libipa: Add AWB algorithm base class

Add a class to provide a generic interface for auto white balance
algorithms. Concrete AWB algorithms are expected to subclass the
AwbAlgorithm class to implement their functionality.

IPAs are expected to subclass the AwbStats class and implement the
necessary functions to give the algorithm access to the hardware
specific statistics data.

Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>

1 files changed, 137 insertions, 0 deletions

diff --git a/src/ipa/libipa/awb.cpp b/src/ipa/libipa/awb.cpp
new file mode 100644
index 00000000..4db97f6a
--- /dev/null
+++ b/src/ipa/libipa/awb.cpp
@@ -0,0 +1,137 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024 Ideas on Board Oy
+ *
+ * Generic AWB algorithms
+ */
+
+#include "awb.h"
+
+#include <libcamera/base/log.h>
+
+/**
+ * \file awb.h
+ * \brief Base classes for AWB algorithms
+ */
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(Awb)
+
+namespace ipa {
+
+/**
+ * \class AwbResult
+ * \brief The result of an awb calculation
+ *
+ * This class holds the result of an auto white balance calculation.
+ */
+
+/**
+ * \var AwbResult::gains
+ * \brief The calculated white balance gains
+ */
+
+/**
+ * \var AwbResult::colourTemperature
+ * \brief The calculated colour temperature in Kelvin
+ */
+
+/**
+ * \class AwbStats
+ * \brief An abstraction class wrapping hardware-specific AWB statistics
+ *
+ * Pipeline handlers using an AWB algorithm based on the AwbAlgorithm class need
+ * to implement this class to give the algorithm access to the hardware-specific
+ * statistics data.
+ */
+
+/**
+ * \fn AwbStats::computeColourError
+ * \brief Compute an error value for when the given gains would be applied
+ * \param[in] gains The gains to apply
+ *
+ * Compute an error value (non-greyness) assuming the given \a gains would be
+ * applied. To keep the actual implementations computationally inexpensive,
+ * the squared colour error shall be returned.
+ *
+ * If the awb statistics provide multiple zones, the sum over all zones needs to
+ * calculated.
+ *
+ * \return The computed error value
+ */
+
+/**
+ * \fn AwbStats::getRGBMeans
+ * \brief Get RGB means of the statistics
+ *
+ * Fetch the RGB means from the statistics. The values of each channel are
+ * dimensionless and only the ratios are used for further calculations. This is
+ * used by the simple gray world model to calculate the gains to apply.
+ *
+ * \return The RGB means
+ */
+
+/**
+ * \class AwbAlgorithm
+ * \brief A base class for auto white balance algorithms
+ *
+ * This class is a base class for auto white balance algorithms. It defines an
+ * interface for the algorithms to implement, and is used by the IPAs to
+ * interact with the concrete implementation.
+ */
+
+/**
+ * \fn AwbAlgorithm::init
+ * \brief Initialize the algorithm with the given tuning data
+ * \param[in] tuningData The tuning data to use for the algorithm
+ *
+ * \return 0 on success, a negative error code otherwise
+ */
+
+/**
+ * \fn AwbAlgorithm::calculateAwb
+ * \brief Calculate awb data from the given statistics
+ * \param[in] stats The statistics to use for the calculation
+ * \param[in] lux The lux value of the scene
+ *
+ * Calculate an AwbResult object from the given statistics and lux value. A \a
+ * lux value of 0 means it is unknown or invalid and the algorithm shall ignore
+ * it.
+ *
+ * \return The awb result
+ */
+
+/**
+ * \fn AwbAlgorithm::gainsFromColourTemperature
+ * \brief Compute white balance gains from a colour temperature
+ * \param[in] colourTemperature The colour temperature in Kelvin
+ *
+ * Compute the white balance gains from a \a colourTemperature. This function
+ * does not take any statistics into account. It is used to compute the colour
+ * gains when the user manually specifies a colour temperature.
+ *
+ * \return The colour gains
+ */
+
+/**
+ * \fn AwbAlgorithm::controls
+ * \brief Get the controls info map for this algorithm
+ *
+ * \return The controls info map
+ */
+
+/**
+ * \fn AwbAlgorithm::handleControls
+ * \param[in] controls The controls to handle
+ * \brief Handle the controls supplied in a request
+ */
+
+/**
+ * \var AwbAlgorithm::controls_
+ * \brief Controls info map for the controls provided by the algorithm
+ */
+
+} /* namespace ipa */
+
+} /* namespace libcamera */