【发布时间】：2019-03-26 02:47:48
【问题描述】：
我是 PyQt 的新手，我正在尝试创建一个视频播放器来截取它检索到的当前帧。我实现了this 方法来抓取视频帧以截取屏幕截图并将其添加到videoplayer GUI。以下是 GUI 的基本外观：
我使用以下代码在VideoWindow class 中为屏幕截图操作创建了一个触发器：
screenshotAction = QAction(QIcon('screenshot.png'), '&Screenshot', self)
screenshotAction.setShortcut('Ctrl+S')
screenshotAction.setStatusTip('Screenshot scenes')
screenshotAction.triggered.connect(self.screenshotCall)
然后我实现了VideoFrameGrabber class，并在截图函数中调用它：
def screenshotCall(self):
#Call video frame grabber
self.grabber = VideoFrameGrabber(self.videoWidget, self)
self.mediaPlayer.setVideoOutput(self.grabber)
self.grabber.frameAvailable.connect(self.process_frame)
self.mediaPlayer.setVideoOutput(self.videoWidget)
完整代码：
# PyQt5 Video player
#!/usr/bin/env python
from PyQt5.QtCore import QDir, Qt, QUrl, pyqtSignal, QPoint, QRect, QObject
from PyQt5.QtMultimedia import QMediaContent, QMediaPlayer, QVideoFrame, QAbstractVideoSurface, QAbstractVideoBuffer, QVideoSurfaceFormat
from PyQt5.QtMultimediaWidgets import QVideoWidget
from PyQt5.QtWidgets import (QApplication, QFileDialog, QHBoxLayout, QLabel,
QPushButton, QSizePolicy, QSlider, QStyle, QVBoxLayout, QWidget)
from PyQt5.QtWidgets import QMainWindow,QWidget, QPushButton, QAction
from PyQt5.QtGui import QIcon, QPainter, QImage
import sys
import os
import os.path as osp
class VideoFrameGrabber(QAbstractVideoSurface):
frameAvailable = pyqtSignal(QImage)
def __init__(self, widget: QWidget, parent: QObject):
super().__init__(parent)
self.widget = widget
def supportedPixelFormats(self, handleType):
return [QVideoFrame.Format_ARGB32, QVideoFrame.Format_ARGB32_Premultiplied,
QVideoFrame.Format_RGB32, QVideoFrame.Format_RGB24, QVideoFrame.Format_RGB565,
QVideoFrame.Format_RGB555, QVideoFrame.Format_ARGB8565_Premultiplied,
QVideoFrame.Format_BGRA32, QVideoFrame.Format_BGRA32_Premultiplied, QVideoFrame.Format_BGR32,
QVideoFrame.Format_BGR24, QVideoFrame.Format_BGR565, QVideoFrame.Format_BGR555,
QVideoFrame.Format_BGRA5658_Premultiplied, QVideoFrame.Format_AYUV444,
QVideoFrame.Format_AYUV444_Premultiplied, QVideoFrame.Format_YUV444,
QVideoFrame.Format_YUV420P, QVideoFrame.Format_YV12, QVideoFrame.Format_UYVY,
QVideoFrame.Format_YUYV, QVideoFrame.Format_NV12, QVideoFrame.Format_NV21,
QVideoFrame.Format_IMC1, QVideoFrame.Format_IMC2, QVideoFrame.Format_IMC3,
QVideoFrame.Format_IMC4, QVideoFrame.Format_Y8, QVideoFrame.Format_Y16,
QVideoFrame.Format_Jpeg, QVideoFrame.Format_CameraRaw, QVideoFrame.Format_AdobeDng]
def isFormatSupported(self, format):
imageFormat = QVideoFrame.imageFormatFromPixelFormat(format.pixelFormat())
size = format.frameSize()
return imageFormat != QImage.Format_Invalid and not size.isEmpty() and \
format.handleType() == QAbstractVideoBuffer.NoHandle
def start(self, format: QVideoSurfaceFormat):
imageFormat = QVideoFrame.imageFormatFromPixelFormat(format.pixelFormat())
size = format.frameSize()
if imageFormat != QImage.Format_Invalid and not size.isEmpty():
self.imageFormat = imageFormat
self.imageSize = size
self.sourceRect = format.viewport()
