[PATCH 2/3] libcamera: Add gamma control id

[Dan Scally]

Hi Stefan

On 16/05/2024 13:41, Stefan Klug wrote:
> A camera gamma of roughly 2.2 is necessary to produce correct output
> images on a standard monitor. Add a control for that.
>
> Further information is available here:
> https://en.wikipedia.org/wiki/SRGB
> https://www.cambridgeincolour.com/tutorials/gamma-correction.htm
>
> Signed-off-by: Stefan Klug <stefan.klug at ideasonboard.com>
> ---
>   src/libcamera/control_ids_core.yaml | 6 ++++++
>   1 file changed, 6 insertions(+)
>
> diff --git a/src/libcamera/control_ids_core.yaml b/src/libcamera/control_ids_core.yaml
> index bf1f1a83..43b85135 100644
> --- a/src/libcamera/control_ids_core.yaml
> +++ b/src/libcamera/control_ids_core.yaml
> @@ -243,6 +243,12 @@ controls:
>           Specify a fixed contrast parameter. Normal contrast is given by the
>           value 1.0; larger values produce images with more contrast.
>   
> +  - Gamma:
> +      type: float
> +      description:  |
> +        Specify a fixed gamma value. Default is 2.2 which closely mimics sRGB
> +        gamma. Note that this is camera gamma, so it is applied as 1.0/gamma

I think I would word it as  "Default must be 2.2" rather than "is"...purely on the grounds that the 
IPA module could have any default value that slips past review. But either way:


Reviewed-by: Daniel Scally <dan.scally at ideasonboard.com>

> +
>     - Lux:
>         type: float
>         description: |