[libcamera-devel] [PATCH v2 1/5] ipa: rpi: histogram: Add interBinMean()

[Jacopo Mondi]

Hi David

On Wed, Aug 23, 2023 at 01:09:11PM +0100, David Plowman via libcamera-devel wrote:
> From: Naushir Patuck <naush at raspberrypi.com>
>
> Add a new helper function Histogram::interBinMean() that essentially
> replaces the existing Histogram::interQuantileMean() logic but working on
> bins instead.
>
> Rework the interQuantileMean() to call into interBinMean() with the
> appropriate convertion from quatiles to bins.
>
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> Reviewed-by: David Plowman <david.plowman at raspberrypi.com>

Reviewed-by: Jacopo Mondi <jacopo.mondi at ideasonboard.com>

> ---
>  src/ipa/rpi/controller/histogram.cpp | 22 ++++++++++++++--------
>  src/ipa/rpi/controller/histogram.h   |  2 ++
>  2 files changed, 16 insertions(+), 8 deletions(-)
>
> diff --git a/src/ipa/rpi/controller/histogram.cpp b/src/ipa/rpi/controller/histogram.cpp
> index 16a9207f..0a27ba2c 100644
> --- a/src/ipa/rpi/controller/histogram.cpp
> +++ b/src/ipa/rpi/controller/histogram.cpp
> @@ -45,20 +45,26 @@ double Histogram::quantile(double q, int first, int last) const
>  	return first + frac;
>  }
>
> -double Histogram::interQuantileMean(double qLo, double qHi) const
> +double Histogram::interBinMean(double binLo, double binHi) const
>  {
> -	assert(qHi > qLo);
> -	double pLo = quantile(qLo);
> -	double pHi = quantile(qHi, (int)pLo);
> +	assert(binHi > binLo);
>  	double sumBinFreq = 0, cumulFreq = 0;
> -	for (double pNext = floor(pLo) + 1.0; pNext <= ceil(pHi);
> -	     pLo = pNext, pNext += 1.0) {
> -		int bin = floor(pLo);
> +	for (double binNext = floor(binLo) + 1.0; binNext <= ceil(binHi);
> +	     binLo = binNext, binNext += 1.0) {
> +		int bin = floor(binLo);
>  		double freq = (cumulative_[bin + 1] - cumulative_[bin]) *
> -			      (std::min(pNext, pHi) - pLo);
> +			      (std::min(binNext, binHi) - binLo);
>  		sumBinFreq += bin * freq;
>  		cumulFreq += freq;
>  	}
>  	/* add 0.5 to give an average for bin mid-points */
>  	return sumBinFreq / cumulFreq + 0.5;
>  }
> +
> +double Histogram::interQuantileMean(double qLo, double qHi) const
> +{
> +	assert(qHi > qLo);
> +	double pLo = quantile(qLo);
> +	double pHi = quantile(qHi, (int)pLo);
> +	return interBinMean(pLo, pHi);
> +}
> diff --git a/src/ipa/rpi/controller/histogram.h b/src/ipa/rpi/controller/histogram.h
> index 6b3e3a9e..e2c5509b 100644
> --- a/src/ipa/rpi/controller/histogram.h
> +++ b/src/ipa/rpi/controller/histogram.h
> @@ -38,6 +38,8 @@ public:
>  	uint64_t total() const { return cumulative_[cumulative_.size() - 1]; }
>  	/* Cumulative frequency up to a (fractional) point in a bin. */
>  	uint64_t cumulativeFreq(double bin) const;
> +	/* Return the mean value between two (fractional) bins. */
> +	double interBinMean(double binLo, double binHi) const;
>  	/*
>  	 * Return the (fractional) bin of the point q (0 <= q <= 1) through the
>  	 * histogram. Optionally provide limits to help.
> --
> 2.30.2
>