[PATCH v4 3/4] ipa: libipa: pwl: Clean up Pwl class to match libcamera
Kieran Bingham
kieran.bingham at ideasonboard.com
Mon Jun 3 13:49:27 CEST 2024
Quoting Paul Elder (2024-05-31 15:43:00)
> Clean up the Pwl class copied from the Raspberry Pi IPA to align it more
> with the libcamera style.
>
> Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> Reviewed-by: Stefan Klug <stefan.klug at ideasonboard.com>
> Acked-by: David Plowman <david.plowman at raspberrypi.com>
>
> ---
> Changes in v4:
> - update to apply to new copy of pwl
> - add documentation
> - fix doxygen
>
> No change in v3
>
> Changes in v2:
> - s/FPoint/PointF/g
> - improve documentation
> - s/matchDomain/extendDomain/
It's not visible in this set of hunks - but there's a PWl capitalisation
issue in findSpan() that could be fixed in this patch.
- "though could review this if large PWls start turning up"
+ "though could review this if large Pwls start turning up"
> ---
> src/ipa/libipa/pwl.cpp | 268 ++++++++++++++++++++++++++++++++++++-----
> src/ipa/libipa/pwl.h | 119 +++++++-----------
> 2 files changed, 285 insertions(+), 102 deletions(-)
>
> diff --git a/src/ipa/libipa/pwl.cpp b/src/ipa/libipa/pwl.cpp
> index e39123767..945914347 100644
> --- a/src/ipa/libipa/pwl.cpp
> +++ b/src/ipa/libipa/pwl.cpp
> @@ -1,19 +1,113 @@
> /* SPDX-License-Identifier: BSD-2-Clause */
> /*
> * Copyright (C) 2019, Raspberry Pi Ltd
> + * Copyright (C) 2024, Ideas on Board Oy
> *
> - * piecewise linear functions
> + * Piecewise linear functions
> */
>
> +#include "pwl.h"
> +
> #include <cassert>
> #include <cmath>
> +#include <sstream>
> #include <stdexcept>
>
> -#include "pwl.h"
> +#include <libcamera/geometry.h>
> +
> +/**
> + * \file pwl.h
> + * \brief Piecewise linear functions
> + */
> +
> +namespace libcamera {
> +
> +namespace ipa {
> +
> +/**
> + * \class Pwl
> + * \brief Describe a univariate piecewise linear function in real space
> + */
>
> -using namespace RPiController;
> +/**
> + * \class Pwl::Interval
> + * \brief Describe an interval in one-dimensional real space
> + */
> +
> +/**
> + * \fn Pwl::Interval::Interval(double _start, double _end)
> + * \brief Construct an interval
> + * \param _start Start of the interval
> + * \param _end End of the interval
> + */
> +
> +/**
> + * \fn Pwl::Interval::contains
> + * \brief Check if a given values falls within the interval
s/values/value/ ?
> + * \param value Value to check
> + */
> +
> +/**
> + * \fn Pwl::Interval::clamp
> + * \brief Clamp a value such that it is within the interval
> + * \param value Value to clamp
> + */
> +
> +/**
> + * \fn Pwl::Interval::len
> + * \brief Compute the length of the interval
> + */
>
> -int Pwl::read(const libcamera::YamlObject ¶ms)
> +/**
> + * \var Pwl::Interval::start
> + * \brief Start of the interval
> + */
> +
> +/**
> + * \var Pwl::Interval::end
> + * \brief End of the interval
> + */
> +
> +/**
> + * \enum Pwl::PerpType
> + * \brief Type of perpendicular found when inverting a piecewise linear function
> + *
> + * \var Pwl::PerpType::None
> + * \brief No perpendicular found
> + *
> + * \var Pwl::PerpType::Start
> + * \brief Start of Pwl is closest point
> + *
> + * \var Pwl::PerpType::End
> + * \brief End of Pwl is closest point
> + *
> + * \var Pwl::PerpType::Vertex
> + * \brief Vertex of Pwl is closest point
> + *
> + * \var Pwl::PerpType::Perpendicular
> + * \brief True perpendicular found
> + */
> +
> +/**
> + * \fn Pwl::Pwl(std::vector<PointF> const &points)
> + * \brief Construct a piecewise linear function from a list of 2D points
> + * \param points Vector of points from which to construct the piecewise linear function
Do any constraints apply to the ordering of the points?
