python - error while printing connected components in a gray scale image

Question

import sys
from PIL import Image
import ImageFilter
import numpy
import PIL.Image
from numpy import array
stack=[]
z=0    
def main():
    connected(drblur)//image in list of lists [[],[],[],[],....[]]
def connected(rdrblur):
    table={}
    #print len(rdrblur),len(rdrblur[0])
    for item in rdrblur:
        item.insert(0,0)
        item.append(0)
    #print len(rdrblur),len(rdrblur[0])
    rdrblur.insert(0,[0]*len(rdrblur[0]))
    rdrblur.append([0]*len(rdrblur[0]))
    copy=[]
    for item in rdrblur:
        copy.append(item[:])
    global z
    count=0 
    for i in range(1,len(rdrblur)-1):
        for j in range(1,len(rdrblur[0])-1):
            if (i,j) not in stack:
                if rdrblur[i][j]==copy[i][j]:
                    z=0
                    times=dfs(i,j,str(count),rdrblur,copy)
                    table[count]=(rdrblur[i][j],times+1)
                    count=count+1
    stack1=[]
    #print table
    for item in table.values():
        stack1.append(item)

    #print stack1
    table2={}
    for item in stack1:
        if item[0] not in table2.keys():
            table2[item[0]]={'coherent':0,'incoherent':0}
    for item in stack1:
        if item[1]>900:
            table2[item[0]]['coherent']=table2[item[0]]['coherent']+item[1]

        else:
            table2[item[0]]['incoherent']=table2[item[0]]['incoherent']+item[1]
    print tablel2
def dfs(x,y,co,b,c):
    dx = [-1,-1,-1,0,0,1,1,1]
    dy = [-1,0,1,-1,1,-1,0,1]
    global z
    #print x,y,co
    c[x][y]=co
    stack.append((x,y))
    #print dx ,dy
    for i in range(8):
        nx = x+(dx[i])
        ny = y+(dy[i])
        #print nx,ny
        if b[x][y] == c[nx][ny]:
            dfs(nx,ny,co,b,c)
            z=z+1
    return z




if __name__ == '__main__':
  main()

error: File "C:UsersAbhiDesktopcbir-pcvv est.py", line 125, in dfs dfs(nx,ny,co,b,c) RuntimeError: maximum recursion depth exceeded

I was trying to find connected components in an image using python.I have used recursive dfs to find the connected components . This code works fine for a 6*6 matrix but gives an error when used for an image .In the above code drblur is a list of lists which has image intensities .

Please help me.

Answer 1

The error is pretty clear.

You have two alternatives. You can increase the allowable recursion depth (you can find out how to do that here), summary:

sys.setrecursionlimit(limit)?

or you can change your DFS to be iterative instead of recursive (you can find out how to do that in any good graph algorithms text book).