在工程中有一些需求需要设置部分遮罩，如二维码扫描区域的图形绘画，类似于头像圆角等，这时候变需要CAShapeLayer，UIBezierPath等进行绘图

简单的代码如下

Simulator Screen Shot - iPhone 6s - 2018-02-24 at 14.25.31.png

//设置背景色为白色
self.view.backgroundColor = [UIColor whiteColor];
//绘制200*200的方框
[self setCropRect:CGRectMake((self.view.bounds.size.width-200)/2,
                                 (self.view.bounds.size.height-200)/2, 200, 200)];

- (void)setCropRect:(CGRect)cropRect{
    _testShaplayer= [[CAShapeLayer alloc] init];
    //绘制两条path
    CGMutablePathRef path = CGPathCreateMutable();
    CGPathAddRect(path, nil, cropRect);
    CGPathAddRect(path, nil, self.view.bounds);
    //填充两条path的非交集
    [_testShaplayer setFillRule:kCAFillRuleEvenOdd];
    [_testShaplayer setPath:path];
    //颜色是黑色透明度0.6
    [_testShaplayer setFillColor:[UIColor blackColor].CGColor];
    [_testShaplayer setOpacity:0.6];
    
    
    [_testShaplayer setNeedsDisplay];
    
    [self.view.layer addSublayer:_testShaplayer];
    
}

Simulator Screen Shot - iPhone 6s - 2018-02-24 at 14.25.05.png

- (void)configRoundShape {
    self.view.backgroundColor = [UIColor whiteColor];
    _testShaplayer = [[CAShapeLayer alloc]init];
    //绘制贝塞尔曲线
    UIBezierPath *roundPath = [UIBezierPath bezierPathWithArcCenter:self.view.center radius:self.view.bounds.size.width/2 startAngle:0.0 endAngle:M_PI*2 clockwise:YES];
    UIBezierPath *rectPath = [UIBezierPath bezierPathWithRect:self.view.bounds];
    [roundPath appendPath:rectPath];
    //同样取非交集绘制
    [_testShaplayer setFillRule:kCAFillRuleEvenOdd];
    [_testShaplayer setPath:roundPath.CGPath];
    [_testShaplayer setFillColor:[UIColor blackColor].CGColor];
    [_testShaplayer setOpacity:0.6];
    
    [_testShaplayer setNeedsDisplay];
    
    [self.view.layer addSublayer:_testShaplayer];
}