PyQt

Question

我正在使用 Windows、Python 3.6、OpenCV3 和 PyQt5。我有一个主 window，它有两个 QLabel 小部件（label1 和 label2）。我想将不同的视频文件拖放到两个 QLabel 小部件中。我的脚本显示了两个视频文件中每一个的第一帧。

如果我将文件拖到label1到label2然后释放鼠标，然后第一个视频帧显示在label1（不是什么我要）。
如果我将文件拖到label1到label2然后释放鼠标，然后第一个视频帧显示在 label2（所需效果).
如果我将文件拖到label2到label1然后释放鼠标，然后第一个视频帧显示在 label1（期望效果).

我希望在 label2 中显示视频，无论我将文件拖动到周围还是到 label1.建议？

import sys, cv2
from PyQt5.QtWidgets import QApplication, QLabel, QFrame, QMainWindow
from PyQt5.QtGui import QImage, QPixmap
from PyQt5.QtCore import Qt

class Example(QMainWindow):

    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):

        self.setGeometry(200, 300, 800, 600)
        self.setAcceptDrops(True)
        self.setMouseTracking(True)

        self.label1 = QLabel(self)
        self.label1.move(10, 10)
        self.label1.resize(780, 280)
        self.label1.setFrameShape(QFrame.Box)
        self.label1.setAcceptDrops(True)

        self.label2 = QLabel(self)
        self.label2.move(10, 310)
        self.label2.resize(780, 280)
        self.label2.setFrameShape(QFrame.Box)
        self.label2.setAcceptDrops(True)

        self.label1.setText("Label 1")
        self.label2.setText("Label 2")
        self.show()

    def dragEnterEvent(self, e):
        if e.mimeData().hasUrls:
            e.accept()
        else:
            e.ignore()

    def dropEvent(self, e):
        if e.mimeData().hasUrls:
            e.accept()
            for url in e.mimeData().urls():
                if self.label1.underMouse():
                    fname = str(url.toLocalFile())
                    self.openFile1(fname)
                elif self.label2.underMouse():
                    fname = str(url.toLocalFile())
                    self.openFile2(fname)
        else:
            e.ignore()

    def openFile1(self, filename):
        self.cap1 = cv2.VideoCapture(str(filename))
        self.cap1.set(cv2.CAP_PROP_POS_FRAMES, 0)
        width = self.cap1.get(cv2.CAP_PROP_FRAME_WIDTH)
        height = self.cap1.get(cv2.CAP_PROP_FRAME_HEIGHT)
        ret, frame = self.cap1.read()
        if ret == True:
            frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
            img = QImage(frame, frame.shape[1], frame.shape[0], QImage.Format_RGB888)
            pix = QPixmap.fromImage(img)
            pix = self.scalePix(self.label1, pix, width, height)
            self.label1.setPixmap(pix)

    def openFile2(self, filename):
        self.cap2 = cv2.VideoCapture(str(filename))
        self.cap2.set(cv2.CAP_PROP_POS_FRAMES, 0)
        width = self.cap2.get(cv2.CAP_PROP_FRAME_WIDTH)
        height = self.cap2.get(cv2.CAP_PROP_FRAME_HEIGHT)
        ret, frame = self.cap2.read()
        if ret == True:
            frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
            img = QImage(frame, frame.shape[1], frame.shape[0], QImage.Format_RGB888)
            pix = QPixmap.fromImage(img)
            pix = self.scalePix(self.label1, pix, width, height)
            self.label2.setPixmap(pix)

    def scalePix(self, label, p, width, height):
        window_width = label.width()
        ratio = height / width
        window_height = int(ratio * window_width)
        window_height = label.height() 
        window_width = int(1 / ratio * window_height)
        p = p.scaledToWidth(window_width, Qt.SmoothTransformation)
        p = p.scaledToHeight(window_height, Qt.SmoothTransformation)
        return p

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

Answer 1

文档表明 underMouse() 可能会在拖放过程中失败：

bool QWidget::underMouse() const

Returns true if the widget is under the mouse cursor; otherwise returns false.

This value is not updated properly during drag and drop operations.

所以最好不要使用，相反我们可以创建一个实现拖放的自定义QLabel：

import sys, cv2
from PyQt5 import QtCore, QtGui, QtWidgets

class OpenCVLabel(QtWidgets.QLabel):
    def __init__(self, *args, **kwargs):
        super(OpenCVLabel, self).__init__(*args, **kwargs)
        self.setFrameShape(QtWidgets.QFrame.Box)
        self.setAcceptDrops(True)

    def dragEnterEvent(self, e):
        if e.mimeData().hasUrls():
            e.accept()
        else:
            e.ignore()

    def dropEvent(self, e):
        if e.mimeData().hasUrls():
            e.accept()
            for url in e.mimeData().urls():
                self.openFile(url.toLocalFile())
        else:
            e.ignore()

    def openFile(self, filename):
        cap = cv2.VideoCapture(str(filename))
        cap.set(cv2.CAP_PROP_POS_FRAMES, 0)
        width = cap.get(cv2.CAP_PROP_FRAME_WIDTH)
        height = cap.get(cv2.CAP_PROP_FRAME_HEIGHT)
        ret, frame = cap.read()
        if ret:
            frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
            img = QtGui.QImage(frame, frame.shape[1], frame.shape[0], QtGui.QImage.Format_RGB888)
            pix = QtGui.QPixmap.fromImage(img)
            pix = pix.scaled(self.size(), QtCore.Qt.KeepAspectRatio, QtCore.Qt.SmoothTransformation)
            self.setPixmap(pix)

class Example(QtWidgets.QMainWindow):
    def __init__(self):
        super().__init__()
        self.initUI()

    def initUI(self):
        label1 = OpenCVLabel("label1")
        label2 = OpenCVLabel("label2")
        central_widget = QtWidgets.QWidget()
        self.setCentralWidget(central_widget)
        lay = QtWidgets.QVBoxLayout(central_widget)
        lay.addWidget(label1)
        lay.addWidget(label2)
        self.resize(780, 560)

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

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