Draw UIBezierPath on UIImageView for image crop - ios

Question

I am working on a photo editing application and need the user to be able to draw a path to crop out the photo. I have a class that works with a UIView for drawing smooth UIBezierPath lines. However I really need to apply this to a UIImageView so that the drawing can be done over the image. If I change the class to subclass UIImageView instead it no longer works. Any ideas on what I can do to fix this? Or better options for achieving the same goal? Below is my implementation:
#import "DrawView.h"
#implementation DrawView
{
UIBezierPath *path;
}
- (id)initWithCoder:(NSCoder *)aDecoder // (1)
{
if (self = [super initWithCoder:aDecoder])
{
[self setMultipleTouchEnabled:NO]; // (2)
[self setBackgroundColor:[UIColor whiteColor]];
path = [UIBezierPath bezierPath];
[path setLineWidth:2.0];
}
return self;
}
- (void)drawRect:(CGRect)rect // (5)
{
[[UIColor blackColor] setStroke];
[path stroke];
}
- (void)touchesBegan:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint p = [touch locationInView:self];
[path moveToPoint:p];
}
- (void)touchesMoved:(NSSet *)touches withEvent:(UIEvent *)event
{
UITouch *touch = [touches anyObject];
CGPoint p = [touch locationInView:self];
[path addLineToPoint:p]; // (4)
[self setNeedsDisplay];
}
- (void)touchesEnded:(NSSet *)touches withEvent:(UIEvent *)event
{
[self touchesMoved:touches withEvent:event];
}
- (void)touchesCancelled:(NSSet *)touches withEvent:(UIEvent *)event
{
[self touchesEnded:touches withEvent:event];
}
#end
If I place a break point on touchesBegan or touchesMoved it does fire when expected.

Answer 1

First problem - userInteractionEnabled property should be set to YES for receiving touch events.
Second one - drawRect: method is not called for UIImageView subclasses:
The UIImageView class is optimized to draw its images to the display.
UIImageView will not call drawRect: a subclass. If your subclass needs
custom drawing code, it is recommended you use UIView as the base
class.
So, DrawView should be UIView subclass, that will draw UIImage in drawRect:, before bezier path drawing. Something like that (only changed parts of code):
// DrawView.h
#interface DrawView : UIView
#property (nonatomic, strong) UIImage* image;
#end
// DrawView.m
#implementation DrawView
- (void)drawRect:(CGRect)rect
{
[image drawInRect:self.bounds];
[[UIColor blackColor] setStroke];
[path stroke];
}
#end