remove the element attached to the image border

Question

I’m using OpenCV to detect Pneumonia in chest-x-ray using Image Processing, so I need to remove the attached area to the image border to get the lung only, can anyone help me code this in python?

This image explains what I want this image after applying this methods: resized, Histogram Equalization, otsu Thresholded and inverse binary Thresholded, morphological processes(opening then closing)

This is the Original Image Original Image

Asked By: mostafa2000

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Answer 1

You can try using a morphological reconstruction with a border as a marker. This is an analogue of the function imclearborder from Matlab or Octave.

import cv2
import numpy as np
img = cv2.imread('5R0Zs.jpg')
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)
thresh = cv2.threshold(gray, 40, 255, cv2.THRESH_BINARY)[1]
kernel = np.ones((7,7),np.uint8)
kernel2 = np.ones((3,3),np.uint8)
marker = thresh.copy()
marker[1:-1,1:-1]=0
while True:
    tmp=marker.copy()
    marker=cv2.dilate(marker, kernel2)
    marker=cv2.min(thresh, marker)
    difference = cv2.subtract(marker, tmp)
    if cv2.countNonZero(difference) == 0:
        break

mask=cv2.bitwise_not(marker)
mask_color = cv2.cvtColor(mask, cv2.COLOR_GRAY2BGR)
out=cv2.bitwise_and(img, mask_color)
cv2.imwrite('out.png', out)
cv2.imshow('result', out )
cv2.waitKey(0) # waits until a key is pressed
cv2.destroyAllWindows()

Answered By: Alex Alex

Answer 2

This is how I would approach the problem in Python/OpenCV. Add a white border all around, flood fill it with black to replace the white, then remove the extra border.

Input:

import cv2
import numpy as np

# read image
img = cv2.imread('lungs.jpg')
h, w = img.shape[:2]

# convert to gray
gray = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY)

# add 1 pixel white border all around
pad = cv2.copyMakeBorder(gray, 1,1,1,1, cv2.BORDER_CONSTANT, value=255)
h, w = pad.shape

# create zeros mask 2 pixels larger in each dimension
mask = np.zeros([h + 2, w + 2], np.uint8)

# floodfill outer white border with black
img_floodfill = cv2.floodFill(pad, mask, (0,0), 0, (5), (0), flags=8)[1]

# remove border
img_floodfill = img_floodfill[1:h-1, 1:w-1]    

# save cropped image
cv2.imwrite('lungs_floodfilled.png',img_floodfill)

# show the images
cv2.imshow("img_floodfill", img_floodfill)
cv2.waitKey(0)
cv2.destroyAllWindows()

Answered By: fmw42

remove the element attached to the image border

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