Image magic

I've been facing the task of manipulating images for web apps and websites from time to time - like cropping, scaling and reducing file size. While some of these tasks can be done with a handy GUI tool like Photoshop (you have to pay for it), Photopea (a very powerful web-based photoshop-like editor that works with a multitude of formats including .psd) or Paint.net, sometimes a shell-based tool will do so much better. 

There is a tool like that and it's called Imagemagick. 

The thing let's you manipulate various raster images in different ways. I would most often use it for resizing and compressing images in batches and sometimes for cropping (here a visual tool may be better, but really depends on the scenario). 

For my own and other's reference, here are some of my usecases. Of course, there is an extensive documentation on the tool's website. 

(Since I'm on windows, I use image magick in Powershell to process many files at once).

Crop

Crop all files in the current directory and save them with a .crop suffix. This one reduces the size of the images to 1080x1732 cutting off 62px on the top (android screenshot).

Get-ChildItem -File | Foreach {convert $_.fullname -crop 1080x1732+0+62 $_.fullname.replace(".png",".crop.png")}

Scale

Scale all files in a directory down to 50% their dimensions (preserves aspect ratio):

Get-ChildItem -File | % {convert -resize 50% $_.fullname $_.fullname}

Compress

Based on this stackoverflow discussion.

Just one file, saving a copy:

convert -strip -interlace Plane -quality 85% .\banner_1.jpg .\banner_1.comp.jpg

All files in the current directory, replacing the originals:

Get-ChildItem -File | % {convert -strip -interlace Plane -quality 85% $_.fullname $_.fullname}

A lot of other usecases - do explore them!