我需要将我的图像转换为Base64字符串，这样我就可以将我的图像发送到服务器。
有JavaScript文件吗?否则，我如何转换它?
当前回答
如果你有一个文件对象，这个简单的函数将工作:
function getBase64 (file, callback) {
const reader = new FileReader();
reader.addEventListener('load', () => callback(reader.result));
reader.readAsDataURL(file);
}
使用的例子:
getBase64(fileObjectFromInput, function(base64Data){
console.log("Base64 of file is", base64Data); // Here you can have your code which uses Base64 for its operation, // file to Base64 by oneshubh
});
其他回答
我发现最安全可靠的方法是使用FileReader()。
演示:映像到Base64
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
</head>
<body>
<input id="myinput" type="file" onchange="encode();" />
<div id="dummy">
</div>
<div>
<textarea style="width:100%;height:500px;" id="txt">
</textarea>
</div>
<script>
function encode() {
var selectedfile = document.getElementById("myinput").files;
if (selectedfile.length > 0) {
var imageFile = selectedfile[0];
var fileReader = new FileReader();
fileReader.onload = function(fileLoadedEvent) {
var srcData = fileLoadedEvent.target.result;
var newImage = document.createElement('img');
newImage.src = srcData;
document.getElementById("dummy").innerHTML = newImage.outerHTML;
document.getElementById("txt").value = document.getElementById("dummy").innerHTML;
}
fileReader.readAsDataURL(imageFile);
}
}
</script>
</body>
</html>
更新-相同的代码与评论@AnniekJ请求:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
</head>
<body>
<input id="myinput" type="file" onchange="encode();" />
<div id="dummy">
</div>
<div>
<textarea style="width:100%;height:500px;" id="txt">
</textarea>
</div>
<script>
function encode() {
// Get the file objects that was selected by the user from myinput - a file picker control
var selectedfile = document.getElementById("myinput").files;
// Check that the user actually selected file/s from the "file picker" control
// Note - selectedfile is an array, hence we check it`s length, when length of the array
// is bigger than 0 than it means the array containes file objects
if (selectedfile.length > 0) {
// Set the first file object inside the array to this variable
// Note: if multiple files are selected we can itterate on all of the selectedfile array using a for loop - BUT in order to not make this example complicated we only take the first file object that was selected
var imageFile = selectedfile[0];
// Set a filereader object to asynchronously read the contents of files (or raw data buffers) stored on the user's computer, using File or Blob objects to specify the file or data to read.
var fileReader = new FileReader();
// We declare an event of the fileReader class (onload event) and we register an anonimous function that will be executed when the event is raised. it is "trick" we preapare in order for the onload event to be raised after the last line of this code will be executed (fileReader.readAsDataURL(imageFile);) - please read about events in javascript if you are not familiar with "Events"
fileReader.onload = function(fileLoadedEvent) {
// AT THIS STAGE THE EVENT WAS RAISED
// Here we are getting the file contents - basiccaly the base64 mapping
var srcData = fileLoadedEvent.target.result;
// We create an image html element dinamically in order to display the image
var newImage = document.createElement('img');
// We set the source of the image we created
newImage.src = srcData;
// ANOTHER TRICK TO EXTRACT THE BASE64 STRING
// We set the outer html of the new image to the div element
document.getElementById("dummy").innerHTML = newImage.outerHTML;
// Then we take the inner html of the div and we have the base64 string
document.getElementById("txt").value = document.getElementById("dummy").innerHTML;
}
// This line will raise the fileReader.onload event - note we are passing the file object here as an argument to the function of the event
fileReader.readAsDataURL(imageFile);
}
}
</script>
</body>
</html>
你也可以简单地提取以64为基数的URL的一部分:
var Base64URL = canvas.toDataURL('image/webp')
var Base64 = Base64URL.split(",")[1] //Returns the base64 part
我最终使用了一个返回Promise的函数。
const getImg64 = async() => { const convertImgToBase64URL = (url) => { console.log(url) return new Promise((resolve, reject) => { const img = new Image(); img.crossOrigin = 'Anonymous'; img.onload = () => { let canvas = document.createElement('CANVAS') const ctx = canvas.getContext('2d') canvas.height = img.height; canvas.width = img.width; ctx.drawImage(img, 0, 0); const dataURL = canvas.toDataURL(); canvas = null; resolve(dataURL) } img.src = url; }) } //for the demonstration purposes I used proxy server to avoid cross origin error const proxyUrl = 'https://cors-anywhere.herokuapp.com/' const image = await convertImgToBase64URL(proxyUrl+'https://image.shutterstock.com/image-vector/vector-line-icon-hello-wave-260nw-1521867944.jpg') console.log(image) } getImg64()
你可以在任何异步函数中使用这种方法。然后，您只需等待转换后的图像并继续执行指示即可。
如果你有一个文件对象，这个简单的函数将工作:
function getBase64 (file, callback) {
const reader = new FileReader();
reader.addEventListener('load', () => callback(reader.result));
reader.readAsDataURL(file);
}
使用的例子:
getBase64(fileObjectFromInput, function(base64Data){
console.log("Base64 of file is", base64Data); // Here you can have your code which uses Base64 for its operation, // file to Base64 by oneshubh
});
假设您在浏览器中执行此操作:
等待:
import axios from 'axios'
const response = await axios.get(url, { responseType: 'blob' });
return window.URL.createObjectURL(response.data);
与承诺
import axios from 'axios'
const response = await axios.get(url, { responseType: 'blob' })
.then((response) => {
const dataUrl = window.URL.createObjectURL(response.data);
// do something with your url
});
