不好的解决方案
使用下面的方式会强制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,会有卡顿的现象出现
self.view.layer.cornerRadius=5;
self.view.layer.masksToBounds=YES;
正确的解决方案:使用绘图技术
- (UIImage*)circleImage
{
// NO代表透明
UIGraphicsBeginImageContextWithOptions(self.size,NO,0.0);
//获得上下文
CGContextRef ctx = UIGraphicsGetCurrentContext();
//添加一个圆
CGRectrect = CGRectMake(0,0,self.size.width,self.size.height);
CGContextAddEllipseInRect(ctx, rect);
//裁剪CGContextClip(ctx);
//将图片画上去
[selfdrawInRect:rect];
UIImage*image = UIGraphicsGetImageFromCurrentImageContext();
//关闭上下文UIGraphicsEndImageContext();
return image;
}
还有一种方案:使用了贝塞尔曲线"切割"个这个图片,给UIImageView添加了的圆角,其实也是通过绘图技术来实现的
UIImageView*imageView = [[UIImageViewalloc]
initWithFrame:CGRectMake(0,0,100,100)];
imageView.center= CGPointMake(200,300);
UIImage*anotherImage = [UIImageimageNamed:@"image"];
UIGraphicsBeginImageContextWithOptions(imageView.bounds.
size,NO,1.0);
[[UIBezierPathbezierPathWithRoundedRect:imageView.bounds
cornerRadius:50] addClip];
[anotherImage drawInRect:imageView.bounds];
imageView.image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
[self.viewaddSubview:imageView];
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