[v8,15/18] libcamera: software_isp: Use floating point for color parameters
diff mbox series

Message ID 20240927134624.801004-16-mzamazal@redhat.com
State Accepted
Commit 8c84efa486270e1bd5566baa1a3fb152bfa14604
Headers show
Series
  • Software ISP refactoring
Related show

Commit Message

Milan Zamazal Sept. 27, 2024, 1:46 p.m. UTC 
It's more natural to represent color gains as floating point numbers
rather than using a particular pixel-related representation.

double is used rather than float because it's a more common floating
point type in libcamera algorithms.  Otherwise there is no obvious
reason to select one over the other here.

The constructed color tables still use integer representation for
efficiency.

Black level still uses pixel (integer) values, for consistency with
other libcamera parts.

Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
---
 src/ipa/simple/algorithms/awb.cpp |  9 ++++-----
 src/ipa/simple/algorithms/lut.cpp | 13 ++++++++-----
 src/ipa/simple/ipa_context.h      |  6 +++---
 3 files changed, 15 insertions(+), 13 deletions(-)

Patch
diff mbox series 

diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp
index 3d76cc2f7..195de41dc 100644
--- a/src/ipa/simple/algorithms/awb.cpp
+++ b/src/ipa/simple/algorithms/awb.cpp
@@ -24,7 +24,7 @@  int Awb::configure(IPAContext &context,
 		   [[maybe_unused]] const IPAConfigInfo &configInfo)
 {
 	auto &gains = context.activeState.gains;
-	gains.red = gains.green = gains.blue = 256;
+	gains.red = gains.green = gains.blue = 1.0;
 
 	return 0;
 }
@@ -53,12 +53,11 @@  void Awb::process(IPAContext &context,
 	/*
 	 * 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 */
+	gains.red = sumR <= sumG / 4 ? 4.0 : static_cast<double>(sumG) / sumR;
+	gains.blue = sumB <= sumG / 4 ? 4.0 : static_cast<double>(sumG) / sumB;
+	/* Green gain is fixed to 1.0 */
 
 	LOG(IPASoftAwb, Debug) << "gain R/B " << gains.red << "/" << gains.blue;
 }
diff --git a/src/ipa/simple/algorithms/lut.cpp b/src/ipa/simple/algorithms/lut.cpp
index 644b4f84a..9744e773a 100644
--- a/src/ipa/simple/algorithms/lut.cpp
+++ b/src/ipa/simple/algorithms/lut.cpp
@@ -63,15 +63,18 @@  void Lut::prepare(IPAContext &context,
 	const unsigned int gammaTableSize = gammaTable.size();
 
 	for (unsigned int i = 0; i < DebayerParams::kRGBLookupSize; i++) {
-		const unsigned int div = static_cast<double>(DebayerParams::kRGBLookupSize) *
-					 256 / gammaTableSize;
+		const double div = static_cast<double>(DebayerParams::kRGBLookupSize) /
+				   gammaTableSize;
 		/* Apply gamma after gain! */
 		unsigned int idx;
-		idx = std::min({ i * gains.red / div, gammaTableSize - 1 });
+		idx = std::min({ static_cast<unsigned int>(i * gains.red / div),
+				 gammaTableSize - 1 });
 		params->red[i] = gammaTable[idx];
-		idx = std::min({ i * gains.green / div, gammaTableSize - 1 });
+		idx = std::min({ static_cast<unsigned int>(i * gains.green / div),
+				 gammaTableSize - 1 });
 		params->green[i] = gammaTable[idx];
-		idx = std::min({ i * gains.blue / div, gammaTableSize - 1 });
+		idx = std::min({ static_cast<unsigned int>(i * gains.blue / div),
+				 gammaTableSize - 1 });
 		params->blue[i] = gammaTable[idx];
 	}
 }
diff --git a/src/ipa/simple/ipa_context.h b/src/ipa/simple/ipa_context.h
index 737bbbc37..cf1ef3fd8 100644
--- a/src/ipa/simple/ipa_context.h
+++ b/src/ipa/simple/ipa_context.h
@@ -26,9 +26,9 @@  struct IPAActiveState {
 	} blc;
 
 	struct {
-		unsigned int red;
-		unsigned int green;
-		unsigned int blue;
+		double red;
+		double green;
+		double blue;
 	} gains;
 
 	static constexpr unsigned int kGammaLookupSize = 1024;