Recently I wrote a script for my avatar (refresh it a couple times) which allows you to randomly grab an image out of a directory and display it.

Although the tutorial is fairly easy, you need to have an understanding of PHP.

In order to fully appreciate this tutorial, you will need access to a web server with support for PHP as well as the GD library. This is the PHP graphics library. I am also assuming that your web server runs Apache.

To figure out if you have the GD extension installed on your web server, create a php file with the following: <?php phpinfo(8); The 8 will display all of your installed modules. Just do a find for 'gd'.

Note: I left off the closing ?> because we aren't outputting any HTML.

Ok, assuming that you have the GD extension installed, let's get started.

The first thing you need to do is setup your folder structure. Mine looks like this:

-avatar_tutorial
--images

Pretty simple.

Now drop a couple images into the images folder.

In your top folder (avatar_tutorial in my case), create a new php file. You can name it whatever you want. Mine is called avatar.php.

<?php
$dir = 'images/'; // obviously the directory where your images are coming from

// we want to be able to detect the extension of the file
function file_ext($f) {
   $ext = substr($f, strrpos($f, '.') + 1);
   // substr returns part of a string and strrpos is used to find the last occurence of a character in a string
   if(strlen($ext) > 2) { // because directories contain a "parent directory" link, this is an easy way to get around it
       return $ext;
   } else {
       return null;
   }
}

function createimg($f) {
   global $dir; // this grabs the $dir var from above so we can use it

   $ext = file_ext($f);

   if($ext) {
       header("Content-type: image/$ext"); // this tells the browser that we're loading an image
   }

   if($ext == 'png') { // if image is a png
       $img = imagecreatefrompng($dir.$f);
       imagealphablending($img, false); // disable so we can enable alpha saving
       imagesavealpha($img, true); // so that alpha is saved
       imagepng($img);
   } else if($ext == 'jpg') { // if image is a jpeg
       $img = imagecreatefromjpeg($dir.$f);
       imagejpeg($img, null, 100); // note the null, 100 is so tha the jpeg is saved with good quality
   } else if($ext == 'gif') { // if image is a gif
       $img = imagecreatefromgif($dir.$f);
       imagegif($img);
   }

   if($ext) {
       imagedestroy($img); // free up the memory used to create the image
   }
}

$dir_contents = scandir($dir); // scandir is used to make an array of the contents of a directory

function randimg() {
   global $dir_contents; // grabs the $dir_contents var from above so we can use it
   // the reason it isn't IN the function is so that the scan only has to take place once

   $rand_img = $dir_contents[rand(0, count($dir_contents) - 1)]; // grabs a random image from the dir contents

   if(file_ext($rand_img)) { // refer to the if statement of the file_ext. this assumes it's > 2
       createimg($rand_img);
   } else {
       randimg(); // otherwise it isn't a valid extension / image and it will re-initiate the function
   }
}

randimg(); // initiate the function

Hopefully the comments in the code explain it enough. Now we come to a problem. On some websites (like proboards), you can't by default display a .php file.

There is an easy way to solve this, assuming you're using Apache (just assume you are - you'd know if you weren't).

In your main directory, create a file called ".htaccess". These files provide rules for how files should be handled.

Inside the file, put in this. RewriteEngine On

RewriteRule avatar.jpg avatar.php [NC]

change "avatar.php" to the name of your script.

Now, when you load avatar.jpg, it will actually load the php script.

The [NC] just means that it's caps-insensitive.


And that's that!