https://github.com/ImageMagick/ImageMagick/issues/663
https://github.com/ImageMagick/ImageMagick/issues/655
static inline void ModulateHWB(const double percent_hue,
  const double percent_whiteness,const double percent_blackness,double *red,
  double *green,double *blue)
{
  double
    blackness,
    hue,
    whiteness;

  /*
    Increase or decrease color blackness, whiteness, or hue.
  */
  ConvertRGBToHWB(*red,*green,*blue,&hue,&whiteness,&blackness);
  hue+=fmod((percent_hue-100.0),200.0)/200.0;
  blackness*=0.01*percent_blackness;
  whiteness*=0.01*percent_whiteness;
  ConvertHWBToRGB(hue,whiteness,blackness,red,green,blue);
}

static inline void ModulateHWB(const double percent_hue,
  const double percent_whiteness,const double percent_blackness,double *red,
  double *green,double *blue)
{
  double
    blackness,
    hue,
    whiteness;

  /*
    Increase or decrease color blackness, whiteness, or hue.
  */
  ConvertRGBToHWB(*red,*green,*blue,&hue,&whiteness,&blackness);
  hue+=fmod((percent_hue-100.0),200.0)/200.0;
  blackness*=0.01*percent_blackness;
  whiteness*=0.01*percent_whiteness;
  ConvertHWBToRGB(hue,whiteness,blackness,red,green,blue);
}
