How to Fix 'Invalid Image' Errors When Converting Base64 Strings to JPEGs?

Convert Base64 String to an Image File

Converting a Base64-encoded string to an image file can be straightforward, but errors may arise if not handled correctly. One such error is an invalid image.

Problem:

When attempting to convert a Base64 string to an image file using the following code:

function base64_to_jpeg($base64_string, $output_file) {
    $ifp = fopen( $output_file, "wb" );
    fwrite( $ifp, base64_decode( $base64_string) );
    fclose( $ifp );
    return( $output_file );
}

$image = base64_to_jpeg( $my_base64_string, 'tmp.jpg' );

you may encounter an error stating "invalid image."

Solution:

The error stems from the inclusion of data:image/png;base64 in the encoded contents. This extra data interferes with the base64 decoding process and results in an invalid image file. To resolve this issue, remove the redundant data before decoding the string:

function base64_to_jpeg($base64_string, $output_file) {
    // open the output file for writing
    $ifp = fopen($output_file, 'wb');

    // split the string on commas
    // $data[0] == "data:image/png;base64"
    // $data[1] == <actual base64 string>
    $data = explode(',', $base64_string);

    // we could add validation here with ensuring count( $data ) > 1
    fwrite($ifp, base64_decode($data[1]));

    // clean up the file resource
    fclose($ifp);

    return $output_file;
}

By removing the unnecessary data and ensuring that only the actual Base64-encoded string is decoded, you will successfully convert the string into a valid image file.

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