Do not draw in headless mode. Optimize.

oi-sensor/oi-sensor.py

@@ -129,20 +129,27 @@ async def main():
                 approx = cv2.approxPolyDP(cnt, 0.02*cv2.arcLength(cnt, True), True)
                 x = approx.ravel()[0]
                 y = approx.ravel()[1]
+                number_of_points = len(approx)
                 if area > designated_area_min and area < designated_area_max:
-                    print("\tDetected area (px)=%.2f" %area)
+                    if not headless:
                         cv2.drawContours(frame, [approx], 0, (0, 0, 0), 5)
-                    number_of_points = len(approx)
                     if number_of_points == 3:
+                        if not headless:
                             cv2.putText(frame, "Triangle", (x, y), font, 1, (0, 0, 0))
-                        await myvar.write_value(1.0)
+                        result = 1.0
                     elif number_of_points == 4:
+                        if not headless:
                             cv2.putText(frame, "Rectangle", (x, y), font, 1, (0, 0, 0))
-                        await myvar.write_value(2.0)
+                        result = 2.0
                     elif 7 < number_of_points < 20:
+                        if not headless:
                             cv2.putText(frame, "Circle (%s)" %number_of_points, (x, y), font, 1, (0, 0, 0))
-                        await myvar.write_value(3.0)
+                        result = 3.0
                     else:
+                        result = 0.0
+                    # printout
+                    print("\tDetected area (px)=%.2f, result=%d" %(area, result))
+                    # update OPC UA server's node attribute
                     await myvar.write_value(0.0)
 
             # show current MASK and camera output windows