[Chicago] OpenALPR - Transformations

Carl Karsten carl at personnelware.com
Fri Nov 4 23:07:11 EDT 2016

This is about a year old, but it is a fun talk:


On Fri, Nov 4, 2016 at 2:38 PM, Robare, Phillip (TEKSystems) <
proba at allstate.com> wrote:

> Some links you may find useful below.  I am surprised ALPR doesn't do this
> already.
> The problems reading license plates by humans have resulted in deaths (due
> to hits on mis-entered license numbers in the context of traffic stops).  I
> hope you are getting a better feeling of how we need to be careful with the
> tasks given to our new robotic overlords.
> An interesting post from a couple years ago is "How to Build a Kick-Ass
> Mobile Document Scanner in Just 5 Minutes" (http://www.pyimagesearch.com/
> 2014/09/01/build-kick-ass-mobile-document-scanner-just-5-minutes/) .  It
> covers sharpening the image, doing a perspective transformation and getting
> the document ready for OCR (but not the OCR step).
> The book "Automate The Boring Stuff With Python" has a chapter on
> "Manipulating Images" that is online and covers how to do the manipulations
> with PIL (https://automatetheboringstuff.com/chapter17/).  This would be
> a good start.  If you are working on your project with Python 3 (if not,
> why not?) I believe Pillow has the same API.
> There have been a number of github projects in the space of preparing
> scanned documents that I have seen over the years.  Unfortunately I can't
> find the best ones I remember so here are ones I found today:
> Scantailor (https://github.com/scantailor/scantailor) is a large C++
> project that appears to be very complete.  ImproveQuality (
> https://github.com/tesseract-ocr/tesseract/wiki/ImproveQuality) is also a
> cpp project meant for text scanning.
> A mathematically interesting approach to deskewing is documented in
> http://www.ijstr.org/final-print/dec2013/An-Integrated-
> Skew-Detection-And-Correction-Using-Fast-Fourier-Transform-And-Dct.pdf
> where a Fast Fourier Transform is used to determine the skew without
> pre-analyzing the image to pull out text lines.
> Phil Robare
> -----Original Message-----
> From: Chicago [mailto:chicago-bounces+proba=allstate.com at python.org] On
> Behalf Of Chris Vinzons
> Sent: Thursday, November 03, 2016 2:52 PM
> To: chicago at python.org
> Subject: [Chicago] OpenALPR - Transformations
> Hi,
> I'm using OpenALPR to read still license plates, but the thing is that my
> sometimes that it doesn't read it correctly. I think this is because of the
> license plate is tilted. Is there a way to untilt it or is there some kind
> of training data I could do in python?
> Thanks
> Chris V
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Carl K
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