I assume they have to be in some sort order? should that be
documented?, is it enforced?
Could be as simple as saying "param points Sorted vector of points..."?
> + */
> +
> +/**
> + * \brief Populate the piecewise linear function from yaml data
> + * \param params Yaml data to populate the piecewise linear function with
> + *
> + * Any existing points in the piecewise linear function will *not* be
> + * overwritten.
Oh!? So they're appended? Are they added in any order? Now I'm confused
What's the use case where we can just add aribtrary points ...
Or ... in fact - I think now I wonder if perhaps they don't have to be
sorted? The Pwl might not require points to be growing in any axis ...?
> + *
> + * The yaml data is expected to be a list with an even number of numerical
> + * elements. These will be parsed in pairs into x and y points in the piecewise
> + * linear function. x must be monotonically increasing.
> + *
> + * \return 0 on success, negative error code otherwise
> + */
> +int Pwl::readYaml(const libcamera::YamlObject ¶ms)
> {
> if (!params.size() || params.size() % 2)
> return -EINVAL;
> @@ -31,29 +125,55 @@ int Pwl::read(const libcamera::YamlObject ¶ms)
> if (!y)
> return -EINVAL;
>
> - points_.push_back(Point(*x, *y));
> + points_.push_back(PointF(*x, *y));
I think I would have split out clean ups from conversions. Probably with
the conversion from Point to PointF first. But maybe not so critical...
> }
>
> return 0;
> }
>
> +/**
> + * \brief Append a point to the end of the piecewise linear function
> + * \param x x-coordinate of the point to add to the piecewise linear function
> + * \param y y-coordinate of the point to add to the piecewise linear function
> + * \param eps Epsilon for the minimum x distance between points (optional)
> + *
> + * The point's x-coordinate must be greater than the x-coordinate of the last
> + * (= greatest) point already in the piecewise linear function.
> + */
> void Pwl::append(double x, double y, const double eps)
> {
> if (points_.empty() || points_.back().x + eps < x)
> - points_.push_back(Point(x, y));
> + points_.push_back(PointF(x, y));
Aha - here's where some sort ordering becomes enforced?
> }
>
> +/**
> + * \brief Prepend a point to the beginning of the piecewise linear function
> + * \param x x-coordinate of the point to add to the piecewise linear function
> + * \param y y-coordinate of the point to add to the piecewise linear function
> + * \param eps Epsilon for the minimum x distance between points (optional)
> + *
> + * The point's x-coordinate must be less than the x-coordinate of the first
> + * (= smallest) point already in the piecewise linear function.
> + */
> void Pwl::prepend(double x, double y, const double eps)
> {
> if (points_.empty() || points_.front().x - eps > x)
> - points_.insert(points_.begin(), Point(x, y));
> + points_.insert(points_.begin(), PointF(x, y));
> }
>
> +/**
> + * \brief Get the domain of the piecewise linear function
> + * \return An interval representing the domain
> + */
> Pwl::Interval Pwl::domain() const
> {
> return Interval(points_[0].x, points_[points_.size() - 1].x);
> }
>
> +/**
> + * \brief Get the range of the piecewise linear function
> + * \return An interval representing the range
> + */
> Pwl::Interval Pwl::range() const
> {
> double lo = points_[0].y, hi = lo;
> @@ -62,11 +182,28 @@ Pwl::Interval Pwl::range() const
> return Interval(lo, hi);
> }
>
> +/**
> + * \brief Check if the piecewise linear function is empty
> + * \return True if there are no points in the function, false otherwise
> + */
> bool Pwl::empty() const
> {
> return points_.empty();
> }
>
> +/**
> + * \brief Evaluate the piecewise linear function
> + * \param[in] x The x value to input into the function
> + * \param[inout] spanPtr Initial guess for span
> + * \param[in] updateSpan Set to true to update spanPtr
> + *
> + * Evaluate Pwl, optionally supplying an initial guess for the
> + * "span". The "span" may be optionally be updated. If you want to know
> + * the "span" value but don't have an initial guess you can set it to
> + * -1.
