17 - Python PyQt (Interfaz gráfica) - Dibujar objetos (addLine, addRect & addEllipse)

En este capítulo del tutorial Python 3 más PyQt5 veremos como agregar objetos como pueden ser líneas, objetos rectángulares y elipses al plano de dibujo (QGraphicsView), este capítulo básicamente es la continuación del capítulo anterior: http://jquery-manual.blogspot.com/2015/07/16-python-pyqt-interfaz-grafica.html. 

Para poder agregar dichos objetos a la escena utilizaremos los siguientes métodos de la clase QGraphicsScene:

Agrega una línea: addLine(x1, y1, x2, y2, QPen) 

Agrega un objeto rectángular: addRect(x, y, width, height, QPen, QBrush)

Agrega un objeto elíptico: addEllipse(x, y, width, height, QPen, QBrush)

La posición inicial x e y será obtenida por el evento MousePressEvent, es decir, cuando el usuario haga click en el plano de dibujo.

La posición final x e y será obtenida por el evento MouseReleaseEvent, es decir, cuando el usuario suelte el mouse en el plano de dibujo.

graficos.pyw

import sys
from PyQt5.QtWidgets import QApplication, QDialog, QGraphicsView, QGraphicsScene, QGridLayout, QPushButton, QComboBox
from PyQt5.QtCore import QPointF, QRectF, Qt
from PyQt5.QtGui import QPen, QBrush
from PyQt5 import uic

class Paint(QGraphicsView):
 def __init__(self):
  QGraphicsView.__init__(self)
  self.setSceneRect(QRectF(self.viewport().rect()))
  self.scene = QGraphicsScene()
  self.isPaint = False
  self.isDelete = False
  self.isClear = False
  self.isObject = None
  self.startX = None
  self.startY = None
  
 def tools(self, e):
  if self.isPaint == True:
   pen = QPen(Qt.black)
   brush = QBrush(Qt.SolidPattern)
   self.scene.addItem(self.scene.addEllipse(e.x(), e.y(), 3, 3, pen, brush))
   self.setScene(self.scene)
  if self.isDelete == True:
   items = self.items(e.x(), e.y())
   for item in items:
    self.scene.removeItem(item)
    
 def paintObject(self, e):
  if self.isObject != None:
   object = self.isObject
   if object == 1: #Line
    pen = QPen(Qt.black)
    self.scene.addItem(self.scene.addLine(self.startX, self.startY, e.x(), e.y(), pen))
    self.setScene(self.scene)
   elif object == 2: #Rect
    pen = QPen(Qt.black)
    brush = QBrush(Qt.SolidPattern)
    self.scene.addItem(self.scene.addRect(self.startX, self.startY, e.x()-self.startX, e.y()-self.startY, pen, brush))
    self.setScene(self.scene)
   elif object == 3: #Ellipse
    pen = QPen(Qt.black)
    brush = QBrush(Qt.SolidPattern)
    self.scene.addItem(self.scene.addEllipse(self.startX, self.startY, e.x()-self.startX, e.y()-self.startY, pen, brush))
    self.setScene(self.scene)
    
    
 def mousePressEvent(self, event):
  e = QPointF(self.mapToScene(event.pos()))
  self.tools(e)
  self.startX = e.x()
  self.startY = e.y()
  
 def mouseReleaseEvent(self, event):
  e = QPointF(self.mapToScene(event.pos()))
  self.paintObject(e)
  
 def mouseMoveEvent(self, event):
  e = QPointF(self.mapToScene(event.pos()))
  self.tools(e)

class Dialogo(QDialog):
 def __init__(self):
  QDialog.__init__(self)
  self.resize(500, 500)
  self.layout = QGridLayout()
  self.setLayout(self.layout)
  self.paint = Paint()
  self.btn_paint = QPushButton("Dibujar")
  self.combo_object = QComboBox()
  self.combo_object.addItem("Seleccionar")
  self.combo_object.addItem("Line")
  self.combo_object.addItem("Rect")
  self.combo_object.addItem("Ellipse")
  self.btn_delete = QPushButton("Borrar")
  self.btn_clear = QPushButton("Clear")
  self.layout.addWidget(self.btn_paint)
  self.layout.addWidget(self.combo_object)
  self.layout.addWidget(self.btn_delete)
  self.layout.addWidget(self.btn_clear)
  self.layout.addWidget(self.paint)
  self.btnDefault = "background-color: grey; border: 0; padding: 10px"
  self.btnActive = "background-color: orange; border: 0; padding: 10px"
  
  self.btn_paint.setStyleSheet(self.btnDefault)
  self.combo_object.setStyleSheet(self.btnDefault)
  self.btn_delete.setStyleSheet(self.btnDefault)
  self.btn_clear.setStyleSheet(self.btnDefault)
  
  self.btn_paint.clicked.connect(self.isPaint)
  self.combo_object.currentIndexChanged.connect(self.isObject)
  self.btn_delete.clicked.connect(self.isDelete)
  self.btn_clear.clicked.connect(self.isClear)
  
 def resizeEvent(self, event):
  self.paint.setSceneRect(QRectF(self.paint.viewport().rect()))
   
 def isPaint(self):
  if self.paint.isPaint == False:
   self.paint.isPaint = True
   self.btn_paint.setStyleSheet(self.btnActive)
  else:
   self.paint.isPaint = False
   self.btn_paint.setStyleSheet(self.btnDefault)
  
  self.paint.isObject = None  
  self.paint.isDelete = False
  self.paint.isClear = False
  self.btn_delete.setStyleSheet(self.btnDefault)
  self.btn_clear.setStyleSheet(self.btnDefault)
  
 def isObject(self):
  object = self.combo_object.currentIndex()
  self.paint.isObject = object
  self.paint.isPaint = False
  self.paint.isDelete = False
  self.paint.isClear = False
  self.btn_paint.setStyleSheet(self.btnDefault)
  self.btn_delete.setStyleSheet(self.btnDefault)
  self.btn_clear.setStyleSheet(self.btnDefault)
  
   
 def isDelete(self):
  if self.paint.isDelete == False:
   self.paint.isDelete = True
   self.btn_delete.setStyleSheet(self.btnActive)
  else:
   self.paint.isDelete = False
   self.btn_delete.setStyleSheet(self.btnDefault)
   
  self.paint.isObject = None 
  self.paint.isPaint = False
  self.paint.isClear = False
  self.btn_paint.setStyleSheet(self.btnDefault)
  self.btn_clear.setStyleSheet(self.btnDefault)
  
 def isClear(self):
  if self.paint.isClear == False:
   self.paint.isClear = True
   self.btn_clear.setStyleSheet(self.btnActive)
  else:
   self.paint.isClear = False
   self.btn_clear.setStyleSheet(self.btnDefault)
   
  self.paint.isObject = None 
  self.paint.isPaint = False
  self.paint.isDelete = False
  self.btn_paint.setStyleSheet(self.btnDefault)
  self.btn_delete.setStyleSheet(self.btnDefault)
  self.paint.scene.clear()
  
app = QApplication(sys.argv)
dialogo = Dialogo()
dialogo.show()
app.exec_()