UIView放大镜

@interface MagnifierView : UIView{
    
}

@property (nonatomic, retain) UIView *viewToMagnify;
@property (nonatomic, assign) CGPoint touchPoint;

@end

@implementation MagnifierView

- (id)initWithFrame:(CGRect)frame {
    if (self = [super initWithFrame:CGRectMake(0, 0, 320, 35)]) {
        
        // make the circle-shape outline with a nice border.
        self.layer.borderColor = [[UIColor lightGrayColor] CGColor];
        self.layer.borderWidth = 0.5;
        self.layer.cornerRadius = 17;
        self.layer.masksToBounds = YES;
    }
    return self;
}

- (void)setTouchPoint:(CGPoint)pt {
    _touchPoint = pt;
    self.center = CGPointMake(pt.x, pt.y);
}

- (void)drawRect:(CGRect)rect {

    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextTranslateCTM(context,1*(self.frame.size.width*0.5),1*(self.frame.size.height*0.5));
    CGContextScaleCTM(context, 1.5, 1.5);
    CGContextTranslateCTM(context,-1*(_touchPoint.x),-1*(_touchPoint.y));
    [self.viewToMagnify.layer renderInContext:context];
}

- (void)dealloc
{
    self.viewToMagnify=nil;
   // [super dealloc];
}

@end

 

里面有坐标旋转和图层复制