<!doctype html>

<html lang="en">

 <head>

  <meta charset="UTF-8">

  <meta name="Generator" content="EditPlus®">

  <meta name="Author" content="">

  <meta name="Keywords" content="">

  <meta name="Description" content="">

  <title>canvas绘制折线图</title>

  <script src="scripts/jquery-1.11.3.js"></script>

  <script src="scripts/recordPaint.js"></script>

  <style>

  </style>

 </head>

 <script>

    $(function(){

         /*

             * 定义绘制折线图的关键数据(12个月的消费记录-金额)

             * 封装函数专门用于绘制折线图

               recordPaint(Elem,Data)方法

               * Elem - 表示<canvas>元素

               * Data - 表示关键数据

          */

         var datas = [1200,2000,3000,500,200,800,1800,2200,2600,1000,600,300];

         recordPaint($("#recordCvs")[0],datas);

    });

 </script>

 <body>

    <div id="recordContent">

        <canvas id="recordCvs" width="600" height="400"></canvas>

    </div>

 </body>

</html>

/**

 * Created by walker on 2015/11/26.

 * 定义recordPaint()方法

 */

function recordPaint(Elem,Data){

    // 1. 创建画布对象

    var context = Elem.getContext('2d');

    // 2. 获取画布的宽度和高度

    const WIDTH = Elem.width;

    const HEIGHT = Elem.height;

    // 3. 定义坐标轴相对画布的内边距

    var padding = 20;//初始化内边距

    var paddingLeft = 60;//至少大于绘制文字的宽度

    var paddingBottom = 30;//至少大于绘制文字的高度

    // 4. 定义绘制坐标轴的关键点的坐标值

    var axisY = {// y轴的起点坐标值

        x : paddingLeft,

        y : padding

    };

    var origin = {// 原点坐标值(x轴与y轴相交点)

        x : paddingLeft,

        y : HEIGHT - paddingBottom

    };

    var axisX = {

        x : WIDTH - padding,

        y : HEIGHT - paddingBottom

    };

    // 5. 绘制坐标轴

    context.beginPath();

    context.moveTo(axisY.x,axisY.y);

    context.lineTo(origin.x,origin.y);

    context.lineTo(axisX.x,axisX.y);

    context.stroke();

    // 6. 绘制坐标轴的箭头

    context.beginPath();

    context.moveTo(axisY.x-5,axisY.y+10);

    context.lineTo(axisY.x,axisY.y);

    context.lineTo(axisY.x+5,axisY.y+10);

    context.stroke();

    context.beginPath();

    context.moveTo(axisX.x-10,axisX.y-5);

    context.lineTo(axisX.x,axisX.y);

    context.lineTo(axisX.x-10,axisX.y+5);

    context.stroke();

    // 定义折点的x轴值

    var pointsX = [];

    // 7. 绘制坐标轴的刻度(x轴的月份和y轴的金额)

    // x轴的月份

    var month = {

        x : paddingLeft,

        y : HEIGHT - paddingBottom

    }

    // 设置字体

    context.font = "14px 微软雅黑";

    // 设置垂直对齐

    context.textBaseline = "top";

    for(var i=1;i<=12;i++){

        pointsX[pointsX.length] = month.x;

        // 绘制月份信息

        context.fillText(i+"月",month.x,month.y);

        // 改变每次绘制的x坐标轴的值

        month.x += (axisX.x - origin.x)/12;

    }

    // 绘制y轴的金额

    // 从众多的关键金额中,取到最高金额

    /*

    var datas = [];

    for(index in Data){

        datas[datas.length] = Data[index];

    }

    function sortNumber(a,b){

        return a - b;

    }

    var max = datas.sort(sortNumber)[datas.length-1];

    */

    var max = Math.max.apply(Math,Data);

    var moneyY = (origin.y - axisY.y)/(max/500+1);

    // 定义绘制的坐标值

    var money = {

        x : axisY.x - 5,

        y : axisY.y + moneyY,

        jin : max

    }

    // 设置水品对齐

    context.textAlign = "right";

    // 遍历"最高值/间隔"次

    for(var i=0;i<max/500;i++){

        // 绘制金额

        context.fillText(money.jin+"元",money.x,money.y);

        // y轴向下移动(增加)

        money.y += moneyY;

        // 金额每次减500

        money.jin -= 500;

    }

    /*

      绘制折线

      * 12个折点的x轴值，对应12个月文字的x轴值

      * 折点的y轴值等于原点的y轴值-折点到原点的距离

        * 折点到原点的距离 = (3000点的y到原点的y的长度)*当前金额/3000

     */

    context.beginPath();

    for(var i=0;i<Data.length;i++){

        // 获取折点的x和y值

        var pointY = origin.y - (origin.y - (axisY.y + moneyY))*Data[i]/max;

        var pointX = pointsX[i];

        // 绘制折线

        if(i == 0){

            context.textAlign = "left";

            //context.textBaseline = "bottom";

            context.moveTo(pointX,pointY);

        }else{

            context.textAlign = "center";

            context.textBaseline = "bottom";

            context.lineTo(pointX,pointY);

        }

        // 绘制折点的金额

        context.fillText(Data[i],pointX,pointY);

    }

    context.stroke();

    // 绘制12个折点的圆

    for(var i=0;i<Data.length;i++){

        // 获取折点的x和y值

        var pointY = origin.y - (origin.y - (axisY.y + moneyY))*Data[i]/max;

        var pointX = pointsX[i];

        // 绘制圆

        context.fillStyle = "red";

        context.beginPath();

        context.arc(pointX,pointY,3,0,Math.PI*2);

        context.fill();

    }

}