尝试在PyQt QLabel上绘制矩形时图像未显示

Question

[尝试在QLabel图像上绘制矩形时，图像不显示。我希望能够在照片上绘制一个矩形，并能够保持该矩形/隐藏它。这是我在这里查看建议后尝试的内容：

• How to draw a rectangle and adjust its shape by drag and drop in PyQt5

from PyQt5.QtGui import QPixmap, QImage, QPainter, QBrush, QColor
from PyQt5.QtWidgets import QMainWindow, QApplication, QDesktopWidget, QVBoxLayout, QWidget, QLabel
from PyQt5.QtCore import QPoint, QRect
import sys
import cv2


class TestRect(QLabel):
    def __init__(self):
        super().__init__()
        self.begin = QPoint()
        self.end = QPoint()

    def paintEvent(self, event):
        qp = QPainter(self)
        br = QBrush(QColor(100, 10, 10, 40))
        qp.setBrush(br)
        qp.drawRect(QRect(self.begin, self.end))

    def mousePressEvent(self, event):
        self.begin = event.pos()
        self.end = event.pos()
        self.update()

    def mouseMoveEvent(self, event):
        self.end = event.pos()
        self.update()

    def mouseReleaseEvent(self, event):
        self.begin = event.pos()
        self.end = event.pos()
        self.update()


class TestWindow(QMainWindow):
    def __init__(self):
        super().__init__()
        self.current_image = None
        win_rectangle = self.frameGeometry()
        center_point = QDesktopWidget().availableGeometry().center()
        win_rectangle.moveCenter(center_point)
        self.move(win_rectangle.topLeft())
        self.main_layout = QVBoxLayout()
        self.central_widget = QWidget(self)
        self.test_image()
        self.show()

    def test_image(self):
        self.central_widget.setLayout(self.main_layout)
        self.setCentralWidget(self.central_widget)
        image = TestRect()
        self.main_layout.addWidget(image)
        uploaded = cv2.imread('test.jpg')
        resized = cv2.resize(uploaded, (500, 500))
        height, width = 500, 500
        self.current_image = QImage(resized, height, width, QImage.Format_RGB888)
        image.setPixmap(QPixmap(self.current_image))


if __name__ == '__main__':
    test = QApplication(sys.argv)
    test_window = TestWindow()
    sys.exit(test.exec_())

Answer 1

如果覆盖一个方法而不通过super调用父方法的实现，那么将不使用以前的行为，这就是您所遇到的情况：QLabel的正常行为是绘制但覆盖而不是调用super，它是被淘汰。解决方案是：

def paintEvent(self, event):
    super().paintEvent(event)
    qp = QPainter(self)
    br = QBrush(QColor(100, 10, 10, 40))
    qp.setBrush(br)
    qp.drawRect(QRect(self.begin, self.end))