Installation

$ sudo apt-get install imagemagick

Hands-on

Convert between formats

$ convert image.png image.jpg

Resize images

ImageMagick will try to preserve the aspect ratio and make the image to fit within the resolution you assigned.

$ convert image.png -resize 100x100 image.png

You can also only assign one param like width or height, and ImageMagick will resize to that param and keep the aspect ratio.

for width:

$ convert image.png -resize 100 image.png

for height:

$ convert image.png -resize x100 image.png

Rotate images

$ convert image.png -rotate 90 image.png

Batch Process

$ for file in *.png; do convert $file -rotate 90 rotated-$file; done