Loading textures from a Texture atlas [ OpenGL / C++ ]

Question

I wanted to know how can I load an array of textures by passing in a texture atlas to a function using C++ and OpenGL
if u know how, can u give me the code

EDIT: I am using the stb_image loader library for my program

Answer 1

do it with texture coordinates.
If you know the width and height of your texture atlas and all the textures in it are the same width and height, you can just do 1/atlas_width.

so if you were texturing a quad, the top left corner's UV would be (1/atlas_width, 1/atlas_height). the lower right UV would be (2*(1/atlas_width), 2*(1/atlas_height))

from there you just multiply by the X,Y index of each texture. so the third along and second down would be
(3*(1/atlas_width), 2*(1/atlas_height)).