Set a background image for a widget and make it to fill the entire widget in the resizeEvent

Question

I'm working on an application where the background of a widget is an image and I want it to fill the entire widget in the case of a resizeEvent.

Firstly, I will also use a stylesheet not in the same widget but surely in its child widgets, it will not cause a problem if I use a palette at the same time to set the background of the widget. Second, can I do this with a stylesheet? If not I tried with a palette but it didn't work, this is what I tried to do:

from PyQt5.QtWidgets import *
from PyQt5.QtCore import *
from PyQt5.QtGui import *
from PyQt5.uic import loadUiType
import sys
MainUI, _ = loadUiType(R'to_do_app.ui')


class Window(QMainWindow,Ui_MainWindow) :
    def __init__(self):
        super(Window, self).__init__()
        self.setupUi(self)
        
    def resizeEvent(self, e):
        image = QPixmap('instagrame.jpg')
        image.scaled(e.size(),Qt.IgnoreAspectRatio)
        palette = self.centralwidget.palette()
        brush = QBrush(image)
        palette.setBrush(QPalette.Background,brush)
        self.centralwidget.setPalette(palette)
        self.repaint()
    


if __name__ =='__main__':
    app= QApplication(sys.argv)
    window =Window()
    window.show()
    sys.exit(app.exec())

to_do_app.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>476</width>
    <height>598</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
  </widget>
 </widget>
 <resources>
  <include location="background_ma_journe.qrc"/>
 </resources>
 <connections/>
</ui>

qrc file

<RCC>
  <qresource prefix="new_image">
    <file>Instagram.jpg</file>
  </qresource>
</RCC>

the used image

Answer 1

The OP's code has several inconsistencies (for example what is Push_Button_, page_2, etc) so I will not refer to the cause of the error.

It is not necessary to use .qrc since for example the QPixmap does not use that resource so I will remove the stylesheet and the qresource from the .ui. On the other hand, you must set the background by enabling the autoFillBackground property of the centralWidget.

├── Instagram.jpg
├── main.py
└── to_do_app.ui

to_do_app.ui

<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
 <class>MainWindow</class>
 <widget class="QMainWindow" name="MainWindow">
  <property name="geometry">
   <rect>
    <x>0</x>
    <y>0</y>
    <width>476</width>
    <height>598</height>
   </rect>
  </property>
  <property name="windowTitle">
   <string>MainWindow</string>
  </property>
  <widget class="QWidget" name="centralwidget">
  </widget>
 </widget>
 <connections/>
</ui>

main.py

import os
import sys
from pathlib import Path

from PyQt5.QtCore import Qt
from PyQt5.QtGui import QBrush, QPalette, QPixmap
from PyQt5.QtWidgets import QApplication, QMainWindow
from PyQt5.uic import loadUiType

CURRENT_DIRECTORY = Path(__file__).resolve().parent

MainUI, _ = loadUiType(os.fspath(CURRENT_DIRECTORY / "to_do_app.ui"))


class Window(QMainWindow, MainUI):
    def __init__(self):
        super(Window, self).__init__()
        self.setupUi(self)
        self.centralwidget.setAutoFillBackground(True)

    def resizeEvent(self, event):
        super().resizeEvent(event)
        pixmap = QPixmap(os.fspath(CURRENT_DIRECTORY / "Instagram.jpg"))
        palette = self.centralwidget.palette()
        brush = QBrush(pixmap.scaled(event.size(), Qt.IgnoreAspectRatio))
        palette.setBrush(QPalette.Window, brush)
        self.centralwidget.setPalette(palette)


if __name__ == "__main__":
    app = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec())