Resize and Pad the image to Square Size

resize_and_pad.py

from torchvision import transforms
from PIL import ImageOps

class ResizeAndPad(object):
    def __init__(self, size, interpolation=Image.BILINEAR):
        assert isinstance(size, int)
        self.size = size
        self.interpolation = interpolation

    def __call__(self, img):
        w, h = img.size
        if w > h:
            ow = self.size
            oh = int(self.size * h / w)
        else:
            ow = int(self.size * w / h)
            oh = self.size
        img = img.resize((ow, oh), self.interpolation)
        delta_w = self.size - ow
        delta_h = self.size - oh
        padding = (
            delta_w//2, delta_h//2,
            delta_w - (delta_w//2),
            delta_h-(delta_h//2))
        img = ImageOps.expand(img, padding)
        return img

    def __repr__(self):
        interpolate_str = transform._pil_interpolation_to_str[self.interpolation]
        return self.__class__.__name__ + '(size={0}, interpolation={1})'.format(self.size, interpolate_str)