Retrieving all 4 coordinates of a rotated UIImageView

Question

How does one get the 4 coordinates for a UIImageView?

I know the CGRect can be obtained and the origin.x and origin.y, but how can all 4 corners be found?

EDIT: I am rotating the UIImageViews, thats why I asked :P

Answer 1

You could add width and height of the rectangle to get the coordinates of the other 3 points.

CGRect rect = view.bounds;

CGPoint topLeft = rect.origin;
CGPoint topRight = CGPointMake(rect.origin.x + rect.size.width, rect.origin.y);
CGPoint bottomLeft =CGPointMake(rect.origin.x, rect.origin.y + rect.size.height);
CGPoint bottomRight = CGPointMake(rect.origin.x + rect.size.width,
                                  rect.origin.y + rect.size.height);

Then you could use CGPointApplyAffineTransform to get the transformed coordinates of them under your specified transform.

CGPoint center = view.center;
CGAffineTransform transf = CGAffineTransformMakeTranslation(-rect.size.width/2,
                                                            -rect.size.height/2);
transf = CGAffineTransformConcat(transf, view.transform);
transf = CGAffineTransformTranslate(transf, center.x, center.y);

topLeft = CGPointApplyAffineTransform(topLeft, transf);
//...

(note: not tested.)

Answer 2

This is my solution:

• [self] is a subclass of UIImageView

• [self.transform] is the transform i make on [self]:

  CGAffineTransform transform = CGAffineTransformMakeTranslation(-center.x, -center.y);
  transform = CGAffineTransformConcat(transform, self.transform);
  CGAffineTransform transform1 = CGAffineTransformMakeTranslation(center.x, center.y);
  transform = CGAffineTransformConcat(transform, transform1);
  
  CGPoint leftTopPoint     = CGPointApplyAffineTransform(leftTopPoint, transform);
  CGPoint rightTopPoint    = CGPointApplyAffineTransform(rightTopPoint, transform);
  CGPoint rightBottomPoint = CGPointApplyAffineTransform(rightBottomPoint, transform);
  CGPoint leftBottomPoint  = CGPointApplyAffineTransform(leftBottomPoint, transform);