Limiting the PictureBox to 2 colors (B&W) and saving the BMP

I need to Limit the PictureBox to 2 colors (B&W) and save the BMP.
thus decreasing the size of the file produced.

later on I would convert it to JPG using imgX

I need the final result to be a small (under 1K) JPG File.

If you know how please help me, it's urgent!

I think that's not possible, but you can create your own bmp writer. It's not hard, first you must get the file format specifications of bmp on www.wotsit.org, and then you can start. Good luck.