PyQT5绘图

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


class Drawing(QWidget):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.setWindowTitle("绘图应用")
        self.pix = QPixmap()
        self.lastPoint = QPoint()
        self.endPoint = QPoint()
        self.initUi()

    def initUi(self):
        self.resize(600, 600)
        # 画布大小为400*400，背景为白色
        self.pix = QPixmap(600, 600)
        self.pix.fill(Qt.white)

    def paintEvent(self, event):
        pp = QPainter(self.pix)
        # 根据鼠标指针前后两个位置绘制直线
        pp.drawLine(self.lastPoint, self.endPoint)
        # 让前一个坐标值等于后一个坐标值，
        # 这样就能实现画出连续的线
        self.lastPoint = self.endPoint
        painter = QPainter(self)
        painter.drawPixmap(0, 0, self.pix)

    def mousePressEvent(self, event):
        if event.button() == Qt.LeftButton:
            self.lastPoint = event.pos()

    def mouseMoveEvent(self, event):
        if event.buttons() and Qt.LeftButton:
            self.endPoint = event.pos()
            self.update()

    def mouseReleaseEvent(self, event):
        # 鼠标左键释放
        if event.button() == Qt.LeftButton:
            self.endPoint == event.pos()
            # 进行重新绘制
            self.update()


if __name__ == "__main__":
    app = QApplication(sys.argv)
    main = Drawing()
    main.show()
    sys.exit(app.exec_())