diff options
| author | David Plowman <david.plowman@raspberrypi.com> | 2020-12-08 20:44:39 +0000 |
|---|---|---|
| committer | Laurent Pinchart <laurent.pinchart@ideasonboard.com> | 2020-12-11 23:31:23 +0200 |
| commit | 1a6a7d4a8e2b26caad00d30283ace1f7d2478270 (patch) | |
| tree | 19d7e31a4c790e4e96e689468c4387d58fd1ae08 /src/ipa/raspberrypi | |
| parent | dbcf4d82473936ce1cfaac0613fba99fb592c957 (diff) | |
ipa: raspberrypi: Compute inverse of piecewise linear function
Add a method to the piecewise linear function (Pwl) class to compute
the inverse of a given Pwl. If the input function is non-monotonic we
can only produce a best effort "pseudo" inverse, and we signal this to
the caller.
Signed-off-by: David Plowman <david.plowman@raspberrypi.com>
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Diffstat (limited to 'src/ipa/raspberrypi')
| -rw-r--r-- | src/ipa/raspberrypi/controller/pwl.cpp | 30 | ||||
| -rw-r--r-- | src/ipa/raspberrypi/controller/pwl.hpp | 3 |
2 files changed, 33 insertions, 0 deletions
diff --git a/src/ipa/raspberrypi/controller/pwl.cpp b/src/ipa/raspberrypi/controller/pwl.cpp index aa134a1f..130c820b 100644 --- a/src/ipa/raspberrypi/controller/pwl.cpp +++ b/src/ipa/raspberrypi/controller/pwl.cpp @@ -114,6 +114,36 @@ Pwl::PerpType Pwl::Invert(Point const &xy, Point &perp, int &span, return PerpType::None; } +Pwl Pwl::Inverse(bool *true_inverse, 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 (true_inverse) + *true_inverse = !(neither || (appended && prepended)); + + return inverse; +} + Pwl Pwl::Compose(Pwl const &other, const double eps) const { double this_x = points_[0].x, this_y = points_[0].y; diff --git a/src/ipa/raspberrypi/controller/pwl.hpp b/src/ipa/raspberrypi/controller/pwl.hpp index 4f168551..484672f6 100644 --- a/src/ipa/raspberrypi/controller/pwl.hpp +++ b/src/ipa/raspberrypi/controller/pwl.hpp @@ -80,6 +80,9 @@ public: }; 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 *true_inverse = 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. |