From a5477631a60b626294ba0cd57c68a7bd3bc151b5 Mon Sep 17 00:00:00 2001
From: Russ Garrett <russ@garrett.co.uk>
Date: Sun, 5 Jan 2025 20:50:04 +0000
Subject: [PATCH 1/2] Dark frame subtraction

---
 marimapper/detector.py         | 12 ++++++++----
 marimapper/detector_process.py |  6 +++++-
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/marimapper/detector.py b/marimapper/detector.py
index 3acdffd..c27cdce 100644
--- a/marimapper/detector.py
+++ b/marimapper/detector.py
@@ -115,10 +115,12 @@ def set_cam_dark(cam: Camera, exposure: int) -> None:
 
 
 def find_led(
-    cam: Camera, threshold: int = 128, display: bool = True
+    cam: Camera, threshold: int = 128, display: bool = True, dark_frame=None
 ) -> Optional[Point2D]:
 
     image = cam.read()
+    if dark_frame is not None:
+        image = cv2.absdiff(image, dark_frame)
     results = find_led_in_image(image, threshold)
 
     if display:
@@ -138,8 +140,10 @@ def enable_and_find_led(
     display: bool = False,
 ) -> Optional[LED2D]:
 
+    dark_frame = cam.read()
+
     # First wait for no leds to be visible
-    while find_led(cam, threshold, display) is not None:
+    while find_led(cam, threshold, display, dark_frame=dark_frame) is not None:
         pass
 
     # Set the led to on and start the clock
@@ -152,7 +156,7 @@ def enable_and_find_led(
     while (
         point is None and time.time() < response_time_start + timeout_controller.timeout
     ):
-        point = find_led(cam, threshold, display)
+        point = find_led(cam, threshold, display, dark_frame)
 
     led_backend.set_led(led_id, False)
 
@@ -161,7 +165,7 @@ def enable_and_find_led(
 
     timeout_controller.add_response_time(time.time() - response_time_start)
 
-    while find_led(cam, threshold, display) is not None:
+    while find_led(cam, threshold, display, dark_frame=dark_frame) is not None:
         pass
 
     return LED2D(led_id, view_id, point)
diff --git a/marimapper/detector_process.py b/marimapper/detector_process.py
index eba79f2..5b70c8e 100644
--- a/marimapper/detector_process.py
+++ b/marimapper/detector_process.py
@@ -86,9 +86,13 @@ def run(self):
 
                 # scan start here
                 set_cam_dark(cam, self._dark_exposure)
+                dark_frame = cam.read()
 
                 # Firstly, if there are leds visible, break out
-                if find_led(cam, self._threshold, self._display) is not None:
+                if (
+                    find_led(cam, self._threshold, self._display, dark_frame=dark_frame)
+                    is not None
+                ):
                     logger.error(
                         "Detector process can detect an LED when no LEDs should be visible"
                     )

From 33adb99d26078a08fe3dabaade8d20a50970aeef Mon Sep 17 00:00:00 2001
From: Samuel <martinsa0182@gmail.com>
Date: Tue, 7 Jan 2025 08:28:45 +0000
Subject: [PATCH 2/2] Replaced cv2.absdiff with cv2.subtract

---
 marimapper/detector.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/marimapper/detector.py b/marimapper/detector.py
index c27cdce..728530b 100644
--- a/marimapper/detector.py
+++ b/marimapper/detector.py
@@ -120,7 +120,7 @@ def find_led(
 
     image = cam.read()
     if dark_frame is not None:
-        image = cv2.absdiff(image, dark_frame)
+        cv2.subtract(image, dark_frame, image)
     results = find_led_in_image(image, threshold)
 
     if display: