[libcamera-devel] [PATCH 07/12] ipa: ipu3: awb: Correct the relevant zones proportion

[Jean-Michel Hautbois]

Hi Laurent,

On 29/09/2021 14:15, Laurent Pinchart wrote:
> Hi Jean-Michel,
> 
> Thank you for the patch.
> 
> On Thu, Sep 23, 2021 at 10:16:20AM +0200, Jean-Michel Hautbois wrote:
>> The algorithm uses the statistics of a cell only if there is not too
>> much saturated pixels in it. The grey world algorithm works fine when
>> there are a limited number of outliers.
>> Consider a valid zone to be at least 80% of unsaturated cells in it.
>> This value could very well be configurable, and make the algorithm more
>> or less tolerant.
>>
>> While at it, implement it in a configure() call as it will not change
>> during execution, and cache the cellsPerZone values.
>>
>> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
>> ---
>>  src/ipa/ipu3/algorithms/awb.cpp | 32 +++++++++++++++++++++++---------
>>  src/ipa/ipu3/algorithms/awb.h   |  5 +++++
>>  2 files changed, 28 insertions(+), 9 deletions(-)
>>
>> diff --git a/src/ipa/ipu3/algorithms/awb.cpp b/src/ipa/ipu3/algorithms/awb.cpp
>> index 51a38d05..800d023c 100644
>> --- a/src/ipa/ipu3/algorithms/awb.cpp
>> +++ b/src/ipa/ipu3/algorithms/awb.cpp
>> @@ -17,7 +17,6 @@ namespace ipa::ipu3::algorithms {
>>  
>>  LOG_DEFINE_CATEGORY(IPU3Awb)
>>  
>> -static constexpr uint32_t kMinZonesCounted = 16;
>>  static constexpr uint32_t kMinGreenLevelInZone = 32;
>>  
>>  /**
>> @@ -169,6 +168,24 @@ Awb::Awb()
>>  
>>  Awb::~Awb() = default;
>>  
>> +int Awb::configure(IPAContext &context,
>> +		   [[maybe_unused]] const IPAConfigInfo &configInfo)
>> +{
>> +	const ipu3_uapi_grid_config &grid = context.configuration.grid.bdsGrid;
>> +
>> +	cellsPerZoneX_ = round(grid.width / static_cast<double>(kAwbStatsSizeX));
> 
> s/round/std::round/
> 
> as you're using cmath (with a small corresponding comment in the commit
> message).

OK :-).

> 
>> +	cellsPerZoneY_ = round(grid.height / static_cast<double>(kAwbStatsSizeY));
>> +
>> +	/*
>> +	 * Configure the minimum proportion of cells counted within a zone
>> +	 * for it to be relevant for the grey world algorithm.
>> +	 * \todo This proportion could be configured.
>> +	 */
>> +	cellsPerZoneThreshold_ = (cellsPerZoneX_ * cellsPerZoneY_) * 80 / 100;
> 
> No need for parentheses.
> 
> The patch looks fine to me, so
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> 
> This however led me to notice that if the grid width isn't a multiple of
> 16, we'll ignore some of the cells. If the grid width is 79, for
> instance, 15 cells will be ignored. Would it be worth fixing that ?

We could still do :
cellsPerZoneX_ = std::round(stride_ / static_cast<double>(kAwbStatsSizeX));

But we haven't included stride yet :-)

> 
>> +
>> +	return 0;
>> +}
>> +
>>  /**
>>   * The function estimates the correlated color temperature using
>>   * from RGB color space input.
>> @@ -205,7 +222,7 @@ void Awb::generateZones(std::vector<RGB> &zones)
>>  	for (unsigned int i = 0; i < kAwbStatsSizeX * kAwbStatsSizeY; i++) {
>>  		RGB zone;
>>  		double counted = awbStats_[i].counted;
>> -		if (counted >= kMinZonesCounted) {
>> +		if (counted >= cellsPerZoneThreshold_) {
>>  			zone.G = awbStats_[i].sum.green / counted;
>>  			if (zone.G >= kMinGreenLevelInZone) {
>>  				zone.R = awbStats_[i].sum.red / counted;
>> @@ -220,19 +237,16 @@ void Awb::generateZones(std::vector<RGB> &zones)
>>  void Awb::generateAwbStats(const ipu3_uapi_stats_3a *stats,
>>  			   const ipu3_uapi_grid_config &grid)
>>  {
>> -	uint32_t cellsPerZoneX = round(grid.width / static_cast<double>(kAwbStatsSizeX));
>> -	uint32_t cellsPerZoneY = round(grid.height / static_cast<double>(kAwbStatsSizeY));
>> -
>>  	/*
>>  	 * Generate a (kAwbStatsSizeX x kAwbStatsSizeY) array from the IPU3 grid which is
>>  	 * (grid.width x grid.height).
>>  	 */
>> -	for (unsigned int cellY = 0; cellY < kAwbStatsSizeY * cellsPerZoneY; cellY++) {
>> -		for (unsigned int cellX = 0; cellX < kAwbStatsSizeX * cellsPerZoneX; cellX++) {
>> +	for (unsigned int cellY = 0; cellY < kAwbStatsSizeY * cellsPerZoneY_; cellY++) {
>> +		for (unsigned int cellX = 0; cellX < kAwbStatsSizeX * cellsPerZoneX_; cellX++) {
>>  			uint32_t cellPosition = (cellY * grid.width + cellX)
>>  					      * sizeof(Ipu3AwbCell);
>> -			uint32_t zoneX = cellX / cellsPerZoneX;
>> -			uint32_t zoneY = cellY / cellsPerZoneY;
>> +			uint32_t zoneX = cellX / cellsPerZoneX_;
>> +			uint32_t zoneY = cellY / cellsPerZoneY_;
>>  
>>  			uint32_t awbZonePosition = zoneY * kAwbStatsSizeX + zoneX;
>>  
>> diff --git a/src/ipa/ipu3/algorithms/awb.h b/src/ipa/ipu3/algorithms/awb.h
>> index 3385ebe7..681d8c2b 100644
>> --- a/src/ipa/ipu3/algorithms/awb.h
>> +++ b/src/ipa/ipu3/algorithms/awb.h
>> @@ -48,6 +48,7 @@ public:
>>  	Awb();
>>  	~Awb();
>>  
>> +	int configure(IPAContext &context, const IPAConfigInfo &configInfo) override;
>>  	void prepare(IPAContext &context, ipu3_uapi_params *params) override;
>>  	void process(IPAContext &context, const ipu3_uapi_stats_3a *stats) override;
>>  
>> @@ -85,6 +86,10 @@ private:
>>  	std::vector<RGB> zones_;
>>  	Accumulator awbStats_[kAwbStatsSizeX * kAwbStatsSizeY];
>>  	AwbStatus asyncResults_;
>> +
>> +	uint32_t cellsPerZoneX_;
>> +	uint32_t cellsPerZoneY_;
>> +	uint32_t cellsPerZoneThreshold_;
>>  };
>>  
>>  } /* namespace ipa::ipu3::algorithms */
>