def pot_square_resize(img, maximum=None):
"""Resize image to power of two square
:type img: QImage
:param img: input image
:type maximum: int or None
:param maximum: maximum size (must be 2**n)
:return: resized image
"""
resized = pot_resize(img, maximum=maximum)
w, h = resized.width(), resized.height()
base = max(w, h)
#pad = base - min(w, h)
new_img = QImage(base, base, img.format())
new_img.fill(QColor(0, 0, 0))
painter = QPainter(new_img)
painter.drawImage(0, 0, resized)
return new_img, w / base, h / base
