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<!DOCTYPE html> <html> <head> <title>画板实验</title> <meta charset="UTF-8"> <meta name="viewport"content="width=device-width, initial-scale=1.0"> <!-- <script type="text/javascript" src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"> </script>--> <style type="text/css"> </style> </head> <body > <canvas id="myCanvas"></canvas> <div> <button onclick="clean();">清 空</button> <button onclick="save();">生成图片</button> </div> <img id=‘img‘ alt=‘请涂鸦……‘/> <textarea id="log"cols="30"rows="5"></textarea> <script type="text/javascript"> var canvas,board,img; canvas = document.getElementById(‘myCanvas‘); img= document.getElementById(‘img‘); canvas.height = 300; canvas.width = 300; board = canvas.getContext(‘2d‘); var mousePress = false; var last = null; function beginDraw(){ mousePress = true; } function drawing(event){ event.preventDefault(); if(!mousePress)return; var xy = pos(event); if(last!=null){ board.beginPath(); board.moveTo(last.x,last.y); board.lineTo(xy.x,xy.y); board.stroke(); } last = xy; } function endDraw(event){ mousePress = false; event.preventDefault(); last = null; } function pos(event){ var x,y; if(isTouch(event)){ x = event.touches[0].pageX; y = event.touches[0].pageY; }else{ x = event.offsetX+event.target.offsetLeft; y = event.offsetY+event.target.offsetTop; } // log(‘x=‘+x+‘ y=‘+y); return {x:x,y:y}; } function log(msg){ var log = document.getElementById(‘log‘); var val = log.value; log.value = msg+‘n‘+val; } function isTouch(event){ var type = event.type; if(type.indexOf(‘touch‘)>=0){ return true; }else{ return false; } } function save(){ //base64 var dataUrl = canvas.toDataURL(); // dataUrl = dataUrl.replace("image/png","image/octet-stream"); img.src = dataUrl; } function clean(){ board.clearRect(0,0,canvas.width,canvas.height); } board.lineWidth = 1; board.strokeStyle="#0000ff"; canvas.onmousedown = beginDraw; canvas.onmousemove = drawing; canvas.onmouseup = endDraw; canvas.addEventListener(‘touchstart‘,beginDraw,false); canvas.addEventListener(‘touchmove‘,drawing,false); canvas.addEventListener(‘touchend‘,endDraw,false); </script> [ lim_{x to 0} ] </body> </html>
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原文地址：http://www.cnblogs.com/yudishow/p/4603561.html
