canvas将图片转为base64

时间：2023-12-19 12:25:20

最简例子

<!DOCTYPE html>

<html>

	<head>

		<meta charset="UTF-8">

		<meta name="viewport" content="width=device-width,initial-scale=1,minimum-scale=1,maximum-scale=1,user-scalable=no" />

		<title>canvas将图片转为base64</title>

		<style type="text/css">

			body {

				margin: 0;

			}

		</style>

	</head>

	<body>

		<img src="//img.alicdn.com/tps/i2/TB1bNE7LFXXXXaOXFXXwFSA1XXX-292-116.png" id="img" />

		<canvas id="load_area" width="100%" height="224px"></canvas>

		<script type="text/javascript">

			var imgEl = document.getElementById('img');

			var loadCanvas = document.getElementById('load_area');

			var context = loadCanvas.getContext('2d');

			var base64Str = '';

			var tmpImage = new Image();

			tmpImage.setAttribute('crossOrigin', 'anonymous');

			tmpImage.src = imgEl.src;

			tmpImage.onload = function() {

				loadCanvas.width = imgEl.width;

				loadCanvas.height = imgEl.height;

				context.drawImage(tmpImage, 10, 10);

				base64Str = loadCanvas.toDataURL('image/jpg');

			};

		</script>

	</body>

</html>

纯js版

var appendCanvas = function() {

	var body = document.body;

	var canvas = document.createElement('canvas');

	body.appendChild(canvas);

	return canvas;

};

var createImage = function(url) {

	var img = new Image();

	img.setAttribute('crossOrigin', 'anonymous');

	img.src = url;

	return img;

};

var imageToBase64 = function(url) {

	var canvas = appendCanvas();

	var context = canvas.getContext('2d');

	var tmpImage = createImage(url);

	var base64Str = '';

	tmpImage.onload = function() {

		canvas.width = tmpImage.width;

		canvas.height = tmpImage.height;

		context.drawImage(tmpImage, 0, 0);

		base64Str = canvas.toDataURL('image/jpg');

		console.log(base64Str);

	};

};

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