super().start(format)
self.widget.updateGeometry()
self.updateVideoRect()
return True
else:
return False
def stop(self):
self.currentFrame = QVideoFrame()
self.targetRect = QRect()
super().stop()
self.widget.update()
def present(self, frame):
if frame.isValid():
cloneFrame = QVideoFrame(frame)
cloneFrame.map(QAbstractVideoBuffer.ReadOnly)
image = QImage(cloneFrame.bits(), cloneFrame.width(), cloneFrame.height(),
QVideoFrame.imageFormatFromPixelFormat(cloneFrame.pixelFormat()))
self.frameAvailable.emit(image) # this is very important
cloneFrame.unmap()
if self.surfaceFormat().pixelFormat() != frame.pixelFormat() or \
self.surfaceFormat().frameSize() != frame.size():
self.setError(QAbstractVideoSurface.IncorrectFormatError)
self.stop()
return False
else:
self.currentFrame = frame
self.widget.repaint(self.targetRect)
return True
def updateVideoRect(self):
size = self.surfaceFormat().sizeHint()
size.scale(self.widget.size().boundedTo(size), Qt.KeepAspectRatio)
self.targetRect = QRect(QPoint(0, 0), size)
self.targetRect.moveCenter(self.widget.rect().center())
def paint(self, painter):
if self.currentFrame.map(QAbstractVideoBuffer.ReadOnly):
oldTransform = self.painter.transform()
if self.surfaceFormat().scanLineDirection() == QVideoSurfaceFormat.BottomToTop:
self.painter.scale(1, -1)
self.painter.translate(0, -self.widget.height())
image = QImage(self.currentFrame.bits(), self.currentFrame.width(), self.currentFrame.height(),
self.currentFrame.bytesPerLine(), self.imageFormat)
self.painter.drawImage(self.targetRect, image, self.sourceRect)
self.painter.setTransform(oldTransform)
self.currentFrame.unmap()
class VideoWindow(QMainWindow):
def __init__(self, parent=None):
super(VideoWindow, self).__init__(parent)
self.setWindowTitle("PyQt Video Player Widget")
self.counter = 0
self.mediaPlayer = QMediaPlayer(None, QMediaPlayer.VideoSurface)
self.videoWidget = QVideoWidget()
self.videoFrame = QVideoFrame()
self.playButton = QPushButton()
self.playButton.setEnabled(False)
self.playButton.setIcon(self.style().standardIcon(QStyle.SP_MediaPlay))
self.playButton.clicked.connect(self.play)
self.positionSlider = QSlider(Qt.Horizontal)
self.positionSlider.setRange(0, 0)
self.positionSlider.sliderMoved.connect(self.setPosition)
self.errorLabel = QLabel()
self.errorLabel.setSizePolicy(QSizePolicy.Preferred,
QSizePolicy.Maximum)
# Create new action
openAction = QAction(QIcon('open.png'), '&Open', self)
openAction.setShortcut('Ctrl+O')
openAction.setStatusTip('Open video')
openAction.triggered.connect(self.openFile)
# Create exit action
exitAction = QAction(QIcon('quit.png'), '&Exit', self)
exitAction.setShortcut('Ctrl+Q')
exitAction.setStatusTip('Exit application')
exitAction.triggered.connect(self.exitCall)
screenshotAction = QAction(QIcon('screenshot.png'), '&Screenshot', self)
screenshotAction.setShortcut('Ctrl+S')
screenshotAction.setStatusTip('Screenshot scenes')
screenshotAction.triggered.connect(self.screenshotCall)
# Create menu bar and add action
menuBar = self.menuBar()
fileMenu = menuBar.addMenu('&File')
