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ipa: rkisp1: awb: Remove bias from gain calculation

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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 <laurent.pinchart@ideasonboard.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
This commit is contained in:
Laurent Pinchart 2022-09-04 04:21:18 +03:00
parent 9b389ce79e
commit 2f1efe50a9
1 changed files with 4 additions and 3 deletions
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7
src/ipa/rkisp1/algorithms/awb.cpp
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@ -280,10 +280,11 @@ void Awb::process(IPAContext &context,
/* /*
* Estimate the red and blue gains to apply in a grey world. The green * 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 redGain = greenMean / std::max(redMean, 1.0);
double blueGain = greenMean / (blueMean + 1); double blueGain = greenMean / std::max(blueMean, 1.0);
/* /*
* Clamp the gain values to the hardware, which expresses gains as Q2.8 * Clamp the gain values to the hardware, which expresses gains as Q2.8