[PATCH v3 15/16] ipa: rkisp1: awb: Take the CCM into account for the AWB gains calculation

[Paul Elder]

On Thu, Apr 03, 2025 at 05:49:20PM +0200, Stefan Klug wrote:
> The AWB measurements are taken after the CCM. This can be seen by
> enabling debug logging on AWB, disabling AWB (stats will still be
> processed) and manually chaning the CCM.
> 
> This means that the estimated colour temperature and the corresponding
> CCM also lead to changed rgbMeans which in turn leads to oscillations.
> Fix that by applying the inverse transform on the rgbMeans.
> 
> Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

Reviewed-by: Paul Elder <paul.elder at ideasonboard.com>

> 
> ---
> 
> Changes in v2:
> - Improved commit message
> - Added comment in the code
> 
> Changes in v3:
> - Fixed typo in comment
> ---
>  src/ipa/rkisp1/algorithms/awb.cpp | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/src/ipa/rkisp1/algorithms/awb.cpp b/src/ipa/rkisp1/algorithms/awb.cpp
> index 47b29725af51..03449e87e1a0 100644
> --- a/src/ipa/rkisp1/algorithms/awb.cpp
> +++ b/src/ipa/rkisp1/algorithms/awb.cpp
> @@ -397,6 +397,12 @@ RGB<double> Awb::calculateRgbMeans(const IPAFrameContext &frameContext, const rk
>  		rgbMeans = rgbMeans.max(0.0);
>  	}
>  
> +	/*
> +	 * The ISP computes the AWB means after applying the CCM. Apply the
> +	 * inverse as we want to get the raw means before the colour gains.
> +	 */
> +	rgbMeans = frameContext.ccm.ccm.inverse() * rgbMeans;
> +
>  	/*
>  	 * 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
> -- 
> 2.43.0
>