
PIRL: Learn Image Representations Immune to Geometric Transformation - amitness
https://amitness.com/2020/03/illustrated-pirl/
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fxtentacle
Thank you @amitness for this wonderful website with graphical explanations :)

The PIRL technique in question here seems useless to me, because its loss
deliberately trains it to behave differently from what a human would do. But
that overview page [https://amitness.com/2020/02/illustrated-self-supervised-
lea...](https://amitness.com/2020/02/illustrated-self-supervised-learning/) is
gold.

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alisterburt
This looks a lot to me like learned image descriptors from the computer vision
community. Some examples are Discriminative learning of local image
descriptors
([http://matthewalunbrown.com/papers/pami2010.pdf](http://matthewalunbrown.com/papers/pami2010.pdf))
DeepDesc
([https://icwww.epfl.ch/~trulls/pdf/iccv-2015-deepdesc.pdf](https://icwww.epfl.ch/~trulls/pdf/iccv-2015-deepdesc.pdf))
L2-net
([http://www.nlpr.ia.ac.cn/fanbin/pub/L2-Net_CVPR17.pdf](http://www.nlpr.ia.ac.cn/fanbin/pub/L2-Net_CVPR17.pdf))

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im3w1l
The issue with this is that you (most of the time) don't want your image
representations to be immune to geometric transformation.

A rotated p should be recognized as a d. In nature pictures you want to
recognize blue at the top as sky and blue at the bottom as water.

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bobbylarrybobby
I think that's taking a dim view of what machine vision should be capable of.
If a picture is rotated 180 degrees, upside down text _should_ be recognized
as its flipped version, i.e., the word "6op" should be read as "dog" having
been rotated. Similarly a machine should be able to tell if it's looking at
the reflection of the sky in a lake. And disregarding entire scenes, any
object upside down (upside down chair, upside down dog, upside down car, ...)
is clearly recognizable as such to a human, and hence should be to a machine
as well.

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im3w1l
Upside down objects and scenes look alien to us. We can recognize them but not
without effort. It's a combination of having seen objects upside down before
and being able to reason about what we are seeing. It does not come for free
from invariance.

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dr_zoidberg
The classic Thatcher illusion[0].

[0]
[https://en.wikipedia.org/wiki/Thatcher_effect](https://en.wikipedia.org/wiki/Thatcher_effect)

Edited for clarity, started writing then wiped half and didn't check first
half.

