16 - Python PyQt (Interfaz gráfica) - QGraphicsView (Herramientas de dibujo)

En este capítulo del tutorial de Python 3 más PyQt5 veremos un ejemplo sencillo de trabajar con gráficos, concretamente, intentaremos crear un programa que de un modo simple emule la herramienta de dibujo de un programa como puede ser Paint de Windows. Este programa nos permitirá dibujar, borrar y limpiar el dibujo realizado. Para ello nos basaremos principalmente en las clases QGraphicsView (Plano de dibujo) y QGraphicsScene (Escenas o capas).

Referencia a la clase QGraphicsView:  http://pyqt.sourceforge.net/Docs/PyQt4/qgraphicsview.html

Referencia a la clase QGraphicsScene: http://pyqt.sourceforge.net/Docs/PyQt4/qgraphicsscene.html

graficos.pyw

import sys
from PyQt5.QtWidgets import QApplication, QDialog, QGraphicsView, QGraphicsScene, QGridLayout, QPushButton
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
  
 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 mousePressEvent(self, event):
  e = QPointF(self.mapToScene(event.pos()))
  self.tools(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.btn_delete = QPushButton("Borrar")
  self.btn_clear = QPushButton("Clear")
  self.layout.addWidget(self.btn_paint)
  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.btn_delete.setStyleSheet(self.btnDefault)
  self.btn_clear.setStyleSheet(self.btnDefault)
  
  self.btn_paint.clicked.connect(self.isPaint)
  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.isDelete = False
  self.paint.isClear = False
  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.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.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_()