ImageCornerRadius

1、最直接的方法如下,但会产生离屏渲染问题,影响性能

 UIImageView *iv_1=[[UIImageView alloc]initWithImage:[UIImage imageNamed:@"test"]];
 iv_1.layer.cornerRadius=50;
 iv_1.clipsToBounds=YES;
 iv_1.frame=CGRectMake(30, 30, 100, 100);
 [self.view addSubview:iv_1];

2、在UIImage层面处理图片,会产生圆角大小误差问题

 -(UIImage *) wp_imageWithCornerRadius:(CGFloat)radius{
 // 构造图片的rect
 CGRect rect=(CGRect){0,0,self.size};
 // 创建上下文
 UIGraphicsBeginImageContextWithOptions(self.size, NO, [UIScreen mainScreen].scale);
 // 利用bezier的一个函数写path路径
 CGContextAddPath(UIGraphicsGetCurrentContext(), [UIBezierPath bezierPathWithRoundedRect:rect cornerRadius:radius].CGPath);
 // 切割
 CGContextClip(UIGraphicsGetCurrentContext());
 // 画出新的来
 [self drawInRect:rect];
 // 获取新图片
 UIImage *image=UIGraphicsGetImageFromCurrentImageContext();
 // 关闭上下文
 UIGraphicsEndImageContext();
 // 返回新图片
 return image;
}

 UIImageView *iv_2=[[UIImageView alloc]initWithImage:[[UIImage imageNamed:@"test"] wp_imageWithCornerRadius:50]];
 iv_2.frame=CGRectMake(30, 180, 100, 100);
 [self.view addSubview:iv_2];

3、在UIImageView层面处理图片,目前看来还不错

/**
 * 返回带有圆角图片的imageView
 *
 * @param rect imageView的尺寸
 * @param img 图片
 * @param radius 半径
 *
 * @return 返回带有圆角图片的ImageView
 */
 -(UIImageView *)initWithRect:(CGRect)rect Image:(UIImage *)img Radius:(CGFloat)radius{
 // 先得到带有圆角的图片
 CGRect imgRect=(CGRect){0,0,rect.size};
 UIGraphicsBeginImageContextWithOptions(rect.size, NO, [UIScreen mainScreen].scale);
 CGContextAddPath(UIGraphicsGetCurrentContext(), [UIBezierPath bezierPathWithRoundedRect:imgRect cornerRadius:radius].CGPath);
 CGContextClip(UIGraphicsGetCurrentContext());
 [img drawInRect:imgRect];
 UIImage *newImg=UIGraphicsGetImageFromCurrentImageContext();
 UIGraphicsEndImageContext();
 // 把新图片和rect赋值给imageView
 UIImageView *iv=[[UIImageView alloc]initWithFrame:rect];
 iv.image=newImg;
 // 返回imageView
 return iv;
}

效果比较图(从上至下就是以上3种处理方法的结果,第二种结果明显圆角设置存在误差)