Delete Original Image is a Wordpress plugin to delete the the original image file uploaded. The problem is that the original image file is ussualy huge (can be 6MB if it is a photograph) and it is never published on the pages so there is no need to keep it on your server.
The plugin gives you an option to enable/disable this to be done automatically when you upload an image. And/or you can do it in bulk for all your previously uploaded images.
Specifically, this plugin copy the 'large' image ( i.e: your-pic-1038x576.jpg ) to the original file path ( i.e.: your-pic.jpg ).
April 2016. Fixed bug! The plugin failed for images that were not uploaded in the current month. Deleting the original image but not copying the 1038x567 image to the original image location.