k means clustering shows only blank image if i loop it k times
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Anirudh Kochhar
on 22 Oct 2021
Answered: Image Analyst
on 8 Nov 2021
If i loop for i = 1:2 i get clustering otherwise i just get a blank image. any idea why?
im = imread("irobot.jpg");
im_as_col = double(im(:));
cluster_membs = kmeans(im_as_col, 3)
labelim = zeros(size(im));
for i=1:3
inds = find(cluster_membs==i);
meanval = mean(im_as_col(inds));
labelim(inds) = meanval;
end
imshow(im)
imshow(labelim);
2 Comments
KSSV
on 22 Oct 2021
Error says there is no image in the path, did you specify the correct path of the image or is image present in the present working directory?
Accepted Answer
yanqi liu
on 5 Nov 2021
clc; clear all; close all;
im = imread("https://ww2.mathworks.cn/matlabcentral/answers/uploaded_files/774998/irobot.jpg");
im_as_col = double(im(:));
cluster_membs = kmeans(im_as_col, 3);
labelim = zeros(size(im));
for i=1:3
inds = find(cluster_membs==i);
meanval = mean(im_as_col(inds));
labelim(inds) = meanval;
end
figure; imshow(im,[])
figure; imshow(mat2gray(labelim),[]);
3 Comments
Image Analyst
on 8 Nov 2021
@Anirudh Kochhar I'm not sure it does work. You wanted 3 classes and that's what I gave you in my answer below. This answer's final image looks like it shows 5 classes: blue, green, cyan, white, and gray classes, though kmeans does return 3. And the classes are not based on colors since all the gray levels are lumped together with this line:
im_as_col = double(im(:));
so you won't find unique/similar colors as in my answer. A color like pure red [1,0,0] would show up as the same class as pure green [0,1,0] or pure blue [0,0,1] because all the gray levels were put into a single column.
But I'm not sure why you wanted only 3 color classes since that image has blue, green, cyan, and a wide variety of grays. Why did you pick 3? This is not an image that has 3 clusters. I mean, just look at the gamut:
colorcloud(im);
Do you see 3 natural clusters there? No.
yanqi liu
on 8 Nov 2021
yes,sir,its make 3 color class,and use label to display different gray level,that can be ref label2rgb
More Answers (2)
Image Analyst
on 22 Oct 2021
See attached demos.
1 Comment
Image Analyst
on 22 Oct 2021
If you want kmeans for a hyperspectral image, see attached.
Image Analyst
on 8 Nov 2021
For what it's worth, attached is my Color Classifier that is based on Discrminant Analysis instead of kmeans. Basically you draw regions that are representative of the colors you want to have as your classes. Then it classifies all the pixels in the image into one of those classes.
Also attaching a KNN classifier demo.
Adapt as needed.
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