c.r = Math.floor(255 - 0.5 * (255 - c.r));
c.g = Math.floor(255 - 0.5 * (255 - c.g));
c.b = Math.floor(255 - 0.5 * (255 - c.b));
c.r = Math.floor(255 - 0.5 * (255 - c.r));
c.g = Math.floor(255 - 0.5 * (255 - c.g));
c.b = Math.floor(255 - 0.5 * (255 - c.b));