[PATCH v5 02/10] libcamera: software_isp: Use RGB type to represent gains

[Laurent Pinchart]

Hi Milan,

Thank you for the patch.

On Thu, Jan 30, 2025 at 07:14:39PM +0100, Milan Zamazal wrote:
> Rather than using a custom struct to represent RGB values, let's use the
> corresponding type.
> 
> Signed-off-by: Milan Zamazal <mzamazal at redhat.com>
> ---
>  src/ipa/simple/algorithms/awb.cpp | 14 ++++++++------
>  src/ipa/simple/algorithms/lut.cpp |  6 +++---
>  src/ipa/simple/ipa_context.h      |  7 ++-----
>  3 files changed, 13 insertions(+), 14 deletions(-)
> 
> diff --git a/src/ipa/simple/algorithms/awb.cpp b/src/ipa/simple/algorithms/awb.cpp
> index 1efc7090..9c85b3f8 100644
> --- a/src/ipa/simple/algorithms/awb.cpp
> +++ b/src/ipa/simple/algorithms/awb.cpp
> @@ -25,7 +25,7 @@ int Awb::configure(IPAContext &context,
>  		   [[maybe_unused]] const IPAConfigInfo &configInfo)
>  {
>  	auto &gains = context.activeState.awb.gains;
> -	gains.red = gains.green = gains.blue = 1.0;
> +	gains = { { 1.0, 1.0, 1.0 } };
>  
>  	return 0;
>  }
> @@ -56,15 +56,17 @@ void Awb::process(IPAContext &context,
>  	 * Clamp max gain at 4.0, this also avoids 0 division.
>  	 */
>  	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 */
> +	gains = { {
> +		sumR <= sumG / 4 ? 4.0 : static_cast<double>(sumG) / sumR,
> +		1.0,
> +		sumB <= sumG / 4 ? 4.0 : static_cast<double>(sumG) / sumB,
> +	} };
>  
> -	RGB<double> rgbGains{ { 1 / gains.red, 1 / gains.green, 1 / gains.blue } };
> +	RGB<double> rgbGains{ { 1 / gains.r(), 1 / gains.g(), 1 / gains.b() } };
>  	context.activeState.awb.temperatureK = estimateCCT(rgbGains);

I've sent "[PATCH] ipa: libipa: vector: Add element-wise division
operator" (https://patchwork.libcamera.org/patch/22721/). If it gets
merged first, I'll replace this with 

	context.activeState.awb.temperatureK = estimateCCT(1.0 / gains);

when merging your series. Otherwise I'll update the patch with this
change.

>  
>  	LOG(IPASoftAwb, Debug)
> -		<< "gain R/B: " << gains.red << "/" << gains.blue
> +		<< "gain R/B: " << gains.r() << "/" << gains.b()
>  		<< "; temperature: " << context.activeState.awb.temperatureK;

You can simplify this to

 	LOG(IPASoftAwb, Debug)
		<< "gains: " << gains << "; temperature: "
		<< context.activeState.awb.temperatureK;

>  }
>  
> diff --git a/src/ipa/simple/algorithms/lut.cpp b/src/ipa/simple/algorithms/lut.cpp
> index d75ff710..bd37a955 100644
> --- a/src/ipa/simple/algorithms/lut.cpp
> +++ b/src/ipa/simple/algorithms/lut.cpp
> @@ -104,13 +104,13 @@ void Lut::prepare(IPAContext &context,
>  				   gammaTableSize;
>  		/* Apply gamma after gain! */
>  		unsigned int idx;
> -		idx = std::min({ static_cast<unsigned int>(i * gains.red / div),
> +		idx = std::min({ static_cast<unsigned int>(i * gains.r() / div),
>  				 gammaTableSize - 1 });
>  		params->red[i] = gammaTable[idx];
> -		idx = std::min({ static_cast<unsigned int>(i * gains.green / div),
> +		idx = std::min({ static_cast<unsigned int>(i * gains.g() / div),
>  				 gammaTableSize - 1 });
>  		params->green[i] = gammaTable[idx];
> -		idx = std::min({ static_cast<unsigned int>(i * gains.blue / div),
> +		idx = std::min({ static_cast<unsigned int>(i * gains.b() / div),
>  				 gammaTableSize - 1 });
>  		params->blue[i] = gammaTable[idx];

This could be written

		const RGB<double> lutGains = (gains * i / div).min(gammaTableSize - 1);
		params->red[i] = gammaTable[static_cast<unsigned int>(lutGains.r())];
		params->green[i] = gammaTable[static_cast<unsigned int>(lutGains.g())];
		params->blue[i] = gammaTable[static_cast<unsigned int>(lutGains.b())];

I wonder, should we add a Vector::cast<T> operator ? Then we could write

		const RGB<unsigned int> lutGains =
			(gains * i / div).cast<unsigned int>().min(gammaTableSize - 1);
		params->red[i] = gammaTable[lutGains.r())];
		params->green[i] = gammaTable[lutGains.g()];
		params->blue[i] = gammaTable[lutGains.b())];

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

>  	}
> diff --git a/src/ipa/simple/ipa_context.h b/src/ipa/simple/ipa_context.h
> index 607af45a..df0552db 100644
> --- a/src/ipa/simple/ipa_context.h
> +++ b/src/ipa/simple/ipa_context.h
> @@ -14,6 +14,7 @@
>  #include <libcamera/controls.h>
>  
>  #include <libipa/fc_queue.h>
> +#include <libipa/vector.h>
>  
>  namespace libcamera {
>  
> @@ -36,11 +37,7 @@ struct IPAActiveState {
>  	} blc;
>  
>  	struct {
> -		struct {
> -			double red;
> -			double green;
> -			double blue;
> -		} gains;
> +		RGB<double> gains;
>  		unsigned int temperatureK;
>  	} awb;
>  

-- 
Regards,

Laurent Pinchart