PyQt5无法显示图片，如何解决？

Question

问题遇到的现象和发生背景

使用PyQt5的label展示cv处理后的图片时，图片无法显示出来

问题相关代码，请勿粘贴截图

下面是主程序代码，要在Mainwindow.label上显示图片

import sys

from PIL import ImageQt, Image
from PyQt5 import QtWidgets
from PyQt5.QtWidgets import QMainWindow
from PyQt5.QtGui import QPixmap
from UI.window import Ui_Form
from PyQt5 import QtCore
from Net.fasterrcnn import Net
import cv2
from PyQt5 import QtGui
import os


def cvImgtoQtImg(cvImg):  # 定义opencv图像转PyQt图像的函数
    qt_img = cv2.cvtColor(cvImg, cv2.COLOR_BGR2RGB)
    qt_img = QtGui.QImage(cvImg.data,  # 数据源
                          cvImg.shape[1],  # 宽度
                          cvImg.shape[0],  # 高度
                          cvImg.shape[1] * 3,  # 行字节数
                          QtGui.QImage.Format_RGB888)
    return QtGui.QPixmap.fromImage(qt_img)


if __name__ == '__main__':
    app = QtWidgets.QApplication(sys.argv)
    Mainwindow = Ui_Form()
    mainwindow = QMainWindow()
    Mainwindow.setupUi(mainwindow)
    # pix = QPixmap("./1.jpeg").scaled(Mainwindow.label.width(), Mainwindow.label.height())
    # Mainwindow.label.setPixmap(pix)
    QtCore.QCoreApplication.addLibraryPath(os.path.join(os.path.dirname(QtCore.__file__), "plugins"))

    img = cv2.imread('1.png')
    # 图片转灰
    gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
    # 实例化网络
    net = Net()
    img = net.get_img(img, gray)

下面是界面的代码

from PyQt5 import QtCore, QtGui, QtWidgets


class Ui_Form(QtWidgets.QWidget):
    def setupUi(self, Form):
        Form.setObjectName("Form")
        Form.resize(905, 809)
        self.label = QtWidgets.QLabel(Form)
        self.label.setGeometry(QtCore.QRect(100, 50, 721, 631))
        self.label.setScaledContents(True)
        self.label.setAlignment(QtCore.Qt.AlignCenter)
        self.label.setObjectName("label")

        self.retranslateUi(Form)
        QtCore.QMetaObject.connectSlotsByName(Form)

    def retranslateUi(self, Form):
        _translate = QtCore.QCoreApplication.translate
        Form.setWindowTitle(_translate("Form", "Form"))
        self.label.setText(_translate("Form", "Video"))

运行结果及报错内容

我的解答思路和尝试过的方法

我想要达到的结果