ipa: ipu3: Add a histogram class

This class will be used at least by AGC algorithm when quantiles are
needed for example. It stores a cumulative frequency histogram. Going from
cumulative frequency back to per-bin values is a single subtraction, while
going the other way is a loop.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Tested-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

1 files changed, 40 insertions, 0 deletions

diff --git a/src/ipa/libipa/histogram.h b/src/ipa/libipa/histogram.h
new file mode 100644
index 00000000..e06f1884
--- /dev/null
+++ b/src/ipa/libipa/histogram.h
@@ -0,0 +1,40 @@
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2019, Raspberry Pi (Trading) Limited
+ *
+ * histogram.h - histogram calculation interface
+ */
+#ifndef __LIBCAMERA_IPA_LIBIPA_HISTOGRAM_H__
+#define __LIBCAMERA_IPA_LIBIPA_HISTOGRAM_H__
+
+#include <assert.h>
+#include <limits.h>
+#include <stdint.h>
+
+#include <vector>
+
+#include <libcamera/span.h>
+
+namespace libcamera {
+
+namespace ipa {
+
+class Histogram
+{
+public:
+	Histogram(Span<uint32_t> data);
+	size_t bins() const { return cumulative_.size() - 1; }
+	uint64_t total() const { return cumulative_[cumulative_.size() - 1]; }
+	uint64_t cumulativeFrequency(double bin) const;
+	double quantile(double q, uint32_t first = 0, uint32_t last = UINT_MAX) const;
+	double interQuantileMean(double lowQuantile, double hiQuantile) const;
+
+private:
+	std::vector<uint64_t> cumulative_;
+};
+
+} /* namespace ipa */
+
+} /* namespace libcamera */
+
+#endif /* __LIBCAMERA_IPA_LIBIPA_HISTOGRAM_H__ */