Class LazyTransform

tensorpack/dataflow/imgaug/transform.py:318–354

A transform that's instantiated at the first call to `apply_image`.

class LazyTransform(BaseTransform):
    """
    A transform that's instantiated at the first call to `apply_image`.
    """
    def __init__(self, get_transform):
        """
        Args:
            get_transform (img -> Transform): a function which will be used to instantiate a Transform.
        """
        self.get_transform = get_transform
        self._transform = None

    def apply_image(self, img):
        if not self._transform:
            self._transform = self.get_transform(img)
        return self._transform.apply_image(img)

    def _apply(self, x, meth):
        assert self._transform is not None, \
            "LazyTransform.{} can only be called after the transform has been applied on an image!"
        return getattr(self._transform, meth)(x)

    def __getattr__(self, name):
        if name.startswith("apply_"):
            return lambda x: self._apply(x, name)
        raise AttributeError("TransformList object has no attribute {}".format(name))

    def __repr__(self):
        if self._transform is None:
            return "LazyTransform(get_transform={})".format(str(self.get_transform))
        else:
            return repr(self._transform)

    __str__ = __repr__

    def apply_coords(self, coords):
        return self._apply(coords, "apply_coords")


if __name__ == '__main__':