h5-画板

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <title>Title</title>
 6     <style>
 7         *
 8         {
 9             margin: 0;
10             padding: 0;
11         }
12         #box
13         {
14             width: 600px;
15             height: 600px;
16             margin: 0 auto;
17         }
18         #ca
19         {
20 
21             background: #ccc;
22         }
23     </style>
24 </head>
25 <body>
26 <div id="box">
27     <canvas id="ca" width="600" height="600">
28 
29     </canvas>
30 </div>
31 
32 <script >
33     var box=document.getElementById('box');
34     var ca=document.getElementById('ca');
35     var ctx=ca.getContext('2d');
36     ca.onmousedown=function (ev) {
37         var event=window.event||ev;
38         var startx=event.clientX-box.offsetLeft;
39         var starty=event.clientY-box.offsetTop;
40         ctx.beginPath();
41         ctx.moveTo(startx,starty);
42         ca.onmousemove=function (ev) {
43             var event=window.event||ev;
44             var endx=event.clientX-box.offsetLeft;
45             var endy=event.clientY-box.offsetTop;
46             ctx.lineTo(endx,endy);
47             ctx.strokeStyle='green';
48             ctx.stroke();
49         }
50         document.onmouseup=function () {
51             ca.onmousemove=null;
52             ctx.closePath();
53         }
54     }
55 </script>
56 </body>
57 </html>
index.html