QGIS API Documentation 3.35.0-Master (f6e073f0eed)
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qgstolerance.cpp
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1/***************************************************************************
2 qgstolerance.cpp - wrapper for tolerance handling
3 ----------------------
4 begin : March 2009
5 copyright : (C) 2009 by Richard Kostecky
6 email : csf.kostej at gmail dot com
7 ***************************************************************************
8 * *
9 * This program is free software; you can redistribute it and/or modify *
10 * it under the terms of the GNU General Public License as published by *
11 * the Free Software Foundation; either version 2 of the License, or *
12 * (at your option) any later version. *
13 * *
14 ***************************************************************************/
15
16#include "qgstolerance.h"
17#include "qgsmapsettings.h"
21#include "qgspointxy.h"
22
23#include <QPoint>
24#include <cmath>
25
26
27// return ratio [mu/lu] between map units and layer units
28// this is of course only an approximation
29double _ratioMU2LU( const QgsMapSettings &mapSettings, QgsMapLayer *layer )
30{
31 const double distMU = mapSettings.mapUnitsPerPixel();
32 const QgsPointXY ptMapCenterMU = mapSettings.visibleExtent().center();
33 const QgsPointXY ptMapCenterRightMU( ptMapCenterMU.x() + distMU, ptMapCenterMU.y() );
34 const QgsPointXY ptMapCenterLU = mapSettings.mapToLayerCoordinates( layer, ptMapCenterMU );
35 const QgsPointXY ptMapCenterRightLU = mapSettings.mapToLayerCoordinates( layer, ptMapCenterRightMU );
36 const double distLU = std::sqrt( ptMapCenterLU.sqrDist( ptMapCenterRightLU ) );
37 const double ratio = distMU / distLU;
38 return ratio;
39}
40
41double QgsTolerance::toleranceInProjectUnits( double tolerance, QgsMapLayer *layer, const QgsMapSettings &mapSettings, Qgis::MapToolUnit units )
42{
43 // converts to map units
44 if ( units == Qgis::MapToolUnit::Project )
45 return tolerance;
46 else if ( units == Qgis::MapToolUnit::Pixels )
47 return tolerance * mapSettings.mapUnitsPerPixel();
48 else // units == LayerUnits
49 {
50 // [mu] = [lu] * [mu/lu]
51 return tolerance * _ratioMU2LU( mapSettings, layer );
52 }
53}
54
55
56double QgsTolerance::toleranceInMapUnits( double tolerance, QgsMapLayer *layer, const QgsMapSettings &mapSettings, Qgis::MapToolUnit units )
57{
58 // converts to layer units
59 if ( units == Qgis::MapToolUnit::Layer )
60 {
61 return tolerance;
62 }
63 else if ( units == Qgis::MapToolUnit::Pixels )
64 {
65 const double layerUnitsPerPixel = computeMapUnitPerPixel( layer, mapSettings );
66 return tolerance * layerUnitsPerPixel;
67 }
68 else // ProjectUnits
69 {
70 // [lu] = [mu] / [mu/lu]
71 return tolerance / _ratioMU2LU( mapSettings, layer );
72 }
73}
74
83
90
97
98
99double QgsTolerance::computeMapUnitPerPixel( QgsMapLayer *layer, const QgsMapSettings &mapSettings )
100{
101 // the layer is projected. Find out how many pixels are in one map unit - either horizontal and vertical direction
102 // this check might not work correctly in some cases
103 // (on a large area the pixels projected around "0,0" can have different properties from the actual point)
104 const QgsPointXY p1 = toLayerCoordinates( layer, mapSettings, QPoint( 0, 1 ) );
105 const QgsPointXY p2 = toLayerCoordinates( layer, mapSettings, QPoint( 0, 2 ) );
106 const QgsPointXY p3 = toLayerCoordinates( layer, mapSettings, QPoint( 1, 0 ) );
107 const QgsPointXY p4 = toLayerCoordinates( layer, mapSettings, QPoint( 2, 0 ) );
108 const double x = p1.sqrDist( p2 );
109 const double y = p3.sqrDist( p4 );
110 if ( x > y )
111 {
112 return std::sqrt( x );
113 }
114 else
115 {
116 return std::sqrt( y );
117 }
118}
119
120
121QgsPointXY QgsTolerance::toLayerCoordinates( QgsMapLayer *layer, const QgsMapSettings &mapSettings, QPoint point )
122{
123 const QgsPointXY pt = mapSettings.mapToPixel().toMapCoordinates( point );
124 return mapSettings.mapToLayerCoordinates( layer, pt );
125}
MapToolUnit
Type of unit of tolerance value from settings.
Definition qgis.h:4030
@ Layer
Layer unit value.
@ Project
Map (project) units.
@ Pixels
Pixels unit of tolerance.
Base class for all map layer types.
Definition qgsmaplayer.h:75
The QgsMapSettings class contains configuration for rendering of the map.
const QgsMapToPixel & mapToPixel() const
double mapUnitsPerPixel() const
Returns the distance in geographical coordinates that equals to one pixel in the map.
QgsRectangle visibleExtent() const
Returns the actual extent derived from requested extent that takes output image size into account.
QgsPointXY mapToLayerCoordinates(const QgsMapLayer *layer, QgsPointXY point) const
transform point coordinates from output CRS to layer's CRS
QgsPointXY toMapCoordinates(int x, int y) const
Transforms device coordinates to map (world) coordinates.
A class to represent a 2D point.
Definition qgspointxy.h:60
double sqrDist(double x, double y) const
Returns the squared distance between this point a specified x, y coordinate.
Definition qgspointxy.h:187
double y
Definition qgspointxy.h:64
double x
Definition qgspointxy.h:63
QgsPointXY center() const
Returns the center point of the rectangle.
T value(const QString &dynamicKeyPart=QString()) const
Returns settings value.
static const QgsSettingsEntryDouble * settingsDigitizingSearchRadiusVertexEdit
Settings entry digitizing search radius vertex edit.
static const QgsSettingsEntryEnumFlag< Qgis::MapToolUnit > * settingsDigitizingDefaultSnappingToleranceUnit
Settings entry digitizing default snapping tolerance unit.
static const QgsSettingsEntryEnumFlag< Qgis::MapToolUnit > * settingsDigitizingSearchRadiusVertexEditUnit
Settings entry digitizing search radius vertex edit unit.
static const QgsSettingsEntryDouble * settingsDigitizingDefaultSnappingTolerance
Settings entry digitizing default snapping tolerance.
static double toleranceInMapUnits(double tolerance, QgsMapLayer *layer, const QgsMapSettings &mapSettings, Qgis::MapToolUnit units=Qgis::MapToolUnit::Layer)
Static function to translate tolerance value into layer units.
static double vertexSearchRadius(const QgsMapSettings &mapSettings)
Static function to get vertex tolerance value.
static double defaultTolerance(QgsMapLayer *layer, const QgsMapSettings &mapSettings)
Static function to get default tolerance value for a layer.
static double toleranceInProjectUnits(double tolerance, QgsMapLayer *layer, const QgsMapSettings &mapSettings, Qgis::MapToolUnit units)
Static function to translate tolerance value into map units.
double _ratioMU2LU(const QgsMapSettings &mapSettings, QgsMapLayer *layer)