> + *
> + * \return The result of evaluating the piecewise linear function at position \a x
> + */
> double Pwl::eval(double x, int *spanPtr, bool updateSpan) const
> {
> int span = findSpan(x, spanPtr && *spanPtr != -1 ? *spanPtr : points_.size() / 2 - 1);
Can that line be wrapped better for clarity?
int span = findSpan(x, spanPtr && *spanPtr != -1
? *spanPtr
: points_.size() / 2 - 1);
But I bet that still won't make checkstyle happy anyway so either way.
> @@ -96,16 +233,29 @@ int Pwl::findSpan(double x, int span) const
> return span;
> }
>
> -Pwl::PerpType Pwl::invert(Point const &xy, Point &perp, int &span,
> +/**
> + * \brief Find perpendicular closest to a given point
> + * \param[in] xy Point to find the perpendicular to
> + * \param[out] perp The found perpendicular
I can't hear 'perp' without thinking we're in a cheesy american crime
movie... :-)
"Sarge, We found the perp..."
> + * \param[inout] span The span+1 to start searching from
> + * \param[in] eps Epsilon for the minimum x distance between points (optional)
> + *
> + * Find perpendicular closest to \a xy, starting from \a span+1 so you can call
> + * it repeatedly to check for multiple closest points (set span to -1 on the
> + * first call). Also returns "pseudo" perpendiculars; see PerpType enum.
> + *
'span+1' is a bit ... something? In fact, isn't the parameter the span-1
?
I guess it could be
* param[inout] span The span left of the point to start searching from
But at that point it's not about 'searching' is it ? Just starting?
> + * \return Type of perpendicular found
> + */
> +Pwl::PerpType Pwl::invert(PointF const &xy, PointF &perp, int &span,
> const double eps) const
> {
> assert(span >= -1);
> bool prevOffEnd = false;
> for (span = span + 1; span < (int)points_.size() - 1; span++) {
> - Point spanVec = points_[span + 1] - points_[span];
> + PointF spanVec = points_[span + 1] - points_[span];
> double t = ((xy - points_[span]) % spanVec) / spanVec.len2();
> - if (t < -eps) /* off the start of this span */
> - {
> + if (t < -eps) {
> + /* off the start of this span */
> if (span == 0) {
> perp = points_[span];
> return PerpType::Start;
> @@ -113,15 +263,15 @@ Pwl::PerpType Pwl::invert(Point const &xy, Point &perp, int &span,
> perp = points_[span];
> return PerpType::Vertex;
> }
> - } else if (t > 1 + eps) /* off the end of this span */
> - {
> + } else if (t > 1 + eps) {
> + /* off the end of this span */
> if (span == (int)points_.size() - 2) {
> perp = points_[span + 1];
> return PerpType::End;
> }
> prevOffEnd = true;
> - } else /* a true perpendicular */
> - {
> + } else {
> + /* a true perpendicular */
> perp = points_[span] + spanVec * t;
> return PerpType::Perpendicular;
> }
> @@ -129,25 +279,36 @@ Pwl::PerpType Pwl::invert(Point const &xy, Point &perp, int &span,
> return PerpType::None;
> }
>
> +/**
> + * \brief Compute the inverse function
> + * \param[out] trueInverse True if the result is a proper/true inverse
> + * \param[in] eps Epsilon for the minimum x distance between points (optional)
> + *
> + * Indicate if it is a proper (true) inverse, or only a best effort (e.g.
> + * input was non-monotonic).
