Redirecting image requests via .htaccess depending on file existence

Question

I implemented an image generator which saves the final file in .jpg format inside /images. Once the file is saved, there is no need to generate it ever again.

This is the route for the image generator:

/gen.php?id=495abc

This is the directory where all the .jpg images are saved:

/images/495abc.jpg

So, the objective is: If a user tries to request http://website.com/images/495abc.jpg, the .htaccess rules have to verify if the file exists and then execute one of two actions depending on the case:

1. if the .jpg exists, serve the file directly.

2. if the .jpg does not exist, redirect the request to the generator at /gen.php?id=495abc (the new image will be displayed at the end of this process with Header("Content-Type: image/jpeg"))

Is that feasible via .htaccess? If not, there is another alternative: Redirect all /images/*.jpg requests to /gen.php?id=* and let gen.php do all the dirty work. Of course, the first alternative is better.

Any ideas? Thanks!

Answer 1

Yes. It is possible with htaccess:

RewriteEngine On
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^images/(\d+)\.(jpe?g|png|gif|ico|bmp)$ /gen.php?id=$1 [L,NC]