Error using reshape To RESHAPE the number of elements must not change.

clear all;
clc;
warning off;
a=rgb2gray(imread('red.jpg'));
figure, imshow(a);
imData = reshape(a, [], 1);
imData=double(imData);
[IDX nn]= kmeans(imData,4);
imIDX= reshape(IDX, size(a));
figure,imshow(imIDX,[]),title('index image');

[Kaushik Lakshminarasimhan]

There are two places where you use reshape. Which one gives you the error?

[Melaku Eneayehu]

This one (second)

imIDX= reshape(IDX, size(a));

[KSSV]

YOu must attach your image....code is working fine for my image...

[Melaku Eneayehu]

[KSSV]

It works fine..no error I am getting....

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[Melaku Eneayehu]

what's your matlab version? mine was 2015a

[Guillaume]

Matlab version is irrelevant, reshape has always behaved the same in all versions. Similarly, I assume kmeans has always returned results the same size.

Image is irrelevant since the data is reshaped the same size it started with.

As per my answer, the code shouldn't error. So, please answer the questions in my answer so we can understand what's particular about your machine.

Answer 1

[Guillaume]

I don't see how the code shown can result in the error stated.

Note that another way to write your first reshape is:

imData = a(:);

Either way, you're simply flatting your image into a single column. You're passing that through kmeans which is guaranteed to return a column of the same length, so you still have as many elements as the original image. You're then reshaping that column into the original image size. It's simply not possible for it to error.

Therefore, the first question is: is the code shown the one you actually use, or a simplification? If it is the actual code, then issue a dbstop if error at the command prompt, run your code, and when it breaks into the debugger because of the error, give us the result of:

size(a)
size(imData)
size(IDX)

so we can understand better what is going on.

edit: also give us the output of

which kmeans

[Melaku Eneayehu]

sir actually am junior for matlab in this example i want to segment the image using k-means clustering, when i try this code i got this error.

[Guillaume]

I perfectly understood what you are trying to do. Once again, do what I said in my answer. Enter dbstop if error at the command line. Run your code and when it breaks into the debugger give us the output of:

size(a)
size(imData)
size(IDX)
which kmeans

and we'll work from there.

Answer 2

[Manochandar Thenralmanoharan]

imData = reshape(a,[],1); what the statement implies?

[Walter Roberson]

That reshapes to one column and as many rows as necessary to hold the entire array.