How to extract RGB matrices from stacked TIFF file?

I have a (512x512x3xN) image array where 3 corresponds to the R,G,B channels, and N corresponds to the number of images. How can I extract the R,G,B channels from each image?

I will eventually want to compute mean and stdev for each R,G,B channel of each of the N images and put these into a txt file.

Thanks

Answer 1

[Walter Roberson]

squeeze(mean(YourArray, [1 2]))
squeeze(std(YourArray, [], [1 2]))

These should give you a 3 x N array of values that are the means or std over each color plane in each image . There is no need to extract each color plane individually.

If your MATLAB is too old to support multiple dimensions, then you can always do

squeeze( mean(reshape(YourArray, [], 3, size(YourArray,4))) )
squeeze( std(reshape(YourArray, [], 3, size(YourArray,4))) )

This reshapes each color plane of each image into a single column and processes each column.

[iontrap]

ans =

78.5000 64.7500 106.2500

ans =

36.5194 12.5797 6.6521

>>

Here is my output for an example tiff file. This seems to be the R,G,B measurements from only one of the N images. I would like to get a matrix with these measurements for all N images. How can I do this?

[Walter Roberson]

N = 5;
YourArray = randi([0 255], 512, 512, 3, N, 'uint8');

squeeze(mean(YourArray, [1 2]))
squeeze(std(double(YourArray), [], [1 2]))

ans =

127.132061004639 127.566165924072 127.579082489014 127.507698059082 127.727783203125

127.585601806641 127.300945281982 127.553031921387 127.218353271484 127.638935089111

127.607196807861 127.465267181396 127.508388519287 127.246562957764 127.548515319824

ans =

73.8924076662466 73.8391486006418 73.8645348408521 73.9474347695904 73.833758311485

73.9576801440049 73.9752296400623 73.9673059233171 73.8467401920338 73.8984297781487

73.8960669386365 73.9675846490088 73.7850595136846 73.8375167219068 73.986046349694

So that is 3 x 5 output arrays when there were 5 panes.

... In other words the code already does what you are asking for.

[iontrap]

Much appreciated, Walter.

Answer 2

[hosein Javan]

not sure.

% A = your matrix after reading the image file
im = cell(1,n);
for i = 1:N
    im{i} = A(:,:,:,i) % im{i} = individual image number(i)
end

[iontrap]

A = imread('My TIFF.tiff');
im = cell(1,4);
for i = 1:4
    im{i} = A(:,:,:,i) % im{i} = individual image number(i)
end

I am getting the error "Index in position 4 exceeds array bounds (must not exceed 1)" - regarding line 4.

[hosein Javan]

A = imread('My TIFF.tiff');
ndims(a) % check if it is 4
N = size(a,4) % number of frames
im = cell(1,N);
for i = 1:N
    im{i} = A(:,:,:,i) % im{i} = individual image number(i)
end

[iontrap]

a has not been defined.

[hosein Javan]

sorry it's A

[iontrap]

Thanks Hosein. Walter's answer above worked well.

[hosein Javan]

you're welcome, good luck.