PyQGIS – Getting Coordinates of Point on Mouse Click in QGIS

coordinatespointpyqgisqgisxy

I want to get x/y coordinates of a point on mouse click for a point and need to use those coordinates to evaluate other values as per other modules already define.

How can I get x/y coordinates on mouse click in QGIS and print those in PyQGIS?

Best Answer

You need QgsMapToolEmitPoint class to do that. Following code works well for that purpose:

from qgis.gui import QgsMapToolEmitPoint

def display_point( pointTool ): 

    print '({:.4f}, {:.4f})'.format(pointTool[0], pointTool[1])

# a reference to our map canvas 
canvas = iface.mapCanvas() 

# this QGIS tool emits as QgsPoint after each click on the map canvas
pointTool = QgsMapToolEmitPoint(canvas)

pointTool.canvasClicked.connect( display_point )

canvas.setMapTool( pointTool )

However, if you prefer a class, following code can also be used:

from qgis.gui import QgsMapToolEmitPoint

class PrintClickedPoint(QgsMapToolEmitPoint):
    def __init__(self, canvas):
        self.canvas = canvas
        QgsMapToolEmitPoint.__init__(self, self.canvas)

    def canvasPressEvent( self, e ):
        point = self.toMapCoordinates(self.canvas.mouseLastXY())
        print '({:.4f}, {:.4f})'.format(point[0], point[1])

canvas_clicked = PrintClickedPoint( iface.mapCanvas() )
iface.mapCanvas().setMapTool( canvas_clicked )

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PyQGIS – Programmatically Check for Mouse Click in PyQGIS

The best way to make a new tool like the Select Single Feature tool is to inherit from the QgsMapTool class. When your tool is active, which can be set using QgsMapCanvas::setMapTool, any keyboard or click events the canvas gets will be passed onto your custom tool.

Here is a basic QgsMapTool class

class PointTool(QgsMapTool):   
    def __init__(self, canvas):
        QgsMapTool.__init__(self, canvas)
        self.canvas = canvas    

    def canvasPressEvent(self, event):
        pass

    def canvasMoveEvent(self, event):
        x = event.pos().x()
        y = event.pos().y()

        point = self.canvas.getCoordinateTransform().toMapCoordinates(x, y)

    def canvasReleaseEvent(self, event):
        #Get the click
        x = event.pos().x()
        y = event.pos().y()

        point = self.canvas.getCoordinateTransform().toMapCoordinates(x, y)

    def activate(self):
        pass

    def deactivate(self):
        pass

    def isZoomTool(self):
        return False

    def isTransient(self):
        return False

    def isEditTool(self):
        return True

You can do what you need in canvasReleaseEvent, etc

To set this tool active you just do:

tool = PointTool(qgis.iface.mapCanvas())
qgis.iface.mapCanvas().setMapTool(tool)

[GIS] Getting polygon shapefile node coordinates and point order

The mmqgis plugin also allows exporting geometry data to csv. The point order will be preserved.

On importing, the plugin does not like multipolygons.

Best Answer

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PyQGIS – Programmatically Check for Mouse Click in PyQGIS

[GIS] Getting polygon shapefile node coordinates and point order

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