PyQt5 事件处理之绘图

摘自《PyQt5快速开发实战》第八章——PyQt5图形与特效 

• 画线

from PyQt5.QtWidgets import QWidget, QApplication
from PyQt5.QtGui import QPainter, QPainterPath, QPixmap
from PyQt5.QtCore import Qt, QPoint
import sys


class Example(QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.setWindowTitle('画线')
        self.pix = QPixmap()
        self.lastPoint = QPoint()
        self.endPoint = QPoint()
        self.initUI()

    def initUI(self):
        self.resize(600, 500)
        self.pix = QPixmap(600, 500)
        self.pix.fill(Qt.white)

    def paintEvent(self, event): #重写paintEvent事件
        pp = QPainter(self.pix)
        pp.drawLine(self.lastPoint, self.endPoint)
        self.lastPoint = self.endPoint
        painter = QPainter(self)
        painter.drawPixmap(0,0,self.pix)

    def mousePressEvent(self, event): #重写鼠标按下事件
        if event.button() == Qt.LeftButton:
            self.lastPoint = event.pos()
            self.endPoint = self.lastPoint

    def mouseMoveEvent(self, event): #重写鼠标移动事件
        if event.buttons() and Qt.LeftButton:
            self.endPoint = event.pos()
            self.update() #更新绘图事件,每次执行update都会触发一次paintEvent(self, event)函数

    def mouseReleaseEvent(self, event): #重写鼠标释放事件
        if event.button() == Qt.LeftButton:
            self.endPoint = event.pos()
            self.update()

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

运行结果：

•  画矩形

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

class Example(QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.setWindowTitle('绘制矩形')
        self.setCursor(Qt.CrossCursor) #设置十字光标
        self.x0 = 0
        self.y0 = 0
        self.x1 = 0
        self.y1 = 0
        self.initUI()

    def initUI(self):
        self.resize(600, 500)
        self.pix = QPixmap(600, 500) #创建一个QPixmap画板
        self.pix.fill(Qt.white)

    def paintEvent(self, event):
        rect = QRect(self.x0, self.y0, abs(self.x1 - self.x0), abs(self.y1 - self.y0))
        painter = QPainter(self)
        painter.setPen(QPen(Qt.red, 2, Qt.SolidLine))
        painter.drawRect(rect)

    def mousePressEvent(self, event): #重写鼠标按下事件
        if event.button() == Qt.LeftButton:
            self.flag = True
            self.x0 = event.x()
            self.y0 = event.y()

    def mouseMoveEvent(self, event): #重写鼠标移动事件
        if event.buttons() and Qt.LeftButton:
            if self.flag:
                self.x1 = event.x()
                self.y1 = event.y()
                self.update() #更新绘图事件,每次执行update都会触发一次paintEvent(self, event)函数

    def mouseReleaseEvent(self, event): #重写鼠标释放事件
        if event.button() == Qt.LeftButton:
            self.flag = False

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

运行结果：

• 多个矩形

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


class Example(QWidget):
    def __init__(self, parent=None):
        super().__init__(parent)
        self.setWindowTitle('双缓冲绘图')
        self.setCursor(Qt.CrossCursor)  # 设置十字光标
        self.pix = QPixmap()
        self.lastPoint = QPoint()
        self.endPoint = QPoint()
        self.tmpPix = QPixmap()
        self.isDrawing = False
        self.initUI()

    def initUI(self):
        self.resize(600, 500)
        self.pix = QPixmap(600, 500)  # 创建一个QPixmap画板
        self.pix.fill(Qt.white)

    def paintEvent(self, event):
        painter = QPainter(self)
        x = self.lastPoint.x()
        y = self.lastPoint.y()
        w = self.endPoint.x() - x
        h = self.endPoint.y() - y
        if self.isDrawing:
            self.tmpPix = self.pix
            pp = QPainter(self.tmpPix)
            pp.drawRect(x,y,w,h)
            painter.drawPixmap(0, 0, self.tmpPix)
        else:
            pp = QPainter(self.pix)
            pp.drawRect(x,y,w,h)
            painter.drawPixmap(0, 0, self.pix)
    def mousePressEvent(self, event):  # 重写鼠标按下事件
        if event.button() == Qt.LeftButton:
            self.lastPoint = event.pos()
            self.endPoint = self.lastPoint
            self.isDrawing = True

    def mouseReleaseEvent(self, event):  # 重写鼠标释放事件
        if event.button() == Qt.LeftButton:
            self.endPoint = event.pos()
            self.update()
            self.isDrawing = False


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

运行结果：

• 画点

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


class Example(QWidget):
    def __init__(self):
        super().__init__()
        self.initUI()
        self.isdraw = False

    def initUI(self):
        self.setGeometry(300, 300, 280, 170)
        self.setWindowTitle("Points")
        self.show()

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

    def drawPoints(self, qp):
        pen = QPen(Qt.black, 5) #创建画笔类并设置画笔属性，第二个参数设置画笔大小
        qp.setPen(pen)
        if self.isdraw:
            qp.drawPoint(self.point)

    def mousePressEvent(self, event):  # 重写鼠标按下事件
        if event.button() == Qt.LeftButton:
            self.isdraw = True
            self.point = event.pos()

    def mouseReleaseEvent(self, event):  # 重写鼠标释放事件
        if event.button() == Qt.LeftButton:
            self.update()

if __name__ == "__main__":
    app = QApplication(sys.argv)
    ex = Example()
    sys.exit(app.exec_())

 运行结果：