[PATCH v3 1/9] libcamera: software_isp: Determine color temperature

[Kieran Bingham]

Quoting Milan Zamazal (2024-12-10 15:34:31)
> The AWB algorithm has data to determine color temperature of the image.
> Let's compute the temperature from it and store it into the context.
> This piece of information is currently unused but it will be needed in a
> followup patch introducing support for color correction matrix.
> 
> Let's store the white balance related information under `awb' subsection
> of the active state, as the hardware pipelines do.
> 
> Signed-off-by: Milan Zamazal <mzamazal at redhat.com>

Looks reasonable.


Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

> ---
>  src/ipa/simple/algorithms/awb.cpp | 13 ++++++++++---
>  src/ipa/simple/algorithms/lut.cpp |  2 +-
>  src/ipa/simple/ipa_context.h      | 11 +++++++----
>  3 files changed, 18 insertions(+), 8 deletions(-)
> 
> diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp
> index 195de41d..f4fe1af6 100644
> --- a/src/ipa/simple/algorithms/awb.cpp
> +++ b/src/ipa/simple/algorithms/awb.cpp
> @@ -12,6 +12,7 @@
>  
>  #include <libcamera/base/log.h>
>  
> +#include "libipa/colours.h"
>  #include "simple/ipa_context.h"
>  
>  namespace libcamera {
> @@ -23,7 +24,7 @@ namespace ipa::soft::algorithms {
>  int Awb::configure(IPAContext &context,
>                    [[maybe_unused]] const IPAConfigInfo &configInfo)
>  {
> -       auto &gains = context.activeState.gains;
> +       auto &gains = context.activeState.awb.gains;
>         gains.red = gains.green = gains.blue = 1.0;
>  
>         return 0;
> @@ -54,12 +55,18 @@ void Awb::process(IPAContext &context,
>          * Calculate red and blue gains for AWB.
>          * Clamp max gain at 4.0, this also avoids 0 division.
>          */
> -       auto &gains = context.activeState.gains;
> +       auto &gains = context.activeState.awb.gains;
>         gains.red = sumR <= sumG / 4 ? 4.0 : static_cast<double>(sumG) / sumR;
>         gains.blue = sumB <= sumG / 4 ? 4.0 : static_cast<double>(sumG) / sumB;
>         /* Green gain is fixed to 1.0 */
>  
> -       LOG(IPASoftAwb, Debug) << "gain R/B " << gains.red << "/" << gains.blue;
> +       RGB<double> rgbGains{ { 1 / gains.red, 1 / gains.green, 1 / gains.blue } };
> +       uint32_t temperature = estimateCCT(rgbGains);
> +       context.activeState.awb.temperatureK = temperature;
> +
> +       LOG(IPASoftAwb, Debug)
> +               << "gain R/B: " << gains.red << "/" << gains.blue
> +               << "; temperature: " << context.activeState.awb.temperatureK;
>  }
>  
>  REGISTER_IPA_ALGORITHM(Awb, "Awb")
> diff --git a/src/ipa/simple/algorithms/lut.cpp b/src/ipa/simple/algorithms/lut.cpp
> index 0ba2391f..d75ff710 100644
> --- a/src/ipa/simple/algorithms/lut.cpp
> +++ b/src/ipa/simple/algorithms/lut.cpp
> @@ -95,7 +95,7 @@ void Lut::prepare(IPAContext &context,
>             context.activeState.gamma.contrast != context.activeState.knobs.contrast)
>                 updateGammaTable(context);
>  
> -       auto &gains = context.activeState.gains;
> +       auto &gains = context.activeState.awb.gains;
>         auto &gammaTable = context.activeState.gamma.gammaTable;
>         const unsigned int gammaTableSize = gammaTable.size();
>  
> diff --git a/src/ipa/simple/ipa_context.h b/src/ipa/simple/ipa_context.h
> index 4af51306..607af45a 100644
> --- a/src/ipa/simple/ipa_context.h
> +++ b/src/ipa/simple/ipa_context.h
> @@ -36,10 +36,13 @@ struct IPAActiveState {
>         } blc;
>  
>         struct {
> -               double red;
> -               double green;
> -               double blue;
> -       } gains;
> +               struct {
> +                       double red;
> +                       double green;
> +                       double blue;
> +               } gains;
> +               unsigned int temperatureK;
> +       } awb;
>  
>         static constexpr unsigned int kGammaLookupSize = 1024;
>         struct {
> -- 
> 2.44.2
>