Bubble Intersection in iOS

BubbleIntersection

@interface MyView : UIView

@property (nonatomic, assign) BOOL isMySelf;

@end

@implementation MyView

- (instancetype)init
{
    self = [super init];
    if (self) {
        self.backgroundColor = [UIColor clearColor];
    }
    return self;
}

- (void)drawUI:(CGRect)rect
{
    UIView *bottomWhite = [[UIView alloc] initWithFrame:CGRectMake(0, rect.size.height - 20, rect.size.width, 20)];
    bottomWhite.backgroundColor = [UIColor whiteColor];
    
    //This is a background image
    UIImage *backgroundImg = [UIImage imageNamed:@"redPacket-bg"];
    UIImageView *backgroundPic = [[UIImageView alloc] initWithImage:backgroundImg];
    CGRect imgRect = rect;
    imgRect.size.height -= 20;
    backgroundPic.frame = imgRect;
    [backgroundPic addSubview:bottomWhite];
    [self addSubview:backgroundPic];
    
    //This is a bubble image
    UIImage *bubbleImg = [UIImage imageNamed:@"pop_position_pressed_left"];
    if (self.isMySelf) {
        bubbleImg = [UIImage imageNamed:@"pop_position_pressed_right"];
    }
    bubbleImg = [bubbleImg stretchableImageWithLeftCapWidth:14 topCapHeight:26];
    UIImageView *imgViewBubble = [[UIImageView alloc] initWithImage:bubbleImg];
    imgViewBubble.frame = rect;
    [self addSubview:imgViewBubble];
    
    //Intersection
    CALayer *layer              = imgViewBubble.layer;
    CGSize size = imgViewBubble.layer.frame.size;
    layer.frame                 = (CGRect){{0,0},size};
    backgroundPic.layer.mask = layer;
    [backgroundPic setNeedsDisplay];
}

@end