I've just joined the site so I hope that I am posting in the correct forum. If not, then I am terribly sorry for the trouble.
I have a question for those who are wise about programming libraries like DirectX, SDL and OpenGL. I have been programming in C++ for almost 4 years now and understand the basics, including the STL. I have picked up a book on DirectX and SDL and understand the code inside them. I think I am ready for moving onto a library to begin using graphics. I also know and understand how to build a Window using the Windows API.
My question is this: What library is the best (not so much easiest) to begin with? I have no hopes of designing a game. I just wish to mess around with the graphics, input, sound, etc. so I obtain a better understanding of how it works and how to write it.