How to get the frame from a picture in objective c?

Question

Objective-C

Hello! Need to get a reverse image from an existing image
there is an image

here white is considered an image on the calayer
need to get this please

help solve the issue, thank you in advance!

Answer 1

You can get an image by mask using CoreGraphics
An example can be viewed here . If you don’t need an image, but just need to do this trick in ui, then look at QuartzCore (google mask CALayer tags)
Now as for the mask ... I didn’t quite understand how variant you can have it, but if it’s a square , then you can simply draw it through coreGraphics (create a context and draw the mask you need through CGContextAddRect)
Or, if you have it drawn in calayer, render it into the same picture as shown here same, you will need to create a mask
CoreImage will theoretically run faster... .
Unfortunately, I am not familiar with third-party computer graphics libraries, but I recommend that you dig into something ala OpenCV