Javascript实现Web颜色值转换

原文：http://my.oschina.net/mailzwj/blog/375624

<!-- lang: js -->
var rgbToHex = function(rgb) {
        var rRgba = /rgba?\((\d{1,3}),(\d{1,3}),(\d{1,3})(,([.\d]+))?\)/,
        r, g, b, a,
        rsa = rgb.replace(/\s+/g, "").match(rRgba);
    if (rsa) {
        r = (+rsa[1]).toString(16);
        r = r.length == 1 ? "0" + r : r;
        g = (+rsa[2]).toString(16);
        g = g.length == 1 ? "0" + g : g;
        b = (+rsa[3]).toString(16);
        b = b.length == 1 ? "0" + b : b;
        a = (+(rsa[5] ? rsa[5] : 1)) * 100
        return {hex: "#" + r + g + b, alpha: Math.ceil(a)};
    } else {
        return {hex: rgb, alpha: 100};
    }
};

<!-- lang: js -->
var hexToRgba = function(hex, al) {
    var hexColor = /^#/.test(hex) ? hex.slice(1) : hex,
        alp = hex === 'transparent' ? 0 : Math.ceil(al),
        r, g, b;
    hexColor = /^[0-9a-f]{3}|[0-9a-f]{6}$/i.test(hexColor) ? hexColor : 'fffff';
    if (hexColor.length === 3) {
        hexColor = hexColor.replace(/(\w)(\w)(\w)/gi, '$1$1$2$2$3$3');
    }
    r = hexColor.slice(0, 2);
    g = hexColor.slice(2, 4);
    b = hexColor.slice(4, 6);
    r = parseInt(r, 16);
    g = parseInt(g, 16);
    b = parseInt(b, 16);
    return {
        hex: '#' + hexColor,
        alpha: alp,
        rgba: 'rgba(' + r + ', ' + g + ', ' + b + ', ' + (alp / 100).toFixed(2) + ')'
    };
};

原作者博客： http://www.seejs.com/