6 files changed, 10 insertions, 9 deletions
diff --git a/src/ipa/libipa/awb.cpp b/src/ipa/libipa/awb.cpp
index 925fac23..214bac8b 100644
--- a/src/ipa/libipa/awb.cpp
+++ b/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
  */
 
 /**
diff --git a/src/ipa/libipa/awb.h b/src/ipa/libipa/awb.h
index 4bab7a45..f4a86038 100644
--- a/src/ipa/libipa/awb.h
+++ b/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
 	{
diff --git a/src/ipa/libipa/awb_bayes.cpp b/src/ipa/libipa/awb_bayes.cpp
index d1d0eaf0..d2bcbd83 100644
--- a/src/ipa/libipa/awb_bayes.cpp
+++ b/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)
diff --git a/src/ipa/libipa/awb_bayes.h b/src/ipa/libipa/awb_bayes.h
index bb933038..47ef3cce 100644
--- a/src/ipa/libipa/awb_bayes.h
+++ b/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:
diff --git a/src/ipa/libipa/awb_grey.cpp b/src/ipa/libipa/awb_grey.cpp
index d3d2132b..d252edb2 100644
--- a/src/ipa/libipa/awb_grey.cpp
+++ b/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 */
diff --git a/src/ipa/libipa/awb_grey.h b/src/ipa/libipa/awb_grey.h
index 7ec7bfa5..f82a368d 100644
--- a/src/ipa/libipa/awb_grey.h
+++ b/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_;