Set cropping values in `p:blipFill/a:srcRect` such that an image of
        *image_size* will stretch to exactly fit *view_size* when its aspect
        ratio is preserved.

def crop_to_fit(self, image_size, view_size):
        """
        Set cropping values in `p:blipFill/a:srcRect` such that an image of
        *image_size* will stretch to exactly fit *view_size* when its aspect
        ratio is preserved.
        """
        self.blipFill.crop(self._fill_cropping(image_size, view_size))