how to read multiple pgm images ?
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I'm working with a database which has 472 pgm files inside a folder named faces. I want to read all 472 and store it I
also each file inside the folder is name cmu_0000.pgm..........cmu_00471.pgm
4 个评论
Stephen23
2017-8-17
Why not read the MATLAB documentation?:
Or any of the hundreds of threads on this forum that explain how to read files in a loop:
etc., etc.
kitty varghese
2017-8-17
编辑：Stephen23
2017-8-17
Stephen23
2017-8-17
@kitty Varghese: today I formatted your code correctly for you. In future you can do this yourself: simply select the code text and then click the {} Code button.
Stephen23
2017-8-17
@kitty Varghese: there is no point in getting dir to search for files with a .m extension:
thepath = ... *.m';
if what you are after is .pgm files. Do not hard-code how many files there are:
for i=1:472,
when it is much more robust to use numel. I would also recommend avoid i as a variable name.
采纳的回答
Something like this perhaps (untested):
P = 'C:\Users\kitty\Dropbox\non negative factorization\faces\face.test\test\face';
D = dir(fullfile(P,'*.pgm'));
C = cell(size(D));
for k = 1:numel(D)
C{k} = imread(fullfile(P,D(k).name));
end
Note I loaded that data into a cell array: this is because images commonly are stored as a 3D matrix: as an alternative you could store them is a 4D numeric array.
12 个评论
@kitty Varghese: after running the code, please show the outputs of these commands:
size(C)
size(D)
disp(D(1).name)
disp(D(end).name)
disp(k)
"only the last file is getting read."
How are you checking this? What are you looking at that tells you that only the last file is being read?
@kitty Varghese: Are you certain that all of the images have the same size?
Note that as I mentioned in my answer, most likely your images are 3D RGB images, which means that concatenating them along the 1st, 2nd, or 3rd dimension will probably not give you a very useful numeric array. That I why I put them into a cell array, then each image is conveniently stored as its own array.
If you really want to merge them into one numeric array then the most important step is to ensure that all of the images have the same size:
cell2mat(cellfun(@size,C(:),'uni',0))
and check that all sizes are the same. You could concatenate them along any dimension that you choose:
cat(4,C{:})
would likely be the most useful for further analysis. Alternatively, if you really have 2D images(e.g. grayscale or indexed) then you could concatenate along the third dimension.
kitty varghese
2017-8-18
kitty varghese
2017-8-18
kitty varghese
2017-8-18
@kitty verghese: If you do not need all of the images stored after the loop then of course you can get rid of the cell array altogether:
I = imread(fullfile(P,D(k).name));
and continue with whatever processing you wish to do.
kitty varghese
2017-8-21
It sounds like each image is sized 19x19, and you want to reshape each image into a column, before concatenating into one array. Here is one solution (untested):
for k = 1:numel(D)
I = imread(fullfile(P,D(k).name));
C{k} = I(:); % reshape image into column
end
M = horzcat({:});
kitty varghese
2017-8-21
kitty varghese
2017-8-21
编辑：Walter Roberson
2017-8-21
Vipasha Sharma
2019-5-23
can anyone help me with code for reading multiple HDF files?
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