HEX十六进制与RGB, HSL颜色的相互转换

1、RGB颜色转换为十六进制

String.prototype.colorHex = function(){
    var that = this;
    //十六进制颜色值的正则表达式
    var reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/;
    // 如果是rgb颜色表示
    if (/^(rgb|RGB)/.test(that)) {
        var aColor = that.replace(/(?:\(|\)|rgb|RGB)*/g, "").split(",");
        var strHex = "#";
        for (var i=0; i<aColor.length; i++) {
            var hex = Number(aColor[i]).toString(16);
            if (hex.length < 2) {
                hex = '0' + hex;    
            }
            strHex += hex;
        }
        if (strHex.length !== 7) {
            strHex = that;    
        }
        return strHex;
    } else if (reg.test(that)) {
        var aNum = that.replace(/#/,"").split("");
        if (aNum.length === 6) {
            return that;    
        } else if(aNum.length === 3) {
            var numHex = "#";
            for (var i=0; i<aNum.length; i+=1) {
                numHex += (aNum[i] + aNum[i]);
            }
            return numHex;
        }
    }
    return that;
};

2、十六进制颜色转为RGB格式

String.prototype.colorRgb = function(){
    var sColor = this.toLowerCase();
    //十六进制颜色值的正则表达式
    var reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/;
    // 如果是16进制颜色
    if (sColor && reg.test(sColor)) {
        if (sColor.length === 4) {
            var sColorNew = "#";
            for (var i=1; i<4; i+=1) {
                sColorNew += sColor.slice(i, i+1).concat(sColor.slice(i, i+1));    
            }
            sColor = sColorNew;
        }
        //处理六位的颜色值
        var sColorChange = [];
        for (var i=1; i<7; i+=2) {
            sColorChange.push(parseInt("0x"+sColor.slice(i, i+2)));    
        }
        return "RGB(" + sColorChange.join(",") + ")";
    }
    return sColor;
};

3、HSL转RGB

/**
 * HSL颜色值转换为RGB. 
 * 换算公式改编自 http://en.wikipedia.org/wiki/HSL_color_space.
 * h, s, 和 l 设定在 [0, 1] 之间
 * 返回的 r, g, 和 b 在 [0, 255]之间
 *
 * @param   Number  h       色相
 * @param   Number  s       饱和度
 * @param   Number  l       亮度
 * @return  Array           RGB色值数值
 */
function hslToRgb(h, s, l) {
    var r, g, b;
    if(s == 0) {
        r = g = b = l; // achromatic
    } else {
        var hue2rgb = function hue2rgb(p, q, t) {
            if(t < 0) t += 1;
            if(t > 1) t -= 1;
            if(t < 1/6) return p + (q - p) * 6 * t;
            if(t < 1/2) return q;
            if(t < 2/3) return p + (q - p) * (2/3 - t) * 6;
            return p;
        }
        var q = l < 0.5 ? l * (1 + s) : l + s - l * s;
        var p = 2 * l - q;
        r = hue2rgb(p, q, h + 1/3);
        g = hue2rgb(p, q, h);
        b = hue2rgb(p, q, h - 1/3);
    }
    return [Math.round(r * 255), Math.round(g * 255), Math.round(b * 255)];
}

4、RGB转HSL

/**
 * RGB 颜色值转换为 HSL.
 * 转换公式参考自 http://en.wikipedia.org/wiki/HSL_color_space.
 * r, g, 和 b 需要在 [0, 255] 范围内
 * 返回的 h, s, 和 l 在 [0, 1] 之间
 *
 * @param   Number  r       红色色值
 * @param   Number  g       绿色色值
 * @param   Number  b       蓝色色值
 * @return  Array           HSL各值数组
 */
function rgbToHsl(r, g, b) {
    r /= 255, g /= 255, b /= 255;
    var max = Math.max(r, g, b), min = Math.min(r, g, b);
    var h, s, l = (max + min) / 2;
    if (max == min){ 
        h = s = 0; // achromatic
    } else {
        var d = max - min;
        s = l > 0.5 ? d / (2 - max - min) : d / (max + min);
        switch(max) {
            case r: h = (g - b) / d + (g < b ? 6 : 0); break;
            case g: h = (b - r) / d + 2; break;
            case b: h = (r - g) / d + 4; break;
        }
        h /= 6;
    }
    return [h, s, l];
}

5、RGB转HSB/HSV

function rgbToHsv(r, g, b) {
    r = r / 255;
    g = g / 255;
    b = b / 255;
    var h, s, v;
    var min = Math.min(r, g, b);
    var max = v = Math.max(r, g, b);
    var l = (min + max) / 2;
    var difference = max - min;
    if (max == min) {
        h = 0;
    } else {
        switch (max) {
        case r:
            h = (g - b) / difference + (g < b ? 6 : 0);
            break;
        case g:
            h = 2.0 + (b - r) / difference;
            break;
        case b:
            h = 4.0 + (r - g) / difference;
            break;
        }
        h = Math.round(h * 60);
    }
    if (max == 0) {
        s = 0;
    } else {
        s = 1 - min / max;
    }
    s = Math.round(s * 100);
    v = Math.round(v * 100);
    return [h, s, v];
}

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本文摘录自：https://www.zhangxinxu.com/wordpress/2010/03/javascript-hex-rgb-hsl-color-convert/