Encrypt Photos is a security tool for Mac that allows you to password protect your images. It is a nice way to prevent people from seeing photos that you want to keep to yourself. The application will display four locations on your Mac by default but you can add other folders by clicking on the plus sign or by dragging a photo or folder to the graphical user interface. Unfortunately, I didn't find a way to import single photos. Whenever I dragged a picture, all the photos in the same directory were imported. By default, they are also selected for encryption but you can change this behavior by unchecking the "select all files" box. Whit that box unchecked, you can simply Cmd+click on the photos that you want to select and click on the padlock at the top of the screen to start the encryption process. You will be asked for a password which you have to repeat and provide a hint for. While you type the password, the app will tell you how strong it is, and it won't let you use a password that is too weak.
After I encrypted some files, they were replaced with an image that read "Encrypted". To see those files again, you have to drag it to the app and type the correct password.