> + *
> + * \return The inverse piecewise linear function
> + */
> Pwl Pwl::inverse(bool *trueInverse, const double eps) const
> {
> bool appended = false, prepended = false, neither = false;
> Pwl inverse;
>
> - for (Point const &p : points_) {
> - if (inverse.empty())
> + for (PointF const &p : points_) {
> + if (inverse.empty()) {
> inverse.append(p.y, p.x, eps);
> - else if (std::abs(inverse.points_.back().x - p.y) <= eps ||
> - std::abs(inverse.points_.front().x - p.y) <= eps)
> + } else if (std::abs(inverse.points_.back().x - p.y) <= eps ||
> + std::abs(inverse.points_.front().x - p.y) <= eps) {
> /* do nothing */;
> - else if (p.y > inverse.points_.back().x) {
> + } else if (p.y > inverse.points_.back().x) {
> inverse.append(p.y, p.x, eps);
> appended = true;
> } else if (p.y < inverse.points_.front().x) {
> inverse.prepend(p.y, p.x, eps);
> prepended = true;
> - } else
> + } else {
> neither = true;
> + }
> }
>
> /*
> @@ -161,18 +322,27 @@ Pwl Pwl::inverse(bool *trueInverse, const double eps) const
> return inverse;
> }
>
> +/**
> + * \brief Compose two piecewise linear functions together
> + * \param[in] other The "other" piecewise linear function
> + * \param[in] eps Epsilon for the minimum x distance between points (optional)
> + *
> + * The "this" function is done first, and "other" after.
Does compose mean merged? or concatenated one after another?
Can it be clearer? As a reader (without reading the implementation) I
don't know the answer from the documentation here ...
> + *
> + * \return The composed piecewise linear function
> + */
> Pwl Pwl::compose(Pwl const &other, const double eps) const
> {
> double thisX = points_[0].x, thisY = points_[0].y;
> int thisSpan = 0, otherSpan = other.findSpan(thisY, 0);
> Pwl result({ { thisX, other.eval(thisY, &otherSpan, false) } });
> +
> while (thisSpan != (int)points_.size() - 1) {
> double dx = points_[thisSpan + 1].x - points_[thisSpan].x,
> dy = points_[thisSpan + 1].y - points_[thisSpan].y;
> if (std::abs(dy) > eps &&
> otherSpan + 1 < (int)other.points_.size() &&
> - points_[thisSpan + 1].y >=
> - other.points_[otherSpan + 1].x + eps) {
> + points_[thisSpan + 1].y >= other.points_[otherSpan + 1].x + eps) {
> /*
> * next control point in result will be where this
> * function's y reaches the next span in other
> @@ -206,18 +376,27 @@ Pwl Pwl::compose(Pwl const &other, const double eps) const
> return result;
> }
>
> +/**
> + * \brief Apply function to (x,y) values at every control point
> + * \param f Function to be applied
> + */
> void Pwl::map(std::function<void(double x, double y)> f) const
> {
> for (auto &pt : points_)
> f(pt.x, pt.y);
> }
>
> +/**
> + * \brief Apply function to (x, y0, y1) values wherever either Pwl has a
> + * control point.
> + */
> void Pwl::map2(Pwl const &pwl0, Pwl const &pwl1,
> std::function<void(double x, double y0, double y1)> f)
> {
> int span0 = 0, span1 = 0;
> double x = std::min(pwl0.points_[0].x, pwl1.points_[0].x);
> f(x, pwl0.eval(x, &span0, false), pwl1.eval(x, &span1, false));
> +
> while (span0 < (int)pwl0.points_.size() - 1 ||
> span1 < (int)pwl1.points_.size() - 1) {
> if (span0 == (int)pwl0.points_.size() - 1)
> @@ -232,6 +411,12 @@ void Pwl::map2(Pwl const &pwl0, Pwl const &pwl1,
> }
> }
>
> +/**
> + * \brief Combine two Pwls
> + *
> + * Create a new Pwl where the y values are given by running f wherever either
> + * has a knot.
