[libcamera-devel] [PATCH 1/5] ipa: ipu3: agc: Drop kMaxLuminance constant

[Jean-Michel Hautbois]

Hi Laurent,

Thanks for the patch !

On 16/11/2021 17:26, Laurent Pinchart wrote:
> The kMaxLuminance constant is badly named, it's not a maximum luminance,
> but the maximum integer value output by the AWB statistics engine for
> per-channel averages. The constant is used in a single place, hardcoding
> the value is actually more readable.
> 
> Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

I hesitated and made it a constexpr to avoid "magic values"... :-)

Reviewed-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>

> ---
>   src/ipa/ipu3/algorithms/agc.cpp | 6 +-----
>   1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
> index bd02c474611c..43a39ffd57d6 100644
> --- a/src/ipa/ipu3/algorithms/agc.cpp
> +++ b/src/ipa/ipu3/algorithms/agc.cpp
> @@ -61,9 +61,6 @@ static constexpr double kEvGainTarget = 0.5;
>   /* Number of frames to wait before calculating stats on minimum exposure */
>   static constexpr uint32_t kNumStartupFrames = 10;
>   
> -/* Maximum luminance used for brightness normalization */
> -static constexpr uint32_t kMaxLuminance = 255;
> -
>   /*
>    * Normalized luma value target.
>    *
> @@ -298,8 +295,7 @@ double Agc::computeInitialY(IPAFrameContext &frameContext,
>   		       greenSum * frameContext.awb.gains.green * .587 +
>   		       blueSum * frameContext.awb.gains.blue * .114;
>   
> -	/* Return the normalized relative luminance. */
> -	return Y_sum / (grid.height * grid.width) / kMaxLuminance;
> +	return Y_sum / (grid.height * grid.width) / 255;
>   }
>   
>   /**
>