[libcamera-devel] [PATCH v4 4/4] ipa: ipu3: awb: Clamp gain values

[Umang Jain]

Hi JM

On 2/24/22 20:41, Jean-Michel Hautbois wrote:
> The gain values are coded as u3.13 fixed point values, ie they can not
> be more than 8. Clampt the values in order to avoid any off limits value


s/Clampt/Clamp

> which could make the IPU3 behave weirdly.
>
> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
> ---
>   src/ipa/ipu3/algorithms/awb.cpp | 8 ++++++++
>   1 file changed, 8 insertions(+)
>
> diff --git a/src/ipa/ipu3/algorithms/awb.cpp b/src/ipa/ipu3/algorithms/awb.cpp
> index 1dc27fc9..dc25be81 100644
> --- a/src/ipa/ipu3/algorithms/awb.cpp
> +++ b/src/ipa/ipu3/algorithms/awb.cpp
> @@ -353,6 +353,14 @@ void Awb::awbGreyWorld()
>   
>   	/* Color temperature is not relevant in Grey world but still useful to estimate it :-) */
>   	asyncResults_.temperatureK = estimateCCT(sumRed.R, sumRed.G, sumBlue.B);
> +
> +	/*
> +	 * Gain values are unsigned integer value, range 0 to 8 with 13 bit


I am not able to decipher "integer value" with "fractional part". The 
redGain and blueGain are floating valuesright..?

> +	 * fractional part.
> +	 */
> +	redGain = std::clamp(redGain, 0.0, 65535.0 / 8192);
> +	blueGain = std::clamp(blueGain, 0.0, 65535.0 / 8192);
> +
>   	asyncResults_.redGain = redGain;
>   	/* Hardcode the green gain to 1.0. */
>   	asyncResults_.greenGain = 1.0;