Pyqt5 rapid development and practice 4.10 window drawing controls

PyQt5 Rapid development and actual combat

4. The first 4 Chapter PyQt5 Basic window control

4.10 Window drawing control

stay PyQt5 in , In general, you can go through QPainter,QPen and QBrush These three classes are used to realize the drawing function . Besides ,QPixmap The function of is to load and render local images , In essence, the presentation of images is also realized by drawing , therefore QPixmap It can also be regarded as a class of drawing .

4.10.1 QPainter

QPainter Class in QWidget（ Control ） Perform drawing operations on , It is a drawing tool , It provides highly optimized functions for most graphical interfaces , send QPainter Class can draw from simple lines to complex pie charts .

The drawing operation is in QWidget.paintEvent() Finish in . The drawing method must be placed in QtGui.QPainter Object's begin() and end() Between .QPainter Class performs lower level graphics rendering functions on controls or other drawing devices .

Related methods ：

Method	describe
begin()	Start drawing on the target device
drawArc()	Draw an arc between the starting angle and the final angle
drawEllipse	Draw an ellipse inside a rectangle
drawLine(int x1, int y1, int x2, int y2)	Draw a line with endpoint coordinates specified . Draw from (xl, yl) To (x2, y2) And set the current brush position to (x2, y2)
drawPixmap()	Extract from image file Pixmap And display it in the specified position
drawPolygon()	Draw polygons using an array of coordinates
drawRect(int x,int y,int w,int h)	With a given width w And height h From the top left coordinates (x,y) Draw a rectangle
drawText()	Displays the text at the given coordinates
fillRect()	Use QColor Parameter fills the rectangle
setBrush()	Set brush style
setPen()	Set the color of the pen used for drawing 、 Size and style

Brush style ：

Enumeration type	describe
Qt.NoPen	No line . such as QPainter.drawRect() fill , But no boundary line was drawn
Qt.SolidLine	A simple line
Qt.DashLine	Text messages separated by some pixels
Qt.DotLine	Dots separated by some pixels
Qt.DashDotLine	Alternating dots and short lines
Qt.DashDotDotLine	A short line 、 Two points
Qt.MPenStyle	Brush style mask

Case study —— Draw text

import sys
from PyQt5.QtWidgets import QApplication , QWidget
from PyQt5.QtGui import QPainter , QColor , QFont
from PyQt5.QtCore import Qt

class Drawing(QWidget):
    def __init__(self,parent = None):
        super(Drawing, self).__init__(parent)
        self.setWindowTitle(" Draw text in the window ")
        self.resize(300 ,200)
        self.text = " It's windy every year , The wind blows every year "

    def paintEvent(self,event):
        painter = QPainter(self)
        painter.begin(self)
        #  Custom drawing method 
        self.drawText(event,painter)
        painter.end()

    def drawText(self,event ,qp):
        #  Set the color of the brush 
        qp.setPen(QColor(168,34,3))
        #  Set the font 
        qp.setFont(QFont('SimSun',20))
        #  Draw text 
        qp.drawText(event.rect(),Qt.AlignCenter,self.text)

if __name__ == '__main__':
    from pyqt5_plugins.examples.exampleqmlitem import QtCore
    QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)
    app = QApplication(sys.argv)
    win = Drawing()
    win.show()
    sys.exit(app.exec_())

Case study —— Draw points

import sys,math
from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
from PyQt5.QtCore import Qt

class Drawing(QWidget):
    def __init__(self,parent = None):
        super(Drawing, self).__init__(parent)
        self.resize(300 ,200)
        self.setWindowTitle(" Draw points in the window ")

    def paintEvent(self,event):
        ##  Initialize the drawing tool 
        qp = QPainter()
        #  Start drawing in the window 
        qp.begin(self)
        #  Custom dot drawing method 
        self.drawPoint(qp)
        #  Finish drawing 
        qp.end()

    def drawPoint(self,qp):
        qp.setPen(Qt.red)
        size = self.size()

        for i in range(1000):
            #  Draw sine function image 
            x = 100 * (-1 + 2.0 * i / 1000) + size.width() / 2.0
            y = -50 * math.sin((x - size.width() / 2.0) * math.pi / 50) + size.height() / 2.0

            qp.drawPoint(x , y)

if __name__ == '__main__':
    from pyqt5_plugins.examples.exampleqmlitem import QtCore
    QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)
    app = QApplication(sys.argv)
    win = Drawing()
    win.show()
    sys.exit(app.exec_())

4.10.2 QPen

QPen（ Pen ） Is a basic graphic object , Used to draw lines 、 Curve or draw a rectangle for the outline 、 ellipse 、 Polygons and other shapes .

