Plot ==pyqt5

• PyQt5 The drawing system can present vector graphics , Images , And outline font-based Text .
• We can also call the system in the program api Custom drawing controls .
• The drawing should be in paintEvent() Method implementation
• stay QPainter Object's begin() And end() Methods to write drawing code . It will perform low-level graphics rendering on controls or other graphics devices .

Draw text

• Let's start with a window Unicode Text drawing as an example .
• Example , Let's draw some Cylliric Text . Align text vertically and horizontally .

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

class Example(QWidget):
    def __init__(self):
        super().__init__()

        self.initUI()

    def initUI(self):
        self.text = u'\u041b\u0435\u0432 \u041d\u0438\u043a\u043e\u043b\u0430\
\u0435\u0432\u0438\u0447 \u0422\u043e\u043b\u0441\u0442\u043e\u0439: \n\
\u0410\u043d\u043d\u0430 \u041a\u0430\u0440\u0435\u043d\u0438\u043d\u0430'

        self.setGeometry(300, 300, 280, 170)
        self.setWindowTitle('Draw text')
        self.show()

    def paintEvent(self, event):# Drawing works in paintEvent Method is completed internally .
        #QPainter Class is responsible for all elementary drawing . Between all the painting methods to start() and end() Method . The actual painting was entrusted to drawText() Method .
        qp = QPainter()
        qp.begin(self)
        self.drawText(event, qp)
        qp.end()

    def drawText(self, event, qp):
        qp.setPen(QColor(168, 34, 3))# Define a brush and a font for drawing text .
        qp.setFont(QFont('Decorative', 10))
        #drawText() Method to draw text on the form , Displayed in the center 
        qp.drawText(event.rect(), Qt.AlignCenter, self.text)

Draw a dot

• Point is the simplest graphic object that can be drawn .
• We drew randomly on the window 1000 A red dot

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

class Example1(QWidget):
    def __init__(self):
        super().__init__()

        self.initUI()

    def initUI(self):
        self.setGeometry(300, 300, 280, 170)# main window 
        self.setWindowTitle('Points')
        self.show()

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

    def drawPoints(self, qp):
        qp.setPen(Qt.red)# Set the brush to red , We use the predefined Qt.red Constant 
        size = self.size()# Next time we change the size of the window , Generate a  paint event  event , Set the brush to red , We use the predefined Qt.red Constant 

        for i in range(1000):
            x = random.randint(1, size.width() - 1)
            y = random.randint(1, size.height() - 1)
            qp.drawPoint(x, y)# adopt drawpoint Draw the dot 

Color

• Color is an object that represents red 、 green 、 Blue intensity value RGB24
  - In the example, we draw 3 A rectangle of different colors

import sys
from PyQt5.QtWidgets import QWidget, QApplication
from PyQt5.QtGui import QPainter, QColor, QBrush

class Example2(QWidget):
    def __init__(self):
        super().__init__()

        self.initUI()

    def initUI(self):
        self.setGeometry(300, 300, 350, 100)
        self.setWindowTitle('Colours')
        self.show()

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

    def drawRectangles(self, qp):
        col = QColor(0, 0, 0)
        col.setNamedColor('#d4d4d4')# We define a color that uses hexadecimal symbols .
        qp.setPen(col)

        # We are QPainter Set a brush (Bursh) Object and draw a rectangle with it 
        #drawRect() Method accepts four parameters , The first two are the starting points x, y coordinate , The last two are the width and height of the rectangle 
        qp.setBrush(QColor(200, 0, 0))
        qp.drawRect(10, 15, 90, 60)

        qp.setBrush(QColor(255, 80, 0, 160))
        qp.drawRect(130, 15, 90, 60)

        qp.setBrush(QColor(25, 0, 90, 200))
        qp.drawRect(250, 15, 90, 60)

OPen（ paint brush ）

• QPen Is a basic graphic object . Used to draw lines 、 Rectangles of curves and contours 、 The ellipse 、 Polygons or other shapes .
• They draw six lines . The lines outline six different pen styles . There are five predefined pen styles . We can also create custom pen styles . The last line uses a custom pen drawing style .

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

class Example3(QWidget):
    def __init__(self):
        super().__init__()

        self.initUI()

    def initUI(self):
        self.setGeometry(300, 300, 280, 270)
        self.setWindowTitle('Pen styles')
        self.show()

    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)# Create a QPen object . The color is black . The width is set to 2 Pixels , In parentheses is the style of the pen 

        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)

        # Here we define a brush style .
        pen.setStyle(Qt.CustomDashLine)
        # Here we define 1 Solid lines of pixels ,4 White space in pixels ,5 Pixel solid line ,4 Pixel blank 
        pen.setDashPattern([1, 4, 5, 4])# Set up Qt.CustomDashLine And called setDashPattern() Method , Its parameters ( A list of numbers ) Defines a style , There must be an even number of digits ; Where an odd number means to draw a solid line , An even number means to leave blank . The greater the numerical 
        qp.setPen(pen)
        qp.drawLine(20, 240, 250, 240)

OBrush（ Brush ）

• QBrush Is a basic graphic object
• It is used to paint the background graphic shape , Like a rectangle 、 Oval or polygon
• Three different types of brushes can : A predefined brush , A gradient , Or texture mode .
• In the example, nine different rectangles are drawn

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

class Example4(QWidget):
    def __init__(self):
        super().__init__()

        self.initUI()

    def initUI(self):
        self.setGeometry(300, 300, 355, 280)
        self.setWindowTitle('Brushes')
        self.show()

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

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

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

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

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

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

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

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

        brush.setStyle(Qt.VerPattern)
        qp.setBrush(brush)
        qp.drawRect(130, 195, 90, 60)
        # We define a brush object , Then set it to QPainter object , And call painter Of drawRect() Method to draw a rectangle 
        brush.setStyle(Qt.BDiagPattern)
        qp.setBrush(brush)
        qp.drawRect(250, 195, 90, 60)

if __name__ == '__main__':
    app = QApplication(sys.argv)
    ex = Example4()
    sys.exit(app.exec_())