[PATCH v4 1/9] libcamera: software_isp: Determine color temperature

[Milan Zamazal]

Hi Laurent,

thank you for review.

Laurent Pinchart <laurent.pinchart at ideasonboard.com> writes:

> Hi Milan,
>
> Thank you for the patch.
>
> On Mon, Jan 13, 2025 at 02:50:58PM +0100, Milan Zamazal wrote:
>> 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>
>> 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;
>
> 	context.activeState.awb.temperatureK = estimateCCT(rgbGains);

Ack.

>> +
>> +	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;
>
> Please add a patch on top (or at the bottom, up to you) to convert this
> to
>
> 		RGB<double> gains;
>
> (don't forget to include vector.h)

I'll add it on top in v5.

> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
>
>> +		unsigned int temperatureK;
>> +	} awb;
>>  
>>  	static constexpr unsigned int kGammaLookupSize = 1024;
>>  	struct {