libipa: agc_mean_luminance: Introduce effectiveYTarget() accessor

The upcoming WDR algorithm needs to know the effective y target (Which
includes the current ExposureValue). Add an accessor for that.

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>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/ipa/libipa/agc_mean_luminance.cpp

@@ -458,8 +458,7 @@ void AgcMeanLuminance::setLimits(utils::Duration minExposureTime,
  */
 double AgcMeanLuminance::estimateInitialGain() const
 {
-	double yTarget = std::min(relativeLuminanceTarget_ * exposureCompensation_,
-				  kMaxRelativeLuminanceTarget);
+	double yTarget = effectiveYTarget();
 	double yGain = 1.0;
 
 	/*
@@ -521,6 +520,19 @@ double AgcMeanLuminance::constraintClampGain(uint32_t constraintModeIndex,
 	return gain;
 }
 
+/**
+ * \brief Get the currently effective y target
+ *
+ * This function returns the current y target including exposure compensation.
+ *
+ * \return The y target value
+ */
+double AgcMeanLuminance::effectiveYTarget() const
+{
+	return std::min(relativeLuminanceTarget_ * exposureCompensation_,
+			kMaxRelativeLuminanceTarget);
+}
+
 /**
  * \brief Apply a filter on the exposure value to limit the speed of changes
  * \param[in] exposureValue The target exposure from the AGC algorithm

src/ipa/libipa/agc_mean_luminance.h

@@ -72,6 +72,8 @@ public:
 	calculateNewEv(uint32_t constraintModeIndex, uint32_t exposureModeIndex,
 		       const Histogram &yHist, utils::Duration effectiveExposureValue);
 
+	double effectiveYTarget() const;
+
 	void resetFrameCount()
 	{
 		frameCount_ = 0;