From 2f1efe50a938b83a6b4b236406b74c20ead29beb Mon Sep 17 00:00:00 2001 From: Laurent Pinchart Date: Sun, 4 Sep 2022 04:21:18 +0300 Subject: ipa: rkisp1: awb: Remove bias from gain calculation The red and blue gains are computed by dividing the green mean by the red and blue means respectively. An offset of 1 is added to the dividers to avoid divisions by zero. This introduces a bias in the gain values. Fix it by clamping the divisors to a minimum of 1.0 instead of adding an offset. Signed-off-by: Laurent Pinchart Reviewed-by: Kieran Bingham Reviewed-by: Jacopo Mondi --- src/ipa/rkisp1/algorithms/awb.cpp | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/src/ipa/rkisp1/algorithms/awb.cpp b/src/ipa/rkisp1/algorithms/awb.cpp index eb32cd72..3349948a 100644 --- a/src/ipa/rkisp1/algorithms/awb.cpp +++ b/src/ipa/rkisp1/algorithms/awb.cpp @@ -280,10 +280,11 @@ void Awb::process(IPAContext &context, /* * Estimate the red and blue gains to apply in a grey world. The green - * gain is hardcoded to 1.0. + * gain is hardcoded to 1.0. Avoid divisions by zero by clamping the + * divisor to a minimum value of 1.0. */ - double redGain = greenMean / (redMean + 1); - double blueGain = greenMean / (blueMean + 1); + double redGain = greenMean / std::max(redMean, 1.0); + double blueGain = greenMean / std::max(blueMean, 1.0); /* * Clamp the gain values to the hardware, which expresses gains as Q2.8 -- cgit v1.2.1