1.直接设置Layer

示例代码:

- (void)demo1 {
    UIImageView *imageView = [[UIImageView alloc] initWithFrame:CGRectMake(0, 0, 200, 200)];
    imageView.center = self.view.center;
    [self.view addSubview:imageView];
    imageView.image = [UIImage imageNamed:@"111.png"];
    
    imageView.layer.cornerRadius = imageView.frame.size.height * 0.5;
    imageView.layer.masksToBounds = YES;
}

缺点:性能不是很好的方法,不适合在tableview中使用
这种方式会强制 Core Animation 提前渲染屏幕的离屏绘制, 而离屏绘制就会给性能带来负面影响,甚至会有卡顿的现象出现

2.使用绘图上下文的方式绘制圆角

示例代码:

- (void)demo2 {
    UIImageView *imageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 200, 200)];
    imageView.center = self.view.center;
    [self.view addSubview:imageView];
    
    UIColor *color = self.view.backgroundColor;
    UIImage *image = [UIImage imageNamed:@"111.png"];
    /*
          开启图形上下文(bitmap类型)
          参数1:尺寸
          参数2:是否不透明
          参数3:缩放比   0->当前屏幕缩放比
    */
    UIGraphicsBeginImageContextWithOptions(imageView.frame.size, YES, 0);
    
    //设置填充颜色
    [color setFill];
    UIRectFill(imageView.bounds);
    
    //使用贝塞尔曲线给图片切割
    UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:imageView.bounds];
    [path addClip];
    
    [image drawInRect:imageView.bounds];
    
    UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext();
    
    UIGraphicsEndImageContext();
    
    imageView.image = resultImage;
}

注意:在填充图片前完成路径切割,如果提前填充图片再切割不会有效果

3.使用分类的方式绘图

- (void)demo3 {
    UIImageView *imageView = [[UIImageView alloc]initWithFrame:CGRectMake(0, 0, 200, 200)];
    imageView.center = self.view.center;
    [self.view addSubview:imageView];
    UIImage *image = [UIImage imageNamed:@"111.png"];
    
    [image lv_cornerImageWithSize:imageView.bounds.size fillColor:[UIColor whiteColor] completion:^(UIImage *image) {
        imageView.image = image;
    }];
}

分类代码:
.h

#import <UIKit/UIKit.h>

@interface UIImage (Extension)

- (void)lv_cornerImageWithSize:(CGSize)size fillColor:(UIColor *)fillColor completion:(void (^)(UIImage *image))completion;

@end

.m

#import "UIImage+Extension.h"

@implementation UIImage (Extension)

- (void)lv_cornerImageWithSize:(CGSize)size fillColor:(UIColor *)fillColor completion:(void (^)(UIImage *))completion {
    //在子线程中进行图片的处理，处理结束后，回到主线程
    dispatch_async(dispatch_get_global_queue(0, 0), ^{
        //开启上下文
        UIGraphicsBeginImageContextWithOptions(size, YES, 0);
        //设置填充的颜色
        CGRect rect = CGRectMake(0, 0, size.width, size.height);
        
        [fillColor setFill];
        UIRectFill(rect);
        
        UIBezierPath *path = [UIBezierPath bezierPathWithOvalInRect:rect];
        [path addClip];
        
        [self drawInRect:rect];
        
        UIImage *resultImage = UIGraphicsGetImageFromCurrentImageContext();
        
        //关闭上下文
        UIGraphicsEndImageContext();
        
        dispatch_async(dispatch_get_main_queue(), ^{
            if (completion) {
                completion(resultImage);
            }
        });
        
    });
}

@end