I am currently have a 'products' table that has a ":has_many" relationship with a 'photos' table.
I am uploading photos to accompany products. Right now, I upload the photo, save the metadata to the 'photos' table and the image to the filesystem. Then, I direct a url from within the products display pages to point to a thumbnail generator. For example, /products, would display all the products with the product's associated images. The images would be formed by <img src="/photos/thumbnailer/? height=200&width=200 ?>. The '/thumbnailer' action then generates, saves (based on sizes), and displays the thumbnail of the uploaded file. If another request comes in for the same page, the saved thumbnails are displayed and the '/thumbnailer' action does not generate any new images. Thus, there is heavy overhead only on the first request. I like this because if I ever wish to change the layout of the site, all I have to do is change the url to meet the new parameters.
However, I have seen that most of the plugins that help with file uploads tend to generate thumbnails at the time of file uploads. For example, maybe a 'small', 'medium', and 'large' thumbnail are generated and served up throughout the site. However, this seems like more of a hassle to update if the design requirements change.
Since I am a new programmer, I am sure there are good reasons why others do it differently (like many of the plugins). Any thoughts? What drawbacks am I missing with my method?
Thanks
Andrew