> + */
> Pwl Pwl::combine(Pwl const &pwl0, Pwl const &pwl1,
> std::function<double(double x, double y0, double y1)> f,
> const double eps)
> @@ -243,7 +428,19 @@ Pwl Pwl::combine(Pwl const &pwl0, Pwl const &pwl1,
> return result;
> }
>
> -void Pwl::matchDomain(Interval const &domain, bool clip, const double eps)
> +/**
> + * \brief Extend the domain of the piecewise linear function
> + * \param[in] domain The domain to extend to
> + * \param[in] clip True to keep the existing edge y values, false to extrapolate
> + * \param[in] eps Epsilon for the minimum x distance between points (optional)
> + *
> + * Extend the domain of the piecewise linear function to match \a domain. If \a
> + * clip is set to true then the y values of the new edges will be the same as
> + * the existing y values of the edge points of the pwl. If false, then the y
> + * values will be extrapolated linearly from the existing edge points of the
> + * pwl.
> + */
> +void Pwl::extendDomain(Interval const &domain, bool clip, const double eps)
> {
> int span = 0;
> prepend(domain.start, eval(clip ? points_[0].x : domain.start, &span),
> @@ -253,6 +450,11 @@ void Pwl::matchDomain(Interval const &domain, bool clip, const double eps)
> eps);
> }
>
> +/**
> + * \brief Multiply the piecewise linear function
> + * \param d Scalar multiplier to multiply the function by
> + * \return This function, after it has been multiplied by \a d
> + */
> Pwl &Pwl::operator*=(double d)
> {
> for (auto &pt : points_)
> @@ -260,10 +462,20 @@ Pwl &Pwl::operator*=(double d)
> return *this;
> }
>
> -void Pwl::debug(FILE *fp) const
> +/**
> + * \brief Assemble and return a string describing the piecewise linear function
> + * \return A string describing the piecewise linear function
> + */
> +std::string Pwl::toString() const
> {
> - fprintf(fp, "Pwl {\n");
> + std::stringstream ss;
> + ss << "Pwl { ";
> for (auto &p : points_)
> - fprintf(fp, "\t(%g, %g)\n", p.x, p.y);
> - fprintf(fp, "}\n");
> + ss << "(" << p.x << ", " << p.y << ") ";
> + ss << "}";
> + return ss.str();
> }
> +
> +} /* namespace ipa */
> +
> +} /* namespace libcamera */
> diff --git a/src/ipa/libipa/pwl.h b/src/ipa/libipa/pwl.h
> index 7d5e7e4d3..9b716c788 100644
> --- a/src/ipa/libipa/pwl.h
> +++ b/src/ipa/libipa/pwl.h
> @@ -2,126 +2,97 @@
> /*
> * Copyright (C) 2019, Raspberry Pi Ltd
> *
> - * piecewise linear functions interface
> + * Piecewise linear functions interface
> */
> #pragma once
>
> #include <functional>
> #include <math.h>
> +#include <string>
> #include <vector>
>
> +#include <libcamera/geometry.h>
> +
> #include "libcamera/internal/yaml_parser.h"
>
> -namespace RPiController {
> +namespace libcamera {
> +
> +namespace ipa {
>
> class Pwl
> {
> public:
> + enum class PerpType {
> + None,
> + Start,
> + End,
> + Vertex,
> + Perpendicular,
> + };
> +
> struct Interval {
> Interval(double _start, double _end)
> - : start(_start), end(_end)
> - {
> - }
> - double start, end;
> + : start(_start), end(_end) {}
> +
> bool contains(double value)
> {
> return value >= start && value <= end;
> }
> - double clip(double value)
> +
> + double clamp(double value)
> {
> return value < start ? start
> : (value > end ? end : value);
> }
> +
> double len() const { return end - start; }
> +
> + double start, end;
> };
> - struct Point {
> - Point() : x(0), y(0) {}
> - Point(double _x, double _y)
> - : x(_x), y(_y) {}
> - double x, y;
> - Point operator-(Point const &p) const
> - {
> - return Point(x - p.x, y - p.y);
> - }
> - Point operator+(Point const &p) const
