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

[Laurent Pinchart]

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).

> +	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 ?

> +
> +	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 */

-- 
Regards,

Laurent Pinchart