Step 1: Tresholding using isodata algorithm:

•   divide the histogram in two parts
    (starting treshold level:
                  t = the mean of the picture)
  
•   consider the means (m1, m2) of the upper and
   lower pixelvalues
  
•   calculate: t= (m1+m2) /2
  
•   If t changes => start from the beginning
          Step 2, otherwise (i.e. convergence)

Step 2: Fill area, closing holes - morphological operation

•   Dilatation
•   Intersection with the complementary of the contour
•   Continue until there are changes

Step 3: Determine the boundary

•   by substracting the result of erosion from the original image

Step 4: Labeling the boundaries of each separate card

Step 5: Determine the chain code

Step 6: Determine the corners of the cards using
            the chain code

•   the final points of the longest diagonal

Step 7: Determine the angles using the diagonals

Step 8: Processing each separated card

•   substract each card
•   rotate the substracted images using the determined angles => the longer edge of a card is vertical (normalization)

Step 9: Pattern matching => determine the shape of each card