在电子应用程序中将文件从 blob 写入磁盘

2022-01-10 00:00:00 node.js electron javascript

我正在创建一个 Electron 应用程序，在其中我正在从网络摄像头和桌面记录数据，在记录会话结束时，我想将数据保存到后台的文件中.我不知道如何将数据从 blob 直接写入文件.有什么建议?以下是我当前对 MediaRecord Stop 事件的处理.

I am creating an Electron Application in which I am recording data from webcam and desktop, at the end of the recording session, I want to save the data to a file in the background. I do not know how to write the data from a blob to a file directly. Any suggestions? Below is my current handling for MediaRecord Stop event.

this.mediaRecorder.onstop = (e) => {                                      
       var blob = new Blob(this.chunks,                                      
                           { 'type' : 'video/mp4; codecs=H.264' });                                                       
       var fs = require('fs');                                               
       var fr = new FileReader();                                            
       var data = null;                                                      
       fr.onload = () => {                                                   
           data = fr.result;                                                 
           fs.writeFile("test.mp4", data, err => {                           
               if(err) {                                                     
                   return console.log(err);                                  
               }                                                             
               console.log("The file was saved!");                           
           });                                                               
       };                                                                    
       fr.readAsArrayBuffer(blob);                                           
   }

推荐答案

您可以使用 FileReader 和 Buffer 来完成.

You can do it using FileReader and Buffer.

在渲染器进程中，将事件发送到主进程以将文件与缓冲区一起保存:

In the renderer process, send the event to the main process to save the file with the buffer:

function saveBlob(blob) {
    let reader = new FileReader()
    reader.onload = function() {
        if (reader.readyState == 2) {
            var buffer = new Buffer(reader.result)
            ipcRenderer.send(SAVE_FILE, fileName, buffer)
            console.log(`Saving ${JSON.stringify({ fileName, size: blob.size })}`)
        }
    }
    reader.readAsArrayBuffer(blob)
}

取回确认:

ipcRenderer.on(SAVED_FILE, (event, path) => {
    console.log("Saved file " + path)
})

(SAVE_FILE 和 SAVED_FILE 是包含事件名称的静态字符串)

(SAVE_FILE and SAVED_FILE are static strings containing event name)

在主进程中:

ipcMain.on(SAVE_FILE, (event, path, buffer) => {
    outputFile(path, buffer, err => {
        if (err) {
            event.sender.send(ERROR, err.message)
        } else {
            event.sender.send(SAVED_FILE, path)
        }
    })
})

outputFile 来自 'fs-extra'

outputFile is from 'fs-extra'

首选在主进程中处理节点操作.请参阅 Electron 安全建议.

Handling node operations in main process is preferred. See Electron Security suggestions.

如果你不想使用主进程，你可以使用 'electron-remote' 创建后台进程来写入文件.此外，您可以在后台进程中调用 ffmpeg 将文件压缩/编码为不同的格式.

If you do want to not use main process, you can use 'electron-remote' to create background processes to write the file. Additionally, you can invoke ffmpeg in the background process to compress/encode the file into different format.

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