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-rw-r--r--src/ipa/simple/algorithms/awb.cpp69
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diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp
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+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Red Hat Inc.
+ *
+ * Auto white balance
+ */
+
+#include "awb.h"
+
+#include <numeric>
+#include <stdint.h>
+
+#include <libcamera/base/log.h>
+
+#include "simple/ipa_context.h"
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(IPASoftAwb)
+
+namespace ipa::soft::algorithms {
+
+int Awb::configure(IPAContext &context,
+ [[maybe_unused]] const IPAConfigInfo &configInfo)
+{
+ auto &gains = context.activeState.gains;
+ gains.red = gains.green = gains.blue = 1.0;
+
+ return 0;
+}
+
+void Awb::process(IPAContext &context,
+ [[maybe_unused]] const uint32_t frame,
+ [[maybe_unused]] IPAFrameContext &frameContext,
+ const SwIspStats *stats,
+ [[maybe_unused]] ControlList &metadata)
+{
+ const SwIspStats::Histogram &histogram = stats->yHistogram;
+ const uint8_t blackLevel = context.activeState.blc.level;
+
+ /*
+ * 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.
+ */
+ auto &gains = context.activeState.gains;
+ gains.red = sumR <= sumG / 4 ? 4.0 : static_cast<double>(sumG) / sumR;
+ gains.blue = sumB <= sumG / 4 ? 4.0 : static_cast<double>(sumG) / sumB;
+ /* Green gain is fixed to 1.0 */
+
+ LOG(IPASoftAwb, Debug) << "gain R/B " << gains.red << "/" << gains.blue;
+}
+
+REGISTER_IPA_ALGORITHM(Awb, "Awb")
+
+} /* namespace ipa::soft::algorithms */
+
+} /* namespace libcamera */