html5之canvas画图 1.写字板功能_H5之家 - 中国HTML5教程资源分享第一站

写字板事例：

写字板分析：1.点击鼠标開始写字（onmosedown）2.按下鼠标写字（onmousemove）3.松开鼠标，停下写字（撤销onmousemove事件）：

代码:

<strong><!doctype html> </strong><html> <head> <meta charset="utf-8"> <title>Canvas</title> <style type="text/css"> body { margin: 0px; padding: 0px; } #canvas { margin: 0px; padding: 0px; border: 1px solid #000000; } </style> </head> <body> <canvas>当前浏览器不支持canvas</canvas> <script type="text/javascript" src="utils.js"></script> <script type="text/javascript" src="arrow.js"></script> <script type="text/javascript"> window.onload=function(){ var canvas=document.getElementById("canvas"); var context=canvas.getContext("2d"); /*var mouse=utils.captureMousePosition(canvas); */ //加入mousedown监听事件。在用户鼠标按下后開始画线。并注冊mousemove事件 canvas.addEventListener("mousedown",function(event){ context.beginPath(); context.moveTo(event.clientX, event.clientY); //alert("-------------") canvas.addEventListener("mousemove",onMouseMove,false); },false); //在鼠标移动时划线 function onMouseMove(event){ context.lineTo(event.clientX,event.clientY); context.stroke(); } //在鼠标按键松开后，注销鼠标移动事件 canvas.addEventListener("mouseup",function(event){ canvas.removeEventListener("mousemove",onMouseMove,false); },false); } </script> </body> </html>