作者：王永存
來(lái)源：CSDN
原文：https://blog.csdn.net/wang1006008051/article/details/80841581
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<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width,initial-scale=1,user-scalable=yes"/>
<title>手寫(xiě)簽名</title>
<style type="text/css">
html,body{
margin: 0;
padding: 0;
}
.saveimg{
text-align: center;
}
.saveimgs span{
display: inline-block;
margin-top:5px;
}
</style>
</head>
<body>
<div align="center">
<canvas id="myCanvas" width="500" height="300" style="border:1px solid #6699cc"></canvas>
<div class="control-ops control">
<button type="button" class="btn btn-primary" onclick="javascript:clearArea();return false;">清空畫(huà)板</button>
Line width : <select id="selWidth" onchange="aaa()">
<option value="1">1</option>
<option value="3" selected="selected">3</option>
<option value="5">5</option>
<option value="7">7</option>
<option value="9">9</option>
<option value="11">11</option>
</select>
Color : <select id="selColor" onchange="aaa2()">
<option value="black" selected="selected">black</option>
<option value="blue">blue</option>
<option value="red">red</option>
<option value="green">green</option>
<option value="yellow">yellow</option>
<option value="gray">gray</option>
</select>
<button type="button" class="saveimg" onclick="javascript:saveImageInfo();return false;">保存</button>
</div>
<div class="saveimgs"></div>
</div>
</body>
<script type="text/javascript">
var mousePressed = false;
var lastX, lastY;
var ctx = document.getElementById('myCanvas').getContext("2d");
var c = document.getElementById("myCanvas");
// console.log(c)
// console.log(c2)
var control = document.getElementsByClassName("control")[0];
var saveimgs = document.getElementsByClassName("saveimgs")[0];
window.onload = function(){
InitThis();
}
function saveImageInfo(){
var image = c.toDataURL("image/png");
var ctximg = document.createElement("span");
ctximg.innerHTML = "<img src='"+image+"' alt='from canvas'/>";
if(saveimgs.getElementsByTagName('span').length >= 1){
var span_old = saveimgs.getElementsByTagName("span")[0];
saveimgs.replaceChild(ctximg,span_old)
}
else{
saveimgs.appendChild(ctximg);
}
// console.log(image)
}
var selected1,selected2;
function aaa(){
var sel = document.getElementById('selWidth');
var value = sel.selectedIndex;
return selected1 = sel[value].value;
}
function aaa2(){
var sel2 = document.getElementById('selColor');
var value = sel2.selectedIndex;
return selected2 = sel2[value].value;
}
function InitThis() {
// 觸摸屏
c.addEventListener('touchstart', function (event) {
console.log(1)
if (event.targetTouches.length == 1) {
event.preventDefault();// 阻止瀏覽器默認(rèn)事件燎悍，重要
var touch = event.targetTouches[0];
mousePressed = true;
Draw(touch.pageX - this.offsetLeft, touch.pageY - this.offsetTop, false);
}
},false);
c.addEventListener('touchmove', function (event) {
console.log(2)
if (event.targetTouches.length == 1) {
event.preventDefault();// 阻止瀏覽器默認(rèn)事件敬惦，重要
var touch = event.targetTouches[0];
if (mousePressed) {
Draw(touch.pageX - this.offsetLeft, touch.pageY - this.offsetTop, true);
}
}
},false);
c.addEventListener('touchend', function (event) {
console.log(3)
if (event.targetTouches.length == 1) {
event.preventDefault();// 阻止瀏覽器默認(rèn)事件，防止手寫(xiě)的時(shí)候拖動(dòng)屏幕谈山，重要
// var touch = event.targetTouches[0];
mousePressed = false;
}
},false);
/*c.addEventListener('touchcancel', function (event) {
console.log(4)
mousePressed = false;
},false);*/
// 鼠標(biāo)
c.onmousedown = function (event) {
mousePressed = true;
Draw(event.pageX - this.offsetLeft, event.pageY - this.offsetTop, false);
};
c.onmousemove = function (event) {
if (mousePressed) {
Draw(event.pageX - this.offsetLeft, event.pageY - this.offsetTop, true);
}
};
c.onmouseup = function (event) {
mousePressed = false;
};
}
function Draw(x, y, isDown) {
if (isDown) {
ctx.beginPath();
ctx.strokeStyle = selected2;
ctx.lineWidth = selected1;
ctx.lineJoin = "round";
ctx.moveTo(lastX, lastY);
ctx.lineTo(x, y);
ctx.closePath();
ctx.stroke();
}
lastX = x; lastY = y;
}
function clearArea() {
// Use the identity matrix while clearing the canvas
ctx.setTransform(1, 0, 0, 1, 0, 0);
ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
// 清除簽名圖片
if(saveimgs.getElementsByTagName('span').length >= 1){
var clearImg = saveimgs.getElementsByTagName('span')[0];
saveimgs.removeChild(clearImg);
}
}
</script>
</html>
