for starters with openGL, you should attempt learning the basics through use of books.
my library of book phocus is :
beginning OpenGL game programming : dave astle , kevin hawkins
more open gl programming game programming : dave astle editor
data structures & other objects using C++ 3rd edition
you should also have a good book for c/c++ standard as used reference to coding.
having a good understanding of data structures, OOP, classes, standard lib functions, macros,
exetra is a must.
as for loading images the true vision extension ".tga" file is mostly or mainly used for textures because of its
qualities of holding alpha values and color values, "RGBA"
