在UIImageView分類里添加方法

@implementation UIImageView (custom)

//設(shè)置圓角
- (void)setImageCornerRadius: (CGFloat)radius {
    self.layer.cornerRadius = radius;
// ios9之后對imageview設(shè)置不會觸發(fā)離屏渲染
    self.layer.masksToBounds = YES;
}

//設(shè)置陰影
- (void)setShadowWithColor:(UIColor *)color shadowXOffset:(CGFloat)xOffset 
              shadowYOffset:(CGFloat)yOffset
              shadowRadius:(CGFloat)radius
              shadowOpacity:(CGFloat)opacity{

    if (self.superview == nil) {
        NSLog(@"WRNING: a parent view of the image view is necessary to add a shadow view.");
        return;
    }

  //shadowContainer  為在imageview的父view中加的 設(shè)置陰影的view
    if (self.shadowContainer != nil) {
        [self.shadowContainer removeFromSuperview];
    }
    self.shadowContainer = [[UIView alloc] initWithFrame: self.frame];
    self.shadowContainer.userInteractionEnabled = NO;
    self.shadowContainer.backgroundColor = [UIColor whiteColor];
    self.shadowContainer.layer.shadowColor = color.CGColor;
    self.shadowContainer.layer.shadowOffset = CGSizeMake(xOffset, yOffset);
    self.shadowContainer.layer.shadowRadius = radius;
    self.shadowContainer.layer.shadowOpacity = opacity;
    self.shadowContainer.layer.cornerRadius = self.layer.cornerRadius;
  //必加該句  直接向Core Animation提供陰影形狀，通過調(diào)用setShadowPath來提供一個CGPath給視圖的Layer，（CGPath為任意你想生成的陰影的形狀)，可以防止離屏渲染
    self.shadowContainer.layer.shadowPath = [UIBezierPath bezierPathWithRoundedRect:self.bounds cornerRadius:radius].CGPath;
    self.shadowContainer.clipsToBounds = NO;
    [self.superview insertSubview:self.shadowContainer atIndex:0];
}
@end