How to save specific color image from the output of Kmeans using python

Question

I am using the below code for color-based segmentation using K-means. In this code, each cluster is saving into one image. In my case requirement is a bit different. I want to save only blue color images. Could you please help me how can I save only blue color images?

import numpy as np
import cv2
import pdb
from matplotlib import pyplot as plt
img = cv2.imread('a.png')
Z = np.float32(img.reshape((-1,3)))

criteria = (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 10, 1.0)
K = 4
_,labels,centers = cv2.kmeans(Z, K, None, criteria, 10, cv2.KMEANS_RANDOM_CENTERS)
labels = labels.reshape((img.shape[:-1]))
reduced = np.uint8(centers)[labels]

result = [np.hstack([img, reduced])]
for i, c in enumerate(centers):
    mask = cv2.inRange(labels, i, i)
    mask = np.dstack([mask]*3) # Make it 3 channel
    ex_img = cv2.bitwise_and(img, mask)
    ex_reduced = cv2.bitwise_and(reduced, mask)
    result.append(np.hstack([ex_img, ex_reduced]))
    pdb.set_trace()

cv2.imwrite('watermelon_out.jpg', np.vstack(result))

Original Image

After using this code I am getting result link below:

Expected Result:

If you want only blue color image choose only the center which represents blue color cluster and plot all point in that cluster. you are plotting for all the clusters. — Rajat Singh
– Rajat Singh, Commented Jul 23, 2020 at 21:18
for all centers find the one closer to (0, 255, 0) distance wise and plot only for that center. — Rajat Singh
– Rajat Singh, Commented Jul 23, 2020 at 21:57
Could you please write the code snippet I am unable to implement this. — Js541
– Js541, Commented Jul 23, 2020 at 23:15
@RajatSingh Sorry I didn't see your code. I am applying it now. I will update you the final status. Thanks for sharing the code. — Js541
– Js541, Commented Jul 23, 2020 at 23:17

Js541 · Accepted Answer · 2020-07-25 17:29:37Z

0

+50

This should only print the blue image. First find the center which is closest to blue color and then plot points only in cluster represented by that center

import numpy as np
import cv2
import pdb
from matplotlib import pyplot as plt
img = cv2.imread('a.png')
Z = np.float32(img.reshape((-1,3)))

criteria = (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 10, 1.0)
K = 4
_,labels,centers = cv2.kmeans(Z, K, None, criteria, 10, cv2.KMEANS_RANDOM_CENTERS)
labels = labels.reshape((img.shape[:-1]))
reduced = np.uint8(centers)[labels]


blue_dis = 99999999
blue_center = -1
b = (255, 50 , 0)
for i, c in enumerate(centers):
    dis = (c[0]-b[0])**2 + (c[1]-b[1])**2 + (c[1]-b[1])**2
    if dis < blue_dis:
        blue_center = i
        blue_dis = dis


    

result = [np.hstack([img, reduced])]
for i, c in enumerate(centers):
    if i!=blue_center:
        continue
    mask = cv2.inRange(labels, i, i)
    mask = np.dstack([mask]*3) # Make it 3 channel
    ex_img = cv2.bitwise_and(img, mask)
    ex_reduced = cv2.bitwise_and(reduced, mask)
    result.append(np.hstack([ex_img, ex_reduced]))
    pdb.set_trace()

cv2.imwrite('watermelon_out.jpg', np.vstack(result))

edited Jul 25, 2020 at 17:29

Js541

1102 silver badges14 bronze badges

answered Jul 23, 2020 at 22:08

Rajat Singh

3202 silver badges8 bronze badges

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8 Comments

Js541 Over a year ago

This code is working for most of the images when I am changing the value of b = (0,255,0) into b = (255,0,0). For few images this code is NOT working properly. In that case, it is showing pink regions. Do you have any permanent solution?

Rajat Singh Over a year ago

i guess i have used wrong rgb value for blue color. The correct value is (0, 0, 255). If you can try with this value it should work. Also the code assumes there is a blue image present in image if not it will plot one that is closest to blue color.

Js541 Over a year ago

b=(0, 0, 255) should work but unfortunately it is not working on different images. I am trying to figuring out the issue. b=(255, 0, 0) is working on 70% images.

Rajat Singh Over a year ago

can you share center values for images where b=(0, 0, 255) is not working. and also the image if possible. Maybe color we are looking for isn't exactly blue.

Js541 Over a year ago

Great!!! Now it working properly. Thanks a lot. I am giving you 50 bounty reputation.

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