core动画：UIImageView如何做渐变色动画，比如前景色从白色渐变为红色

[cdzsg2008]

UIView beginAnimations:@"" context:nil];

UIView setAnimationDelay:5];

UIView setAnimationRepeatCount:1];

imgkf.ImageView.layer.anchorPoint = apoint;

imgkf.ImageView.transform = p_in;

// 下面怎么设置颜色？？

// ...

UIView commitAnimations];