how do i read random jpeg frames from a folder?

Question

sidra Rafique 2020-1-3

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/498792-how-do-i-read-random-jpeg-frames-from-a-folder

回答： Image Analyst 2020-1-3

采纳的回答： Bhaskar R

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i have a folder consisting of 2000 images .jpg, i want to made random selection of these images.

e.g;

i am using

mgs = dir(fullfile(Directory, '\*.jpg'));
for j=1:length(Imgs)
{
   img = imread(fullfile(Directory,Imgs(j).name));
-----
---
----
}

but i want to select random imgaes in one go as i have same functionalities for all of them.

e.g;

i want to make range for frame 14,25,36,47,58,69,80 etc ( i have observed that these are every 11th frame which i am needing)

is there any way of making such selection.?

i am waiting for response.

thanku in advance

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Stephen23 2020-1-3

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"is there any way of making such selection.?"

Sure, use indexing.

Also note that one of the main reasons for using fullfile is that it handles the file separator character automatically, so you should use it like this:

fullfile(Directory,'*.jpg')

Walter Roberson 2020-1-3

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for j = 14:11:length(Imgs)

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Answer 1

Bhaskar R 2020-1-3

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https://ww2.mathworks.cn/matlabcentral/answers/498792-how-do-i-read-random-jpeg-frames-from-a-folder#answer_408545

编辑：Bhaskar R 2020-1-3

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% assuming your image file names are in sequence as 1.jpg,2.jpg,..., 2000.jpg
n_imges = 10;    % number of random images you want to pick
Imgs = randi([1, 2000], 1, n_imges);    % its the range between 1, 2000 images

( i have observed that these are every 11th frame which i am needing) -This means you need the 11th frame in the range 14 to 80 then

Imgs = 14:11:80;

Your code

mgs = dir(fullfile(Directory, '*.jpg'));
for j=1:length(Imgs)
{
   img = imread(fullfile(Directory,mgs(Imgs(j)).name));
    %-----
    %---
    %----
}

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Answer 2

Image Analyst 2020-1-3

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Try randperm():

fileList = dir(fullfile(Directory, '\*.jpg'));
order = randperm(length(fileList));
for k = 1 : length(fileList)
    index = order(k); % Get random index.
    fullFileName = fullfile(Directory, fileList(index).name)
    fprintf('Reading %s\n', fullFileName)
    img = imread(fullFileName);
    % More code .....
end