I am starting to get my grasp on 2d graphics under control. I am learning DirectX and I am now learning different ways to manipulate bitmaps. I understand the general concepts of what the computer is doing to read these files and display them, but overall the code is pretty horendous. My question is, how far should I study into this? Should I just learn the layout of the programs and how they are called? Is it necessary that I know how do code my bmp and palette reader from scratch? I assume I will need to know the concepts a little more deeply with 3d graphics. I feel as long as I know the general concepts of 2d graphics I dont have to memorize the specifics, but I dont want to be surprised later. Any thoughts?

What i would do (and what i do) is to take notes on anything that you are unsure of; and when it is necessary; go back to them.

i am currently learning DirectX and one thing that im doing (and is helping me alot for understanding and coding options) is to go through code (say a generic game or whatever), and add in comments by looking up a function or struct in the help files or whatever and list all the parameters, what they''re for, what type they are... etc.
and dont optimize anything (well, maybe if you know a real good trick, comment on that) and save it.
whenever you arent sure on how something works or how to do it, you can look at that code and see clearly how you did it because you have all paths laid out and explained to you.
as you learn more, try and incorporate as many things as possible into it (broken up into as logical to find pieces as you can). but remember its for you. try to specialize the comments to a good way for you to understand.

an example is that i even went through and described the parameters for WinMain. if i ever think about putting something in the 2nd parameter, ill look up my code and know not to do it.
sorry, but its the only example i could think of off the top of my head.