Why I cannot use Alexnet on my images dataset

Question

Hiba Basim Alwan 2018-1-27

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https://ww2.mathworks.cn/matlabcentral/answers/379353-why-i-cannot-use-alexnet-on-my-images-dataset

回答： Rasaq Kotun 2019-2-12

clc;
clear;
images = imageDatastore('C:\Users\HIBA\Documents\Cancellable Biometrics\Datasets\NIST Faces 1','IncludeSubfolders',true,'LabelSource','foldernames');
[trainingImages,testingImages] = splitEachLabel(images,0.7,'randomized');
net = alexnet;
net.Layers;
layer = 'fc7';
trainingFeatures = activations(net,trainingImages,layer,'outputAs','channels');
testFeatures = activations(net,testingImages,layer);

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Answer 1

Walter Roberson 2018-1-28

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https://ww2.mathworks.cn/matlabcentral/answers/379353-why-i-cannot-use-alexnet-on-my-images-dataset#answer_302116

alexnet needs R2016b or later, and requires Neural Network toolbox and requires Neural Network Toolbox Model for AlexNet Network support package

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Walter Roberson 2018-1-28

编辑：Walter Roberson 2018-1-29

在 MATLAB Online 中打开

One of your images is a different size than the others.

The below code assumes you are using a newer release of MATLAB, which you indicate you are.

projectdir = 'C:\Users\HIBA\Documents\Cancellable Biometrics\Datasets\NIST Faces 1';
dinfo = dir(fullfile(projectdir, '**', '*.*'));
dinfo([dinfo.isdir]) = [];
filenames = fullfile({dinfo.folder}, {dinfo.name});
numfile = length(filenames);
info_struct = struct('filename', '', 'Width', nan, 'Height', nan, 'ColorType', '', 'Message', 'not a valid image file');
image_info(numfile) = info_struct;
info_valid = false(numfile, 1);
for idx = 1 : numfile
    thisfile = filenames{idx};
    this_info = info_struct;
    this_info.filename = thisfile;
    try
        lastwarn('');
        info = imfinfo(thisfile);
        msgstr = lastwarn();
        if ~isempty(msgstr)
            this_info.Message = msgstr;
            info_valid(idx) = true;
        elseif length(info) == 1
            this_info.Message = '';
            info_valid(idx) = true;
        elseif length(info) > 1
            this_info.Message = 'image file with multiple images';
            info = info(1);
            info_valid(idx) = true;
        end
        if length(info) == 1
            this_info.Width = info.Width;
            this_info.Height = info.Height;
            this_info.ColorType = info.ColorType;
        end
    catch ME
    end
    image_info(idx) = this_info;
end
image_info = image_info(info_valid);

After this, image_info will be a struct with information about all of the image files under the given directory. You can examine, for example

unique([image_info.Width])
unique([image_info.Height])

Sometimes imfinfo produces warnings as it goes: the warnings will be stored in the Message field of the structure. Some image files store multiple images, and in some image file formats those are not guaranteed to be the same size. Only the size information about the first image is returned by the above code, but in such case the Message field is set to 'image file with multiple images'

Hiba Basim Alwan 2018-1-29

Thank you so much for your helping

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Answer 2

Rabia Afzal 2018-2-4

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https://ww2.mathworks.cn/matlabcentral/answers/379353-why-i-cannot-use-alexnet-on-my-images-dataset#answer_303390

i'm also facing the same issue. Can anyone help me in my code?

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Walter Roberson 2018-2-6

Start with the code I posted in https://www.mathworks.com/matlabcentral/answers/379353-why-i-cannot-use-alexnet-on-my-images-dataset#comment_529351 but replace projectdir with a character vector that is the top level directory under which all of the images of interest are stored. Run the code and examine the returned information, such as unique([image_info.Width]) to determine what widths actually occur in your files.

Hiba Basim Alwan 2018-2-6

Dear Rabia Afzal

I run the code provided by Walter Roberson and I found that my images is not on the accepted size stated by Alexnet ([227, 227, 3], but in your mind that your images should be color images with three channels). So, I embedded the below code found on Matlab Answers in my program to fix all my images size to 227, 227.

Regards,

images_set.ReadFcn=@(images_set)imresize(imread(images_set),[227 227]);

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