This has probably been asked many times, but frankly I am too confused and frustrated to search properly. I am trying to remove the white corners from an image that I wish to use as a texture in some scenery that I am making. No matter what I do, I can't get rid of the corners. I wish to have only the octagonal image. If someone can tell me (in very simple language) what I have to do, I will eat my first born male child in your honor. Here is image I am trying to edit: