Question

I have two image (image1 and image2). Image 2 is moving around the screen. I want to “do something” when image 2 is near (20pixels) of image1. How can I do this ?

Answer 1

Create a frame that adds 20 pixel to each side of your image1’s frame:

CGRect image1Frame = image1.frame;
CGRect collisionFrame = CGRectMake(image1Frame.origin.x-20.0, image1Frame.origin.y-20.0, image1Frame.size.width+20.0, image1Frame.size.height+20.0);

Then just check if the frame of image2 collides with collisionFrame:

CGRectIntersectsRect(image2.frame, collisionFrame);