access to each image channel existing in a folder

Hello folks,

I'm trying to access to each image channel existing in the folder and calculate after PSNR and SSIM of each channel. I developped this code but I still have an error to access to each image channel. Any idea to make it work please.

imgFolderStokes = fullfile('saveAssia/StokesPaarameters/');
imgFolderLinear = fullfile('saveAssia/Linear_Separable_Model/');
imgStokes = imageDatastore(imgFolderStokes);
imgLinear = imageDatastore(imgFolderLinear);
numOfImgStokes = length(imgStokes.Files);
numOfImgLinear = length(imgLinear.Files);

for ii = 1:numOfImgStokes
    for jj = 1:numOfImgLinear
        Stokes{ii} = fitsread(imgStokes.Files{ii})
        Linear{jj} = fitsread(imgLinear.Files{ii})

        Iu_s = Stokes(:,:,1);
        Ip_s = Stokes(:,:,2);
        Theta_s = Stokes(:,:,3);
        Iu_L = Linear(:,:,1);
        Iu_L = imresize( Iu_L,[size(Iu_s,1) size(Iu_s,2)]);
        Ip_L = Linear(:,:,2);
        Theta_L = Linear(:,:,3);
        [ssim] = ssim(uint8(Iu_s),uint8(Iu_L));
        [psnr] = psnr(uint8(Iu_s),uint8(Iu_L));
    end
end

avr_peaksnr = sum([psnr]) / len([psnr])
avr_snr = sum([ssim]) / len([psnr])
fprintf('\n The      Peak-SNR value is %0.4f', avr_peaksnr);
fprintf('\n The SNR value is %0.4f \n', avr_snr);

ERROR

Index in position 3 exceeds array bounds (must not exceed 1).

Error in PSNR_SSIM (line 96)
        Ip_s = Stokes(:,:,2);

[Jan]

Whenever you mention in the forum, that you get an error, post a copy of the complete message. It is easier to solve a problem than to guess, what the problem is.

[assia assia]

Thank you. I just edit my question.

[Yongjian Feng]

Is it a black and white image?

[assia assia]

The first one has a 3 channels and the second one has 6 channels

Stokes =

  1×1 cell array

    {300×300×3 double}


Linear =

  1×1 cell array

    {234×244×6 double}

Answer 1

[Image Analyst]

Evidently

Error in PSNR_SSIM (line 96)

Ip_s = Stokes(:,:,2);

means that there is no third dimension to your Stokes array. The third dimension has a max of 1, basically meaning there is no third dimension. It's a gray scale monochrome image, not a RGB color, or multispectral, or volumetric image with multiple slices along the third (Z) dimension.

In fact, Stokes is not an image at all - it's a cell array because you did this:

Stokes{ii} = fitsread(imgStokes.Files{ii})

so it's a cell array - a 1-D array of cells. Inside each cell may be an image but you have to use braces to get to it:

thisImage = Stokes{ii}; % Get contents of cell.

See the FAQ:

https://matlab.fandom.com/wiki/FAQ#What_is_a_cell_array.3F

[assia assia]

Stokes =

  1×1 cell array

    {300×300×3 double}

How can I access to each channel in that case please

[Jan]

Stokes{1}(:, :, 3)

[assia assia]

Thank you for your help.