Grid Drawing - I dont know what i have to do now.

So i am trying to make a tetris bot so far i have made it so you can select the play field.
But now i dont know what to do next. i have read that i need to visualize the blocks + playing field so the computer know where the gaps are or where the blocks are. but i dont realy know how to do that.
So heres what i have:

Attachment 117331

And on the left you see the playing bord but i wanted to draw a grid on the right side so the computer sees black for blocks and white for no blocks.
But i dont know how to do it and still let the computer knows what blocks are filled and where the gaps are. anyone could help ?