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

[Kieran Bingham]

Quoting David Plowman via libcamera-devel (2023-07-31 10:46:37)
> 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.

/convertion/conversion/

> 
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>


Reviewed-by: Kieran Bingham <kieran.bingham 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
>