I personally use photoshop for most of my graphics need, but I know that this is not an option for a lot of folks, and I've decided to make a couple of RP specific tutorials using Photopea (free, web based, no software to install) and Krita (free, install required).
This first post is for Photopea.
You can grab your screenshots of comic books (for instance) with picpick or another software that allows you to screengrab specific shapes / pixel sizes. I use picpick (I purchased pro for my use, but if you don't intend to do sell your icons you may use the free version. It is as complete as the paying version) to screen grab at 150x150px. Tutorial from RPCheapos here. (For live action/animated, I recommend using "free video to jpg converter" for better results)
Now on to the resizing (Very Easy To Do imo) with a bunch of screen shots to show you the steps.
First step is to open www.photopea.com. You can create an account if you'd like. As it is a free site that lives thanks to ads, I would recommend turning off adblocker for this specific site.
Click File > Automate > resize image:
It will open a little pop up called "Resize". Click on Source Images. They're your screen grabs that you want to resize to a smaller size:
Caveat: I never tried more than a hundred screenshots at once. So do with that what you will. I've read posts of folks who have issues if they put too many pictures into photopea at once, but I never experienced that type of issues.
Once your images are loaded:
Change the parameters to your desired width/height. Note: it does NOT crop. If your screen grabs aren't square now, they won't be square after! Also select your favored format (I favor PNG over JPG: higher quality & supports transparency if needed)
After you click resize, it will open a popup in order to save your newly resized icons into a zip folder. Save it wherever you'd like with a name that talks to you, unzip the file, and now you have your resized icons!
This is pretty powerful but also! pretty limited. No cropping, no coloring, no sharpening, etc. But it is a good jumping point imo when you get started and just want all your icons to be the same size.
