What if the rank and suit changed position on the card? What if the rank and suit also changed shape somewhat and shifted color as well? How effective are those measures I've seen on websites for registration and such? -- the ones specifically to thwart bots where you input the displayed characters which look kind of like the ones when you take a color blindness test? Or is this all easily bypassed by readily available existing code.
Don't most poker sites display cards as individual files stored on the user's computer? A bot could easily detect which file was being accessed, so it wouldn't matter how the appearance changed whenever a new version of the software was loaded. Presumably the same files would always be used.
Most sensible applications will load frequently used images from files or resources once at startup and then use the in-memory representation, rather than relying on file system caching to deliver the images quickly. An image could then be dithered with random noise or otherwise transformed after loading or before each use. This doesn't make it impossible, but instead turns it into a "machine vision" problem.
-- Stephen H. Landrum <slandrum(deleted the rest)>