镂空效果（中间透明，四周不透明）

常用于二维码扫描区域透明效果定制

#define SCREEN_WIDTH    ([UIScreen mainScreen].bounds.size.width)

//TODO: 矩形镂空
-(void)addRectHoleView
{
    // 1
    UIBezierPath *overlayPath = [UIBezierPath bezierPathWithRect:self.view.bounds];
    
    // 2
    UIBezierPath *transparentPath = [UIBezierPath bezierPathWithRect:CGRectMake((SCREEN_WIDTH-200)*0.5, 120, 200, 200)];
    [overlayPath appendPath:transparentPath];
    [overlayPath setUsesEvenOddFillRule:YES];
    
    // 3
    CAShapeLayer *fillLayer = [CAShapeLayer layer];
    fillLayer.path = overlayPath.CGPath;
    fillLayer.fillRule = kCAFillRuleEvenOdd;
    fillLayer.fillColor = [[UIColor blackColor] colorWithAlphaComponent:0.5].CGColor;
    
    // 4
    [self.view.layer addSublayer:fillLayer];
}

写法2

//TODO: 圆形镂空
- (void)addArcHoleView{
    //中间镂空的矩形框
    CGRect myRect =CGRectMake((SCREEN_WIDTH-200)*0.5, 120, 200, 200);
    //背景
    UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:[UIScreen mainScreen].bounds cornerRadius:0];
    
    //镂空
    UIBezierPath *circlePath = [UIBezierPath bezierPathWithOvalInRect:myRect];
    [path appendPath:circlePath];
    [path setUsesEvenOddFillRule:NO];
    
    
    CAShapeLayer *fillLayer = [CAShapeLayer layer];
    fillLayer.fillColor = [UIColor blackColor].CGColor;
    fillLayer.opacity = 0.5;
    fillLayer.path = path.CGPath;
    
    fillLayer.fillRule = kCAFillRuleEvenOdd;//设置填充规则(重点)
    [self.view.layer addSublayer:fillLayer];
}

//写法2
- (void)addArcHoleView2{
UIView *maskView0 = [[UIView alloc] initWithFrame:CGRectMake(0,0,SCREEN_WIDTH,SCREEN_HEIGHT)];
    maskView0.layer.opacity=0.5;
    maskView0.backgroundColor = [[UIColor blackColor] colorWithAlphaComponent:0.5];
    [self.view addSubview:maskView0];
    maskView0.layer.mask = ({
        CGRect roundedRect = self.view.bounds;
        roundedRect.origin.x = roundedRect.size.width / 4.0f;
        roundedRect.origin.y = roundedRect.size.height / 4.0f;
        roundedRect.size.width /= 2.0f;
        roundedRect.size.height= roundedRect.size.width;
        
        CGFloat cornerRadius = roundedRect.size.height / 2.0f;//高度=宽度
        
        UIBezierPath *path = [UIBezierPath bezierPathWithRect:self.view.bounds];
        UIBezierPath *croppedPath = [UIBezierPath bezierPathWithRoundedRect:roundedRect cornerRadius:cornerRadius];
        [path appendPath:croppedPath];
        [path setUsesEvenOddFillRule:YES];
        
        CAShapeLayer *mask = [CAShapeLayer layer];
        mask.path = path.CGPath;
        mask.fillRule = kCAFillRuleEvenOdd;
        mask;
    });
}

微信聊天泡泡

-(void)drawChatBubble
{
    /*右边聊天泡泡*/
    UIImage *rightBubbleImage = [UIImage  imageNamed:@"Information-box_blue_nor"];
    rightBubbleImage = [rightBubbleImage stretchableImageWithLeftCapWidth:rightBubbleImage.size.height * 0.3 topCapHeight:rightBubbleImage.size.height * 0.8];
    UIImageView  *bubbleView=[[UIImageView alloc]init];
    bubbleView.image=rightBubbleImage;
    bubbleView.frame=CGRectMake(200, 200.0f,rightBubbleImage.size.width*3, rightBubbleImage.size.height*3);
    [self.view  addSubview:bubbleView];
    
    //聊天图片
    UIImageView  *ChatPicture=[[UIImageView alloc]initWithFrame:bubbleView.frame];
    ChatPicture.image=[UIImage imageNamed:@"chatDefaultImage.jpg"];
    [self.view addSubview:ChatPicture];
    
    //画图 仿weixin
    CALayer *layer              = bubbleView.layer;
    layer.frame                 = (CGRect){{0,0},bubbleView.layer.frame.size};
    ChatPicture.layer.mask = layer;
}

How To Implement A Circular Image Loader Animation with CAShapeLayer