NodeJS：将base64编码的图像保存到磁盘

我的Express应用程序正在从浏览器接收base64编码的PNG（使用toDataURL（）从canvas生成）并将其写入文件。但是该文件不是有效的图像文件，因此“文件”实用程序只是将其标识为“数据”。

var body = req.rawBody,
  base64Data = body.replace(/^data:image\/png;base64,/,""),
  binaryData = new Buffer(base64Data, 'base64').toString('binary');

require("fs").writeFile("out.png", binaryData, "binary", function(err) {
  console.log(err); // writes out file without error, but it's not a valid image
});

我认为您正在转换的数据比您需要的更多。一旦使用正确的编码创建了缓冲区，您只需要将缓冲区写入文件即可。

var base64Data = req.rawBody.replace(/^data:image\/png;base64,/, "");

require("fs").writeFile("out.png", base64Data, 'base64', function(err) {
  console.log(err);
});

new Buffer（...，'base64'）通过将输入解释为base64编码的字符串，将输入字符串转换为Buffer，它只是字节数组。然后，您可以将该字节数组写入文件。

更新资料

如评论中所述，req.rawBody已不再是一回事。如果使用express/ connect，则应使用bodyParser()中间件并使用req.body，并且如果使用标准Node进行此操作，则需要聚集传入的data事件Buffer对象，并在end回调中进行此图像数据解析。

这是我的完整解决方案，它将读取任何base64图像格式并将其以适当的格式保存在数据库中：

    // Save base64 image to disk
    try
    {
        // Decoding base-64 image
        // Source: http://stackoverflow.com/questions/20267939/nodejs-write-base64-image-file
        function decodeBase64Image(dataString) 
        {
          var matches = dataString.match(/^data:([A-Za-z-+\/]+);base64,(.+)$/);
          var response = {};

          if (matches.length !== 3) 
          {
            return new Error('Invalid input string');
          }

          response.type = matches[1];
          response.data = new Buffer(matches[2], 'base64');

          return response;
        }

        // Regular expression for image type:
        // This regular image extracts the "jpeg" from "image/jpeg"
        var imageTypeRegularExpression      = /\/(.*?)$/;      

        // Generate random string
        var crypto                          = require('crypto');
        var seed                            = crypto.randomBytes(20);
        var uniqueSHA1String                = crypto
                                               .createHash('sha1')
                                                .update(seed)
                                                 .digest('hex');

        var base64Data = 'data:image/jpeg;base64,/9j/4AAQSkZJRgABAQEAZABkAAD/4Q3zaHR0cDovL25zLmFkb2JlLmN...';

        var imageBuffer                      = decodeBase64Image(base64Data);
        var userUploadedFeedMessagesLocation = '../img/upload/feed/';

        var uniqueRandomImageName            = 'image-' + uniqueSHA1String;
        // This variable is actually an array which has 5 values,
        // The [1] value is the real image extension
        var imageTypeDetected                = imageBuffer
                                                .type
                                                 .match(imageTypeRegularExpression);

        var userUploadedImagePath            = userUploadedFeedMessagesLocation + 
                                               uniqueRandomImageName +
                                               '.' + 
                                               imageTypeDetected[1];

        // Save decoded binary image to disk
        try
        {
        require('fs').writeFile(userUploadedImagePath, imageBuffer.data,  
                                function() 
                                {
                                  console.log('DEBUG - feed:message: Saved to disk image attached by user:', userUploadedImagePath);
                                });
        }
        catch(error)
        {
            console.log('ERROR:', error);
        }

    }
    catch(error)
    {
        console.log('ERROR:', error);
    }

更新

我找到了一个有趣的链接，该链接如何解决PHP中的问题。我认为您忘了替换space为+，如链接中所示。

我从http://images-mediawiki-sites.thefullwiki.org/04/1/7/5/6204600836255205.png提取了一个圆圈，如下所示：

