嘗試在 PyQt QLabel 上繪制矩形時未顯示圖像

Question

嘗試在QLabel圖像上繪制矩形時，圖像不顯示。 我希望能夠在照片上繪制一個矩形並能夠保留該矩形/隱藏它。 這是我在這里檢查建議后嘗試的：

• 如何在PyQt5中通過拖放繪制矩形並調整其形狀

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

如果您在不通過 super 調用父級實現的情況下覆蓋一個方法，則將不會使用先前的行為，這就是您的情況： QLabel 的正常行為是繪制但覆蓋而不是調用 super it was removed 。 解決辦法是：

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))