Implemented guess for draw_pixel

src/lib.rs

@@ -210,7 +210,18 @@ impl DoubleFrame<AutomaticPartialWindow> {
 
 impl<PartialWindow: ApplyPartialWindow> DoubleFrame<PartialWindow> {
     pub fn draw_pixel(&mut self, x: u16, y: u16, colour: PixelColour) {
-        todo!()
+        self.partial_window.update_partial_window(x, x, y, y);
+        let x_i = x / 8;
+        let x_shift = x % 8;
+        let i = y * (EPD_WIDTH as u16 / 8) + x_i;
+        match colour {
+            PixelColour::Black => {
+                self.new.0[i as usize] &= !(1 << x_shift);
+            },
+            PixelColour::White => {
+                self.new.0[i as usize] |= 1 << x_shift;
+            },
+        }
     }
 }