一，在要遮罩的UIView上面添加UIImageView，然后生成一张中间镂空的UIImage，赋给UIImageView，设置UIImageView的alphe。
- (UIImage*)holeImageWithContentSize:(CGSize)size cornerRadius:(CGFloat)cR{
UIGraphicsBeginImageContextWithOptions(size, NO, [UIScreen mainScreen].scale);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextSetFillColorWithColor(context, [UIColor blackColor].CGColor);
CGContextFillRect(context,CGRectMake(0,0, size.width, size.height));
CGContextAddEllipseInRect(context,CGRectMake((size.width-cR)/2, (size.height-cR)/2, cR, cR));
CGContextSetBlendMode(context, kCGBlendModeClear);
CGContextFillPath(context);
UIImage *returnImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return returnImage;
}
二，绘制一个中间镂空的CAShapeLayer，然后添加在要遮罩的UIView的layer上面。
- (void)holeLayerWithContentSize:(CGSize)size cornerRadius:(CGFloat)cR {
CAShapeLayer *fillLayer = [CAShapeLayer layer];
fillLayer.fillRule = kCAFillRuleEvenOdd;
fillLayer.fillColor= [UIColor blackColor].CGColor;
fillLayer.opacity=0.3;
[self.view.layer addSublayer:fillLayer];
UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, size.width, size.height) cornerRadius:0];
UIBezierPath*circlePath = [UIBezierPath bezierPathWithRoundedRect:CGRectMake((size.width-cR)/2, (size.height-cR)/2, cR, cR)cornerRadius:cR];
[path appendPath:circlePath];
[path setUsesEvenOddFillRule:YES];
fillLayer.path= path.CGPath;
}
三，初始化一个UIView，设置UIView的mask，形成一个中间镂空的UIView，然后添加在要遮罩的UIView上面。
- (void)HoleMaskWithContentSize:(CGSize)size cornerRadius:(CGFloat)cR{
UIView*maskView = [[UIView alloc]initWithFrame:CGRectMake(0,0, size.width, size.height)];
maskView.backgroundColor= [UIColor blackColor];
maskView.alpha=0.3;
[self.view addSubview:maskView];
UIBezierPath *path = [UIBezierPath bezierPathWithRoundedRect:CGRectMake(0, 0, size.width, size.height) cornerRadius:0];
UIBezierPath *roundPath = [[UIBezierPath bezierPathWithRoundedRect:CGRectMake((size.width-cR)/2, (size.height-cR)/2, cR, cR) cornerRadius:cR] bezierPathByReversingPath];
[path appendPath:roundPath];
CAShapeLayer *shapeLayer = [CAShapeLayer layer];
shapeLayer.path= path.CGPath;
maskView.layer.mask= shapeLayer;
}
四，自定义一个UIView，在- (void)drawRect:(CGRect)rect中绘制中间镂空，然后添加在要遮罩的UIView上面，要注意一点，自定义的UIView的backgroundColor必须设置成clearColor。（注释掉的上下两段代码，是两种生成中间镂空的矩形）
#import "HoleView.h"
@implementation HoleView
- (void)drawRect:(CGRect)rect {
// CGContextRef context = UIGraphicsGetCurrentContext();
// CGContextAddRect(context, rect);
// [[UIColor colorWithWhite:0 alpha:0.3] set];
// CGContextFillRect(context, rect);
// CGContextClearRect(context, CGRectMake((rect.size.width-100)/2, (rect.size.height-100)/2, 100, 100));
// CGContextDrawPath(context, kCGPathFillStroke);
CGContextRef context = UIGraphicsGetCurrentContext();
[[UIColor colorWithWhite:0 alpha:0.3] set];
CGContextAddRect(context, rect);
CGContextFillPath(context);
CGContextSetBlendMode(context, kCGBlendModeClear);
CGContextAddEllipseInRect(context, CGRectMake(100, 100, 200, 200));
CGContextFillPath(context);
// [[UIColor colorWithWhite:0 alpha:0.3] setFill];
// UIRectFill(rect);
// CGRect holeRection = CGRectMake(100, 200, 200, 200);
// // 交集
// CGRect holeiInterSection = CGRectIntersection(holeRection, rect);
// [[UIColor clearColor] setFill];
// UIRectFill(holeiInterSection);
}
@end
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