//轉(zhuǎn)到固定長度的十六進制字符串，不夠則補0
function zero_fill_hex(num, digits) {
var s = num.toString(16);
while (s.length < digits)
s = "0" + s;
return s;
}

//媽的，怎么都沒搜到怎么用javascript找出一個背景色的數(shù)值，只好自己解析
function rgb2hex(rgb) {
//nnd, Firefox / IE not the same, fxck
if (rgb.charAt(0) == '#')
return rgb;
var n = Number(rgb);
var ds = rgb.split(//D+/);
var decimal = Number(ds[1]) * 65536 + Number(ds[2]) * 256 + Number(ds[3]);
return "#" + zero_fill_hex(decimal, 6);
}