public static double calculateContrastRatio(double lum1,double lum2){
  if ((lum1 < 0.0d) || (lum2 < 0.0d)) {
    throw new IllegalArgumentException("Luminance values may not be negative.");
  }
  return (Math.max(lum1,lum2) + 0.05d) / (Math.min(lum1,lum2) + 0.05d);
}

public static double calculateContrastRatio ( double lum1 , double lum2 ) { if ( ( lum1 < 0.0d ) || ( lum2 < 0.0d ) ) { throw new IllegalArgumentException ( "Luminance values may not be negative." ) ; } return ( Math . max ( lum1 , lum2 ) + 0.05d ) / ( Math . min ( lum1 , lum2 ) + 0.05d ) ; }
calculates the contrast ratio of two order - independent luminance values . < p > derived from formula at http : / / gmazzocato . altervista . org / colorwheel / algo . php
