JavaScript 实现颜色明暗调整：获取更亮或更暗颜色值

function LightenDarkenColor(col, amt) {
 
 var usePound = false;
 
 if (col[0] == "#") {
 col = col.slice(1);
 usePound = true;
 }
 
 var num = parseInt(col,16);
 
 var r = (num >> 16) + amt;
 
 if (r > 255) r = 255;
 else if (r < 0) r = 0;
 
 var b = ((num >> 8) & 0x00FF) + amt;
 
 if (b > 255) b = 255;
 else if (b < 0) b = 0;
 
 var g = (num & 0x0000FF) + amt;
 
 if (g > 255) g = 255;
 else if (g < 0) g = 0;
 
 return (usePound?"#":"") + (g | (b << 8) | (r << 16)).toString(16);
 
}

// Lighten
var NewColor = LightenDarkenColor("#F06D06", 20); 

// Darken
var NewColor = LightenDarkenColor("#F06D06", -20);