How can I save a base64-encoded image to disk?
UPDATE
I found this interesting link how to solve your problem in PHP. I think you forgot to replace space by +as shown in the link.
I took this circle from http://images-mediawiki-sites.thefullwiki.org/04/1/7/5/6204600836255205.png as sample which looks like:
Next I put it through http://www.greywyvern.com/code/php/binary2base64 which returned me:
data:image/png;base64,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
saved this string to base64 which I read from in my code.
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
});
I get a circle back, but the funny thing is that the filesize has changed :)...
END
When you read back image I think you need to setup headers
Take for example imagepng from PHP page:
<?php
$im = imagecreatefrompng("test.png");
header('Content-Type: image/png');
imagepng($im);
imagedestroy($im);
?>
I think the second line header('Content-Type: image/png');, is important else your image will not be displayed in browser, but just a bunch of binary data is shown to browser.
In Express you would simply just use something like below. I am going to display your gravatar which is located at http://www.gravatar.com/avatar/cabf735ce7b8b4471ef46ea54f71832d?s=32&d=identicon&r=PG
and is a jpeg file when you curl --head http://www.gravatar.com/avatar/cabf735ce7b8b4471ef46ea54f71832d?s=32&d=identicon&r=PG. I only request headers because else curl will display a bunch of binary stuff(Google Chrome immediately goes to download) to console:
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
This did it for me simply and perfectly.
Excellent explanation by Scott Robinson
From image to base64 string
let buff = fs.readFileSync('stack-abuse-logo.png');
let base64data = buff.toString('base64');
From base64 string to image
let buff = Buffer.from(data, 'base64');
fs.writeFileSync('stack-abuse-logo-out.png', buff);
this is my full solution which would read any base64 image format and save it in the proper format in the database:
// 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);
}
I think you are converting the data a bit more than you need to. Once you create the buffer with the proper encoding, you just need to write the buffer to the file.
var base64Data = req.rawBody.replace(/^data:image\/png;base64,/, "");
require("fs").writeFile("out.png", base64Data, 'base64', function(err) {
console.log(err);
});
new Buffer(..., 'base64') will convert the input string to a Buffer, which is just an array of bytes, by interpreting the input as a base64 encoded string. Then you can just write that byte array to the file.
Update
As mentioned in the comments, req.rawBody is no longer a thing. If you are using express/connect then you should use the bodyParser() middleware and use req.body, and if you are doing this using standard Node then you need to aggregate the incoming data event Buffer objects and do this image data parsing in the end callback.