18 September 2007

This is a blog item that needs to be converted to the new Bliki format

Dynamic image resizing via URL

Wikimedia does URL-based image resizing on the fly as in the following example URL's. You can change the number of pixels to anything and it will return the image at that size.

• http://upload.wikimedia.org/wikipedia/commons/thumb/2/2a/FIRE_01.JPG/100px-FIRE_01.JPG
• http://upload.wikimedia.org/wikipedia/commons/thumb/2/2a/FIRE_01.JPG/226px-FIRE_01.JPG
• http://upload.wikimedia.org/wikipedia/commons/thumb/2/2a/FIRE_01.JPG/701px-FIRE_01.JPG

This process uses the /wiki/thumb.php script which accepts two query-string parameters, f for the name of the image and w for the width of the re-sized image to be returned. Mod-rewrite can then be used to map requests to re-sized thumbnails to the script, eg:

RewriteCond %{REQUEST_URI} ^/files/thumb/./../.+?([0-9]+)px-(.+)$
RewriteRule ([0-9]+)px-(.+)$ /wiki/thumb.php?w=$1&f=$2 [L]