接下来，我将其放置在http://www.greywyvern.com/code/php/binary2base64中，它返回了我：

data:image/png;base64,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

保存了base64我在代码中读取的字符串。

var fs      = require('fs'),
data        = fs.readFileSync('base64', 'utf8'),
base64Data,
binaryData;

base64Data  =   data.replace(/^data:image\/png;base64,/, "");
base64Data  +=  base64Data.replace('+', ' ');
binaryData  =   new Buffer(base64Data, 'base64').toString('binary');

fs.writeFile("out.png", binaryData, "binary", function (err) {
    console.log(err); // writes out file without error, but it's not a valid image
});

我回来了一个圈子，但有趣的是文件大小已更改：）...

结束

当您读回图像时，我认为您需要设置标题

以PHP页面中的imagepng为例：

<?php
$im = imagecreatefrompng("test.png");

header('Content-Type: image/png');

imagepng($im);
imagedestroy($im);
?>

我认为第二行header('Content-Type: image/png');很重要，否则您的图像将不会显示在浏览器中，而只是一堆二进制数据显示给浏览器。

在Express中，您只需要使用以下内容即可。我将显示位于http://www.gravatar.com/avatar/cabf735ce7b8b4471ef46ea54f71832d?s=32&d=identicon&r=PG的 gravatar， 当您时为jpeg文件curl --head http://www.gravatar.com/avatar/cabf735ce7b8b4471ef46ea54f71832d?s=32&d=identicon&r=PG。我只请求标头，因为curl会显示一堆二进制文件（Google Chrome立即下载）以进行控制台：

curl --head "http://www.gravatar.com/avatar/cabf735ce7b8b4471ef46ea54f71832d?s=32&d=identicon&r=PG"
HTTP/1.1 200 OK
Server: nginx
Date: Wed, 03 Aug 2011 12:11:25 GMT
Content-Type: image/jpeg
Connection: keep-alive
Last-Modified: Mon, 04 Oct 2010 11:54:22 GMT
Content-Disposition: inline; filename="cabf735ce7b8b4471ef46ea54f71832d.jpeg"
Access-Control-Allow-Origin: *
Content-Length: 1258
X-Varnish: 2356636561 2352219240
Via: 1.1 varnish
Expires: Wed, 03 Aug 2011 12:16:25 GMT
Cache-Control: max-age=300
Source-Age: 1482

$ mkdir -p ~/tmp/6922728
$ cd ~/tmp/6922728/
$ touch app.js

app.js

var app = require('express').createServer();

app.get('/', function (req, res) {
    res.contentType('image/jpeg');
    res.sendfile('cabf735ce7b8b4471ef46ea54f71832d?s=32&d=identicon&r=PG');
});

app.get('/binary', function (req, res) {
    res.sendfile('cabf735ce7b8b4471ef46ea54f71832d?s=32&d=identicon&r=PG');
});

app.listen(3000);

$ wget "http://www.gravatar.com/avatar/cabf735ce7b8b4471ef46ea54f71832d?s=32&d=identicon&r=PG"
$ node app.js

我还必须保存作为数据URL一部分的Base64编码图像，因此我最终制作了一个小型npm模块来执行此操作，以防万一我（或其他人）将来需要再次执行此操作。叫做ba64。

简而言之，它使用带有Base64编码图像的数据URL，并将图像保存到文件系统中。它可以同步或异步保存。它还具有两个帮助器功能，一个用于获取图像的文件扩展名，另一个用于将Base64编码与data:方案前缀分开。

这是一个例子：

var ba64 = require("ba64"),
    data_url = "data:image/jpeg;base64,[Base64 encoded image goes here]";

// Save the image synchronously.
ba64.writeImageSync("myimage", data_url); // Saves myimage.jpeg.

