PAID: Looking for advice/solution for processing png images with questions

[hristopeev]

Hello,

This topic is moved from Users section.

I have a large number of scanned images which are from a book with some exam questions. Examples:
https://dl.dropboxusercontent.com/u/639 ... ge-236.png
https://dl.dropboxusercontent.com/u/639 ... ge-237.png
https://dl.dropboxusercontent.com/u/639 ... ge-238.png
https://dl.dropboxusercontent.com/u/639 ... ge-329.png
https://dl.dropboxusercontent.com/u/639 ... ge-240.png
https://dl.dropboxusercontent.com/u/639 ... ge-239.png

What I try to achieve is the following:
1. Clean the noise from scanner - I mean these little dots and dashes that are around the text
2. Rotate the image - the middle vertical line should be perpendicular to the image's top and bottom edges
3. Crop each question in separate image
4. Remove white space from each individual image

I managed to partially achieve 1. Clean the noise from scanner using the following commands:

Code: Select all

convert file.png \
          -write MPR:source \
          -morphology close rectangle:3x2 \
          file_rectangle_3x2.png

OR

convert file.png \
          -write MPR:source \
          -morphology close diamond \
          -morphology erode square    MPR:source -compose Lighten -composite \
          -morphology erode square    MPR:source -composite \
          -morphology erode square    MPR:source -composite \
          -morphology erode square    MPR:source -composite \
          -morphology erode square    MPR:source -composite \
          -morphology erode square    MPR:source -composite \
          -morphology erode square    MPR:source -composite \
          -morphology erode square    MPR:source -composite \
          -morphology erode square    MPR:source -composite \
          file_diamond.png

Both are giving relatively satisfactory results. The problems are when on the page there is a drawing. This cleaning cleans even some pixels from the drawings. If someone can recommend better method for cleaning the noise will be great.

For 2 Rotate the image I tried http://fmwconcepts.com/imagemagick/unrotate/index.php from Fred's scripts but I didn't manage to make it work. Can someone advice how can I approach this?

For 3. Crop each question in separate image - I am not even sure if this is possible only with ImageMagic. Maybe I will need some OCR which detects where the question starts and ends and having these coordinates I can use ImageMagic to crop the image in several pieces? Any suggestions for tools/libraries will be highly appreciated.

For 4. This is clear, I had done it before.

I am using ImageMagick's command line too convert on Mac OS Sierra, version:
Version: ImageMagick 6.9.6-3 Q16 x86_64 2016-10-31 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2016 ImageMagick Studio LLC
License: http://www.imagemagick.org/script/license.php
Features: Cipher DPC Modules
Delegates (built-in): bzlib freetype jng jpeg ltdl lzma png tiff xml zlib


Since the amount of scanned images is huge the processing will be migrated to a ubuntu server.

If you need more information about the tools I am using or the images I am ready to assist.

Any help or directions for achieving the output will be really appreciated and we are ready to pay for them.

Thanks!

[fmw42]

1) Clean the scanner glass and scan as PDF, so that you can get higher resolution

2) try my script textdeskew, thought it might not work any better than my unrotate, which is totally unsuitable. textdeskew really requires a bunch of regularly spaced lines of text. So it may not be suitable either. Or try IM -deskew

3) Use the question icon as a template and do a compare search to find all the locations of the icon. That will help identify where the questions start (and stop) so you can crop them

4) Use -fuzz XX% -trim +repage on each cropped question.