_imageView.layer.shadowColor = [UIColor blackColor].CGColor;
//shadowColor陰影顏色
_imageView.layer.shadowOffset = CGSizeMake(4,4);
//shadowOffset陰影偏移,x向右偏移4癣诱，y向下偏移4救军，默認(rèn)(0, -3),這個跟shadowRadius配合使用
_imageView.layer.shadowOpacity = 0.8;
//陰影透明度，默認(rèn)0
_imageView.layer.shadowRadius = 4;
//陰影半徑，默認(rèn)3
UIBezierPath path路徑
