Notes After Skimming PyImageSearch

I’m glad I learned of PyImageSearch from Evan and spent some time to sit down to look it over. The amount of information available on this site is large enough that I resorted to skimming, with the intent to revisit specific subjects later as need arise.

I appreciate the intent of making computer vision accessible to beginners, it is always good to make sure people interested in exploring an area are not frustrated by problems unrelated to the problem domain. Kudos to the guides on command line basics, and on Python’s NoneType errors that are bewildering to beginners.

That said, this site does frequently dive into areas that I felt lacked sufficient explanation for beginners. I remember the difficulty I had in understanding how matrix math related to computer graphics. The guide on rotation discussed the corresponding rotation matrix. Readers got the assurance “This matrix looks scary, but I promise you: it’s not.” but the explanation that followed would not have been enlightening to me back when I was learning the topic. Perhaps a link to more details would be helpful? Still, the effort is appreciated.

There are also bits of Python code that would be confusing to a beginner. Not just Python itself, but also when leveraging the very powerful NumPy library. I had no idea what was going on between tuple and argmin in the code on this page:

extLeft = tuple(c[c[:, :, 0].argmin()][0])

Right now it’s a black box of voodoo magic to me, a sting of non-alphanumeric operators that more closely resemble something I associated with Perl programming. At some point I need to sit down with Python documentation to work through this step by step in Python REPL (read – evaluation – print loop) to understand this syntax. It would be good if the author included footnotes with links to the appropriate Python terminology for these operations.

A fact of life of learning from information on PyImageSearch is the sales pitch for the author’s books. It’s not necessarily a good thing or a bad thing, but it is very definitely a thing. Constant and repetitive reminder “and in my book you will also learn…” on every page. This site exists to draw people in and, if they want to take it further, sell them on the book. I appreciate this obviously stated routine over the underhanded ways some other people make money online, but that doesn’t make it any less repetitive.

Likely related to the above is the fact this site also wants to collect e-mail addresses. None of the code download links takes us to an actual download, they instead take us to a form where we have to fill in our e-mail address before we are given a link to download. Fortunately the simple bits I’ve followed along so far are easy to recreate without the download but I’m sure it will be unavoidable if I go much further.

And finally, this site is focused on OpenCV in Python running on Unix-derived operating systems. Other language bindings for  OpenCV are out of scope, as is the Windows operating system. For my project ideas that involve embedded platforms without Python, or those that will be deployed on Windows, I would need to go elsewhere for help.

But what is within scope is covered well, with an eye towards beginner friendliness, and available freely online in a searchable collection. For that I am thankful to the author, even as I acknowledge that there are interesting OpenCV resources beyond this scope.

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