canvas绘制经典折线图(一)
最终效果图如下：
实现步骤如下：注-引用了jQuery
HTML代码
<!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>
JS代码：即HTML中引用的外部JS文件<script src="scripts/recordPaint.js"></script>
/**
* 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();
}
}
总结：每个拐点的坐标值要清晰
-----------------------------------------------------------------------小二给我来二两轮子！
