In this series of blog posts I introduce my favourite PHP libraries.
Today’s library is:
SLIR
SLIR – or ”Smart Lencioni Image Resizer” – was developed by Joe Lencioni. It’s purpose is on-the-fly scaling and cropping of images.
SLIR works by scaling the image on request, rather than on import.
The benefit is that you can change your image sizes on the fly. If your page layout changes, you can just request images with a size that fits.
It’s basically a clever PHP script that “acts” as like image, combined with a .htaccess-file, that disguises the PHP-file as an actual image file.
This means you activate the resizer just by putting a url into your img-tags.
The url holds the resize parameters and the path to the original image file.
Example:
Original image:
<img src="http://www.jakobloekkemadsen.com/wp-content/uploads/2010/02/DSC_1225_maj-30-2009.jpg" alt="" />
Scaled to fit 100px width:
<img src="http://www.jakobloekkemadsen.com/slir/w100/wp-content/uploads/2010/02/DSC_1225_maj-30-2009.jpg" alt="" />
Scaled to fit 25px width and cropped to square:
<img src="http://www.jakobloekkemadsen.com/slir/w25-c1:1/wp-content/uploads/2010/02/DSC_1225_maj-30-2009.jpg" alt="" />
”What about performance?”, I hear you ask. “Won’t the server choke on having to process all image requests?”
No, it won’t. (-:
SLIR caches the image the first time it’s requested, so all subsequent requests are served just as fast as any other image file on the server. The redirect is handled by an alias to the cachefile. Only if no matching cache file exists, or if it’s too old, or if the original has changed, then SLIR is invoked and a new image is generated and cached.
”Ok. But what about security, then?”
In theory this script enables a hacker to flood your server with files just by changing the url and requesting all imaginable combinations of width and height. This issue has been discussed in the comments on http://shiftingpixel.com/2008/03/03/smart-image-resizer/ and the current version of the script can be made to restrict access to any other combinations than the ones you specify.
Personally I haven’t found an easier, more futureproof and flexible solution for handling image scaling.
And it’s free!
Simply put: I love this script!
Stay tuned for part two of “Useful PHP libraries”. Coming soon …
