PyQt 程序崩溃 QPixmap 问题

Question

我有一个 PyQt 代码，它不断崩溃给我错误消息QPixmap::fromImage: QPixmap cannot be created without a QGuiApplication QPixmap: Must construct a QGuiApplication before a QPixmap

这是一个相当简单的应用程序，我从一个名为 CameraWidget 的类中读取帧并应用函数 def transform_perspective(self, frame, points) 来获取该帧的变换透视图。我将屏幕分成两部分，右半部分显示相机看到的框架，左半部分显示它的透视变换（为此我从另一个名为 Canvas 的类中获取坐标）。

还有一个问题：左半部分没有占据整个区域。很多部分只是看起来是黑色的。这是一张供您参考的图片

这是一个相当长的程序，所以下面我将包括我认为问题所在的课程。

class TopView(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(TopView, self).__init__(parent)

        self.original_frame = CameraWidget('Abc.ts')

        # Layouts and frames
        self.frame = QtWidgets.QFrame()

        layout = QtWidgets.QVBoxLayout()
        layout.addWidget(self.frame)
        layout.setContentsMargins(0,0,0,0)
        layout.setSpacing(0)
        self.setLayout(layout)

        # frame left
        self.frame_left = QtWidgets.QFrame()

        self.get_frame_thread = Thread(target=self.transform_frame, args=())
        self.get_frame_thread.daemon = True
        self.get_frame_thread.start()

        self.top_view_label = QtWidgets.QLabel()
        self.top_view_label.setScaledContents(True)

        self.layout_left = QtWidgets.QVBoxLayout()
        self.layout_left.addWidget(self.top_view_label)
        self.layout_left.setContentsMargins(0,0,0,0)
        self.layout_left.setSpacing(0)
        self.frame_left.setLayout(self.layout_left)

        # frame right
        self.frame_right = QtWidgets.QFrame()
        self.frame_right.setStyleSheet("background-color: rgb(153, 187, 255)")

        self.video_frame_1 = self.original_frame

        # Create camera widgets
        print('Creating Camera Widgets...')
        self.layout_right = QtWidgets.QVBoxLayout()
        self.layout_right.addWidget(self.video_frame_1)
        self.layout_right.setContentsMargins(5,5,5,5)
        self.frame_right.setLayout(self.layout_right)

        self.layout_inner = QtWidgets.QHBoxLayout()
        self.layout_inner.addWidget(self.frame_left, 50)
        self.layout_inner.addWidget(self.frame_right, 50)
        self.layout_inner.setContentsMargins(0,0,0,0)
        self.layout_inner.setSpacing(0)
        self.frame.setLayout(self.layout_inner)

        self.setLayout(layout)

        sizeObject = QtWidgets.QDesktopWidget().screenGeometry(0)
        self.screen_width = int(0.7*sizeObject.width())
        self.screen_height = int(0.7*sizeObject.height())

    def event(self, e):
        if e.type() in (QtCore.QEvent.Show, QtCore.QEvent.Resize):
            print('')
        return QtWidgets.QWidget.event(self, e)

    def transform_frame(self):
        while True:
            try:
                self.top_view_frame = self.transform_perspective(self.original_frame.get_video_frame(), self.original_frame.canvas.mapped_list)

                h, w, ch = self.top_view_frame.shape
                bytesPerLine = ch * w
                self.img = QtGui.QImage(self.top_view_frame, w, h, bytesPerLine, QtGui.QImage.Format_RGB888)
                self.pix = QtGui.QPixmap.fromImage(self.img)
                if not sip.isdeleted(self.top_view_label):
                    self.top_view_label.setPixmap(self.pix)
            
            except Exception as e:
                print(e)

    def transform_perspective(self, frame, points):
        points = np.float32(points)
        p2 = np.float32([[0, 0], [600, 0], [0, 600], [600, 600]])
        self.matrix = cv2.getPerspectiveTransform(points, p2)
        frame = cv2.warpPerspective(frame, self.matrix, (400, 600))

