[libcamera-devel] [PATCH 11/11] ipa: ipu3: tonemapping: Add the documentation for ToneMapping

[Jean-Michel Hautbois]

The Tonemapping algorithm is currently undocumented.

Provide an introduction and overview to the implementation as the class
definition and document how the algorithm operates in the process and
prepare methods.

Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---
 src/ipa/ipu3/algorithms/tone_mapping.cpp | 35 +++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/src/ipa/ipu3/algorithms/tone_mapping.cpp b/src/ipa/ipu3/algorithms/tone_mapping.cpp
index 40337f9d..15e9ab3f 100644
--- a/src/ipa/ipu3/algorithms/tone_mapping.cpp
+++ b/src/ipa/ipu3/algorithms/tone_mapping.cpp
@@ -10,15 +10,40 @@
 #include <cmath>
 #include <string.h>
 
+/**
+ * \file tone_mapping.h
+ */
+
 namespace libcamera {
 
 namespace ipa::ipu3::algorithms {
 
+/**
+ * \class ToneMapping
+ * \brief A class to handle tone mapping based on gamma
+ *
+ * This algorithm improves the image dynamic using a look-up table which is
+ * generated based on a gamma parameter.
+ *
+ * Gamma values less than one have the effect of compressing the image histogram
+ * while values over 1 will expand it.
+ *
+ * Expanding the histogram has the effect of providing better overall contrast.
+ */
+
 ToneMapping::ToneMapping()
 	: gamma_(1.0)
 {
 }
 
+/**
+ * \brief Fill in the parameter structure, and enable gamma control
+ * \param context The shared IPA context
+ * \param params The IPU3 parameters
+ *
+ * Populate the IPU3 parameter structure with our gamma correction table, and
+ * enable the gamma control module in the accelerator cluster.
+ */
 void ToneMapping::prepare([[maybe_unused]] IPAContext &context,
 			  ipu3_uapi_params *params)
 {
@@ -33,7 +58,15 @@ void ToneMapping::prepare([[maybe_unused]] IPAContext &context,
 	params->acc_param.gamma.gc_ctrl.enable = 1;
 }
 
-void ToneMapping::process([[maybe_unused]] IPAContext &context,
+/**
+ * \brief Calculate the Gamma curve
+ * \param context The shared IPA context
+ * \param stats The IPU3 statistics and ISP results
+ *
+ * The gamma correction look up table is generated as an inverse power curve
+ * from our gamma setting.
+ */
+void ToneMapping::process(IPAContext &context,
 			  [[maybe_unused]] const ipu3_uapi_stats_3a *stats)
 {
 	/*
-- 
2.30.2