how can i split an image into 25 blocks using for loop?

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eman 2015-1-5

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编辑： Mohammad Abouali 2015-1-6

i have a lot of images i need to split each image into blocks then i have to convert each block into one vector (now i have 25 vectors) i need to concatenate these vectors in one row vector finally i want to obtain an array each row in this array is a large vector(25 concatenated vectors) of one image how can i do this thanks in advance

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Answer 1

Mohammad Abouali 2015-1-5

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https://ww2.mathworks.cn/matlabcentral/answers/168980-how-can-i-split-an-image-into-25-blocks-using-for-loop#answer_164048

编辑：Mohammad Abouali 2015-1-5

在 MATLAB Online 中打开

B = im2col(your_image,[m n],'distinct');
B=B(:)';

m and n are the image block sizes.

B at the end is one row vector with your image blocks in it.

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Mohammad Abouali 2015-1-5

编辑：Mohammad Abouali 2015-1-5

在 MATLAB Online 中打开

What about im2col function!?

im2col is a built-in MATLAB function that splits an image into blocks based on the given block size. For more information click here .

Each block would be one column on B. and then B(:)' will concatenate all blocks in a row vector that you wanted.

Pretty much that two lines of code above does everything that you asked.

If you want 25 image block (let's say you divide the image 5 by 5) then m and n are calculated as:

[r,c,~]=size(your_image);
m=floor(r/5);
n=floor(c/5);

If image size is exactly divisible by 5 then no problem but if it is not, then some rows and column ad the end are omitted. If you want you can also use imresize to first resize the image into something that is divisible by 5 and then do the procedure.

You have to reiterate this for each image that you read. if your images are of size R*C and you have n images then something like this:

for i=1:n
  I=read image n % write appropriate code here.
  B = im2col(your_image,[m n],'distinct');
  myDataVector(i,:)=B(:)';
end

Each row of myDataVector would be for one image.

Image Analyst 2015-1-6

allvectors = [];

Mohammad Abouali 2015-1-6

编辑：Mohammad Abouali 2015-1-6

在 MATLAB Online 中打开

As image analyst mentioned before entering the loop initialize all vectors to an empty variable. Something like this:

allvectors=[];
some code here
for i=1:n
  some more code
  vector= ....
  allvectors = [allvectors, vector];
end

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Answer 2

Image Analyst 2015-1-5

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在 MATLAB Online 中打开

See the FAQ: http://matlab.wikia.com/wiki/FAQ#How_do_I_split_an_image_into_non-overlapping_blocks.3F For each block, you can turn it from a 2D subimage into a 1D vector with

vector1d = image2d(:);

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Answer 3

Matt J 2015-1-5

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https://ww2.mathworks.cn/matlabcentral/answers/168980-how-can-i-split-an-image-into-25-blocks-using-for-loop#answer_164071

在 MATLAB Online 中打开

Using MAT2TILES ( Download ),

blocks=mat2tiles(YourImage,25,25);

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how can i split an image into 25 blocks using for loop?

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how can i split an image into 25 blocks using for loop?

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