求两个颜色之间的渐变值

/**
 * 求两个颜色之间的渐变值
 * @param {string} startColor 开始的颜色
 * @param {string} endColor 结束的颜色
 * @param {number} step 颜色等分的份额
 * */
function colorGradient(startColor = 'rgb(0, 0, 0)', endColor = 'rgb(255, 255, 255)', step = 10) {
    let startRGB = hexToRgb(startColor, false); //转换为rgb数组模式
    let startR = startRGB[0];
    let startG = startRGB[1];
    let startB = startRGB[2];

    let endRGB = hexToRgb(endColor, false);
    let endR = endRGB[0];
    let endG = endRGB[1];
    let endB = endRGB[2];

    let sR = (endR - startR) / step; //总差值
    let sG = (endG - startG) / step;
    let sB = (endB - startB) / step;
    let colorArr = [];
    for (let i = 0; i < step; i++) {
        //计算每一步的hex值 
        let hex = rgbToHex('rgb(' + Math.round((sR * i + startR)) + ',' + Math.round((sG * i + startG)) + ',' + Math.round((sB *
            i + startB)) + ')');
        colorArr.push(hex);
    }
    return colorArr;
}

// 将hex表示方式转换为rgb表示方式(这里返回rgb数组模式)
function hexToRgb(sColor, str = true) {
    let reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/;
    sColor = sColor.toLowerCase();
    if (sColor && reg.test(sColor)) {
        if (sColor.length === 4) {
            let sColorNew = "#";
            for (let i = 1; i < 4; i += 1) {
                sColorNew += sColor.slice(i, i + 1).concat(sColor.slice(i, i + 1));
            }
            sColor = sColorNew;
        }
        //处理六位的颜色值
        let sColorChange = [];
        for (let i = 1; i < 7; i += 2) {
            sColorChange.push(parseInt("0x" + sColor.slice(i, i + 2)));
        }
        if(!str) {
            return sColorChange;
        } else {
            return `rgb(${sColorChange[0]},${sColorChange[1]},${sColorChange[2]})`;
        }
    } else if (/^(rgb|RGB)/.test(sColor)) {
        let arr = sColor.replace(/(?:\(|\)|rgb|RGB)*/g, "").split(",")
        return arr.map(val => Number(val));
    } else {
        return sColor;
    }
};

// 将rgb表示方式转换为hex表示方式
function rgbToHex(rgb) {
    let _this = rgb;
    let reg = /^#([0-9a-fA-f]{3}|[0-9a-fA-f]{6})$/;
    if (/^(rgb|RGB)/.test(_this)) {
        let aColor = _this.replace(/(?:\(|\)|rgb|RGB)*/g, "").split(",");
        let strHex = "#";
        for (let i = 0; i < aColor.length; i++) {
            let hex = Number(aColor[i]).toString(16);
            hex = String(hex).length == 1 ? 0 + '' + hex : hex; // 保证每个rgb的值为2位
            if (hex === "0") {
                hex += hex;
            }
            strHex += hex;
        }
        if (strHex.length !== 7) {
            strHex = _this;
        }
        return strHex;
    } else if (reg.test(_this)) {
        let aNum = _this.replace(/#/, "").split("");
        if (aNum.length === 6) {
            return _this;
        } else if (aNum.length === 3) {
            let numHex = "#";
            for (let i = 0; i < aNum.length; i += 1) {
                numHex += (aNum[i] + aNum[i]);
            }
            return numHex;
        }
    } else {
        return _this;
    }
}


/**
* JS颜色十六进制转换为rgb或rgba,返回的格式为 rgba（255，255，255，0.5）字符串
* sHex为传入的十六进制的色值
* alpha为rgba的透明度
*/
function colorToRgba(color, alpha = 0.3) {
    color = rgbToHex(color)
    // 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})$/
    /* 16进制颜色转为RGB格式 */
    let sColor = color.toLowerCase()
    if (sColor && reg.test(sColor)) {
        if (sColor.length === 4) {
            var sColorNew = '#'
            for (let 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 (let i = 1; i < 7; i += 2) {
            sColorChange.push(parseInt('0x' + sColor.slice(i, i + 2)))
        }
        // return sColorChange.join(',')
        return 'rgba(' + sColorChange.join(',') + ',' + alpha + ')'
    } 
    else {
        return sColor
    }
}

标签：颜色,渐变,hex,sColor,rgb,let,之间,sColorChange,return
来源： https://www.cnblogs.com/guiyh/p/16387825.html