Don't try to hide access to an image on your blog, Website, photo gallery, etc., simply because you can't hide it. Even the best of the photography or image Websites for photographers can only disguise the pathname to the image where it takes time to sift through the layers of code to find the image.
As a test once someone with a Smugmug account said his images were impossible to download. It took me just over an hour through three scripts to find the server name, pathname and image file to download it. I sent one of the images to him with the note, "Is this the image you're protecting?"
I see this a lot with Websites like Tumblr, Flckr, etc. where you right click and either it won't allow you to open the image in a new tab or window or popup a window it's a copyright image and can't be downloaded. Sorry it can.
This is because all images on Web pages must be a single filename to display the image. Even attempts to slice the photo (called image slicing) must reassemble the image into a single file for the Web page where you can find it.
This is also because you can simply read the code for the filename and search for "jpg", "png", or "gif" since all image files must be one of those formats, except ".gif" files are usually animation files instead of one image.
Anyway, I'm only a novice compared to others, which is the point, if you put it on the Internet, people can and will download it, so don't try to hide or disguise the filename for it. Just let them right click and be done.