How to Install and Use GraphicsMagick to Edit Images CLI

GraphicsMagick is a tool that allows to edit images from terminal. It claims to be a handy tool for those cases in which you have to do some quick image editing and don't want to open a heavy program such as Photoshop or GIMP.

This tool increases the productivity by not having to navigate through a GUI. It is based in commands instead, so all you have to do is to type a line and you'll have your image edited very quickly.

Features

This tools offers different options for editing your images:

Resize
Crop
Change colors
Animate
Create montages
Compare images
Mirror

And a cool thing is that you can combine all this options, getting really interesting results.

Installation

Ubuntu

Release: Xubuntu 17.10 (also tested in Ubuntu 16.04 LTS)
Kernel: 4.13.9-300.fc27.x86_64
Architecture: x86_64

$ sudo apt-get install graphicsmagick

Arch

Release: 2017.11.01
Kernel: 4.13.9
Architecture: x86_64

$ sudo pacman -S graphicsmagick

Fedora

Release: Fedora 27 Workstation
Kernel: 4.13.9-300.fc27.x86_64
Architecture: x86_64

$ sudo dnf install GraphicsMagick

Usage

GraphicsMagick has different image editing options. You can list them all by typing in a terminal:

$ gm

In this tutorial I'll show you how to use some of these options. We will use this image for the examples, original size is 600x333px:

example villa traful

Resize

There are several ways to resize an image with GraphicsMagic:

Specify a new width, and the height will scale proportionally: gm convert -resize <newWidth> <inputImage> <outputImage>

$ gm convert -resize 300 example-villa-traful.png example-resize-300.png

example resize 300

You can specify a width and a height, and the program will resize the image to that dimensions without changing the proportions: gm convert -resize <newWidth>x<newHeight> <inputImage> <outputImage>

$ gm convert -resize 150x100 example-villa-traful.png example-resize-150x100.png

example resize 150x100

Resize by using a percentage: gm convert -resisze <percentage>% <inputImage> <outputImage>

$ gm convert -resize 50% example-villa-traful.png example-resize-50%.png

example resize 50 percent

You can also composite the image on a background color canvas image: gm convert -gravity center -extent <canvasWidth>x<canvasHeight> \-background black <inputImage> <outputImage>

$ gm convert -gravity center -extent 300x300 \-background black example-resize-50%.png example-composite.png

example composite

Crop

You can crop an image this way: gm convert -crop <newWidth>x<newHeight> <inputImage> <outputImage>

$ gm convert -crop 300x300 example-villa-traful.png example-crop-300x300.png

example crop 300x300

As you can see, the image is not centered. You can center it by specifying an offset in the crop dimensions: gm convert -crop <newWidth>x<newHeight>+<offset> \<inputImage> <outputImage>

$ gm convert -crop 300x300+150 \example-villa-traful.png example-crop-centered-300x300.png

example crop centered

You can also combine options, for example:

$ gm convert -crop 300x300 -resize 150 \example-villa-traful.png example-combined-options.png

Try your own combinations!

Mirror

You can mirror images in the horizontal axis: gm convert -flop <inputImage> <outputImage>

Or in the vertical axis: gm convert -flip <inputImage> <outputImage>

For example:

$ gm convert -flip example-villa-traful.png example-flip.png

example flip

Montage

You can combine a multiple images and create a montage. For example:

$  gm montage -geometry 600x333 \example-villa-traful.png example-flop.png example-montage.png

example montage

Convert to black and white

You can change an image to black and white: gm convert -monochrome <inputImage> <outputImage>

And also convert one to greyscale: gm convert -modulate 100,0 <inputImage> <outputImage>

Example:

$ gm convert -monochrome example-villa-traful.png example-monochrome.png

example-monochrome

And thats all for today. After trying these options, read the official documentation and discover new features!

Conclusion

GraphicsMagick is a nice software with lots of features. It gives the user a very simple way to edit its images without using a GUI. Also, there are a lot of combinations possible using the different options of the tool, so if you edit images frequently, I recommend you to download and try it!