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12:00:14
这是网上的一个手绘板，中间还是有很多不足，但是也有很多可以学习的地方。我发上来仅供参考，代码见下：
<!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">
<style type="text/css">
body{background-color: white;}
</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……‘/>
<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;
//开始
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>
</body>
</html>
ps：报一下这个的缺点吧
1.功能太少，只有保存和清空，没有其他的撤销，反撤销
2.没有图片截取最小大小，没有自动大小（这个好解决）
（上面两个是根据我自己的需求得出的、、下面是真·问题）
3.鼠标点击完屏幕，移出区域之后会可以直接不点就能画，需要再在区域里点一下才可以取消效果，原因是仅仅定义了鼠标点击提起mouseup，并没有相应匹配的移出的事件。
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原文地址：http://www.cnblogs.com/tzz-ing/p/5021306.html
