rectangleAreaTool.py

# -*- coding: utf-8 -*-
"""
/***************************************************************************
 DsgTools
                                 A QGIS plugin
 Brazilian Army Cartographic Production Tools
                              -------------------
        begin                : 2015-04-07
        git sha              : $Format:%H$
        copyright            : (C) 2014 by Luiz Andrade - Cartographic Engineer @ Brazilian Army
        email                : luiz.claudio@dsg.eb.mil.br
 ***************************************************************************/

/***************************************************************************
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/
"""
from qgis.gui import QgsMapTool, QgsRubberBand
from qgis.core import QgsWkbTypes, QgsPointXY, QgsCoordinateReferenceSystem, QgsCoordinateTransform, QgsProject
from qgis.PyQt.QtGui import QColor
from qgis.PyQt.QtCore import pyqtSignal

class RectangleAreaTool(QgsMapTool):

    rectangleCreated = pyqtSignal(float, float, float, float)

    def __init__(self, canvas, action):
        QgsMapTool.__init__(self, canvas)

        self.canvas = canvas
        self.active = False
        self.setAction(action)
        self.rubberBand = QgsRubberBand(self.canvas, QgsWkbTypes.PolygonGeometry)
        mFillColor = QColor(254, 178, 76, 63)
        self.rubberBand.setColor(mFillColor)
        self.rubberBand.setWidth(1)
        self.reset()

    def reset(self):
        self.startPoint = self.endPoint = None
        self.isEmittingPoint = False
        self.rubberBand.reset(QgsWkbTypes.PolygonGeometry)

    def canvasPressEvent(self, e):
        self.startPoint = self.toMapCoordinates(e.pos())
        self.endPoint = self.startPoint
        self.isEmittingPoint = True
        self.showRect(self.startPoint, self.endPoint)

    def canvasReleaseEvent(self, e):
        self.isEmittingPoint = False
        self.rubberBand.hide()
        self.transformCoordinates()
        self.rectangleCreated.emit(self.startPoint.x(), self.startPoint.y(), self.endPoint.x(), self.endPoint.y())

    def canvasMoveEvent(self, e):
        if not self.isEmittingPoint:
            return
        self.endPoint = self.toMapCoordinates( e.pos() )
        self.showRect(self.startPoint, self.endPoint)

    def showRect(self, startPoint, endPoint):
        self.rubberBand.reset(QgsWkbTypes.PolygonGeometry)
        if startPoint.x() == endPoint.x() or startPoint.y() == endPoint.y():
            return
        point1 = QgsPointXY(startPoint.x(), startPoint.y())
        point2 = QgsPointXY(startPoint.x(), endPoint.y())
        point3 = QgsPointXY(endPoint.x(), endPoint.y())
        point4 = QgsPointXY(endPoint.x(), startPoint.y())

        self.rubberBand.addPoint(point1, False)
        self.rubberBand.addPoint(point2, False)
        self.rubberBand.addPoint(point3, False)
        self.rubberBand.addPoint(point4, True)    # true to update canvas
        self.rubberBand.show()

    def transformCoordinates(self):
        if self.startPoint is None or self.endPoint is None:
            return None
        elif self.startPoint.x() == self.endPoint.x() or self.startPoint.y() == self.endPoint.y():
            return None

        # Defining the crs from src and destiny
        epsg = self.canvas.mapSettings().destinationCrs().authid()
        crsSrc = QgsCoordinateReferenceSystem(epsg)
        crsDest = QgsCoordinateReferenceSystem(4326)
        # Creating a transformer
        coordinateTransformer = QgsCoordinateTransform(crsSrc, crsDest, QgsProject.instance())
        # Transforming the points
        self.startPoint = coordinateTransformer.transform(self.startPoint)
        self.endPoint = coordinateTransformer.transform(self.endPoint)

    def deactivate(self):
        self.rubberBand.hide()
        QgsMapTool.deactivate(self)