// Or save the image asynchronously.
ba64.writeImage("myimage", data_url, function(err){
    if (err) throw err;

    console.log("Image saved successfully");

    // do stuff
});

安装它：npm i ba64 -S。回购在GitHub上：https : //github.com/HarryStevens/ba64。

PS后来我想到ba64可能对模块不是一个好名字，因为人们可能会认为ba64可以进行Base64编码和解码，而实际上并没有（很多模块已经这样做了）。那好吧。

这对我来说简单而完美。

Scott Robinson的精彩解释

从图像到base64字符串

let buff = fs.readFileSync('stack-abuse-logo.png');
let base64data = buff.toString('base64');

从base64字符串到图像

let buff = new Buffer(data, 'base64');
fs.writeFileSync('stack-abuse-logo-out.png', buff);

将base64图像转换为文件并另存为一些随机ID或名称的简便方法。

// to create some random id or name for your image name
const imgname = new Date().getTime().toString();

// to declare some path to store your converted image
const path = yourpath.png    

// image takes from body which you uploaded
const imgdata = req.body.image;    

// to convert base64 format into random filename
const base64Data = imgdata.replace(/^data:([A-Za-z-+/]+);base64,/, '');
fs.writeFile(path, base64Data, 'base64', (err) => {
    console.log(err);
});

// assigning converted image into your database
req.body.coverImage = imgname

从具有base64字符串的文件转换为png图像。

4种有效的变体。

var {promisify} = require('util');
var fs = require("fs");

var readFile = promisify(fs.readFile)
var writeFile = promisify(fs.writeFile)

async function run () {

  // variant 1
  var d = await readFile('./1.txt', 'utf8')
  await writeFile("./1.png", d, 'base64')

  // variant 2
  var d = await readFile('./2.txt', 'utf8')
  var dd = new Buffer(d, 'base64')
  await writeFile("./2.png", dd)

  // variant 3
  var d = await readFile('./3.txt')
  await writeFile("./3.png", d.toString('utf8'), 'base64')

  // variant 4
  var d = await readFile('./4.txt')
  var dd = new Buffer(d.toString('utf8'), 'base64')
  await writeFile("./4.png", dd)

}

run();

下面的功能是保存文件，只需传递您的base64文件，它将返回文件名保存在DB中。

import fs from 'fs';
 const uuid = require('uuid/v1');

/*Download the base64 image in the server and returns the filename and path of image.*/
function saveImage(baseImage) {
    /*path of the folder where your project is saved. (In my case i got it from config file, root path of project).*/
    const uploadPath = "/home/documents/project";
    //path of folder where you want to save the image.
    const localPath = `${uploadPath}/uploads/images/`;
    //Find extension of file
    const ext = baseImage.substring(baseImage.indexOf("/")+1, baseImage.indexOf(";base64"));
    const fileType = baseImage.substring("data:".length,baseImage.indexOf("/"));
    //Forming regex to extract base64 data of file.
    const regex = new RegExp(`^data:${fileType}\/${ext};base64,`, 'gi');
    //Extract base64 data.
    const base64Data = baseImage.replace(regex, "");
    const filename = `${uuid()}.${ext}`;

    //Check that if directory is present or not.
    if(!fs.existsSync(`${uploadPath}/uploads/`)) {
        fs.mkdirSync(`${uploadPath}/uploads/`);
    }
    if (!fs.existsSync(localPath)) {
        fs.mkdirSync(localPath);
    }
    fs.writeFileSync(localPath+filename, base64Data, 'base64');
    return filename;
}

您可以使用诸如base64-img或base64-to-image之类的第三方库。

1. base64-img

const base64Img = require('base64-img');

const data = 'data:image/png;base64,...';
const destpath = 'dir/to/save/image';
const filename = 'some-filename';

base64Img.img(data, destpath, filename, (err, filepath) => {}); // Asynchronous using

const filepath = base64Img.imgSync(data, destpath, filename); // Synchronous using

2. base64到图像

const base64ToImage = require('base64-to-image');

const base64Str = 'data:image/png;base64,...';
const path = 'dir/to/save/image/'; // Add trailing slash
const optionalObj = { fileName: 'some-filename', type: 'png' };

const { imageType, fileName } = base64ToImage(base64Str, path, optionalObj); // Only synchronous using