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.