> - {
> - return Point(x + p.x, y + p.y);
> - }
> - double operator%(Point const &p) const
> - {
> - return x * p.x + y * p.y;
> - }
> - Point operator*(double f) const { return Point(x * f, y * f); }
> - Point operator/(double f) const { return Point(x / f, y / f); }
> - double len2() const { return x * x + y * y; }
> - double len() const { return sqrt(len2()); }
> - };
> +
> Pwl() {}
> - Pwl(std::vector<Point> const &points) : points_(points) {}
> - int read(const libcamera::YamlObject ¶ms);
> + Pwl(std::vector<PointF> const &points)
> + : points_(points) {}
> + int readYaml(const libcamera::YamlObject ¶ms);
> +
> void append(double x, double y, const double eps = 1e-6);
> void prepend(double x, double y, const double eps = 1e-6);
> +
> Interval domain() const;
> Interval range() const;
> +
> bool empty() const;
> - /*
> - * Evaluate Pwl, optionally supplying an initial guess for the
> - * "span". The "span" may be optionally be updated. If you want to know
> - * the "span" value but don't have an initial guess you can set it to
> - * -1.
> - */
> +
> double eval(double x, int *spanPtr = nullptr,
> bool updateSpan = true) const;
> - /*
> - * Find perpendicular closest to xy, starting from span+1 so you can
> - * call it repeatedly to check for multiple closest points (set span to
> - * -1 on the first call). Also returns "pseudo" perpendiculars; see
> - * PerpType enum.
> - */
> - enum class PerpType {
> - None, /* no perpendicular found */
> - Start, /* start of Pwl is closest point */
> - End, /* end of Pwl is closest point */
> - Vertex, /* vertex of Pwl is closest point */
> - Perpendicular /* true perpendicular found */
> - };
> - PerpType invert(Point const &xy, Point &perp, int &span,
> +
> + PerpType invert(PointF const &xy, PointF &perp, int &span,
> const double eps = 1e-6) const;
> - /*
> - * Compute the inverse function. Indicate if it is a proper (true)
> - * inverse, or only a best effort (e.g. input was non-monotonic).
> - */
> Pwl inverse(bool *trueInverse = nullptr, const double eps = 1e-6) const;
> - /* Compose two Pwls together, doing "this" first and "other" after. */
> Pwl compose(Pwl const &other, const double eps = 1e-6) const;
> - /* Apply function to (x,y) values at every control point. */
> +
> void map(std::function<void(double x, double y)> f) const;
> - /*
> - * Apply function to (x, y0, y1) values wherever either Pwl has a
> - * control point.
> - */
> +
> static void map2(Pwl const &pwl0, Pwl const &pwl1,
> std::function<void(double x, double y0, double y1)> f);
> - /*
> - * Combine two Pwls, meaning we create a new Pwl where the y values are
> - * given by running f wherever either has a knot.
> - */
> +
> static Pwl
> combine(Pwl const &pwl0, Pwl const &pwl1,
> std::function<double(double x, double y0, double y1)> f,
> const double eps = 1e-6);
> - /*
> - * Make "this" match (at least) the given domain. Any extension my be
> - * clipped or linear.
> - */
> - void matchDomain(Interval const &domain, bool clip = true,
> - const double eps = 1e-6);
> +
> + void extendDomain(Interval const &domain, bool clip = true,
> + const double eps = 1e-6);
> +
> Pwl &operator*=(double d);
> - void debug(FILE *fp = stdout) const;
> +
> + std::string toString() const;
>
> private:
> int findSpan(double x, int span) const;
> - std::vector<Point> points_;
> + std::vector<PointF> points_;
> };
>
> -} /* namespace RPiController */
> +} /* namespace ipa */
> +
> +} /* namespace libcamera */
> --
> 2.39.2
>
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