[PATCH v4] ipa: libipa: histogram: Add transform parameter to constructor
Paul Elder
paul.elder at ideasonboard.com
Thu May 9 08:17:01 CEST 2024
On Wed, May 08, 2024 at 06:23:18PM +0300, Laurent Pinchart wrote:
> Hi Paul,
>
> Thank you for the patch.
>
> On Wed, May 08, 2024 at 11:59:24PM +0900, Paul Elder wrote:
> > Add a parameter to the histogram constructor that takes a transformation
> > function to apply to all the bins upon construction.
> >
> > This is necessary notably for the rkisp1, as the values reported from
> > the hardware are 20 bits where the upper 16-bits are meaningful integer
> > values and the lower 4 bits are fractional and meant to be discarded. As
> > adding a right-shift parameter is probably too specialized, a generic
> > function is added as a parameter instead.
> >
> > Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> > Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> > Reviewed-by: Daniel Scally <dan.scally at ideasonboard.com>
> >
> > ---
> > Changes in v4:
> > - fix compilation when called with no transform function
> >
> > Changes in v3:
> > - make the transform function a template parameter, and optimize the
> > constructor
> >
> > This used to be "ipa: libipa: histogram: Add rshift parameter to
> > constructor"
> >
> > Changes in v2:
> > - change rshift parameter to a function parameter
> > ---
> > src/ipa/libipa/histogram.cpp | 14 ++++++++++----
> > src/ipa/libipa/histogram.h | 13 ++++++++++++-
> > 2 files changed, 22 insertions(+), 5 deletions(-)
> >
> > diff --git a/src/ipa/libipa/histogram.cpp b/src/ipa/libipa/histogram.cpp
> > index c1aac59b..212acfdf 100644
> > --- a/src/ipa/libipa/histogram.cpp
> > +++ b/src/ipa/libipa/histogram.cpp
> > @@ -43,12 +43,18 @@ namespace ipa {
> > */
> > Histogram::Histogram(Span<const uint32_t> data)
> > {
> > - cumulative_.reserve(data.size());
> > - cumulative_.push_back(0);
> > - for (const uint32_t &value : data)
> > - cumulative_.push_back(cumulative_.back() + value);
> > + cumulative_.resize(data.size() + 1);
> > + cumulative_[0] = 0;
> > + for (const auto &[i, value] : utils::enumerate(data))
> > + cumulative_[i + 1] = cumulative_[i] + value;
>
> This is a nice optimization. I would have split it to another patch
> though, or at least mentioned it in the commit message.
>
Oh yeah true.
> > }
> >
> > +/**
> > + * \brief Create a cumulative histogram
> > + * \param[in] data A pre-sorted histogram to be passed
>
> Looks like there's room for improvement in the existing documentation of
> the constructor. "pre-sorted" doesn't make too much sense here, and
> neither does "to be passed".
"But it does have to be pre-sorted... oh wait, we're passing in a
non-cumulative histogram... so it's already sorted by definition... ok
I see"
>
> > + * \param[in] transform The transformation function to apply to every bin
> > + */
> > +
> > /**
> > * \fn Histogram::bins()
> > * \brief Retrieve the number of bins currently used by the Histogram
> > diff --git a/src/ipa/libipa/histogram.h b/src/ipa/libipa/histogram.h
> > index 54bb2a19..0e9bef2a 100644
> > --- a/src/ipa/libipa/histogram.h
> > +++ b/src/ipa/libipa/histogram.h
> > @@ -10,10 +10,10 @@
> > #include <assert.h>
> > #include <limits.h>
> > #include <stdint.h>
>
> You need to include <type_traits> for std::enable_if_t and
> std::is_invocable_v.
ack
>
> With these small issues fixed,
>
> Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
Thanks,
Paul
>
> > -
> > #include <vector>
> >
> > #include <libcamera/base/span.h>
> > +#include <libcamera/base/utils.h>
> >
> > namespace libcamera {
> >
> > @@ -24,6 +24,17 @@ class Histogram
> > public:
> > Histogram() { cumulative_.push_back(0); }
> > Histogram(Span<const uint32_t> data);
> > +
> > + template<typename Transform,
> > + std::enable_if_t<std::is_invocable_v<Transform, uint32_t>> * = nullptr>
> > + Histogram(Span<const uint32_t> data, Transform transform)
> > + {
> > + cumulative_.resize(data.size() + 1);
> > + cumulative_[0] = 0;
> > + for (const auto &[i, value] : utils::enumerate(data))
> > + cumulative_[i + 1] = cumulative_[i] + transform(value);
> > + }
> > +
> > size_t bins() const { return cumulative_.size() - 1; }
> > uint64_t total() const { return cumulative_[cumulative_.size() - 1]; }
> > uint64_t cumulativeFrequency(double bin) const;
>
> --
> Regards,
>
> Laurent Pinchart
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