[v2,2/4] ipa: libipa: Copy pwl from rpi
diff mbox series

Message ID 20240426073612.1230283-3-paul.elder@ideasonboard.com
State Superseded
Headers show
Series
  • ipa: Move Pwl from Raspberry Pi to libipa
Related show

Commit Message

Paul Elder April 26, 2024, 7:36 a.m. UTC
Copy the piecewise linear function code from Raspberry Pi.

Signed-off-by: Paul Elder <paul.elder@ideasonboard.com>
Reviewed-by: Stefan Klug <stefan.klug@ideasonboard.com>

---
No change in v2
---
 src/ipa/libipa/meson.build |   2 +
 src/ipa/libipa/pwl.cpp     | 267 +++++++++++++++++++++++++++++++++++++
 src/ipa/libipa/pwl.h       | 123 +++++++++++++++++
 3 files changed, 392 insertions(+)
 create mode 100644 src/ipa/libipa/pwl.cpp
 create mode 100644 src/ipa/libipa/pwl.h

Patch
diff mbox series

diff --git a/src/ipa/libipa/meson.build b/src/ipa/libipa/meson.build
index 7ce885da..1b3faf8d 100644
--- a/src/ipa/libipa/meson.build
+++ b/src/ipa/libipa/meson.build
@@ -8,6 +8,7 @@  libipa_headers = files([
     'fc_queue.h',
     'histogram.h',
     'module.h',
+    'pwl.h',
 ])
 
 libipa_sources = files([
@@ -18,6 +19,7 @@  libipa_sources = files([
     'fc_queue.cpp',
     'histogram.cpp',
     'module.cpp',
+    'pwl.cpp'
 ])
 
