ImageMagick on CentOS 8: Install, Convert, Batch, Rotate & Resize via CLI

Installing ImageMagick on CentOS 8

Download the RPM packages and install them with yum:

wget https://download.imagemagick.org/ImageMagick/download/linux/CentOS/x86_64/ImageMagick-7.1.0-17.x86_64.rpm
wget https://download.imagemagick.org/ImageMagick/download/linux/CentOS/x86_64/ImageMagick-libs-7.1.0-17.x86_64.rpm
yum localinstall ImageMagick-*

Converting image formats

Use convert to change a file from JPG to PNG: convert penguins.jpg penguins.png The resulting PNG looks identical to the original JPG but has a different file size and extension. Verify the file header with od if needed:

od -bc penguins.jpg | head -6
od -bc penguins.png | head -6

Batch conversion script

A Bash loop can convert many files automatically:

#!/bin/bash
for file in *.jpg; do
    newfile=$(echo $file | sed 's/jpg/png/')
    convert "$file" "$newfile"
done

Run the script with ./batch_convert.sh to process all JPG files in the directory.

Rotate and flip images

Rotate an image 45° clockwise or flip it vertically:

convert penguins.jpg -rotate 45 penguins_45.png
convert penguins.jpg -flip penguins_flip.png

Appending images

Combine two images vertically with -append or horizontally with +append:

convert penguins.jpg penguins_flip.png -append append_vertical.png
convert penguins.jpg penguins_flip.png +append append_horizontal.png

Resizing images

Adjust image dimensions using -resize. The examples shrink the image to 65 % of its original size or enlarge it to 150 %:

convert penguins.jpg -resize 65% pen_65.jpg
convert penguins.jpg -resize 150% pen_150.jpg