
Debanding the World - akalin
https://blog.mapbox.com/debanding-the-world-94439af16e7f
======
derefr
This is a cool example of the intersection of two fields: computational
geometry/GIS, and image filtering algorithms.

In this case, information from GIS land (e.g. the orientation of the
satellite’s aperture relative to true north on the ground below) was fed into
the image filter’s autocalibration, because “natural” grid-like structures
that should be preserved (cities, farm plots) tend to be aligned to true
north, unlike the camera’s distortion, which is aligned to the aperture. (In
the article, this is the part where they draw a diagonal mask stripe across
the FFT image.)

Anyone working on a cross-subdisciplinary problem like this? Have any
interesting “systems of algorithms” to share?

~~~
morganherlocker
Maps involve a wide range of these. Navigation involves a lot of computational
geometry mixed with graph theory. Telematics deals with signal processing and
machine learning. Cartography mixes GIS with rendering algorithms. The need
for high performance and accuracy means there is a lot of motivation to
continue pushing deeper into integration of the fields.

------
baq
working on FFT-transformed images is quite the dark magic if you don't
understand what you're looking at; this is especially interesting when you
look at what e.g. H.264 does to images in FFT: [https://sidbala.com/h-264-is-
magic/](https://sidbala.com/h-264-is-magic/) (look at the 2% mask and the
resulting image - it provokes a 'this shouldn't be possible' reaction).

~~~
stronglikedan
Honestly, I'm more impressed with the 11% image compared to the 100% image
than I am with the 2% image compared to any of the others. But, then again, I
have no idea what I'm doing.

------
anc84
(2014)

------
abruzzi
I remember an image processing application back in the late 90s that would do
FFT/reverse FFT that I used a couple of times to “paint out” certain regular
artifacts. Same basic idea as this, but not nearly as successful. I can’t
remember the app name though.

