fix canvas rendering blurred result, close #320

import numpy as np

from typing import List, Union, Tuple

from typing import List, Union

import os

from qtpy.QtWidgets import QSlider, QMenu, QGraphicsScene, QGraphicsView, QGraphicsSceneDragDropEvent, QGraphicsRectItem, QGraphicsItem, QScrollBar, QGraphicsPixmapItem, QGraphicsSceneMouseEvent, QGraphicsSceneContextMenuEvent, QRubberBand

        old_ilayer_pixmap = self.inpaintLayer.pixmap()

        self.inpaintLayer.setPixmap(ipainted_layer_pixmap)

        result = QImage(self.img_window_size(), QImage.Format.Format_ARGB32)

        canvas_sz = ipainted_layer_pixmap.size()

        result = QImage(canvas_sz, QImage.Format.Format_ARGB32)

        painter = QPainter(result)

        painter.setRenderHint(QPainter.RenderHint.Antialiasing)

        self.render(painter)

        rect = QRectF(0, 0, canvas_sz.width(), canvas_sz.height())

        self.render(painter, rect, rect)    # produce blurred result if target/source rect not specified #320

        painter.end()

        self.inpaintLayer.setPixmap(old_ilayer_pixmap)