satvik007 / Scanner_OP

Repository for sharing codes concerned with the prototyping part of the app.

Scanner_OP

1.   Canny example 1

• Taken from https://www.pyimagesearch.com/2014/09/01/build-kick-ass-mobile-document-scanner-just-5-minutes/
• added median blur and tweaked few parameters.
• Results are simply horrible.
• Works only for 1 of the examples.
• Transform library provided also yields the most horrible results I have ever seen.
• Run it with python src/ex01/canny.py --image data/img_02.jpg

2.   Canny example 2

• Taken from https://stackoverflow.com/a/18908023/8558040
• Much better than 1st example but doesn't work on all.
• Run it with python src/ex02/canny.py data/img_02.jpg
• The updated code is in the jupyter notebook.
• Improved the original code with median filter and dilation with unit kernel.
• Tried to add code for selection the best 4 points if the contour has more and failed. Will try again with more robust geometry.
• Will study bilateral filter, could be an improvement over gaussian filter in preserving edges.
• I am postponing it and will come later after trying other examples.

3.   Magic Filter

• Taken from https://stackoverflow.com/questions/32913157/how-to-get-magic-color-effect-like-cam-scanner-using-opencv
• Comparing Global V/S Adaptive thresholding
• Involves: Grey scaling, thresholding, denoising
• Run it with python src/ex03/thresholding.py data/img_03.png

4.   Magic Filter 2nd attempt

• Taken from https://stackoverflow.com/questions/32913157/how-to-get-magic-color-effect-like-cam-scanner-using-opencv#62634900
• https://answers.opencv.org/question/66125/object-detection-in-nonuniform-illumination/#79578
• Was hoping for shadow and paper cringes removal.
• Didn't get satisfactory results.
• Tried
  • Histogram equalization
  • CLAHE
  • Tophat addition and Blackhat removal
  • Adaptive Threshold
  • fastNlMeansDenoising
• https://stackoverflow.com/questions/49997681/scanned-document-text-background-clarity-not-good-using-opencv-ios in file filter.cpp yields very promising results. There is an unimplemented part related to no text found in the image.
• Tried Flat field correction - doesn't work so well.
• Best version till now on non-white b.g. is to simply multiply the image by 1.5 (and subtract 40, somehow this lead to bit more noise but preserves information that is otherwise lost), basically increase contrast.

5.   bwfilter

• (Would welcome the owner to fill it)

6.   filters_cpp

• https://github.com/mauvilsa/imgtxtenh
• The procedure for compiling is:
  • cd build
  • cmake -DCMAKE_BUILD_TYPE=Release ..
  • make
• Run with ./imgtxtenh img_path
• All the important functions from the purpose of the project are defined in filters.hpp and documented in filters.cpp
• Good parameters for magic filter usage will be alpha=1.4, beta=40

7.   corners_cpp

• C++ implementation of ex02 with modifications learned during experiments.
• The procedure for compiling is: g++ main.cpp corners.cpp -o main.o `pkg-config --cflags --libs opencv` -DDEBUG
• Run with ./main.o [img_in_path] [img_out_path] [] is for optional arguments.
• Implements the function find_best_corners which takes in img and returns the best rectangle the algorithm managed to find.
• Implements four point transform for cropping and warping.
• Implements order points.
• Implements validate points.
• Completed with documentation.

Remaining resources for corner detection

• https://stackoverflow.com/questions/6555629/algorithm-to-detect-corners-of-paper-sheet-in-photo
• https://hypjudy.github.io/2017/03/28/cvpr-A4-paper-sheet-detection-and-cropping/
• https://github.com/ctodobom/OpenNoteScanner
• https://stackoverflow.com/questions/8667818/opencv-c-obj-c-detecting-a-sheet-of-paper-square-detection
• https://stackoverflow.com/questions/49365609/get-bottomleft-topleft-corners

Filtering and Other resources

• User manual from camscanner - http://s.intsig.net/r/manual/CamScanner_Android3.0_en-us.html
• http://www.recogniform.net/eng/how-to-enhance-scanned-documents.html
• Document Image Processing for Scanning and Printing by Ilia V. Safonov, Ilya V. Kurilin, Michael N. Rychagov, Ekaterina V. Tolstaya. Added book in Resources. (Who's going to read this. LOL)

OCR Resources

• https://tesseract-ocr.github.io/tessdoc/APIExample.html
• how-to-integrate-tesseract-ocr-library-to-a-c-program
• https://dropbox.tech/machine-learning/creating-a-modern-ocr-pipeline-using-computer-vision-and-deep-learning
• https://docparser.com/blog/improve-ocr-accuracy/
• https://stackoverflow.com/questions/23506105/extracting-text-opencv?rq=1
• https://stackoverflow.com/questions/9152803/

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