问题描述
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。我将屏幕分成两个相等的部分，右半部分显示相机看到的帧，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。很多部分只是出现黑色。这是一张图片供您参考
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)
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)
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)
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)
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,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,points):
points = np.float32(points)
p2 = np.float32([[0,0],[600,[0,600],600]])
self.matrix = cv2.getPerspectiveTransform(points,p2)
frame = cv2.warpPerspective(frame,self.matrix,(400,600))
return frame
解决方法
虽然 OP 不提供 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，然后在 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,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,[0,600],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,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)
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)
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)
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)
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)