[PATCH v2 17/17] ipa: rkisp1: awb: Avoid division by zero

[Laurent Pinchart]

Hi Stefan,

Thank you for the patch.

On Wed, Mar 19, 2025 at 05:11:22PM +0100, Stefan Klug wrote:
> As the gains can also be specified manually, the regulation can run into
> numeric instabilities by dividing by near zero. Mitigate that by
> applying a small minium value.
> 
> Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> 
> ---
> 
> Changes in v2:
> - Collected tag
> ---
>  src/ipa/rkisp1/algorithms/awb.cpp | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/src/ipa/rkisp1/algorithms/awb.cpp b/src/ipa/rkisp1/algorithms/awb.cpp
> index e8b04d03748d..eb4545439ae3 100644
> --- a/src/ipa/rkisp1/algorithms/awb.cpp
> +++ b/src/ipa/rkisp1/algorithms/awb.cpp
> @@ -421,9 +421,9 @@ RGB<double> Awb::calculateRgbMeans(const IPAFrameContext &frameContext, const rk
>  	/*
>  	 * The ISP computes the AWB means after applying the colour gains,
>  	 * divide by the gains that were used to get the raw means from the
> -	 * sensor.
> +	 * sensor. Apply a minimum value to avoid divisions by near-zero.

Shouldn't we instead prevent the user from setting zero (or near-zero)
gains ? 

>  	 */
> -	rgbMeans /= frameContext.awb.gains;
> +	rgbMeans /= frameContext.awb.gains.max(0.01);
>  
>  	return rgbMeans;
>  }

-- 
Regards,

Laurent Pinchart