lsst::afw::geom::ellipses::PixelRegion Class Reference

A pixelized region containing all pixels whose centers are within an Ellipse. More...

#include <PixelRegion.h>

Public Types
using	Iterator = std::vector< Span >::const_iterator
	Iterator type used by begin() and end(). More...

Public Member Functions
	PixelRegion (Ellipse const &ellipse)
	Construct a PixelRegion from an Ellipse. More...
	PixelRegion (PixelRegion const &)=default
	PixelRegion is copy and move constructable and assignable. More...
	PixelRegion (PixelRegion &&)=default
PixelRegion &	operator= (PixelRegion const &)=default
PixelRegion &	operator= (PixelRegion &&)=default
	~PixelRegion ()=default
Iterator	begin () const
	Iterator range over Spans whose pixels are within the Ellipse. More...
Iterator	end () const
lsst::geom::Box2I const &	getBBox () const
	Return the bounding box of the pixel region. More...
Span const	getSpanAt (int y) const
	Return the span at the given y coordinate value. More...

Detailed Description

A pixelized region containing all pixels whose centers are within an Ellipse.

The pixel region for an ellipse may be larger or smaller in area than the ellipse itself, depending on the details of where pixel centers land, and it may be empty even if the area of the ellipse is nonzero.

Definition at line 46 of file PixelRegion.h.

Member Typedef Documentation

Iterator

using lsst::afw::geom::ellipses::PixelRegion::Iterator = std::vector<Span>::const_iterator

Iterator type used by begin() and end().

Definition at line 50 of file PixelRegion.h.

Constructor & Destructor Documentation

PixelRegion() [1/3]

lsst::afw::geom::ellipses::PixelRegion::PixelRegion ( Ellipse const &  ellipse )

explicit

Construct a PixelRegion from an Ellipse.

Definition at line 100 of file PixelRegion.cc.

    : _bbox(ellipse.computeBBox(), lsst::geom::Box2I::EXPAND)
{
    // Initial temporary bounding box that may be larger than the final one.
    lsst::geom::Box2I envelope(ellipse.computeBBox(), lsst::geom::Box2I::EXPAND);
 
    if (envelope.isEmpty()) {
        // If the outer bbox is empty, we know there can't be any spans that
        // contain ellipse pixels.
        return;
    }
 
    // Helper class that does the hard work: compute the boundary points of the
    // ellipse in x that intersect a horizontal line at some given y.
    EllipseHorizontalLineIntersection intersection(ellipse);
 
    // Iterate over pixel rows in the bounding box, computing the intersection
    // of the ellipse with that y coordinate.
    int const yEnd = envelope.getEndY();
    for (int y = envelope.getBeginY(); y != yEnd; ++y) {
        auto x = intersection.xAt(y);
        if (x) {
            int xMin = std::ceil(x->first);
            int xMax = std::floor(x->second);
            if (xMax < xMin) continue;
            _spans.emplace_back(y, xMin, xMax);
            _bbox.include(lsst::geom::Point2I(xMin, y));
            _bbox.include(lsst::geom::Point2I(xMax, y));
        }
    }
}

PixelRegion() [2/3]

lsst::afw::geom::ellipses::PixelRegion::PixelRegion ( PixelRegion const &  )

default

PixelRegion is copy and move constructable and assignable.

PixelRegion() [3/3]

lsst::afw::geom::ellipses::PixelRegion::PixelRegion ( PixelRegion &&  )

default

~PixelRegion()

lsst::afw::geom::ellipses::PixelRegion::~PixelRegion ( )

default

Member Function Documentation

begin()

Iterator lsst::afw::geom::ellipses::PixelRegion::begin ( ) const

inline

Iterator range over Spans whose pixels are within the Ellipse.

Definition at line 68 of file PixelRegion.h.

{ return _spans.begin(); }

end()

Iterator lsst::afw::geom::ellipses::PixelRegion::end ( ) const

inline

Definition at line 69 of file PixelRegion.h.

{ return _spans.end(); }

getBBox()

lsst::geom::Box2I const& lsst::afw::geom::ellipses::PixelRegion::getBBox ( ) const

inline

Return the bounding box of the pixel region.

This is guaranteed to be the smallest box that includes all Spans. It has no guaranteed relationship with the Ellipse's direct (floating-point) bounding box as computed by Ellipse::computeBBox(), and may be empty even if the Ellipse's bounding box is not.

Definition at line 80 of file PixelRegion.h.

{ return _bbox; }

getSpanAt()

Span const lsst::afw::geom::ellipses::PixelRegion::getSpanAt

(

int

y

)

const

Return the span at the given y coordinate value.

Exceptions

lsst::pex::exceptions::OutOfRangeError

Thrown if y is not within the y bounds of getBBox().

Definition at line 132 of file PixelRegion.cc.

                                             {
    if (_bbox.isEmpty()) {
        throw LSST_EXCEPT(
            pex::exceptions::OutOfRangeError,
            "PixelRegion is empty."
        );
    }
    if (y < _bbox.getMinY() || y > _bbox.getMaxY()) {
        throw LSST_EXCEPT(
            pex::exceptions::OutOfRangeError,
            (boost::format("No span at y=%s in pixel region with rows between y=%s and y=%s")
            % y % _bbox.getMinY() % _bbox.getMaxY()).str()
        );
    }
    return _spans[y - _bbox.getBeginY()];
}

operator=() [1/2]

PixelRegion& lsst::afw::geom::ellipses::PixelRegion::operator= ( PixelRegion &&  )

default

operator=() [2/2]

PixelRegion& lsst::afw::geom::ellipses::PixelRegion::operator= ( PixelRegion const &  )

default

---

The documentation for this class was generated from the following files:

• /j/snowflake/release/lsstsw/stack/lsst-scipipe-0.7.0/Linux64/afw/22.0.1-42-gca6935d93+ba5e5ca3eb/include/lsst/afw/geom/ellipses/PixelRegion.h
• /j/snowflake/release/lsstsw/stack/lsst-scipipe-0.7.0/Linux64/afw/22.0.1-42-gca6935d93+ba5e5ca3eb/src/geom/ellipses/PixelRegion.cc