UIImage couldn't load some png picture.

Question

I Use the following code to load png image: UIImage *imageBack1 = [UIImage imageNamed:@"Bar1.png"]; UIImage *imageBack2 = [UIImage imageNamed:@"Bar2.png"]; imageBack1 work right when imageBack2's value is nil, Bar1.png and Bar2.png are located at the same place,but why Bar2.png couldn't be load?

Answer 1

alpha channel ?

Answer 2

In fact , the problem come from the png file,but not cocoa. Iphoto couldn't recognize it.