I am trying to use DBSCAN from scikitlearn to segment an image based on color. The results I'm getting are . As you can see there are 3 clusters. My goal is to separate the buoys in the picture into different clusters. But obviously they are showing up as the same cluster. I've tried a wide range of eps values and min_samples but those two things always cluster together. My code is:
img= cv2.imread("buoy1.jpg)
labimg = cv2.cvtColor(img, cv2.COLOR_BGR2LAB)
n = 0
while(n<4):
labimg = cv2.pyrDown(labimg)
n = n+1
feature_image=np.reshape(labimg, [-1, 3])
rows, cols, chs = labimg.shape
db = DBSCAN(eps=5, min_samples=50, metric = 'euclidean',algorithm ='auto')
db.fit(feature_image)
labels = db.labels_
plt.figure(2)
plt.subplot(2, 1, 1)
plt.imshow(img)
plt.axis('off')
plt.subplot(2, 1, 2)
plt.imshow(np.reshape(labels, [rows, cols]))
plt.axis('off')
plt.show()
I assume this is taking the euclidean distance and since its in lab space euclidean distance would be different between different colors. If anyone can give me guidance on this I'd really appreciate it.
Update: The below answer works. Since DBSCAN requires an array with no more then 2 dimensions I concatenated the columns to the original image and reshaped to produce a n x 5 matrix where n is the x dimension times the y dimension. This seems to work for me.
indices = np.dstack(np.indices(img.shape[:2]))
xycolors = np.concatenate((img, indices), axis=-1)
np.reshape(xycolors, [-1,5])
If the database has data points that form clusters of varying density, then DBSCAN fails to cluster the data points well, since the clustering depends on ϵ and MinPts parameter, they cannot be chosen separately for all clusters.
This characteristic of the DBSCAN algorithm makes it a perfect fit for outlier detection and making clusters of arbitrary shape. The algorithms like K-Means Clustering lack this property and make spherical clusters only and are very sensitive to outliers.
In layman's terms, we find a suitable value for epsilon by calculating the distance to the nearest n points for each point, sorting and plotting the results. Then we look to see where the change is most pronounced (think of the angle between your arm and forearm) and select that as epsilon.
DBSCAN Algorithm Then, finds the connected components of all the core points, ignoring non-core points. Assign each non-core point to the nearest cluster if the cluster is its epsilon-neighbor. Otherwise, assign it to noise.
You need to use both color and position.
Right now, you are using colors only.
Could you please add the enitre code in the answer? Im not able to understand where do I add the those 3 lines which have worked for you – user8306074 Sep 4 at 8:58
Let me answer for you, and here is the full version of the code:
import numpy as np
import cv2
import matplotlib.pyplot as plt
from sklearn.cluster import DBSCAN
img= cv2.imread('your image')
labimg = cv2.cvtColor(img, cv2.COLOR_BGR2LAB)
n = 0
while(n<4):
labimg = cv2.pyrDown(labimg)
n = n+1
feature_image=np.reshape(labimg, [-1, 3])
rows, cols, chs = labimg.shape
db = DBSCAN(eps=5, min_samples=50, metric = 'euclidean',algorithm ='auto')
db.fit(feature_image)
labels = db.labels_
indices = np.dstack(np.indices(labimg.shape[:2]))
xycolors = np.concatenate((labimg, indices), axis=-1)
feature_image2 = np.reshape(xycolors, [-1,5])
db.fit(feature_image2)
labels2 = db.labels_
plt.figure(2)
plt.subplot(2, 1, 1)
plt.imshow(img)
plt.axis('off')
# plt.subplot(2, 1, 2)
# plt.imshow(np.reshape(labels, [rows, cols]))
# plt.axis('off')
plt.subplot(2, 1, 2)
plt.imshow(np.reshape(labels2, [rows, cols]))
plt.axis('off')
plt.show()
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