A OCR application for chess boards

The goal of this application is to read an image, detect the chess boards in it and export them using the FEN notation (https://en.wikipedia.org/wiki/Forsyth–Edwards_Notation).

    virtualenv env
    source env/bin/activate
    pip install -r requirements.txt
    python src/main.py <filename>

• Read Image from file

• Convert image to grayscale.

• Convert to black and white taking into account average image brightness.

• Find contours using cv2.findContours

• Filter irrelevant contours:
  • Area either too small or too large.
  • Ratio height/width not close to 1.

• Draw each contour in an individual black buffer.

• Find lines by using the standard Hough transform. This is done, iteratively, progressively decreasing the accumulator threshold parameter until there exactly 2 horizontal lines and 2 vertical lines (with some degree of freedom).
  • Lines that are too close to each other are ignored

• Calculate the perspective correction transformation using the 4 points of intersection.

• Apply the transformation to a copy of the original image and crop it to size.

• Using OpenCV to detect grids

• Using Canny algorithm for edge detection

• Find lines by using the standard Hough transform. This is done, iteratively, progressively decreasing the accumulator threshold parameter until there are at least 8 horizontal lines and 8 vertical lines. Lines that are too close to each other are ignored

  

  

• Calculate the line intersections