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Skew detection and correction in images containing text

<img src="/examples/4.jpg" width=400px></img>

<h5>Image with skew</h5> <img src="sample_output.jpg" height=300px> <h5>Image after deskew</h5>

Install and use via pip!

Recommended way(using virtualenv):

  1. mkdir alyn-test
  2. cd alyn test
  3. mkvirtualenv .
  4. pip install alyn
  5. source bin/activate

To detect skew angle in image:

from alyn import SkewDetect
sd = SkewDetect(
	input_file='path_to_file',
	batch_path='optional_batch_processing_path',
	output_file='optional_text_file_output_path',
	display_output='Yes/No')
sd.run()
Extra options:

To deskew image:

from alyn import Deskew
d = Deskew(
	input_file='path_to_file',
	display_image='preview the image on screen',
	output_file='path_for_deskewed image',
	r_angle='offest_angle_in_degrees_to_control_orientation')`
d.run()

Requires

Techniques used

Features

How the skew detection works

The skew detection script takes image file as input, then performs the following steps:

The deskew script uses the skew angle determined using skew detection script to remove the skew from the image.

Using scripts directly(older method)

Image skew calculation using skew_detect.py

To calculate the skew angle for a given image file, use -i option followed by the path to file:

./skew_detect.py -i image.jpg

To save output in a text file add -o option followed by the output file name:

./skew_detect.py -i image.jpg -o output.txt

To display output information add -d option followed by a string Yes:

./skew_detect.py -i image.jpg -d Yes

To batch process files in a directory, use -b option followed by the path to directory:

./skew_detect.py  -b examples

To display Hough Transform plot for an image,:

./skew_detect.py -i image.jpg -p Yes
Output of the Hough Transform:
<img src="hough.jpg" width="400px">

To set the value of sigma for Gaussian blurring in Canny Edge Detection, use -s option followed by the desired value:

./skew_detect.py -i image.jpg -s 3

To set the number of peaks collected from Hough Transform, use -n option followed by the desired value:

./skew_detect.py -i image.jpg -n 10

Image Deskew using deskew.py

To perform a simple deskew and display the output:

./deskew.py -i image.jpg -d Yes

To save the deskewed image, use the following:

./deskew.py -i image.jpg -o rotated.jpg

In some cases the result image might be upside down or the text may be running vertical, To fix this, use -r followed by the desired angle in int:

./deskew.py -i image.jpg -o rotated.jpg -r 90

To generate data for experimental purposes, run the test_img_gen.py in test_data folder. This will generate images containing a white line having angle between 0 to 180 degrees.