python - 无法将帧从相机流式传输到 QML

Question

我正在使用 PyQT5。我想使用 QQuickPaintedItem 将帧从 Opencv 发送到 QML。我在这里写了一个示例实现。我似乎无法找到为什么仅在加载应用程序时调用 paint 事件一次。它仅绘制从相机到 QML 组件的一帧，并且 self.update() 未调用绘制事件。

from OpenGL import GL
from PyQt5.QtQuick import QQuickPaintedItem, QQuickView
from PyQt5.QtGui import QPainter, QPixmap, QImage
from PyQt5.QtQml import qmlRegisterType
import sys
from PyQt5.QtGui import QColor
from PyQt5.QtCore import QUrl,QObject,pyqtSignal
import cv2.cv2 as cv2
from PyQt5.QtWidgets import QApplication


class ImageWriter(QQuickPaintedItem):

    cam_frame = None

    def __init__(self, *args, **kwargs):
        super(ImageWriter, self).__init__(*args, **kwargs)        
        self.setRenderTarget(QQuickPaintedItem.FramebufferObject) 

    def paint(self, painter):
        print(ImageWriter.cam_frame)
        painter.drawPixmap(0,0,ImageWriter.cam_frame)

    def update_frame(self,frame):
        frame = cv2.resize(frame, (700, 500), cv2.INTER_AREA)
        frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGBA)
        frame = QImage(frame, frame.shape[1], frame.shape[0], 17)
        ImageWriter.cam_frame = QPixmap.fromImage(frame) 
        self.update()

def get_frames(app):
    cap = cv2.VideoCapture(0)
    num = 0
    imgw = ImageWriter()
    while True:
        while num != 30:
            _ , bgframe = cap.read()
            num += 1
        _ , frame = cap.read()
        imgw.update_frame(frame)            
        print("get frames") 
        app.processEvents()


if __name__ == '__main__':
    app = QApplication(sys.argv) 
    qmlRegisterType(ImageWriter, "imageWriter", 1, 0, "ImageWriter")
    view = QQuickView()
    view.setSource(QUrl('test.qml'))
    rootObject = view.rootObject()
    view.show()
    get_frames(app)
    sys.exit(app.exec_())

这是我为此编写的 QML，

import QtQuick 2.0
import imageWriter 1.0

Item {
    width: 800
    height: 600

    ImageWriter  {
        id : imageWriter
        width : 800
        height : 600
    }

}

我不太明白为什么 self.update() 没有调用绘画事件。我不能使用 QWidgets，我必须使用它。我在这里遗漏了什么吗？

Answer 1

问题是由 2 个 ImageWriter 对象引起的，一个在 imgw = ImageWriter() 中创建，另一个在 QML 中创建，您可以通过在 .py 中的 .qml 中添加打印来组合它:

*.py

def get_frames(app):
    cap = cv2.VideoCapture(0)
    num = 0
    imgw = ImageWriter()
    print("Python:", imgw)
    ...

*.qml

...
Component.onCompleted: console.log("QML:", imageWriter)
...

输出:

qml: >>>> ImageWriter(0x55bf2927e770)
Python:  <__main__.ImageWriter object at 0x7fce8e4ff798>

如您所见，有 2 个对象指向不同的内存地址，因此一个可能的解决方案是使用 this library 创建一个单例。 :

from OpenGL import GL
import sys
from PyQt5 import QtCore, QtGui, QtQml, QtQuick
import cv2

try: from PyQt5.QtCore import pyqtWrapperType
except ImportError:
    from sip import wrappertype as pyqtWrapperType

class Singleton(pyqtWrapperType, type):
    def __init__(cls, name, bases, dict):
        super().__init__(name, bases, dict)
        cls.instance=None

    def __call__(cls,*args,**kw):
        if cls.instance is None:
            cls.instance=super().__call__(*args, **kw)
        return cls.instance


class ImageWriter(QtQuick.QQuickPaintedItem, metaclass=Singleton):

    def __init__(self, *args, **kwargs):
        super(ImageWriter, self).__init__(*args, **kwargs)        
        self.setRenderTarget(QtQuick.QQuickPaintedItem.FramebufferObject) 
        self.cam_frame = QtGui.QImage()

    def paint(self, painter):
        painter.drawImage(0, 0, self.cam_frame)

