```py
from PySide6.QtCore import *
from PySide6.QtGui import *
from PySide6.QtWidgets import *
from glob import glob
import os
import sys
app = QApplication([])

i = 0
pngs = []
while os.path.exists(fn:=f"{i}.png"):
  pngs.append(fn)
  i += 1

pixmaps = [ QPixmap(png) for png in pngs ]
idx = 0

# How to draw regions of a pixmap
class Canvas(QWidget):
  def __init__(self,*xs,**kw):
    super().__init__(*xs,**kw)
    self.resize(800,600)
  def paintEvent(self,e):
    pixmap = pixmaps[0]
    rect = self.rect()
    srect = QRect(200,200,1200,500)
    trect = QRect(10,10,400,300)
    with QPainter(self) as qp:
      qp.fillRect(rect,Qt.red)
      qp.drawPixmap(trect,pixmap,srect)

canvas = Canvas()
canvas.show()

exit(app.exec())
```