I've uploaded images directly to my WordPress server through FTP. I want to add these images to a post, so right now I'm using the Add from Server plugin that allows me to browse images on the server and add them to the media library. The only thing I don't like about this is that adding an image to the media library generates two smaller versions of the image that are used for thumbnails. Is it not possible to completely bypass the media library and add images directly from the server?
I think that the best option here would be to disable the generation of additional image sizes on adding an image to the media library. Doing so is fairly straight-forward:
Visit the Settings > Media page of your WordPress dashboard. Under the Image Sizes section, change all of the values to 0.
Save the changes. This will stop WordPress generating thumbnails, medium, and large sizes of every image you upload.
You will also notice that when you go to insert an image, the "Size" dropdown box is missing.