iOS颜色渐变效果

UIColor *colorOne = [UIColor colorWithRed:(255/255.0)  green:(255/255.0)  blue:(255/255.0)  alpha:0];
    UIColor *colorTwo = [UIColor colorWithRed:(255/255.0)  green:(255/255.0)  blue:(255/255.0)  alpha:1.0];
    NSArray *colors = [NSArray arrayWithObjects:(id)colorOne.CGColor, colorTwo.CGColor, nil];
    NSNumber *stopOne = [NSNumber numberWithFloat:0.0];
    NSNumber *stopTwo = [NSNumber numberWithFloat:1.0];

    NSArray *locations = [NSArray arrayWithObjects:stopOne, stopTwo, nil];

    CAGradientLayer *headerLayer = [CAGradientLayer layer];

    headerLayer.colors = colors;
    headerLayer.locations = locations;
    headerLayer.frame = frame;

        headerLayer.startPoint = CGPointMake(1, 0);
        headerLayer.endPoint = CGPointMake(0, 0);


//    [self.view.layer insertSublayer:headerLayer atIndex:0];
    [self.carousel.layer addSublayer:headerLayer];