How to get inverse color from UIColor?

Question

e.g. The inverse color from black should be white.

Answer 1

---- EDIT ----

Based on @amleszk's answer, I updated the UIColor extension/category with this method:

Swift

func inverseColor() -> UIColor {     var alpha: CGFloat = 1.0      var red: CGFloat = 0.0, green: CGFloat = 0.0, blue: CGFloat = 0.0     if self.getRed(&red, green: &green, blue: &blue, alpha: &alpha) {         return UIColor(red: 1.0 - red, green: 1.0 - green, blue: 1.0 - blue, alpha: alpha)     }      var hue: CGFloat = 0.0, saturation: CGFloat = 0.0, brightness: CGFloat = 0.0     if self.getHue(&hue, saturation: &saturation, brightness: &brightness, alpha: &alpha) {         return UIColor(hue: 1.0 - hue, saturation: 1.0 - saturation, brightness: 1.0 - brightness, alpha: alpha)     }      var white: CGFloat = 0.0     if self.getWhite(&white, alpha: &alpha) {         return UIColor(white: 1.0 - white, alpha: alpha)     }      return self } 

Objective-C

- (UIColor *)inverseColor {     CGFloat alpha;      CGFloat red, green, blue;     if ([self getRed:&red green:&green blue:&blue alpha:&alpha]) {         return [UIColor colorWithRed:1.0 - red green:1.0 - green blue:1.0 - blue alpha:alpha];     }      CGFloat hue, saturation, brightness;     if ([self getHue:&hue saturation:&saturation brightness:&brightness alpha:&alpha]) {         return [UIColor colorWithHue:1.0 - hue saturation:1.0 - saturation brightness:1.0 - brightness alpha:alpha];     }      CGFloat white;     if ([self getWhite:&white alpha:&alpha]) {         return [UIColor colorWithWhite:1.0 - white alpha:alpha];     }      return nil; } 

---- DEPRECATED ----

Based on @grc's answer, I create a UIColor category with this method:

- (UIColor *)inverseColor {      CGColorRef oldCGColor = self.CGColor;      int numberOfComponents = CGColorGetNumberOfComponents(oldCGColor);      // can not invert - the only component is the alpha     // e.g. self == [UIColor groupTableViewBackgroundColor]     if (numberOfComponents == 1) {         return [UIColor colorWithCGColor:oldCGColor];     }      const CGFloat *oldComponentColors = CGColorGetComponents(oldCGColor);     CGFloat newComponentColors[numberOfComponents];      int i = numberOfComponents - 1;     newComponentColors[i] = oldComponentColors[i]; // alpha     while (--i >= 0) {         newComponentColors[i] = 1 - oldComponentColors[i];     }      CGColorRef newCGColor = CGColorCreate(CGColorGetColorSpace(oldCGColor), newComponentColors);     UIColor *newColor = [UIColor colorWithCGColor:newCGColor];     CGColorRelease(newCGColor);      return newColor; }