python - opencv morphologyEx remove specific color

Question

After remove captcha\'s background.
The image remain digits and noise.
Noise line is all in one color : RGB(127,127,127)
And then using morphology method.

Answer 1

Here is my solution.
Your answer is obvious better than my.

 def mop_close(self):
    def morphological(operator=min):
        height, width, _ = self.im.shape
        # create empty image
        out_im = np.zeros((height,width,3), np.uint8)
        out_im.fill(255) # fill with white
        for y in range(height):
            for x in range(width):
                try:
                    if self.im[y,x][0] ==127 and self.im[y,x][1] ==127 and self.im[y,x][2] ==127:
                        nlst = neighbours(self.im, y, x)

                        out_im[y, x] = operator(nlst,key = lambda x:np.mean(x))
                    else:
                        out_im[y,x] = self.im[y,x]
                except Exception as e:
                    print(e)
        return out_im

    def neighbours(pix,y, x):
        nlst = []
        # search pixels around im[y,x] add them to nlst
        for yy in range(y-1,y+1):
            for xx in range(x-1,x+1):
                try:
                    nlst.append(pix[yy, xx])
                except:
                    pass
        return np.array(nlst)

    def erosion(im):
        return morphological(min)

    def dilation(im):
        return morphological(max)

    self.im = dilation(self.im)
    self.im = erosion(self.im)

final result:

Answer 2

In order to eliminate color within a particular range you have to use cv2.inRange() function.

Here is the code:

lower = np.array([126,126,126])  #-- Lower range --
upper = np.array([127,127,127])  #-- Upper range --
mask = cv2.inRange(img, lower, upper)
res = cv2.bitwise_and(img, img, mask= mask)  #-- Contains pixels having the gray color--
cv2.imshow('Result',res)

This is what I got for the two images you have:

Image 1:

Image 2:

You carry on from here.