[RFC,v4,2/7] libcamera: software_isp: Add LSC data to DebayerParams
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Message ID 20260504182658.590233-3-mzamazal@redhat.com
State New
Headers show
Series
  • LSC for SoftISP simple pipeline
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Commit Message

Milan Zamazal May 4, 2026, 6:26 p.m. UTC 
From: Xander Pronk <xander.c.pronk@gmail.com>

Add a lookup table for grid-based lens shading correction to debayer
params.  The lookup table is in the format of an RGB texture to be
passed to debayering.

The parameter is filled in by LSC algorithm implemented in a followup
patch.  If the algorithm is not enabled, the parameter content is
arbitrary and the parameter may not be used.  The parameter is currently
unused, its handling is implemented in a followup patch.

There is no special meaning about the selected grid size, it's
just one of the smaller common sizes.

Co-developed-by: Rick ten Wolde <rick_libcamera@wolde.info>
Signed-off-by: Rick ten Wolde <rick_libcamera@wolde.info>
Signed-off-by: Xander Pronk <xander.c.pronk@gmail.com>
Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
---
 .../internal/software_isp/debayer_params.h    |  8 ++++++
 src/libcamera/software_isp/debayer.cpp        | 28 +++++++++++++++++++
 2 files changed, 36 insertions(+)

Patch
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diff --git a/include/libcamera/internal/software_isp/debayer_params.h b/include/libcamera/internal/software_isp/debayer_params.h
index 6772b43bc..47f2c3ac2 100644
--- a/include/libcamera/internal/software_isp/debayer_params.h
+++ b/include/libcamera/internal/software_isp/debayer_params.h
@@ -10,6 +10,7 @@ 
 
 #pragma once
 
+#include <array>
 #include <stdint.h>
 
 #include "libcamera/internal/matrix.h"
@@ -25,6 +26,13 @@  struct DebayerParams {
 	float gamma = 1.0;
 	float contrastExp = 1.0;
 	RGB<float> gains = RGB<float>({ 1.0, 1.0, 1.0 });
+
+	static constexpr unsigned int kLscGridSize = 16;
+	static constexpr unsigned int kLscValuesPerCell = 3;
+	using LscValueType = float;
+	using LscLookupTable =
+		std::array<LscValueType, kLscGridSize * kLscGridSize * kLscValuesPerCell>;
+	LscLookupTable lscLut{};
 };
 
 } /* namespace libcamera */
diff --git a/src/libcamera/software_isp/debayer.cpp b/src/libcamera/software_isp/debayer.cpp
index 2d7abfb83..d91a7aff5 100644
--- a/src/libcamera/software_isp/debayer.cpp
+++ b/src/libcamera/software_isp/debayer.cpp
@@ -43,6 +43,34 @@  namespace libcamera {
  * \brief Contrast value to be used as an exponent
  */
 
+/**
+ * \var DebayerParams::kLscGridSize
+ * \brief Number of lens shading grid areas in one direction
+ */
+
+/**
+ * \var DebayerParams::kLscValuesPerCell
+ * \brief Number of pixel values per each of the lens shading grid areas
+ */
+
+/**
+ * \typedef DebayerParams::LscValueType
+ * \brief Type of LSC grid values
+ */
+
+/**
+ * \typedef DebayerParams::LscLookupTable
+ * \brief Lookup table for lens shading correction
+ *
+ * It's an array of values to be later used as a texture.
+ * The values are in row - column - RGB order.
+ */
+
+/**
+ * \var DebayerParams::lscLut
+ * \brief Lens shading lookup table
+ */
+
 /**
  * \class Debayer
  * \brief Base debayering class