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diff --git a/src/ipa/raspberrypi/controller/rpi/lux.cpp b/src/ipa/raspberrypi/controller/rpi/lux.cpp
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+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2019, Raspberry Pi (Trading) Limited
+ *
+ * lux.cpp - Lux control algorithm
+ */
+#include <math.h>
+
+#include "linux/bcm2835-isp.h"
+
+#include "../device_status.h"
+#include "../logging.hpp"
+
+#include "lux.hpp"
+
+using namespace RPi;
+
+#define NAME "rpi.lux"
+
+Lux::Lux(Controller *controller)
+ : Algorithm(controller)
+{
+ // Put in some defaults as there will be no meaningful values until
+ // Process has run.
+ status_.aperture = 1.0;
+ status_.lux = 400;
+}
+
+char const *Lux::Name() const
+{
+ return NAME;
+}
+
+void Lux::Read(boost::property_tree::ptree const &params)
+{
+ RPI_LOG(Name());
+ reference_shutter_speed_ =
+ params.get<double>("reference_shutter_speed");
+ reference_gain_ = params.get<double>("reference_gain");
+ reference_aperture_ = params.get<double>("reference_aperture", 1.0);
+ reference_Y_ = params.get<double>("reference_Y");
+ reference_lux_ = params.get<double>("reference_lux");
+ current_aperture_ = reference_aperture_;
+}
+
+void Lux::Prepare(Metadata *image_metadata)
+{
+ std::unique_lock<std::mutex> lock(mutex_);
+ image_metadata->Set("lux.status", status_);
+}
+
+void Lux::Process(StatisticsPtr &stats, Metadata *image_metadata)
+{
+ // set some initial values to shut the compiler up
+ DeviceStatus device_status =
+ { .shutter_speed = 1.0,
+ .analogue_gain = 1.0,
+ .lens_position = 0.0,
+ .aperture = 0.0,
+ .flash_intensity = 0.0 };
+ if (image_metadata->Get("device.status", device_status) == 0) {
+ double current_gain = device_status.analogue_gain;
+ double current_shutter_speed = device_status.shutter_speed;
+ double current_aperture = device_status.aperture;
+ if (current_aperture == 0)
+ current_aperture = current_aperture_;
+ uint64_t sum = 0;
+ uint32_t num = 0;
+ uint32_t *bin = stats->hist[0].g_hist;
+ const int num_bins = sizeof(stats->hist[0].g_hist) /
+ sizeof(stats->hist[0].g_hist[0]);
+ for (int i = 0; i < num_bins; i++)
+ sum += bin[i] * (uint64_t)i, num += bin[i];
+ // add .5 to reflect the mid-points of bins
+ double current_Y = sum / (double)num + .5;
+ double gain_ratio = reference_gain_ / current_gain;
+ double shutter_speed_ratio =
+ reference_shutter_speed_ / current_shutter_speed;
+ double aperture_ratio = reference_aperture_ / current_aperture;
+ double Y_ratio = current_Y * (65536 / num_bins) / reference_Y_;
+ double estimated_lux = shutter_speed_ratio * gain_ratio *
+ aperture_ratio * aperture_ratio *
+ Y_ratio * reference_lux_;
+ LuxStatus status;
+ status.lux = estimated_lux;
+ status.aperture = current_aperture;
+ RPI_LOG(Name() << ": estimated lux " << estimated_lux);
+ {
+ std::unique_lock<std::mutex> lock(mutex_);
+ status_ = status;
+ }
+ // Overwrite the metadata here as well, so that downstream
+ // algorithms get the latest value.
+ image_metadata->Set("lux.status", status);
+ } else
+ RPI_WARN(Name() << ": no device metadata");
+}
+
+// Register algorithm with the system.
+static Algorithm *Create(Controller *controller)
+{
+ return (Algorithm *)new Lux(controller);
+}
+static RegisterAlgorithm reg(NAME, &Create);