Drawing a shape in a UIImageView IOS

Question

I am trying to draw some circles inside a UIImageView with a specific image. This is what I was trying to do:

UIGraphicsBeginImageContext(self.view.bounds.size);
CGContextRef contextRef = UIGraphicsGetCurrentContext();
CGContextSetLineWidth(contextRef, 2.0);
CGContextSetStrokeColorWithColor(contextRef, [color CGColor]);
CGRect circlePoint = (CGRectMake(coordsFinal.x, coordsFinal.y, 50.0, 50.0));

CGContextStrokeEllipseInRect(contextRef, circlePoint);

UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

[photoView addSubview:image];

The circle is drawn fine, but I would like the PhotoView to act as a mask to it. So if for example I move the UIImageView out of the UIView using an animation, I would like the circle to move with it. Important is the fact that the coordinates are relative to the whole screen.

Answer 1

Use Core Animation's shape layer instead.

CAShapeLayer *circleLayer = [CAShapeLayer layer];
// Give the layer the same bounds as your image view
[circleLayer setBounds:CGRectMake(0.0f, 0.0f, [photoView bounds].size.width, 
                                              [photoView bounds].size.height)];
// Position the circle anywhere you like, but this will center it
// In the parent layer, which will be your image view's root layer
[circleLayer setPosition:CGPointMake([photoView bounds].size.width/2.0f, 
                                    [photoView bounds].size.height/2.0f)];
// Create a circle path.
UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:
                                    CGRectMake(0.0f, 0.0f, 50.0f, 50.0f)];
// Set the path on the layer
[circleLayer setPath:[path CGPath]];
// Set the stroke color
[circleLayer setStrokeColor:[[UIColor redColor] CGColor]];
// Set the stroke line width
[circleLayer setLineWidth:2.0f];

// Add the sublayer to the image view's layer tree
[[photoView layer] addSublayer:circleLayer];

Now, if you animate the UIImageView that contains this layer, the layer will move with it since it is a child layer. And there is now no need to override drawRect:.