The Prisma photo app is pretty cool, using fancy software to product works of art out of your snaps. The only real issue was that it took a very long time to process your images, leading to a frustrating user experience.
Thankfully that has now been fixed with a new update dramatically improving the time it takes to see your finished piece. That's great news, and you'll also find the latest version of the app on iOS and Android now includes the ability to crop an image and also rotate it to the left and right.
These manipulations of the image are only available for snaps you've already taken that you load from your album using the control on the bottom right. So if you think you'll need to crop don't take a picture inside the app.
The performance increase is definitely most welcome as it makes the app actually useful if you're interested in seeing more than one preview. It still has a long way to go to be anything close to instantaneous but there's a lot of processing going on which is handled on the server side by Prisma so it's pretty impressive that it works at all.