How do I draw on an image in Swift?

Question

I need to be able to programmatically draw on an image, and save that image for later use. Say, draw a line on specific x and y coordinates on the image, save the image, and

Answer 1

It's simple:

1. Make an image graphics context. (Before iOS 10, you would do this by calling UIGraphicsBeginImageContextWithOptions. In iOS 10 there's another way, UIGraphicsImageRenderer, but you don't have to use it if you don't want to.)

2. Draw (i.e. copy) the image into the context. (UIImage actually has draw... methods for this very purpose.)

3. Draw your line into the context. (There are CGContext functions for this.)

4. Extract the resulting image from the context. (For example, if you used UIGraphicsBeginImageContextWithOptions, you would use UIGraphicsGetImageFromCurrentImageContext.) Then close the context.