gd - php - synchronization

[pribram]

Hi,
I'm in troubles now:
I'm using php_gd.dll for working with images. My code is:

$input = fopen($image_file_url, "rb");
$image_data = fread($input, 2000000);
fclose($input);

$image_file = tmpfile();
$output = fopen($image_file, "w+b");
fwrite($output, $image_data);
fclose($output);

$image_tmp = imageCreateFromPNG ($image_file);

if ($image_tmp) $image_unlink = unlink($image_file);

ImageCopy($image_base, $image_tmp, 0, 0, 0, 0, $map_width, $map_height);
ImageDestroy ( $image_tmp );

Almost every process in this script creates a temp file (for a second) named as "Resource id #X", where X is a number unique for one client, but NOT unique for concurrent client requests!!
It means that in some cases the script crashes with "'Resource id #6' is not a valid PNG file" or "Permission denied" etc.

I have tryied to lock files using flock() - no success.

Is there any way how to synchronize concurrent processes/threads (create a queue)?

Thank you for ANY suggestion!

Pribram

[undertow]

I don't know if this would solve your problem, but couldn't you use the imagecreatefrompng() function directly on the URL?

[pribram]

No, it's not possible. The purpose of the script is to merge PNGs together (in loop), so I need to use something like this.

Thanks anyway

[Atom]

I looked around on php.net for a little while looking for an easy solution to this problem...I couldn't find one. But you can put in tests to see if the resource is currently used already or somehow make the resouce id unique by using it in conjuction with something unique from the client (i.e.: client id?) I wish I could be of more help...good luck.

Atom

[pribram]

Hi Atom,

I have put the test to the code like this:

$input = fopen($image_file_url, "rb");
flock($input, LOCK_EX);
$image_data = fread($input, 2000000);
fclose($input);

echo $input." - input<br>";

Then I accessed the script many times from 2 browsers.

That was the way how I recognized my problem.

I hope you'll find something! Thanks!

Pribram

[pribram]

I think I've got it:

$image_file = tmpfile(); =>> $image_file = tempnam("/tmp", "tmp");