Bounding box on clusters in a 2D list

[superprad at gmail.com]

Bearophile,I have written the floodfill in python with stack. But i
think I am making something wrong I dont get what i need.Need your
opinion.the code follows

def connected(m, foreground=1, background=0):
    def floodFill4(m, r,c, newCol, oldCol):
        if newCol == oldCol:
            print "empty stack"
            return -1
        while(m[r].pop(c)):
            m[r][c] = newCol
            if r+1 < maxr and m[r+1][c]==oldCol:
                if m[r+1][c] == 0:return
            if r-1 >= 0 and m[r-1][c]==oldCol:
                if m[r-1][c] == 0:return
            if c+1 < maxc and m[r][c+1]==oldCol:
                if m[r][c+1] == 0:return
            if c-1 >= 0 and m[r][c-1]==oldCol:
                if m[r][c-1] == 0:return

    maxr = len(m)
    maxc = len(m[0])
    newCol = 2
    oldCol = foreground
    for r in xrange(maxr):
        for c in xrange(maxc):
            if m[r][c] == oldCol:
                floodFill4(m, r,c, newCol=newCol, oldCol=oldCol)
                newCol += 1