Block animated avatars

On my forums we try to enhance the reading experience, and do not allow our members to use animated avatars. One of my members have written the following hack for my forums, and I got his permission to post it here on vbulletin.org.

What this hack does is to prevent your users from uploading an animated image. It does this by checking if the image contains more than one frame. It is not retroactive, and your current avatars will remain as is.

Hope you will enjoy this.

Changes:
1 New Phrase
1 File to edit (profile.php)

Installtime: 45 sec


In profile.php, find:

// ####################### SET PHP ENVIRONMENT ###########################

Above that, add:

// Block Animated Avatars Hack - by Scha at freakforum.nu
// start

function isAnimated($filename, $isurl = 0)
{
        $fp = fopen($filename, "rb");
        if(!$fp)
                return false;
        if($isurl)
                $whole = fread($fp, remote_filesize($filename));
        else
                $whole = fread($fp, filesize($filename));
        $i = -1;
        while($i = strpos($whole, 0x2C, $i+1))
        {
                if(strpos($whole, 0x00, $i-1) == $i-1)
                $c++;
        }
        if($c > 1)
                return true;
        return false;
}

// end
// Block Animated Avatars Hack - by Scha at freakforum.nu

In profile.php, find:

                if ($avatarid == 0)
                {
                        // begin custom avatar code
                      require_once('./includes/functions_upload.php');
                      require_once('./includes/functions_file.php');

REPLACE that with:

// Block Animated Avatars Hack - by Scha at freakforum.nu   
//start

                require_once('./includes/functions_upload.php');
                require_once('./includes/functions_file.php');

                if(isset($_FILES['upload']) && strtolower(substr($_FILES['upload']['name'], -3)) == 'gif' )    
                        if (isAnimated($_FILES['upload']['tmp_name']))
                                eval(print_standard_error('error_avataranimated'));
                if ( strlen($_POST['avatarurl']) && strtolower(substr($_POST['avatarurl'], -3)) == 'gif' )
                        if(isAnimated($_POST['avatarurl'], 1 && strtolower(substr($_POST['avatarurl'], -3)) == 'gif'))
                                eval(print_standard_error('error_avataranimated'));

// end
// Block Animated Avatars Hack - by Scha at freakforum.nu   
         
                if ($avatarid == 0)
                {
                        // begin custom avatar code

Add phrase 'avataranimated' under the category 'Front-End Error Messages' with the following content

We do not allow the usage of animated avatars on our forums. Please consider uploading a static image instead.

Done.


Please leave a comment if there is something you are wondering about, or if you encounter a bug.

[nso]

Ah yes. That one.
The hack works by detecting a certain pattern in the file

PHP Code:

        while($i = strpos($whole, 0x2C, $i+1))
        {
                if(strpos($whole, 0x00, $i-1) == $i-1)
                $c++;
        } 


This pattern may actually occur without there actually being a new frame. I only recently discovered this myself, and as far as I can see there is no foolproof way of doing this without the false positives.

Suggestion on this part would be highly appreciated. I know that you also could do a check for the string "NETSCAPE" in the header of the gif, but that won't suffice.
Does anyone know how an image processing application like, for example, Adobes Imagemagic (isn't that the right one?) seperate the frames?

[trulylowcarb]

Back to click install again ... the Geek helped me sort out whatever was causing the conflict, and this is working again for me. Guess I could have waited for my earlier feedback, but when I put things off, they never get done, so ...

Thanks again for this hack!

[TCM]

Seems like a nice hack. I prefer to just allow users the option to freeze them, however.