[v5] ipa: libipa: histogram: Add transform parameter to constructor
diff mbox series

Message ID 20240509062752.2758995-1-paul.elder@ideasonboard.com
State Superseded
Headers show
Series
  • [v5] ipa: libipa: histogram: Add transform parameter to constructor
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Commit Message

Paul Elder May 9, 2024, 6:27 a.m. UTC 
Add a parameter to the histogram constructor that takes a transformation
function to apply to all the bins upon construction.

This is necessary notably for the rkisp1, as the values reported from
the hardware are 20 bits where the upper 16-bits are meaningful integer
values and the lower 4 bits are fractional and meant to be discarded. As
adding a right-shift parameter is probably too specialized, a generic
function is added as a parameter instead.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

---
Changes in v5:
- mention the constructor optimization to the commit message
- improve documentation of constructors
- add missing #include

Changes in v4:
- fix compilation when called with no transform function

Changes in v3:
- make the transform function a template parameter, and optimize the
  constructor

This used to be "ipa: libipa: histogram: Add rshift parameter to
constructor"

Changes in v2:
- change rshift parameter to a function parameter
---
 src/ipa/libipa/histogram.cpp | 16 +++++++++++-----
 src/ipa/libipa/histogram.h   | 14 +++++++++++++-
 2 files changed, 24 insertions(+), 6 deletions(-)

Patch
diff mbox series 

diff --git a/src/ipa/libipa/histogram.cpp b/src/ipa/libipa/histogram.cpp
index c1aac59b..13a7e44f 100644
--- a/src/ipa/libipa/histogram.cpp
+++ b/src/ipa/libipa/histogram.cpp
@@ -39,16 +39,22 @@  namespace ipa {
 
 /**
  * \brief Create a cumulative histogram
- * \param[in] data A pre-sorted histogram to be passed
+ * \param[in] data A (non-cumulative) histogram
  */
 Histogram::Histogram(Span<const uint32_t> data)
 {
-	cumulative_.reserve(data.size());
-	cumulative_.push_back(0);
-	for (const uint32_t &value : data)
-		cumulative_.push_back(cumulative_.back() + value);
+	cumulative_.resize(data.size() + 1);
+	cumulative_[0] = 0;
+	for (const auto &[i, value] : utils::enumerate(data))
+		cumulative_[i + 1] = cumulative_[i] + value;
 }
 
+/**
+ * \brief Create a cumulative histogram
+ * \param[in] data A (non-cumulative) histogram
+ * \param[in] transform The transformation function to apply to every bin
+ */
+
 /**
  * \fn Histogram::bins()
  * \brief Retrieve the number of bins currently used by the Histogram
diff --git a/src/ipa/libipa/histogram.h b/src/ipa/libipa/histogram.h
index 54bb2a19..a57546f4 100644
--- a/src/ipa/libipa/histogram.h
+++ b/src/ipa/libipa/histogram.h
@@ -10,10 +10,11 @@ 
 #include <assert.h>
 #include <limits.h>
 #include <stdint.h>
-
+#include <type_traits>
 #include <vector>
 
 #include <libcamera/base/span.h>
+#include <libcamera/base/utils.h>
 
 namespace libcamera {
 
@@ -24,6 +25,17 @@  class Histogram
 public:
 	Histogram() { cumulative_.push_back(0); }
 	Histogram(Span<const uint32_t> data);
+
+	template<typename Transform,
+		 std::enable_if_t<std::is_invocable_v<Transform, uint32_t>> * = nullptr>
+	Histogram(Span<const uint32_t> data, Transform transform)
+	{
+		cumulative_.resize(data.size() + 1);
+		cumulative_[0] = 0;
+		for (const auto &[i, value] : utils::enumerate(data))
+			cumulative_[i + 1] = cumulative_[i] + transform(value);
+	}
+
 	size_t bins() const { return cumulative_.size() - 1; }
 	uint64_t total() const { return cumulative_[cumulative_.size() - 1]; }
 	uint64_t cumulativeFrequency(double bin) const;