What are the methods to convert images to base64 in js
This time I will bring you the methods of converting images to base64 in js, and what are the precautions for converting images to base64 in js. The following is a practical case, let's take a look.
Method 1: Blob and FileReader objects
Implementation principle: Use xhr to request images, and set the returned file type to Blob object [xhr .responseType = "blob"]Use FileReader object to receive blob<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>js 图片转base64方式</title>
</head>
<body>
<p id="container1"></p>
<script>
getBase64("https://z649319834.github.io/Learn_Example/video_track/webvtt.jpg")
function getBase64(imgUrl) {
window.URL = window.URL || window.webkitURL;
var xhr = new XMLHttpRequest();
xhr.open("get", imgUrl, true);
// 至关重要
xhr.responseType = "blob";
xhr.onload = function () {
if (this.status == 200) {
//得到一个blob对象
var blob = this.response;
console.log("blob", blob)
// 至关重要
let oFileReader = new FileReader();
oFileReader.onloadend = function (e) {
let base64 = e.target.result;
console.log("方式一》》》》》》》》》", base64)
};
oFileReader.readAsDataURL(blob);
//====为了在页面显示图片，可以删除====
var img = document.createElement("img");
img.onload = function (e) {
window.URL.revokeObjectURL(img.src); // 清除释放
};
let src = window.URL.createObjectURL(blob);
img.src = src
document.getElementById("container1").appendChild(img);
//====为了在页面显示图片，可以删除====
}
}
xhr.send();
}
</script>
</body>
</html>Method 2: canvas.toDataURL() method
Implementation principle:Use the canvas.toDataURL() methodNeed to solve the cross-domain problem of images image.crossOrigin = '';Used the $.Deferred() method of the Jquery library<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>js 图片转base64方式</title>
</head>
<body>
<p id="container2"></p>
<script src="https://apps.bdimg.com/libs/jquery/2.1.1/jquery.min.js"></script>
<script>
let imgSrc = "https://z649319834.github.io/Learn_Example/video_track/webvtt.jpg";
//width、height调用时传入具体像素值，控制大小 ,不传则默认图像大小
function getBase64Image(img, width, height) {
var canvas = document.createElement("canvas");
canvas.width = width ? width : img.width;
canvas.height = height ? height : img.height;
var ctx = canvas.getContext("2d");
ctx.drawImage(img, 0, 0, canvas.width, canvas.height);
var dataURL = canvas.toDataURL();
return dataURL;
}
function getCanvasBase64(img) {
var image = new Image();
//至关重要
image.crossOrigin = '';
image.src = img;
//至关重要
var deferred = $.Deferred();
if (img) {
image.onload = function () {
deferred.resolve(getBase64Image(image));//将base64传给done上传处理
document.getElementById("container2").appendChild(image);
}
return deferred.promise();//问题要让onload完成后再return sessionStorage['imgTest']
}
}
getCanvasBase64(imgSrc)
.then(function (base64) {
console.log("方式二》》》》》》》》》",base64);
}, function (err) {
console.log(err);
});
</script>
</body>
</html>Vue beforeEnter uses the hook function
Vue implements tabs and switching functions in detail
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