利用html2canvas.js將網頁中dom元素轉換成圖片，html2canvas.js的鏈接是：http://html2canvas.hertzen.com/
實現效果demo的代碼如下：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>網頁轉圖片</title>
<style>
#img {
position: fixed;
top: 0px;
left: 0px;
opacity: 1;
transform: scale(0.8);
z-index: 99999999;
transition: transform 0.3s cubic-bezier(0.42, 0, 0.58, 1), opacity 0.3s cubic-bezier(0.42, 0, 0.58, 1), -webkit-transform 0.3s cubic-bezier(0.42, 0, 0.58, 1)
}
</style>
<script type="text/javascript" src="http://html2canvas.hertzen.com/dist/html2canvas.min.js"></script>
<script src="http://code.jquery.com/jquery-1.8.3.min.js"></script>
</head>
<body>
<div id="capture" style="padding: 10px; background: #f5da55">
<h4 style="color: #000; ">Hello world!</h4>
</div>
<button id="btn">點擊</button>
<img id="img" />
<script type="text/javascript">
var element = document.querySelector('body');
var image = document.querySelector('#img');
$('#btn').on('click', function() {
html2image(element, image);
})
function html2image(source, image) {
html2canvas(source).then(canvas => {
var imageData = canvas.toDataURL("image/png");
image.src = imageData;
// document.body.appendChild(canvas);
sessionStorage.setItem('imageSrc', imageData);
});
}
$.fn.longPress = function(fn) { //移動端長按屏幕方法
var timeout = undefined;
var $this = this;
for (var i = 0; i < $this.length; i++) {
$this[i].addEventListener('touchstart', function(event) {
timeout = setTimeout(fn, 2000); //長按時間超過2000ms，則執行傳入的方法
}, false);
$this[i].addEventListener('touchend', function(event) {
clearTimeout(timeout); //長按時間少於2000ms，不會執行傳入的方法
}, false);
}
}
$('body').longPress(function() {
html2image(element, image);
});
</script>
</body>
</html>