无法将帧从摄像机传输到QML

Question

我用的是PyQT5。我想用QQuickPaintedItem将帧从Opencv发送到QML。我在这里编写了一个示例实现。为什么只有一次调用事件时我才发现应用程序无法加载。它只绘制从摄影机到QML组件和自我更新（）未调用绘制事件。在

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_())

这是我为此写的QML

^{pr2}$

为什么我不能画得很坚强自我更新（）。我不能使用QWidgets，我必须使用这个。我有什么遗漏吗？在

Answer 1

这个问题是由两个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 in.QML中添加prints来组合它：

*.py

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

*.qml

^{pr2}$

输出：

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

如您所见，有两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_())

有了以上应该工作的图像采集我觉得还有更好的方法，过一会儿我会展示出一个更好的选择。

---

以my previous answer为基础，我创建了一个模块，该模块使用opencv实现了摄像机的处理程序，除了一个查看器，还有一个允许添加过滤器的泛型类，为此项目必须具有以下结构

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

PyCVQML公司/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公司/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/\uu init\uy.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，因为这个CVCapture具有filters属性，其中过滤器被传递给它，它们将按照它们建立的顺序执行。要实现一个新的过滤器，您必须从CVAbstractFilter继承并重写process_image()方法，该方法以np.ndarray的形式接收图像，并在过滤器之后返回结果。

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_())

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()
    }
}