imagemagick

This thing is powerful. It's a suite for editing and manipulating images from the command line. There are hundreds of possibilities here, but I normally find myself using just a couple of functionalities, such as resizing images or converting them across different formats. For example, here's something I do almost every day:

# Reducing the size of a screenshot
magick original-image.png -resize 900 new-image.png

But we can be a little more practical:

# Reducing the size of the file, moving it elsewhere and removing the original
magick ~/Desktop/image.png -resize 900 /desired/directory/resized-image.png && rm ~/Desktop/image.png

And there's a whole lot more this beauty can do. The other day, I ended up having to run a for loop inside a directory to convert all images into a specific format, and then move them into a new directory. All in one go. That was pretty amazing.

There's just so much you can do with the magick command. Check the official website and have fun.