I don't think there's a way to upload a full-length image to the body of post from the disc of of computer directly. As Supada indicated in Post 2 of this thread.
1. Put the mouse on the image you desire, and then click the right side of mouse and save it in your computer.And what if the image is just part of a page of a website? That's why I take a Grab of the image with my Apple Mac and save it, then want to post it as a full-length picture.
2. Upload the image to other website, such as your blog, and secure a URL of the image.
I think my approach about this is rather clumsy. Hope someone else can come up with better ideas if they have.