Manual exposure support for OpenCV

src/cli/test.py

@@ -37,6 +37,17 @@ if fw != -1:
 if fh != -1:
 	video_capture.set(cv2.CAP_PROP_FRAME_HEIGHT, fh)
 
+# Disable autoexposure
+exposure = config.getint("video", "exposure", fallback=-1)
+if exposure != -1:
+	# For a strange reason on some cameras (e.g. Lenoxo X1E)
+	# setting manual exposure works only after a couple frames
+	# are captured.
+	for i in range(6):
+		video_capture.grab()
+	video_capture.set(cv2.CAP_PROP_AUTO_EXPOSURE, 1.0)  # 1 = Manual
+	video_capture.set(cv2.CAP_PROP_EXPOSURE, 167.0)
+
 # Let the user know what's up
 print("""
 Opening a window with a test feed

src/compare.py

@@ -144,6 +144,17 @@ if fh != -1:
 # This will let the camera adjust its light levels while we're importing for faster scanning
 video_capture.grab()
 
+# Disable autoexposure
+exposure = config.getint("video", "exposure", fallback=-1)
+if exposure != -1:
+	# For a strange reason on some cameras (e.g. Lenoxo X1E)
+	# setting manual exposure works only after a couple frames
+	# are captured.
+	for i in range(5):
+		video_capture.grab()
+	video_capture.set(cv2.CAP_PROP_AUTO_EXPOSURE, 1.0)  # 1 = Manual
+	video_capture.set(cv2.CAP_PROP_EXPOSURE, 167.0)
+
 # Note the time it took to open the camera
 timings["ic"] = time.time() - timings["ic"]
 

src/config.ini

@@ -70,6 +70,11 @@ device_format = v4l2
 # OPENCV only.
 force_mjpeg = false
 
+# Specify exposure value explicitly. This disables autoexposure.
+# Use qv4l2 to determine an appropriate value.
+# OPENCV only.
+exposure = -1
+
 [debug]
 # Show a short but detailed diagnostic report in console
 end_report = false