    def update_frame(self,frame):
        frame = cv2.resize(frame, (700, 500), cv2.INTER_AREA)
        frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGBA)
        frame = QtGui.QImage(frame, frame.shape[1], frame.shape[0], 17)
        self.cam_frame = frame.copy()
        self.update()

def get_frames(app):
    cap = cv2.VideoCapture(0)
    num = 0
    imgw = ImageWriter()
    while True:
        while num != 30:
            _ , bgframe = cap.read()
            num += 1
        ret, frame = cap.read()
        if ret:
            imgw.update_frame(frame)            
            #print("get frames") 
            app.processEvents()


if __name__ == '__main__':
    app = QtGui.QGuiApplication(sys.argv) 
    QtQml.qmlRegisterType(ImageWriter, "imageWriter", 1, 0, "ImageWriter")
    view = QtQuick.QQuickView()
    view.setSource(QtCore.QUrl('test.qml'))
    rootObject = view.rootObject()
    view.show()
    get_frames(app)
    sys.exit(app.exec_())

通过上面的方法应该可以获取图像我认为有更好的方法，稍后我会展示一个更好的选择。

---

使用 my previous answer作为基础，我创建了一个使用 opencv 实现相机处理程序的模块，以及一个查看器和一个允许添加过滤器的通用类，为此，该项目必须具有以下结构

├── main.py
├── main.qml
└── PyCVQML
    ├── cvcapture.py
    ├── cvitem.py
    └── __init__.py

PyCVQML/cvcapture.py

import numpy as np
import threading

import cv2

from PyQt5 import QtCore, QtGui, QtQml

gray_color_table = [QtGui.qRgb(i, i, i) for i in range(256)]


class CVAbstractFilter(QtCore.QObject):
    def process_image(self, src):
        dst = src
        return dst


class CVCapture(QtCore.QObject):
    started = QtCore.pyqtSignal()
    imageReady = QtCore.pyqtSignal()
    indexChanged = QtCore.pyqtSignal()

    def __init__(self, parent=None):
        super(CVCapture, self).__init__(parent)
        self._image = QtGui.QImage()
        self._index = 0

        self.m_videoCapture = cv2.VideoCapture()
        self.m_timer = QtCore.QBasicTimer()
        self.m_filters = []
        self.m_busy = False

    @QtCore.pyqtSlot()
    @QtCore.pyqtSlot(int)
    def start(self, *args):
        if args:
            self.setIndex(args[0])
        self.m_videoCapture.release()
        self.m_videoCapture = cv2.VideoCapture(self._index)
        if self.m_videoCapture.isOpened():
            self.m_timer.start(0, self)
            self.started.emit()

    @QtCore.pyqtSlot()
    def stop(self):
        self.m_timer.stop()

    def timerEvent(self, e):
        if e.timerId() != self.m_timer.timerId(): return
        ret, frame = self.m_videoCapture.read()
        if not ret:
            self.m_timer.stop()
            return
        if not self.m_busy:
            threading.Thread(target=self.process_image, args=(np.copy(frame),)).start()

    @QtCore.pyqtSlot(np.ndarray)
    def process_image(self, frame):
        self.m_busy = True
        for f in self.m_filters:
            frame = f.process_image(frame)
        image = CVCapture.ToQImage(frame)
        self.m_busy = False
        QtCore.QMetaObject.invokeMethod(self,
                                        "setImage",
                                        QtCore.Qt.QueuedConnection,
                                        QtCore.Q_ARG(QtGui.QImage, image))

    @staticmethod
    def ToQImage(im):
        if im is None:
            return QtGui.QImage()
        if im.dtype == np.uint8:
            if len(im.shape) == 2:
                qim = QtGui.QImage(im.data, im.shape[1], im.shape[0], im.strides[0], QtGui.QImage.Format_Indexed8)
                qim.setColorTable(gray_color_table)
                return qim.copy()

            elif len(im.shape) == 3:
                if im.shape[2] == 3:
                    w, h, _ = im.shape
                    rgb_image = cv2.cvtColor(im, cv2.COLOR_BGR2RGB)
                    flip_image = cv2.flip(rgb_image, 1)
                    qim = QtGui.QImage(flip_image.data, h, w, QtGui.QImage.Format_RGB888)
                    return qim.copy()
        return QtGui.QImage()

    def image(self):
        return self._image

    @QtCore.pyqtSlot(QtGui.QImage)
    def setImage(self, image):
        if self._image == image: return
        self._image = image
        self.imageReady.emit()

    def index(self):
        return self._index

    def setIndex(self, index):
        if self._index == index: return
        self._index = index
        self.indexChanged.emit()

