How to save images as jpgs from .mat files struct

Hi ,I have 3064 .mat files dataset of brain tumors ,Prepareing data with lables for CNN.Each .mat file has struct 1x1 . Struct has following has these information: cjdata.image and cjdata.label.

And image is stored as cjdata.image.

I want to load all the .mat files:

1.mat ,2.mat ,3.mat ........................3064.mat

Want to apply these three opertions on each .mat file iteratively using a loop

1- accessing image from struct

2.convert into gray scale

3.save grayscale image as as 1.jpg 2.jpg.....3065.jpg

% Reading folder that has 3064 .mat files
myFolder = 'C:\Users\join2\Desktop\FIGSHARE\figshare data progress\figshare jpg data\3064 images';
filePattern = fullfile(myFolder, '*.mat');
Pgraymap = dir(filePattern);
 for I = 1:length(Pgraymap)
   baseFileName = Pgraymap(I).name;
   str = fullfile(myFolder, baseFileName);
   fprintf(1, 'Now reading %s\n', str);
   img1 = imread(str); % new
%  load .mat
   d=load(filePattern);
% acessing  images from  .mat files. each .mat has image as strcture,that
% is "cjdata.image"
   d.cjdata.image;
% gray scale conversion
   d=im2uint8(d);
% save all d.cjdata.image as jpgs in myFolder .plz help i don't know how to save
end

Answer 1

[Akira Agata]

To save matrix as an image, please use imwrite function.

In addition, if you save your data as an image file, I would recommend saving as .tiff or .png to keep data accuracy, because .jpg is a lossy compression method.

The following is a simple example.

inputFolder = 'C:\Users\join2\Desktop\FIGSHARE\figshare data progress\figshare jpg data\3064 images';
outputFolder = pwd; % Please change, if needed.
fileList = dir(fullfile(inputFolder,'*.mat'));

for kk = 1:numel(fileList)
  S = load(fullfile(fileList(kk).folder,fileList(kk).name));
  I = S.cjdata.image;
  I = mat2gray(I);
  fileName = replace(fileList(kk).name,'.mat','.tiff');
  imwrite(I,fullfile(outputFolder,fileName));
end

[Mamoona Nisar]

thankyou for replying sir.

I have tried your code and it is giving error:

Reference to non-existent field 'folder'.

Error in x (line 6)

S = load(fullfile(fileList(kk).folder,fileList(kk).name));

thanks

[Stephen23]

Replace

fileList(kk).folder

with

inputFolder

[Mamoona Nisar]

now this error

Undefined function 'replace' for input arguments of type 'char'.

Error in x (line 9)

fileName = replace(fileList(kk).name,'.mat','.png');

[Stephen23]

Replace

replace

with

strrep

(Actually using replace or strrep is fragile and I would not recommend doing this: it will replace exactly that substring even if occurs in the middle of the filename. The robust way to write this code would be to use the second output of fileparts).

[Mamoona Nisar]

thankyou so much for your help. @Akira Agata

Successfully saved all data as jpgs.

[Akira Agata]

Hi Mamoona-san,

I'm glad to hear that you successfully saved all data!

By the way, the errors you mentioned here would be due to your MATLAB version.

The field 'folder' for ourput variable of dir function was added in R2016b, and replace function was introduced in R2016b as well. So, if your MATLAB version is R2016a or earlier, these error appears.

[Mahesh Potdar]

Hello ,

I think I am also using same data.(.mat file).

Code is running with no error.

Where I will check .tiff images data/ how to show image?

I am using Matlab 2016a.

[Mamoona Nisar]

open the folder where you have saved the file. @mahesh

outputfolder="path"

[Mahesh Potdar]

Thanks .. I will check..

[Mahesh Potdar]

@Mamoona Nisar- Will you share your Email Id, Please?

[Asaf Raza]

Mamoona kindly can you share the images data with me

[Meenakshi]

can you share the image data?