在 JavaScript 中将 Blob 对象转换为 base64

2022-01-21 00:00:00 image blob google-chrome base64 javascript

我正在尝试实现一个粘贴处理程序以从用户的剪贴板获取图像.我希望它只在 Google Chrome 上运行，我不担心其他浏览器.

I am trying to implement a paste handler to get an image from user's clipboard. I want this to run only on Google Chrome, I am not worried with other browsers.

这是我在 Internet 上找到的方法的一部分，我正在尝试对其进行调整.

This is a part of a method that I found on Internet and I am trying to adapt it.

// Get the items from the clipboard
var items = e.clipboardData.items;
    if (items) {
    // Loop through all items, looking for any kind of image
        for (var i = 0; i < items.length; i++) {
            if (items[i].type.indexOf("image") !== -1) {
                // We need to represent the image as a file,
                var blob = items[i].getAsFile();
                // and use a URL or webkitURL (whichever is available to the browser)
                // to create a temporary URL to the object
                var URLObj = window.URL || window.webkitURL;
                var source = URLObj.createObjectURL(blob);
                createImage(source);
                }
            }
        }

该方法有效，如果我使用源"作为图像对象的 src，我可以显示图像.问题是谷歌浏览器中的图像源将是这样的:blob:http://localhost:8080/d1328e65-ade2-45b3-a814-107cc2842ef9

The method works and I can show the image if I use my "source" as the src of a image object. The problem is that the image source in google chrome will be something like this: blob:http://localhost:8080/d1328e65-ade2-45b3-a814-107cc2842ef9

我需要将此图像发送到服务器，因此我想将其转换为 base64 版本.例如:

I need to send this image to the server, so I want to convert it to a base64 version. For example:

<代码>数据:图像/PNG; BASE64，iVBORw0KGgoAAAANSUhEUgAAArgAAAAjCAIAAADwnO7RAAAKMWlDQ1BJQ0MgUHJvZmlsZQAASImdlndUU9kWh8 + 9N71QkhCKlNBraFICSA29SJEuKjEJEErAkAAiNkRUcERRkaYIMijggKNDkbEiioUBUbHrBBlE1HFwFBuWSWStGd + 8EE/Nm98f935rn73P3Wfvfda6AJD8gwXCTFgJgAyhWBTh58WIjYtnYAcBDPAAA2wA4HCzs0IW + EYCmQJ82IxsmRP4F726DiD5 + yrTP4zBAP + flLlZIjEAUJiM5/L42VwZF8k4PVecJbdPyZi2NE3OMErOIlmCMlaTc/IsW3z2mWUPOfMyhDwZy3PO4mXw5Nwn4405Er6MkWAZF + CI + LkyviZjg3RJhkDGb + SxGXxONgAoktwu5nNTZGwtY5IoMoIt43kA4EjJX/DSL1jMzxPLD8XOzFouEiSniBkmXFOGjZMTi + HPz03ni8XM ... iCIBWnh + P9w9C + 9eMzvhCl1iOElK09ruc2wqGhfH/uKEV30FlJkmRZJklydFuW/FdwhYFCkCBBggQJEuS/gWC4FCRIkCBBggQZlmCgECRIkCBBggQZlmCgECRIkCBBggQZFmzhwoXXWoYgQYIECRIkyHUK5vF4rrUMQYIECRIkSJDrFHLktYOCBAkSJEiQIP/NkLt3777WMgT5thLstwoSJEiQ7zxYsEUhyJWxbdu2u ++++ 1pLESRIkCBBvl6Csx6CBAkSJEiQIMPy3dkMOsg3T7A5KkiQIEG + 8wQDhSBXTjBQCBIkSJDvPMGuhyBBggQJEiTIsFwXLQr9H6bOjtYeP2mONbOj2Hut9y6/X + nlJ​​SBCQnXkgG3Brh8Q4lqbOpAmPDqUGShex9lPDlfB4sU5I97b/8kuevygYUgYsAksAPg9fkbDQN/e1kNvVw76nfYeiTCG6sjLd5fv58rsFmxRCBIkSJDvPP8f+HtxbDVRPI8AAAAAASUVORK5CYII=

在第一段代码中，我有一个代表文件的 blob 对象.我尝试了几种方法，但没有得到正确的表示.如何使用它来创建 base64 表示?

In the first piece of code I have a blob object representing the file. I have tried a couple of methods but I am not getting the correct representation. How I can use it to create a base64 representation?

推荐答案

Nick Retallack 在本页的回答 剪贴板功能中的粘贴图像如何在 Gmail 和 Google Chrome 12+ 中工作? 完全符合我的要求.

Nick Retallack's answer at this page How does the paste image from clipboard functionality work in Gmail and Google Chrome 12+? does exactly what I want.

所以新的代码是:

var items = e.clipboardData.items;
if (items) {
// Loop through all items, looking for any kind of image
    for (var i = 0; i < items.length; i++) {
        if (items[i].type.indexOf("image") !== -1) {
            // We need to represent the image as a file,
            var blob = items[i].getAsFile();

            var reader = new FileReader();
                reader.onload = function(event){
                    createImage(event.target.result); //event.target.results contains the base64 code to create the image.
                };
                reader.readAsDataURL(blob);//Convert the blob from clipboard to base64
            }
        }
    }

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