Hi Mr. Mohamed,

It sounds like you are trying to do vector graphics as opposed to bitmap graphics. I am not familiar with Keil, but first I would look to see which graphic functions are available.

That being said, it isn't difficult to calculate the pixels for your arbitrary line. You have said that you know (x1, y1) and (x2, y2), the endpoints of the line segment. The general equation for a line is

y = mx + c

You need to calculate m and c. From your known data, you can calculate

m = (y2 - y1)/(x2 - x1)
and
c = y1 - x1*m

Now the n points (pixels) along the line can be calculated as

y_i = m*x_i + c | i = {1, 2, 3, ..., n}

Good luck.