读取bundel里的图片

//假设图片是存放在projectStatic.bundle的文件里：名叫blue_back@2x.png
NSString *bundlePath = [[NSBundle
mainBundle] pathForResource:@"projectStatic"
ofType:@"bundle"];
    NSString *imageName =
@"blue_back@2x.png";
    imageName = [bundlePath stringByAppendingPathComponent:imageName];
    
    [btn setBackgroundImage:[UIImage
imageNamed:imageName] forState:UIControlStateNormal];