 libipa_includes = include_directories('..')
diff --git a/src/ipa/libipa/pwl.cpp b/src/ipa/libipa/pwl.cpp
new file mode 100644
index 00000000..09f5d65c
--- /dev/null
+++ b/src/ipa/libipa/pwl.cpp
@@ -0,0 +1,267 @@ 
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2019, Raspberry Pi Ltd
+ *
+ * pwl.cpp - piecewise linear functions
+ */
+
+#include <cassert>
+#include <cmath>
+#include <stdexcept>
+
+#include "pwl.h"
+
+int Pwl::read(const libcamera::YamlObject &params)
+{
+	if (!params.size() || params.size() % 2)
+		return -EINVAL;
+
+	const auto &list = params.asList();
+
+	for (auto it = list.begin(); it != list.end(); it++) {
+		auto x = it->get<double>();
+		if (!x)
+			return -EINVAL;
+		if (it != list.begin() && *x <= points_.back().x)
+			return -EINVAL;
+
+		auto y = (++it)->get<double>();
+		if (!y)
+			return -EINVAL;
+
+		points_.push_back(Point(*x, *y));
+	}
+
+	return 0;
+}
+
+void Pwl::append(double x, double y, const double eps)
+{
+	if (points_.empty() || points_.back().x + eps < x)
+		points_.push_back(Point(x, y));
+}
+
+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));
+}
+
+Pwl::Interval Pwl::domain() const
+{
+	return Interval(points_[0].x, points_[points_.size() - 1].x);
+}
+
+Pwl::Interval Pwl::range() const
+{
+	double lo = points_[0].y, hi = lo;
+	for (auto &p : points_)
+		lo = std::min(lo, p.y), hi = std::max(hi, p.y);
+	return Interval(lo, hi);
+}
+
+bool Pwl::empty() const
+{
+	return points_.empty();
+}
+
+double Pwl::eval(double x, int *spanPtr, bool updateSpan) const
+{
+	int span = findSpan(x, spanPtr && *spanPtr != -1 ? *spanPtr : points_.size() / 2 - 1);
+	if (spanPtr && updateSpan)
+		*spanPtr = span;
+	return points_[span].y +
+	       (x - points_[span].x) * (points_[span + 1].y - points_[span].y) /
+		       (points_[span + 1].x - points_[span].x);
+}
+
+int Pwl::findSpan(double x, int span) const
+{
+	/*
+	 * Pwls are generally small, so linear search may well be faster than
+	 * binary, though could review this if large PWls start turning up.
+	 */
+	int lastSpan = points_.size() - 2;
+	/*
+	 * some algorithms may call us with span pointing directly at the last
+	 * control point
+	 */
+	span = std::max(0, std::min(lastSpan, span));
+	while (span < lastSpan && x >= points_[span + 1].x)
+		span++;
+	while (span && x < points_[span].x)
+		span--;
+	return span;
+}
+
+Pwl::PerpType Pwl::invert(Point const &xy, Point &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];
+		double t = ((xy - points_[span]) % spanVec) / spanVec.len2();
+		if (t < -eps) /* off the start of this span */
+		{
+			if (span == 0) {
+				perp = points_[span];
+				return PerpType::Start;
+			} else if (prevOffEnd) {
+				perp = points_[span];
+				return PerpType::Vertex;
+			}
+		} 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 */
+		{
+			perp = points_[span] + spanVec * t;
+			return PerpType::Perpendicular;
+		}
+	}
+	return PerpType::None;
+}
+
+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())
+			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)
+			/* do nothing */;
+		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
+			neither = true;
+	}
+
+	/*
+	 * This is not a proper inverse if we found ourselves putting points
+	 * onto both ends of the inverse, or if there were points that couldn't
+	 * go on either.
+	 */
+	if (trueInverse)
+		*trueInverse = !(neither || (appended && prepended));
+
+	return inverse;
+}
+
+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) {
+			/*
+			 * next control point in result will be where this
+			 * function's y reaches the next span in other
+			 */
+			thisX = points_[thisSpan].x +
+				(other.points_[otherSpan + 1].x -
+				 points_[thisSpan].y) *
+					dx / dy;
+			thisY = other.points_[++otherSpan].x;
+		} else if (std::abs(dy) > eps && otherSpan > 0 &&
+			   points_[thisSpan + 1].y <=
+				   other.points_[otherSpan - 1].x - eps) {
+			/*
+			 * next control point in result will be where this
+			 * function's y reaches the previous span in other
+			 */
+			thisX = points_[thisSpan].x +
+				(other.points_[otherSpan + 1].x -
+				 points_[thisSpan].y) *
+					dx / dy;
+			thisY = other.points_[--otherSpan].x;
+		} else {
+			/* we stay in the same span in other */
+			thisSpan++;
+			thisX = points_[thisSpan].x,
+			thisY = points_[thisSpan].y;
+		}
+		result.append(thisX, other.eval(thisY, &otherSpan, false),
+			      eps);
+	}
+	return result;
+}
+
+void Pwl::map(std::function<void(double x, double y)> f) const
+{
+	for (auto &pt : points_)
+		f(pt.x, pt.y);
+}
+
+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)
+			x = pwl1.points_[++span1].x;
+		else if (span1 == (int)pwl1.points_.size() - 1)
+			x = pwl0.points_[++span0].x;
+		else if (pwl0.points_[span0 + 1].x > pwl1.points_[span1 + 1].x)
+			x = pwl1.points_[++span1].x;
+		else
+			x = pwl0.points_[++span0].x;
+		f(x, pwl0.eval(x, &span0, false), pwl1.eval(x, &span1, false));
+	}
+}
+
+Pwl Pwl::combine(Pwl const &pwl0, Pwl const &pwl1,
+		 std::function<double(double x, double y0, double y1)> f,
+		 const double eps)
+{
+	Pwl result;
+	map2(pwl0, pwl1, [&](double x, double y0, double y1) {
+		result.append(x, f(x, y0, y1), eps);
+	});
+	return result;
+}
+
+void Pwl::matchDomain(Interval const &domain, bool clip, const double eps)
+{
+	int span = 0;
+	prepend(domain.start, eval(clip ? points_[0].x : domain.start, &span),
+		eps);
+	span = points_.size() - 2;
+	append(domain.end, eval(clip ? points_.back().x : domain.end, &span),
+	       eps);
+}
+
+Pwl &Pwl::operator*=(double d)
+{
+	for (auto &pt : points_)
+		pt.y *= d;
+	return *this;
+}
+
+void Pwl::debug(FILE *fp) const
+{
+	fprintf(fp, "Pwl {\n");
+	for (auto &p : points_)
+		fprintf(fp, "\t(%g, %g)\n", p.x, p.y);
+	fprintf(fp, "}\n");
+}
diff --git a/src/ipa/libipa/pwl.h b/src/ipa/libipa/pwl.h
new file mode 100644
index 00000000..7a6a6452
--- /dev/null
+++ b/src/ipa/libipa/pwl.h
@@ -0,0 +1,123 @@ 
+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2019, Raspberry Pi Ltd
+ *
+ * pwl.h - piecewise linear functions interface
+ */
+#pragma once
+
+#include <functional>
+#include <math.h>
+#include <vector>
+
+#include "libcamera/internal/yaml_parser.h"
+
+class Pwl
+{
+public:
+	struct Interval {
+		Interval(double _start, double _end)
+			: start(_start), end(_end)
+		{
+		}
+		double start, end;
+		bool contains(double value)
+		{
+			return value >= start && value <= end;
+		}
+		double clip(double value)
+		{
+			return value < start ? start
+					     : (value > end ? end : value);
+		}
+		double len() const { return end - start; }
+	};
+	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 &params);
+	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,
+			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);
+	Pwl &operator*=(double d);
+	void debug(FILE *fp = stdout) const;
+
+private:
+	int findSpan(double x, int span) const;
+	std::vector<Point> points_;
+};