UIImageView 图片框圆角处理

//圆角设置
imageView.layer.cornerRadius = 8;(值越大，角就越圆)
imageView.layer.masksToBounds = YES;
//边框宽度及颜色设置
[imageView.layer setBorderWidth:2];
[imageView.layer setBorderColor:[UIColor blueColor]];  //设置边框为蓝色

//自动适应,保持图片宽高比
imageView.contentMode = UIViewContentModeScaleAspectFit;