Was messing with replacing color in an image with another color. Didn't work that well, mostly saturation and brightness problems

gistfile1.m

- (UIImage *)imageByShiftingFromColor:(UIColor *)startColor toColor:(UIColor *)endColor
{
    CGFloat startHue, startSaturation, startBrightness, startAlpha;
    BOOL parsedStartColor = [startColor getHue:&startHue saturation:&startSaturation brightness:&startBrightness alpha:&startAlpha];
    NSLog(@"start success: %i hue: %0.2f, saturation: %0.2f, brightness: %0.2f, alpha: %0.2f", parsedStartColor, startHue, startSaturation, startBrightness, startAlpha);

    CGFloat endHue, endSaturation, endBrightness, endAlpha;
    BOOL parsedEndColor = [endColor getHue:&endHue saturation:&endSaturation brightness:&endBrightness alpha:&endAlpha];
    NSLog(@"end success:   %i hue: %0.2f, saturation: %0.2f, brightness: %0.2f, alpha: %0.2f", parsedEndColor, endHue, endSaturation, endBrightness, endAlpha);

    CIImage *ciImage = [CIImage imageWithCGImage:[self CGImage]];

    CGFloat radianShift = (endHue - startHue) * M_PI * 2;
    NSLog(@"hue shift: %f, radians: %f", endHue - startHue, radianShift);

    CIFilter *adjustHue = [CIFilter filterWithName:@"CIHueAdjust"];
    [adjustHue setDefaults];
    [adjustHue setValue:ciImage forKey:@"inputImage"];
    [adjustHue setValue:[NSNumber numberWithFloat:radianShift] forKey:@"inputAngle"];
    ciImage = [adjustHue outputImage];


    CGFloat saturationShift = 1 + endSaturation - startSaturation;
    CGFloat brightnessShift = endBrightness - startBrightness;
    NSLog(@"saturation shift: %f", saturationShift);
    NSLog(@"brightness shift: %f", brightnessShift);
    //    saturationShift = 1.2;
    //    brightnessShift = -0.1;

    CIFilter *adjustBrightness = [CIFilter filterWithName:@"CIColorControls"];
    [adjustBrightness setDefaults];
    [adjustBrightness setValue:ciImage forKey:@"inputImage"];
    [adjustBrightness setValue:[NSNumber numberWithFloat:saturationShift] forKey:@"inputSaturation"];
    [adjustBrightness setValue:[NSNumber numberWithFloat:brightnessShift] forKey:@"inputBrightness"];
    ciImage = [adjustBrightness outputImage];

    CIContext *context = [CIContext contextWithOptions:nil];
    CGImageRef imageRef = [context createCGImage:ciImage fromRect:[ciImage extent]];
    UIImage *image = [UIImage imageWithCGImage:imageRef];
    CGImageRelease(imageRef);

    return image;
}