    @QtCore.pyqtProperty(QtQml.QQmlListProperty)
    def filters(self):
        return QtQml.QQmlListProperty(CVAbstractFilter, self, self.m_filters)

    image = QtCore.pyqtProperty(QtGui.QImage, fget=image, notify=imageReady)
    index = QtCore.pyqtProperty(int, fget=index, fset=setIndex, notify=indexChanged)

PyCVQML/cvitem.py

from PyQt5 import QtCore, QtGui, QtQuick


class CVItem(QtQuick.QQuickPaintedItem):
    imageChanged = QtCore.pyqtSignal()

    def __init__(self, parent=None):
        super(CVItem, self).__init__(parent)
        # self.setRenderTarget(QtQuick.QQuickPaintedItem.FramebufferObject)
        self.m_image = QtGui.QImage()

    def paint(self, painter):
        if self.m_image.isNull(): return
        image = self.m_image.scaled(self.size().toSize())
        painter.drawImage(QtCore.QPoint(), image)

    def image(self):
        return self.m_image

    def setImage(self, image):
        if self.m_image == image: return
        self.m_image = image
        self.imageChanged.emit()
        self.update()

    image = QtCore.pyqtProperty(QtGui.QImage, fget=image, fset=setImage, notify=imageChanged)

PyCVQML/__init__.py

from PyQt5 import QtQml

from .cvcapture import CVCapture, CVAbstractFilter
from .cvitem import CVItem


def registerTypes(uri = "PyCVQML"):
    QtQml.qmlRegisterType(CVCapture, uri, 1, 0, "CVCapture")
    QtQml.qmlRegisterType(CVItem, uri, 1, 0, "CVItem")

然后在 main.py 中使用它，我添加了 2 个示例过滤器，因为此 CVCapture 具有将过滤器传递给它的 filters 属性，并且他们将按照建立的顺序执行。要实现新的过滤器，您必须继承自 CVAbstractFilter 并覆盖 process_image() 方法，该方法将图像作为 np.ndarray 接收并应返回过滤后的结果。

主.py

import cv2
import numpy as np
from PyQt5 import QtGui, QtCore, QtQuick, QtQml
import PyCVQML


def max_rgb_filter(image):
    # split the image into its BGR components
    (B, G, R) = cv2.split(image)

    # find the maximum pixel intensity values for each
    # (x, y)-coordinate,, then set all pixel values less
    # than M to zero
    M = np.maximum(np.maximum(R, G), B)
    R[R < M] = 0
    G[G < M] = 0
    B[B < M] = 0

    # merge the channels back together and return the image
    return cv2.merge([B, G, R])


def rgb_to_gray(image):
    gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
    return gray


class MaxRGBFilter(PyCVQML.CVAbstractFilter):
    def process_image(self, src):
        return max_rgb_filter(src)


class GrayFilter(PyCVQML.CVAbstractFilter):
    def process_image(self, src):
        return rgb_to_gray(src)


if __name__ == '__main__':
    import os
    import sys

    app = QtGui.QGuiApplication(sys.argv)

    PyCVQML.registerTypes()
    QtQml.qmlRegisterType(MaxRGBFilter, "Filters", 1, 0, "MaxRGBFilter")
    QtQml.qmlRegisterType(GrayFilter, "Filters", 1, 0, "GrayFilter")

    view = QtQuick.QQuickView()
    view.setTitle("PyCVQML Example")
    dir_path = os.path.dirname(os.path.realpath(__file__)
    view.setSource(QtCore.QUrl.fromLocalFile(QtCore.QDir(dir_path).absoluteFilePath("main.qml")))
    view.show()
    sys.exit(app.exec_())

ma​​in.qml

import QtQuick 2.0
import PyCVQML 1.0
import Filters 1.0

Item {
    width: 800
    height: 600

    CVItem  {
        id: imageWriter
        anchors.fill: parent
        image: capture.image
    }

    MaxRGBFilter{
        id: max_rgb_filter
    }
    GrayFilter{
        id: gray_filter
    }

    CVCapture{
        id: capture
        index: 0
        filters: [max_rgb_filter, gray_filter]
        Component.onCompleted: capture.start()
    }
}