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Add method to test whether 3 points are collinear

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This commit is contained in:
Nyall Dawson 2023-06-23 13:57:00 +10:00
parent b14d42d147
commit 933db142c5
4 changed files with 36 additions and 0 deletions
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8
python/core/auto_generated/geometry/qgsgeometryutils.sip.in
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@ -797,6 +797,14 @@ Returns a weighted point inside the triangle denoted by the points (``aX``, ``aY
- pointY: y-coordinate of generated point
.. versionadded:: 3.10
%End
static bool pointsAreCollinear( double x1, double y1, double x2, double y2, double x3, double y3, double epsilon );
%Docstring
Given the points (``x1``, ``y1``), (``x2``, ``y2``) and (``x3``, ``y3``) returns ``True`` if these
points can be considered collinear with a specified tolerance.
.. versionadded:: 3.32
%End
static bool setZValueFromPoints( const QgsPointSequence &points, QgsPoint &point ) /Deprecated/;

5
src/core/geometry/qgsgeometryutils.cpp
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@ -1864,6 +1864,11 @@ void QgsGeometryUtils::weightedPointInTriangle( const double aX, const double aY
pointY = rBy + rCy + aY;
}
bool QgsGeometryUtils::pointsAreCollinear( double x1, double y1, double x2, double y2, double x3, double y3, double epsilon )
{
return qgsDoubleNear( x1 * ( y2 - y3 ) + x2 * ( y3 - y1 ) + x3 * ( y1 - y2 ), 0, epsilon );
};
bool QgsGeometryUtils::transferFirstMValueToPoint( const QgsPointSequence &points, QgsPoint &point )
{
bool rc = false;

8
src/core/geometry/qgsgeometryutils.h
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@ -819,6 +819,14 @@ class CORE_EXPORT QgsGeometryUtils
static void weightedPointInTriangle( double aX, double aY, double bX, double bY, double cX, double cY,
double weightB, double weightC, double &pointX SIP_OUT, double &pointY SIP_OUT ) SIP_HOLDGIL;
/**
* Given the points (\a x1, \a y1), (\a x2, \a y2) and (\a x3, \a y3) returns TRUE if these
* points can be considered collinear with a specified tolerance.
*
* \since QGIS 3.32
*/
static bool pointsAreCollinear( double x1, double y1, double x2, double y2, double x3, double y3, double epsilon );
/**
* A Z dimension is added to \a point if one of the point in the list
* \a points is in 3D. Moreover, the Z value of \a point is updated

15
tests/src/core/geometry/testqgsgeometryutils.cpp
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@ -75,6 +75,7 @@ class TestQgsGeometryUtils: public QObject
void testInterpolatePointOnLineByValue();
void testPointOnLineWithDistance();
void testPointFractionAlongLine();
void testPointsAreCollinear();
void interpolatePointOnArc();
void testSegmentizeArcHalfCircle();
void testSegmentizeArcHalfCircleOtherDirection();
@ -1386,6 +1387,20 @@ void TestQgsGeometryUtils::testPointFractionAlongLine()
QGSCOMPARENEAR( QgsGeometryUtils::pointFractionAlongLine( 0, 10, 20, 10, 10, 10 ), 0.5, 0.00001 );
}
void TestQgsGeometryUtils::testPointsAreCollinear()
{
QVERIFY( QgsGeometryUtils::pointsAreCollinear( 0, 10, 10, 10, 20, 10, 0.00001 ) );
QVERIFY( QgsGeometryUtils::pointsAreCollinear( 10, 10, 0, 10, 20, 10, 0.00001 ) );
QVERIFY( QgsGeometryUtils::pointsAreCollinear( 20, 10, 10, 10, 0, 10, 0.00001 ) );
QVERIFY( !QgsGeometryUtils::pointsAreCollinear( 20, 15, 10, 10, 0, 10, 0.00001 ) );
QVERIFY( !QgsGeometryUtils::pointsAreCollinear( 20, 10, 10, 15, 0, 10, 0.00001 ) );
QVERIFY( !QgsGeometryUtils::pointsAreCollinear( 20, 10, 10, 10, 0, 15, 0.00001 ) );
QVERIFY( QgsGeometryUtils::pointsAreCollinear( 10, 0, 10, 10, 10, 20, 0.00001 ) );
QVERIFY( QgsGeometryUtils::pointsAreCollinear( 10, 0, 10, 20, 10, 10, 0.00001 ) );
QVERIFY( QgsGeometryUtils::pointsAreCollinear( 10, 20, 10, 0, 10, 10, 0.00001 ) );
QVERIFY( !QgsGeometryUtils::pointsAreCollinear( 15, 20, 10, 10, 10, 20, 0.00001 ) );
}
void TestQgsGeometryUtils::interpolatePointOnArc()
{
QgsPoint p;