#fileMenu.addAction(newAction)
fileMenu.addAction(openAction)
fileMenu.addAction(screenshotAction)
fileMenu.addAction(exitAction)
# Create a widget for window contents
wid = QWidget(self)
self.setCentralWidget(wid)
# Create layouts to place inside widget
controlLayout = QHBoxLayout()
controlLayout.setContentsMargins(0, 0, 0, 0)
controlLayout.addWidget(self.playButton)
controlLayout.addWidget(self.positionSlider)
layout = QVBoxLayout()
layout.addWidget(self.videoWidget)
layout.addLayout(controlLayout)
layout.addWidget(self.errorLabel)
# Set widget to contain window contents
wid.setLayout(layout)
self.mediaPlayer.setVideoOutput(self.videoWidget)
self.mediaPlayer.stateChanged.connect(self.mediaStateChanged)
self.mediaPlayer.positionChanged.connect(self.positionChanged)
self.mediaPlayer.durationChanged.connect(self.durationChanged)
self.mediaPlayer.error.connect(self.handleError)
def openFile(self):
fileName, _ = QFileDialog.getOpenFileName(self, "Open Movie",
QDir.homePath())
self.path = osp.dirname(str(fileName))
if fileName != '':
self.mediaPlayer.setMedia(
QMediaContent(QUrl.fromLocalFile(fileName)))
self.playButton.setEnabled(True)
def exitCall(self):
sys.exit(app.exec_())
def screenshotCall(self):
#Call video frame grabber
self.grabber = VideoFrameGrabber(self.videoWidget, self)
self.mediaPlayer.setVideoOutput(self.grabber)
self.mediaPlayer.pause()
self.grabber.frameAvailable.connect(self.process_frame)
self.errorLabel.setText("Taking a screenshot of image "+str(self.counter)+" ....")
self.mediaPlayer.play()
self.mediaPlayer.setVideoOutput(self.videoWidget)
def play(self):
if self.mediaPlayer.state() == QMediaPlayer.PlayingState:
self.mediaPlayer.pause()
else:
self.mediaPlayer.play()
def mediaStateChanged(self, state):
if self.mediaPlayer.state() == QMediaPlayer.PlayingState:
self.playButton.setIcon(
self.style().standardIcon(QStyle.SP_MediaPause))
else:
self.playButton.setIcon(
self.style().standardIcon(QStyle.SP_MediaPlay))
def positionChanged(self, position):
self.positionSlider.setValue(position)
def durationChanged(self, duration):
self.positionSlider.setRange(0, duration)
def setPosition(self, position):
self.mediaPlayer.setPosition(position)
def handleError(self):
self.playButton.setEnabled(False)
self.errorLabel.setText("Error: " + self.mediaPlayer.errorString())
def process_frame(self, image):
# Save image here
filename = "screenshot" + str(self.counter).zfill(6)
self.path = 'C:/Desktop/temp'
image.save(self.path+'/{}.png'.format(str(filename)))
self.counter = self.counter+1
if __name__ == '__main__':
app = QApplication(sys.argv)
player = VideoWindow()
player.resize(720, 480)
player.show()
sys.exit(app.exec_())
但是，每当我尝试截屏时，视频显示都会变黑。根据音频，视频仍在播放，但从截取屏幕截图的那一刻起，在整个视频期间，当前显示始终保持黑色。当播放器暂停和仍在播放时都会发生这种情况。我认为是因为self.mediaPlayer.setVideoOutput(self.grabber) 行，因为它用抓取器覆盖了屏幕上的当前显示。
我试过回调videoWidget并将其设置为抓取帧后的视频输出，但它似乎覆盖了抓取器并且根本不产生任何屏幕截图。
有没有办法让我在截屏的同时仍然在 GUI 上显示视频？
【问题讨论】：
-
@eyllanesc 感谢您指出这一点。我希望新的编辑更容易理解。
-
你了解什么是 MCVE 吗？如果您不知道它是什么，请阅读链接
标签： python pyqt5 qmediaplayer qvideowidget