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image – PHP Data-URI to file

Posted by: admin April 23, 2020 Leave a comment

Questions:

I have a data URI I am getting from javascript and trying to save via php. I use the following code which gives a apparently corrupt image file:

  $data = $_POST['logoImage'];

  $uri = substr($data,strpos($data,",")+1);

  file_put_contents($_POST['logoFilename'], base64_decode($uri));



data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAoAAAAKCAYAAACNMs 9AAAACXBIWXMAAAsTAAALEwEAmpwYAAAAxklEQVQYlYWQMW7CUBBE33yITYUUmwbOkBtEcgUlTa7COXIVV5RUkXKC5AxU EdyZVD4kyKxkwIrr9vd0c7Oih aopinLNsF6Qkg2XW4XJ7LGFsAAcTV6lF5/jLdbALA9XDAXYfthFQVx OrmqKYK88/7rbbMFksALieTnzu9wDYTj6f70PKsp2kwAiSvjXNcvkWpAfNZkzWa/5a9yT7fdoX7rrB7hYh2fXo9HdjPYQZu3MIU8bYIlW20y0RUlXG2Kpv/vfwLxhTaSQwWqwhAAAAAElFTkSuQmCC

Below the code is the actual image as a Data-URI. ‘logoImage’ is the string above, and $uri is the string minus ‘image/jpeg;base64,’.

How to&Answers:

A quick look at the PHP manual yields the following:

If you want to save data that is derived from a Javascript
canvas.toDataURL() function, you have to convert blanks into plusses.
If you do not do that, the decoded data is corrupted:

<?php
  $encodedData = str_replace(' ','+',$encodedData);
  $decodedData = base64_decode($encodedData);
?>

Answer:

The data URI you have in your example is not a valid PNG image. This will never work and is unrelated to the code, it’s related to the data.


Does not apply but might be of interest:

file_put_contents($_POST['logoFilename'], file_get_contents($data));

The idea behind: PHP itself can read the contents of data URIs (data://) so you don’t need to decode it on your own.

Note that the official data URI scheme (ref: The “data” URL scheme RFC 2397) does not include a double slash (“//“) after the colon (“:“). PHP supports with or without the two slashes.

 # RFC 2397 conform
 $binary = file_get_contents($uri);

 # with two slashes
 $uriPhp = 'data://' . substr($uri, 5);
 $binary = file_get_contents($uriPhp);

Answer:

The all code that works :

$imgData = str_replace(' ','+',$_POST['image']);
$imgData =  substr($imgData,strpos($imgData,",")+1);
$imgData = base64_decode($imgData);
// Path where the image is going to be saved
$filePath = $_SERVER['DOCUMENT_ROOT']. '/ima/temp2.png';
// Write $imgData into the image file
$file = fopen($filePath, 'w');
fwrite($file, $imgData);
fclose($file);