libipa: awb: Make result of gainsFromColourTemp optional

In the grey world AWB case, if no colour gains are contained in the
tuning file, the colour gains get reset to 1 when the colour temperature
is set manually. This is unexpected and undesirable. Allow the
gainsFromColourTemp() function to return a std::nullopt to handle that
case.

While at it, remove an unnecessary import from rkisp1/algorithms/awb.h.

Signed-off-by: Stefan Klug <stefan.klug@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Paul Elder <paul.elder@ideasonboard.com>

src/ipa/libipa/awb.cpp

@@ -114,7 +114,7 @@ namespace ipa {
  * 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
+ * \return The colour gains or std::nullopt if the conversion is not possible
  */
 
 /**

src/ipa/libipa/awb.h

@@ -8,6 +8,7 @@
 #pragma once
 
 #include <map>
+#include <optional>
 
 #include <libcamera/control_ids.h>
 #include <libcamera/controls.h>
@@ -39,7 +40,7 @@ public:
 
 	virtual int init(const YamlObject &tuningData) = 0;
 	virtual AwbResult calculateAwb(const AwbStats &stats, unsigned int lux) = 0;
-	virtual RGB<double> gainsFromColourTemperature(double colourTemperature) = 0;
+	virtual std::optional<RGB<double>> gainsFromColourTemperature(double colourTemperature) = 0;
 
 	const ControlInfoMap::Map &controls() const
 	{

src/ipa/libipa/awb_bayes.cpp

@@ -270,7 +270,7 @@ void AwbBayes::handleControls(const ControlList &controls)
 	}
 }
 
-RGB<double> AwbBayes::gainsFromColourTemperature(double colourTemperature)
+std::optional<RGB<double>> AwbBayes::gainsFromColourTemperature(double colourTemperature)
 {
 	/*
 	 * \todo In the RaspberryPi code, the ct curve was interpolated in
@@ -278,7 +278,7 @@ RGB<double> AwbBayes::gainsFromColourTemperature(double colourTemperature)
 	 * intuitive, as the gains are in linear space. But I can't prove it.
 	 */
 	const auto &gains = colourGainCurve_.getInterpolated(colourTemperature);
-	return { { gains[0], 1.0, gains[1] } };
+	return RGB<double>{ { gains[0], 1.0, gains[1] } };
 }
 
 AwbResult AwbBayes::calculateAwb(const AwbStats &stats, unsigned int lux)

src/ipa/libipa/awb_bayes.h

@@ -27,7 +27,7 @@ public:
 
 	int init(const YamlObject &tuningData) override;
 	AwbResult calculateAwb(const AwbStats &stats, unsigned int lux) override;
-	RGB<double> gainsFromColourTemperature(double temperatureK) override;
+	std::optional<RGB<double>> gainsFromColourTemperature(double temperatureK) override;
 	void handleControls(const ControlList &controls) override;
 
 private:

src/ipa/libipa/awb_grey.cpp

@@ -98,15 +98,15 @@ AwbResult AwbGrey::calculateAwb(const AwbStats &stats, [[maybe_unused]] unsigned
  * \return The colour gains if a colour temperature curve is available,
  * [1, 1, 1] otherwise.
  */
-RGB<double> AwbGrey::gainsFromColourTemperature(double colourTemperature)
+std::optional<RGB<double>> AwbGrey::gainsFromColourTemperature(double colourTemperature)
 {
 	if (!colourGainCurve_) {
 		LOG(Awb, Error) << "No gains defined";
-		return RGB<double>({ 1.0, 1.0, 1.0 });
+		return std::nullopt;
 	}
 
 	auto gains = colourGainCurve_->getInterpolated(colourTemperature);
-	return { { gains[0], 1.0, gains[1] } };
+	return RGB<double>{ { gains[0], 1.0, gains[1] } };
 }
 
 } /* namespace ipa */

src/ipa/libipa/awb_grey.h

@@ -25,7 +25,7 @@ public:
 
 	int init(const YamlObject &tuningData) override;
 	AwbResult calculateAwb(const AwbStats &stats, unsigned int lux) override;
-	RGB<double> gainsFromColourTemperature(double colourTemperature) override;
+	std::optional<RGB<double>> gainsFromColourTemperature(double colourTemperature) override;
 
 private:
 	std::optional<Interpolator<Vector<double, 2>>> colourGainCurve_;

src/ipa/rkisp1/algorithms/awb.cpp

@@ -127,8 +127,12 @@ int Awb::configure(IPAContext &context,
 		   const IPACameraSensorInfo &configInfo)
 {
 	context.activeState.awb.manual.gains = RGB<double>{ 1.0 };
-	context.activeState.awb.automatic.gains =
+	auto gains = awbAlgo_->gainsFromColourTemperature(kDefaultColourTemperature);
-		awbAlgo_->gainsFromColourTemperature(kDefaultColourTemperature);
+	if (gains)
+		context.activeState.awb.automatic.gains = *gains;
+	else
+		context.activeState.awb.automatic.gains = RGB<double>{ 1.0 };
+
 	context.activeState.awb.autoEnabled = true;
 	context.activeState.awb.manual.temperatureK = kDefaultColourTemperature;
 	context.activeState.awb.automatic.temperatureK = kDefaultColourTemperature;
@@ -185,11 +189,13 @@ void Awb::queueRequest(IPAContext &context,
 		 */
 		update = true;
 	} else if (colourTemperature) {
-		const auto &gains = awbAlgo_->gainsFromColourTemperature(*colourTemperature);
-		awb.manual.gains.r() = gains.r();
-		awb.manual.gains.b() = gains.b();
 		awb.manual.temperatureK = *colourTemperature;
-		update = true;
+		const auto &gains = awbAlgo_->gainsFromColourTemperature(*colourTemperature);
+		if (gains) {
+			awb.manual.gains.r() = gains->r();
+			awb.manual.gains.b() = gains->b();
+			update = true;
+		}
 	}
 
 	if (update)

src/ipa/rkisp1/algorithms/awb.h

@@ -7,8 +7,6 @@
 
 #pragma once
 
-#include <optional>
-
 #include "libcamera/internal/vector.h"
 
 #include "libipa/awb.h"