1 <!DOCTYPE html>
2 <html lang="en">
3 <head>
4 <meta charset="UTF-8">
5 <title>用canvas绘制折线图</title>
6 </head>
7 <body>
8 <canvas id="cv"></canvas>
9 </body>
10 </html>
11 <script>
12 var cv = document.getElementById("cv");
13 cv.width = 600;
14 cv.height = 400;
15 cv.style.border = "1px solid red";
16 var ctx = cv.getContext("2d");
17 var data2 = [.3, .1, .2, .4, .2, .7, .3, .9];
18 var data3 = [3, 12, 14, 17, 29, 33, 40, 52];
19
20 getBrokenLine(data2, "#f00");
21 getBrokenLine(data3, "#0f0");
22
23 //封装一个折线图的函数
24 function getBrokenLine(data, color) {
25 var maxNum = Math.max.apply(null, data); //求数组中的最大值
26 var padding = 20, //边距
27 x0 = padding, //原点x轴坐标
28 y0 = cv.height - padding, //原点y轴坐标
29 xArrow_x = padding, //x轴箭头处坐标x
30 xArrow_y = padding, //x轴箭头处坐标y
31 yArrow_x = cv.width - padding, //y轴箭头处坐标x
32 yArrow_y = cv.height - padding, //y轴箭头处坐标y
33 arrowWidth = 10, //箭头的宽度
34 xLength = cv.width - 2*padding - arrowWidth, //x轴的长度
35 yLength = cv.height - 2*padding - arrowWidth, //y轴的长度
36 pointsWidth = xLength/(data.length + 1); //折线上每个点之间的距离
37
38 ctx.beginPath();//控制绘制的折线不受坐标轴样式属性的影响
39 //绘制x轴
40 ctx.moveTo(x0, y0);
41 ctx.lineTo(xArrow_x, xArrow_y);
42 ctx.moveTo(xArrow_x, xArrow_y);
43 ctx.lineTo(xArrow_x - arrowWidth, xArrow_y + arrowWidth);
44 ctx.moveTo(xArrow_x, xArrow_y);
45 ctx.lineTo(xArrow_x + arrowWidth, xArrow_y + arrowWidth);
46
47 //绘制y轴
48 ctx.moveTo(x0, y0);
49 ctx.lineTo(yArrow_x, yArrow_y);
50 ctx.moveTo(yArrow_x, yArrow_y);
51 ctx.lineTo(yArrow_x - arrowWidth, yArrow_y - arrowWidth);
52 ctx.moveTo(yArrow_x, yArrow_y);
53 ctx.lineTo(yArrow_x - arrowWidth, yArrow_y + arrowWidth);
54 ctx.strokeStyle = "#000";
55
56 //中断（坐标轴和折线的）连接
57 ctx.stroke();
58 ctx.beginPath();
59
60 //绘制折线
61 for (var i = 0; i < data.length; i++) {
62 var pointX = padding + (i + 1) * pointsWidth;
63 var pointY = padding + arrowWidth + (1 - data[i]/maxNum) * yLength;
64 ctx.lineTo(pointX, pointY);
65 }
66 ctx.strokeStyle = color;
67 ctx.stroke();
68 }
69 </script>
效果图如下：
时间： 2024-10-18 23:50:30