Case study ——QPen Use

import sys
from PyQt5.QtWidgets import *
from PyQt5.QtGui import *
from PyQt5.QtCore import Qt

class Drawing(QWidget):
    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        self.setGeometry(300 ,300 ,280, 270)
        self.setWindowTitle(" Pen style case ")

    def paintEvent(self,e):
        qp = QPainter()
        qp.begin(self)
        self.drawLines(qp)
        qp.end()

    def drawLines(self,qp):
        pen = QPen(Qt.black , 2, Qt.SolidLine)

        qp.setPen(pen)
        qp.drawLine(20 , 40 ,250 ,40)

        pen.setStyle(Qt.DashLine)
        qp.setPen(pen)
        qp.drawLine(20, 80 , 250 , 80)

        pen.setStyle(Qt.DashDotLine)
        qp.setPen(pen)
        qp.drawLine(20 , 120 , 250 , 120)

        pen.setStyle(Qt.DotLine)
        qp.setPen(pen)
        qp.drawLine(20, 160, 250, 160)

        pen.setStyle(Qt.DashDotDotLine)
        qp.setPen(pen)
        qp.drawLine(20 ,200 , 250,200)

        pen.setStyle(Qt.CustomDashLine)
        pen.setDashPattern([1,4,5,4])
        qp.setPen(pen)
        qp.drawLine(20 ,240, 250 ,240)

if __name__ == '__main__':
    from pyqt5_plugins.examples.exampleqmlitem import QtCore
    QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)
    app = QApplication(sys.argv)
    win = Drawing()
    win.show()
    sys.exit(app.exec_())

4.10.3 QBrush

QBrush（ A brush ） Is a basic graphic object , Used to fill a rectangle 、 Oval or polygonal shape .QBrush There are three types : predefined 、 Transition and texture patterns .

Case study ——QBrush Use

# -*- coding: utf-8 -*-
 
""" 【 brief introduction 】  In drawing QBrush  Example  , Draw nine rectangles of different styles . """

import sys 
from PyQt5.QtWidgets import *  
from PyQt5.QtGui import *
from PyQt5.QtCore import Qt 

class Drawing(QWidget): 
   def __init__(self):
      super().__init__()  
      self.initUI()

   def initUI(self):   
      self.setGeometry(300, 300, 365, 280)
      self.setWindowTitle(' Brush case ')
      self.show()

   def paintEvent(self, e): 
      qp = QPainter()
      qp.begin(self)
      self.drawLines(qp)
      qp.end()

   def drawLines(self, qp): 
      brush = QBrush(Qt.SolidPattern)
      qp.setBrush(brush)
      qp.drawRect(10, 15, 90, 60)

      brush = QBrush(Qt.Dense1Pattern)
      qp.setBrush(brush)
      qp.drawRect(130, 15, 90, 60)

      brush = QBrush(Qt.Dense2Pattern)
      qp.setBrush(brush)
      qp.drawRect(250, 15, 90, 60)

      brush = QBrush(Qt.Dense3Pattern)
      qp.setBrush(brush)
      qp.drawRect(10, 105, 90, 60)

      brush = QBrush(Qt.DiagCrossPattern)
      qp.setBrush(brush)
      qp.drawRect(10, 105, 90, 60)

      brush = QBrush(Qt.Dense5Pattern)
      qp.setBrush(brush)
      qp.drawRect(130, 105, 90, 60)

      brush = QBrush(Qt.Dense6Pattern)
      qp.setBrush(brush)
      qp.drawRect(250, 105, 90, 60)

      brush = QBrush(Qt.HorPattern)
      qp.setBrush(brush)
      qp.drawRect(10, 195, 90, 60)

      brush = QBrush(Qt.VerPattern)
      qp.setBrush(brush)
      qp.drawRect(130, 195, 90, 60)

      brush = QBrush(Qt.BDiagPattern)
      qp.setBrush(brush)
      qp.drawRect(250, 195, 90, 60)
                              
if __name__ == '__main__':
    from pyqt5_plugins.examples.exampleqmlitem import QtCore
    QtCore.QCoreApplication.setAttribute(QtCore.Qt.AA_EnableHighDpiScaling)
    app = QApplication(sys.argv)
    win = Drawing()
    win.show()
    sys.exit(app.exec_())

4.10.4 QPixmap

QPixmap Class is used for image display of drawing equipment , It can be used as a QPaintDevice object , It can also be loaded into a control , Usually labels or buttons , Used to display images on labels or buttons .
QPixmap The types of image files that can be read are BMP、GIF、JPG、JPEG、PNG、PBM、PGM、PPM、XBM 、XPM etc. .

QPixmap Class

Method	describe
copy()	from QRect Object to QPixmap object
fromImage()	take Qlmage Object to QPixmap object
grabWidget()	Create a pixel map from a given widget
grabWindow()	Create a pixel map of data in the window
load()	Load the image file as QPixmap object
save()	take QPixmap Objects are saved as files
toImage()	take QPixmap Object to QImage object

Case study ——QPixmap Use

import sys
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.QtWidgets import *

if __name__ == '__main__':
   app = QApplication(sys.argv)
   win = QWidget()
   lab1 = QLabel()
   lab1.setPixmap(QPixmap("../ Package resource files /pic/python.jpg"))
   vbox=QVBoxLayout()
   vbox.addWidget(lab1)
   win.setLayout(vbox)
   win.setWindowTitle("QPixmap  Example ")
   win.show()
   sys.exit(app.exec_())