1 files changed, 70 insertions, 0 deletions
diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp
new file mode 100644
index 00000000..3d76cc2f
--- /dev/null
+++ b/src/ipa/simple/algorithms/awb.cpp
@@ -0,0 +1,70 @@
+/* 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 = 256;
+
+	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.
+	 * Gain: 128 = 0.5, 256 = 1.0, 512 = 2.0, etc.
+	 */
+	auto &gains = context.activeState.gains;
+	gains.red = sumR <= sumG / 4 ? 1024 : 256 * sumG / sumR;
+	gains.blue = sumB <= sumG / 4 ? 1024 : 256 * sumG / sumB;
+	/* Green gain is fixed to 256 */
+
+	LOG(IPASoftAwb, Debug) << "gain R/B " << gains.red << "/" << gains.blue;
+}
+
+REGISTER_IPA_ALGORITHM(Awb, "Awb")
+
+} /* namespace ipa::soft::algorithms */
+
+} /* namespace libcamera */