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diff --git a/src/ipa/simple/black_level.cpp b/src/ipa/simple/black_level.cpp
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+++ b/src/ipa/simple/black_level.cpp
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+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Red Hat Inc.
+ *
+ * black_level.cpp - black level handling
+ */
+
+#include "black_level.h"
+
+#include <numeric>
+
+#include <libcamera/base/log.h>
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(IPASoftBL)
+
+/**
+ * \class BlackLevel
+ * \brief Object providing black point level for software ISP
+ *
+ * Black level can be provided in hardware tuning files or, if no tuning file is
+ * available for the given hardware, guessed automatically, with less accuracy.
+ * As tuning files are not yet implemented for software ISP, BlackLevel
+ * currently provides only guessed black levels.
+ *
+ * This class serves for tracking black level as a property of the underlying
+ * hardware, not as means of enhancing a particular scene or image.
+ *
+ * The class is supposed to be instantiated for the given camera stream.
+ * The black level can be retrieved using BlackLevel::get() method. It is
+ * initially 0 and may change when updated using BlackLevel::update() method.
+ */
+
+BlackLevel::BlackLevel()
+	: blackLevel_(255), blackLevelSet_(false)
+{
+}
+
+/**
+ * \brief Return the current black level
+ *
+ * \return The black level, in the range from 0 (minimum) to 255 (maximum).
+ * If the black level couldn't be determined yet, return 0.
+ */
+unsigned int BlackLevel::get() const
+{
+	return blackLevelSet_ ? blackLevel_ : 0;
+}
+
+/**
+ * \brief Update black level from the provided histogram
+ * \param[in] yHistogram The histogram to be used for updating black level
+ *
+ * The black level is property of the given hardware, not image. It is updated
+ * only if it has not been yet set or if it is lower than the lowest value seen
+ * so far.
+ */
+void BlackLevel::update(SwIspStats::Histogram &yHistogram)
+{
+	/*
+	 * The constant is selected to be "good enough", not overly conservative or
+	 * aggressive. There is no magic about the given value.
+	 */
+	constexpr float ignoredPercentage_ = 0.02;
+	const unsigned int total =
+		std::accumulate(begin(yHistogram), end(yHistogram), 0);
+	const unsigned int pixelThreshold = ignoredPercentage_ * total;
+	const unsigned int histogramRatio = 256 / SwIspStats::kYHistogramSize;
+	const unsigned int currentBlackIdx = blackLevel_ / histogramRatio;
+
+	for (unsigned int i = 0, seen = 0;
+	     i < currentBlackIdx && i < SwIspStats::kYHistogramSize;
+	     i++) {
+		seen += yHistogram[i];
+		if (seen >= pixelThreshold) {
+			blackLevel_ = i * histogramRatio;
+			blackLevelSet_ = true;
+			LOG(IPASoftBL, Debug)
+				<< "Auto-set black level: "
+				<< i << "/" << SwIspStats::kYHistogramSize
+				<< " (" << 100 * (seen - yHistogram[i]) / total << "% below, "
+				<< 100 * seen / total << "% at or below)";
+			break;
+		}
+	};
+}
+} /* namespace libcamera */