public static Expression darken(Generator generator, FunctionCall input) {
        Color color = input.getExpectedColorParam(0);
        int decrease = input.getExpectedIntParam(1);
        return changeLighteness(color, -decrease);
    }
public static Expression darken ( Generator generator , FunctionCall input ) { Color color = input . getExpectedColorParam ( 0 ) ; int decrease = input . getExpectedIntParam ( 1 ) ; return changeLighteness ( color , - decrease ) ; }
Decreases the lightness of the given color by N percent.

@param generator the surrounding generator
@param input     the function call to evaluate
@return the result of the evaluation