我的Express应用程序正在从浏览器接收base64编码的PNG(从画布生成的toDataURL())，并将其写入一个文件。但该文件不是有效的图像文件，“file”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
});
更新
我发现这个有趣的链接如何解决你的PHP问题。我想你忘记用+替换空格，如链接所示。
我从http://images-mediawiki-sites.thefullwiki.org/04/1/7/5/6204600836255205.png上取了这个圆作为样本，看起来像:
然后我把它输入http://www.greywyvern.com/code/php/binary2base64，结果是:
data:image/png;base64,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
将这个字符串保存到base64，我从我的代码中读取。
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
});
我得到一个圈回来，但有趣的是，文件大小已经改变了:)…
END
当你读回图像时，我认为你需要设置标题
以PHP页面图像为例:
<?php
$im = imagecreatefrompng("test.png");
header('Content-Type: image/png');
imagepng($im);
imagedestroy($im);
?>
我认为第二行标题('Content-Type: image/png');很重要，否则你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，您只需使用如下所示的内容。我将显示位于http://www.gravatar.com/avatar/cabf735ce7b8b4471ef46ea54f71832d?s=32&d=identicon&r=PG的您的gravatar 并且是一个jpeg文件，当你卷曲——头http://www.gravatar.com/avatar/cabf735ce7b8b4471ef46ea54f71832d?s=32&d=identicon&r=PG。我只请求头，因为否则卷曲将显示一堆二进制的东西(谷歌Chrome立即去下载)到控制台:
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
我认为你转换的数据比你需要的多一点。一旦您使用适当的编码创建了缓冲区，您只需要将缓冲区写入文件。
var base64Data = req.rawBody.replace(/^data:image\/png;base64,/, "");
require("fs").writeFile("out.png", base64Data, 'base64', function(err) {
console.log(err);
});
新缓冲区(…， 'base64')将通过将输入解释为base64编码的字符串，将输入字符串转换为Buffer，这只是一个字节数组。然后你就可以把这个字节数组写到文件中。
更新
正如评论中提到的，req。rawBody不再是一个东西。如果您正在使用express/connect，那么您应该使用bodyParser()中间件并使用req。如果您使用标准Node来执行此操作，那么您需要聚合传入的数据事件Buffer对象，并在结束回调中进行图像数据解析。
这是我的完整解决方案，它将读取任何base64图像格式，并将其保存在数据库中的适当格式:
// 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);
}
简单的方法将base64图像转换为文件，并保存为一些随机id或名称。
// 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
我还必须保存Base64编码的图像，这些图像是数据url的一部分，所以我最终制作了一个小的npm模块来做这件事，以防我(或其他人)将来需要再次这样做。叫做ba64。
简单地说，它接受一个带有Base64编码图像的数据URL，并将图像保存到您的文件系统中。它可以同步或异步保存。它还有两个辅助函数，一个用于获取图像的文件扩展名，另一个用于从数据中分离Base64编码:方案前缀。
这里有一个例子:
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:npm i ba64 -S。Repo在GitHub上:https://github.com/HarryStevens/ba64。
P.S.后来我想到ba64可能是一个不好的模块名称，因为人们可能认为它进行Base64编码和解码，但事实并非如此(有很多模块已经这样做了)。哦。
从base64字符串文件转换为png图像。
有4个变体。
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();
下面的函数保存文件，只要传递你的base64文件，它返回文件名保存在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;
}
这对我来说简单而完美。
斯科特·罗宾逊的精彩解释
从映像到base64字符串
let buff = fs.readFileSync('stack-abuse-logo.png');
let base64data = buff.toString('base64');
从base64字符串到映像
let buff = Buffer.from(data, 'base64');
fs.writeFileSync('stack-abuse-logo-out.png', buff);
您可以使用第三方库，如base64-img或base64-to-image。
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
base64-to-image
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
非常简单
const path = require('path');
const { readFile, stat, writeFile } = require("fs/promises");
(async () => {
try {
const contents = await readFile(path.join(__dirname, 'clau.jpg'), { encoding: 'base64' });
console.log(contents);
await writeFile(path.join(__dirname, 'claumia.jpg'), Buffer.from(contents, 'base64'));
} catch (error) {
console.log(error)
}
})()