        return frame

Answer 1

虽然 OP 没有提供 MRE，但很容易注意到错误是它正在禁止的辅助线程中创建 QPixmap。相反，您应该将 QImage 发送到 GUI 线程，并在 GUI 线程中将其转换为 QPixmap：

class ImageProcessor(QtCore.QObject):
    imageChanged = QtCore.pyqtSignal(QtGui.QImage)

    def process(self, video_frame, mapped_list):
        thread = Thread(
            target=self._execute,
            args=(
                video_frame,
                mapped_list,
            ),
        )
        thread.daemon = True
        thread.start()

    def _execute(self, video_frame, mapped_list):
        top_view_frame = self.transform_perspective(video_frame, mapped_list)
        qimage = self.convert_np_to_qimage(top_view_frame)
        self.imageChanged.emit(qimage.copy())

    def transform_perspective(self, frame, points):
        points = np.float32(points)
        p2 = np.float32([[0, 0], [600, 0], [0, 600], [600, 600]])
        matrix = cv2.getPerspectiveTransform(points, p2)
        frame = cv2.warpPerspective(frame, matrix, (400, 600))
        return frame

    def convert_np_to_qimage(self, array):
        h, w, ch = array.shape
        bytesPerLine = ch * w
        img = QtGui.QImage(array.data, w, h, bytesPerLine, QtGui.QImage.Format_RGB888)
        return img.copy()


class TopView(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(TopView, self).__init__(parent)

        self.original_frame = CameraWidget("Abc.ts")

        # Layouts and frames
        self.frame = QtWidgets.QFrame()

        layout = QtWidgets.QVBoxLayout(self)
        layout.addWidget(self.frame)
        layout.setContentsMargins(0, 0, 0, 0)
        layout.setSpacing(0)

        # frame left
        self.frame_left = QtWidgets.QFrame()

        self.top_view_label = QtWidgets.QLabel()
        self.top_view_label.setScaledContents(True)

        self.layout_left = QtWidgets.QVBoxLayout(self.frame_left)
        self.layout_left.addWidget(self.top_view_label)
        self.layout_left.setContentsMargins(0, 0, 0, 0)
        self.layout_left.setSpacing(0)

        # frame right
        self.frame_right = QtWidgets.QFrame()
        self.frame_right.setStyleSheet("background-color: rgb(153, 187, 255)")

        self.video_frame_1 = self.original_frame

        # Create camera widgets
        print("Creating Camera Widgets...")
        self.layout_right = QtWidgets.QVBoxLayout(self.frame_right)
        self.layout_right.addWidget(self.video_frame_1)
        self.layout_right.setContentsMargins(5, 5, 5, 5)

        self.layout_inner = QtWidgets.QHBoxLayout(self.frame)
        self.layout_inner.addWidget(self.frame_left, 50)
        self.layout_inner.addWidget(self.frame_right, 50)
        self.layout_inner.setContentsMargins(0, 0, 0, 0)
        self.layout_inner.setSpacing(0)

        sizeObject = QtWidgets.QDesktopWidget().screenGeometry(0)
        self.screen_width = int(0.7 * sizeObject.width())
        self.screen_height = int(0.7 * sizeObject.height())

        self.processor = ImageProcessor()
        self.processor.imageChanged.connect(self.handle_imageChanged)
        self.launch_processor()

    def launch_processor(self):
        self.processor.process(
            self.original_frame.get_video_frame(),
            self.original_frame.canvas.mapped_list,
        )

    @QtCore.pyqtSlot(QtGui.QImage)
    def handle_imageChanged(self, qimage):
        qpixmap = QtGui.QPixmap.fromImage(qimage)
        self.top_view_label.setPixmap(qpixmap)
        QtCore.QTimer.singleShot(0, self.launch_processor)