Add keywords to image files when saving to a specific folder

I am super green when it comes to applescript and automation on a Mac.

That being said, I would like to add keyword tags to image files as I save them to a specified folder.

I draw, and I like to save images I find on the web of things I’d like to draw or add to a drawing in the future. So I would like to be able to, from a web browser, right-click the image, choose save as…, choose a specific folder to save the file, which triggers a script that asks me to assign keywords to the image file.

I currently use Picasa to add keywords to images, but would much prefer assigning keywords as I save them to my hard drive.

Is this feasible?

Any and all help would be greatly appreciated!