1 files changed, 60 insertions, 19 deletions

diff --git a/src/ipa/simple/soft_simple.cpp b/src/ipa/simple/soft_simple.cpp
index b9fb58b5..b7746ce0 100644
--- a/src/ipa/simple/soft_simple.cpp
+++ b/src/ipa/simple/soft_simple.cpp
@@ -2,9 +2,12 @@
 /*
  * Copyright (C) 2023, Linaro Ltd
  *
- * soft_simple.cpp - Simple Software Image Processing Algorithm module
+ * Simple Software Image Processing Algorithm module
  */
 
+#include <cmath>
+#include <numeric>
+#include <stdint.h>
 #include <sys/mman.h>
 
 #include <linux/v4l2-controls.h>
@@ -82,6 +85,10 @@ private:
 	ControlInfoMap sensorInfoMap_;
 	BlackLevel blackLevel_;
 
+	static constexpr unsigned int kGammaLookupSize = 1024;
+	std::array<uint8_t, kGammaLookupSize> gammaTable_;
+	int lastBlackLevel_ = -1;
+
 	int32_t exposureMin_, exposureMax_;
 	int32_t exposure_;
 	double againMin_, againMax_, againMinStep_;
@@ -240,27 +247,61 @@ void IPASoftSimple::stop()
 
 void IPASoftSimple::processStats(const ControlList &sensorControls)
 {
+	SwIspStats::Histogram histogram = stats_->yHistogram;
+	if (ignoreUpdates_ > 0)
+		blackLevel_.update(histogram);
+	const uint8_t blackLevel = blackLevel_.get();
+
+	/*
+	 * Black level must be subtracted to get the correct AWB ratios, they
+	 * would be off if they were computed from the whole brightness range
+	 * rather than from the sensor range.
+	 */
+	const uint64_t nPixels = std::accumulate(
+		histogram.begin(), histogram.end(), 0);
+	const uint64_t offset = blackLevel * nPixels;
+	const uint64_t sumR = stats_->sumR_ - offset / 4;
+	const uint64_t sumG = stats_->sumG_ - offset / 2;
+	const uint64_t sumB = stats_->sumB_ - offset / 4;
+
 	/*
 	 * Calculate red and blue gains for AWB.
 	 * Clamp max gain at 4.0, this also avoids 0 division.
+	 * Gain: 128 = 0.5, 256 = 1.0, 512 = 2.0, etc.
 	 */
-	if (stats_->sumR_ <= stats_->sumG_ / 4)
-		params_->gainR = 1024;
-	else
-		params_->gainR = 256 * stats_->sumG_ / stats_->sumR_;
+	const unsigned int gainR = sumR <= sumG / 4 ? 1024 : 256 * sumG / sumR;
+	const unsigned int gainB = sumB <= sumG / 4 ? 1024 : 256 * sumG / sumB;
+	/* Green gain and gamma values are fixed */
+	constexpr unsigned int gainG = 256;
+
+	/* Update the gamma table if needed */
+	if (blackLevel != lastBlackLevel_) {
+		constexpr float gamma = 0.5;
+		const unsigned int blackIndex = blackLevel * kGammaLookupSize / 256;
+		std::fill(gammaTable_.begin(), gammaTable_.begin() + blackIndex, 0);
+		const float divisor = kGammaLookupSize - blackIndex - 1.0;
+		for (unsigned int i = blackIndex; i < kGammaLookupSize; i++)
+			gammaTable_[i] = UINT8_MAX *
+					 std::pow((i - blackIndex) / divisor, gamma);
+
+		lastBlackLevel_ = blackLevel;
+	}
 
-	if (stats_->sumB_ <= stats_->sumG_ / 4)
-		params_->gainB = 1024;
-	else
-		params_->gainB = 256 * stats_->sumG_ / stats_->sumB_;
+	for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++) {
+		constexpr unsigned int div =
+			DebayerParams::kRGBLookupSize * 256 / kGammaLookupSize;
+		unsigned int idx;
 
-	/* Green gain and gamma values are fixed */
-	params_->gainG = 256;
-	params_->gamma = 0.5;
+		/* Apply gamma after gain! */
+		idx = std::min({ i * gainR / div, (kGammaLookupSize - 1) });
+		params_->red[i] = gammaTable_[idx];
 
-	if (ignoreUpdates_ > 0)
-		blackLevel_.update(stats_->yHistogram);
-	params_->blackLevel = blackLevel_.get();
+		idx = std::min({ i * gainG / div, (kGammaLookupSize - 1) });
+		params_->green[i] = gammaTable_[idx];
+
+		idx = std::min({ i * gainB / div, (kGammaLookupSize - 1) });
+		params_->blue[i] = gammaTable_[idx];
+	}
 
 	setIspParams.emit();
 
@@ -281,7 +322,7 @@ void IPASoftSimple::processStats(const ControlList &sensorControls)
 	 * https://www.araa.asn.au/acra/acra2007/papers/paper84final.pdf
 	 */
 	const unsigned int blackLevelHistIdx =
-		params_->blackLevel / (256 / SwIspStats::kYHistogramSize);
+		blackLevel / (256 / SwIspStats::kYHistogramSize);
 	const unsigned int histogramSize =
 		SwIspStats::kYHistogramSize - blackLevelHistIdx;
 	const unsigned int yHistValsPerBin = histogramSize / kExposureBinsCount;
@@ -329,8 +370,8 @@ void IPASoftSimple::processStats(const ControlList &sensorControls)
 
 	LOG(IPASoft, Debug) << "exposureMSV " << exposureMSV
 			    << " exp " << exposure_ << " again " << again_
-			    << " gain R/B " << params_->gainR << "/" << params_->gainB
-			    << " black level " << params_->blackLevel;
+			    << " gain R/B " << gainR << "/" << gainB
+			    << " black level " << static_cast<unsigned int>(blackLevel);
 }
 
 void IPASoftSimple::updateExposure(double exposureMSV)
@@ -389,7 +430,7 @@ extern "C" {
 const struct IPAModuleInfo ipaModuleInfo = {
 	IPA_MODULE_API_VERSION,
 	0,
-	"SimplePipelineHandler",
+	"simple",
 	"simple",
 };