[PATCH 1/2] ipa: rkisp1: agc: Fix metering modes

[Stefan Klug]

The weights for a given metering mode are applied to the histogram data
inside the histogram statistics block. The AE statistics do not contain
any weights. Therefore the weights are honored when AgcMeanLuminance
calculates the upper or lower constraints, but ignored in the
calculation of the frame luminance. Fix that by manually applying the
weights in the luminance calculation.

Fixes: 4c5152843a2a ("ipa: rkisp1: Derive rkisp1::algorithms::Agc from AgcMeanLuminance")
Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
---
 src/ipa/rkisp1/algorithms/agc.cpp | 13 ++++++++++---
 src/ipa/rkisp1/algorithms/agc.h   |  1 +
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/src/ipa/rkisp1/algorithms/agc.cpp b/src/ipa/rkisp1/algorithms/agc.cpp
index 5a3ba0131cf1..101cad5d0893 100644
--- a/src/ipa/rkisp1/algorithms/agc.cpp
+++ b/src/ipa/rkisp1/algorithms/agc.cpp
@@ -439,15 +439,20 @@ void Agc::fillMetadata(IPAContext &context, IPAFrameContext &frameContext,
  */
 double Agc::estimateLuminance(double gain) const
 {
+	ASSERT(expMeans_.size() == weights_.size());
 	double ySum = 0.0;
+	double wSum = 0.0;
 
 	/* Sum the averages, saturated to 255. */
-	for (uint8_t expMean : expMeans_)
-		ySum += std::min(expMean * gain, 255.0);
+	for (unsigned i = 0; i < expMeans_.size(); i++) {
+		double w = weights_[i];
+		ySum += std::min(expMeans_[i] * gain, 255.0) * w;
+		wSum += w;
+	}
 
 	/* \todo Weight with the AWB gains */
 
-	return ySum / expMeans_.size() / 255;
+	return ySum / wSum / 255;
 }
 
 /**
@@ -515,6 +520,8 @@ void Agc::process(IPAContext &context, [[maybe_unused]] const uint32_t frame,
 	Histogram hist({ params->hist.hist_bins, context.hw->numHistogramBins },
 		       [](uint32_t x) { return x >> 4; });
 	expMeans_ = { params->ae.exp_mean, context.hw->numAeCells };
+	std::vector<uint8_t> &modeWeights = meteringModes_.at(frameContext.agc.meteringMode);
+	weights_ = { modeWeights.data(), modeWeights.size() };
 
 	/*
 	 * Set the AGC limits using the fixed exposure time and/or gain in
diff --git a/src/ipa/rkisp1/algorithms/agc.h b/src/ipa/rkisp1/algorithms/agc.h
index 62bcde999fe3..7867eed9c4e3 100644
--- a/src/ipa/rkisp1/algorithms/agc.h
+++ b/src/ipa/rkisp1/algorithms/agc.h
@@ -55,6 +55,7 @@ private:
 				  utils::Duration frameDuration);
 
 	Span<const uint8_t> expMeans_;
+	Span<const uint8_t> weights_;
 
 	std::map<int32_t, std::vector<uint8_t>> meteringModes_;
 };
-- 
2.43.0