adding data to a cell array without loosing the order

Question

vania todorova 2021-7-27

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https://ww2.mathworks.cn/matlabcentral/answers/886609-adding-data-to-a-cell-array-without-loosing-the-order

评论： vania todorova 2021-7-27

I have images in a imagedatastore that i want to add to a cell array but i need them to stay in the same order as they are frames from a vid really . how do i do that? i tried this but it does not keep the order . i have 24000 images that i want in stacks of 5. so it needs to have 4800 rows and 5 columns

C{(4800),5} = [];
for i = 1:length(ds.Files) 
    img = readimage(ds,i);
    C{i}=img(i) ;
    
end 

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Stephen23 2021-7-27

Why are you using imagedatastore if you just want to store all of the image data in a cell array?

The whole point of an imagedatastore is that it is a special class which is a collection of image files that does not load them all into memory. As far as I can tell, your current approach does not utilize the imagedatastore at all.

Note that unless you are working with tiny images, importing all 24000 of them into memory at once is going to require quite a bit of memory: does your computer have sufficient memory to store all images at once and perform whatever operations you want on them?

Most likely you need to re-think your approach (hint: use the imagedatastore instead of a cell array).

vania todorova 2021-7-27

a good part of the answer wuld be i m not that familiar with matlab.the goal is to create a stack of 5 frames. all the images in the subfolders are frames from a vid and i need them in a group of 5 for block matching .i thought that a cell array be easier in they are in a row of 5 together to just pull from each column. maybe i can just feed i+5 from the imagedatastore directly ? how do i read more about how to utalize the image datastore? i see the images are printing but honestly having hard time understand how does it work

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Answer 1

KSSV 2021-7-27

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/886609-adding-data-to-a-cell-array-without-loosing-the-order#answer_754504

编辑：KSSV 2021-7-27

在 MATLAB Online 中打开

idx = 1:24000;
id = reshape(idx,5,[])' ;
[m,n] = size(id) ; 
C = cell(m,n) ; 
for i = 1:m
    for j = 1:n
        C{i,j} = readimage(ds,id(i,j));        
    end        
end 

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KSSV 2021-7-27

The order is maintained, you need not to worry. I suspect there might be memory issues if you read all the images.

vania todorova 2021-7-27

ya it is! no , no issues as i have a pretty powerfull pc. now trying to figure out how to pull a column out of the array to feed for each frame .. thank you again!

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