Basically I started by implementing a map loading system which was extremely primitive at first (it read map tile pixel from a screen instead of a buffer).

However I then discover the surface_get_pixel (shown in the code segment below) function in Game Maker which mimics the draw_get_pixel function except it works on a buffer (which Mark "The Evil Delphi Heretic" Overmars seems to refer to as a surface) as opposed to the screen.

I also discovered that my computer was unable to handle a double for loop in for building the map and thus had to create a step based loop as opposed to a cycle based loop.

So now my code looks like this.