ipa: rpi: lux: Handle camera mode sensitivity correctly

The camera mode sensitivity needs to be taken into account for the lux
calculation. For example, the IMX708 binned mode (with a sensitivity
of 2.0) would otherwise show double the correct lux value.

Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/ipa/rpi/controller/rpi/lux.cpp

@@ -20,7 +20,7 @@ LOG_DEFINE_CATEGORY(RPiLux)
 #define NAME "rpi.lux"
 
 Lux::Lux(Controller *controller)
-	: Algorithm(controller)
+	: Algorithm(controller), sensitivity_(1.0)
 {
 	/*
 	 * Put in some defaults as there will be no meaningful values until
@@ -68,6 +68,13 @@ void Lux::setCurrentAperture(double aperture)
 	currentAperture_ = aperture;
 }
 
+void Lux::switchMode(CameraMode const &cameraMode, [[maybe_unused]] Metadata *metadata)
+{
+	/* We will need to compensate for the camera sensitivity. */
+	ASSERT(cameraMode.sensitivity);
+	sensitivity_ = cameraMode.sensitivity;
+}
+
 void Lux::prepare(Metadata *imageMetadata)
 {
 	std::unique_lock<std::mutex> lock(mutex_);
@@ -88,10 +95,12 @@ void Lux::process(StatisticsPtr &stats, Metadata *imageMetadata)
 		double yRatio = currentY * (65536 / stats->yHist.bins()) / referenceY_;
 		double estimatedLux = exposureTimeRatio * gainRatio *
 				      apertureRatio * apertureRatio *
-				      yRatio * referenceLux_;
+				      yRatio * referenceLux_ / sensitivity_;
+
 		LuxStatus status;
 		status.lux = estimatedLux;
 		status.aperture = currentAperture;
+
 		LOG(RPiLux, Debug) << ": estimated lux " << estimatedLux;
 		{
 			std::unique_lock<std::mutex> lock(mutex_);

src/ipa/rpi/controller/rpi/lux.h

@@ -10,6 +10,7 @@
 
 #include <libcamera/base/utils.h>
 
+#include "../camera_mode.h"
 #include "../lux_status.h"
 #include "../algorithm.h"
 
@@ -23,6 +24,7 @@ public:
 	Lux(Controller *controller);
 	char const *name() const override;
 	int read(const libcamera::YamlObject &params) override;
+	void switchMode(CameraMode const &cameraMode, Metadata *metadata) override;
 	void prepare(Metadata *imageMetadata) override;
 	void process(StatisticsPtr &stats, Metadata *imageMetadata) override;
 	void setCurrentAperture(double aperture);
@@ -40,6 +42,7 @@ private:
 	double currentAperture_;
 	LuxStatus status_;
 	std::mutex mutex_;
+	double sensitivity_;
 };
 
 } /* namespace RPiController */