网页源码直接贴了：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>文档标题</title>
<style type="text/css">
.aaa {
cursor: url("http://192.168.12.144:8080/drawimg/icon/erase111111111111.ico"),auto;
}
</style>
<script src="js/jquery-1.8.3.min.js" ></script>
<script src="js/html2canvas.min.js" ></script>
<script src="js/printScreen.js" ></script> <script text="javascript">
var s;
$(function(){
s = new PrintScreen(document.getElementById('myCanvas'));
}); function imageData(str)
{
var img = new Image();
img.src=str;
$('#ddd').append(img);
}
</script>
</head>
<body>
<div align="center" id="ddd" >
<canvas id="myCanvas" class="aaa" width="1000" height="650" style="border:2px solid #6699cc;background-image: url('http://192.168.12.144:8080/drawimg/movie.png');background-repeat:no-repeat;"></canvas>
<div class="control-ops">
<button type="button" class="btn btn-primary" onclick="javascript:clearArea();return false;">清空画板</button>
<button type="button" class="btn btn-primary" onclick="javascript:s.setEdit();">笔</button>
<button type="button" class="btn btn-primary" onclick="javascript:s.setErase();">橡皮</button>
<button type="button" class="btn btn-primary" onclick="javascript:s.getImage(imageData);">复制</button>
Line width :
<select id="selWidth">
<option value="1">1</option>
<option value="3">3</option>
<option value="5">5</option>
<option value="7">7</option>
<option value="9" selected="selected">9</option>
<option value="11">11</option>
</select>
Color :
<select id="selColor">
<option value="black">black</option>
<option value="blue" selected="selected">blue</option>
<option value="red">red</option>
<option value="green">green</option>
<option value="yellow">yellow</option>
<option value="gray">gray</option>
</select>
</div>
</div>
</body>
</html>
printScreen.js 源码：
function PrintScreen(canvas)
{
this.mousePressed = false;
var lastX, lastY;
var ctx;
var isEdit = false;
var isErase = false; this.InitThis = function(){
ctx = canvas.getContext("2d");
canvas.onmousedown = function (e) {
this.mousePressed = true;
console.log('down>>'+this.mousePressed);
if (isEdit)
Draw(e.pageX - $(this).offset().left, e.pageY - $(this).offset().top, false); if (isErase)
Clear(e.pageX - $(this).offset().left, e.pageY - $(this).offset().top);
} canvas.onmousemove= function (e) {
console.log('over>>'+this.mousePressed+',edit='+isEdit);
if (this.mousePressed) { if (isEdit)
Draw(e.pageX - $(this).offset().left, e.pageY - $(this).offset().top, true); if (isErase)
Clear(e.pageX - $(this).offset().left, e.pageY - $(this).offset().top);
}
} canvas.onmouseup = function (e) {
this.mousePressed = false;
} canvas.onmouseleave = function (e) {
this.mousePressed = false;
}
} function Draw(x, y, isDown) {
if (isDown) {
ctx.beginPath();
ctx.strokeStyle = $('#selColor').val();
ctx.lineWidth = $('#selWidth').val();
ctx.lineJoin = "round";
ctx.moveTo(lastX, lastY);
ctx.lineTo(x, y);
ctx.closePath();
ctx.stroke();
}
lastX = x; lastY = y;
} function Clear(x, y)
{
ctx.clearRect(x-8, y-8, 16, 16);
} function clearArea() {
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
} this.setEdit = function()
{
console.log('edit>>');
isErase=false;isEdit=true;
} this.setErase = function()
{
isEdit = false;
isErase = true;
} // 从 canvas 提取图片 image
function convertCanvasToImage(canv) {
//新Image对象，可以理解为DOM
var image = new Image();
// canvas.toDataURL 返回的是一串Base64编码的URL，当然,浏览器自己肯定支持
// 指定格式 PNG
image.src = canv.toDataURL("image/png");
return image;
} this.getImage = function(callBack)
{
html2canvas(canvas, {
onrendered: function(canv) {
callBack(canv.toDataURL("image/png"));
}
});
}
this.InitThis();
}
html2canvas(canvas, {
onrendered: function(canv) {
callBack(canv.toDataURL("image/png"));
}
});
这段代码是 基于 html2canvas 库的截图功能 canv 是截图之后返回的canvas对象，
canv.toDataURL("image/png") 方法返回 涂改过后 图片的base64码