Ask HN: Trying to Extract Roll Call Votes of Cambridge City Council

Re:Ask HN: Trying to Extract Roll Call Votes of Cambridge Ci... by dagw on Tuesday October 06, 2015 @05:09AM (#10337578)

Start by looking for the words YEA, NAY, ABSENT and PRESENT using simple OCR or pattern matching. Clip the images into 4 vertical columns the same width as the text, starting just below the text. Use a horizontal line detection algorithm to try to find the boundary of each 'box'. Clip out each box and count the number of black pixels. If it's greater than some level, then that box contains a tick.

OpenCV should be able to do all these things.

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Re:Ask HN: Trying to Extract Roll Call Votes of Cambridge Ci... by dagw on Tuesday October 06, 2015 @03:43PM (#10341763)

Actually forget OCR. Just find the y and x coordinates of each horizontal and vertical line, and then clip out each box in the grid using those coordinates. Count black pixels and done.

I hacked together something in python (because I had laundry to do :) ) and it seems to work pretty well.

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Re:Ask HN: Trying to Extract Roll Call Votes of Cambridge Ci... by dagw on Tuesday October 06, 2015 @05:14PM (#10342444)

Quick hack, badly tested, but seems to work: https://gist.github.com/dwastberg/9faea8a4ceb6dc05b52e

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Re:Ask HN: Trying to Extract Roll Call Votes of Cambridge Ci... by dagw on Wednesday October 07, 2015 @04:40AM (#10344852)

Of course this code breaks if the scan isn't straight.

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Re:Ask HN: Trying to Extract Roll Call Votes of Cambridge Ci... by semiquaver on Wednesday October 07, 2015 @04:46PM (#10348969)

You're already using imagemagick's `convert` in that script - there's also `textcleaner -u`[1] which among other things automatically straightens slightly crooked text in scans (less than 5 degrees).

[1] http://www.fmwconcepts.com/imagemagick/textcleaner/

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