How to save each image generated in a for loop?

for i=1:20
    volume=randi([2 10], 1,1)
    location=randi([10 100], 1, 1)
    
    imagegenerator(volume,location)
end

^This is a simplified example of my code.

I generate random variables which are inputted into a function called imagegenerator, which generates an image.

With the for loop, I'm generating several random images.

I want to

1) save each image with a different name each time (i.e "image 1" "image 2" "image 3", etc.)

2) also save the inputs (volume, location) associated with each image (preferably in the same folder/ with the same name "image 1" "image 2" , etc.)

How can I do this? Thanks!

P.S. I want to be able to use all these images/ their inputs later to put into a machine learning algorithm that'll cluster the images based off the pixels or the inputs (not sure yet).

[Stephen23]

1) use the sprintf method shown here:

https://www.mathworks.com/help/matlab/import_export/process-a-sequence-of-files.html

2) use saveas:

https://www.mathworks.com/help/matlab/ref/saveas.html

or download export_fig:

https://www.mathworks.com/matlabcentral/fileexchange/23629-export_fig

Answer 1

[Abolfazl Chaman Motlagh]

Hi ,you Can use imwrite for saving images. Also use save for 'volume' and 'location'. (you can make datastore and write a Read_function for datastore to import them sequentially for your ML training).

for datastore see this : datastore

Also for images you can use this : imageDatastore

here's some hint: (consider your imagegenerator has image in output).

for i=1:20
    volume=randi([2 10], 1,1)
    location=randi([10 100], 1, 1)
    Name=['image ' num2str(i)];
    save([Name '.mat'],'volume','location');
    I=imagegenerator(volume,location);
    imwrite(I,[Name '.jpg'])
end

[Rachel Dawn]

I tried saving imagegenerator as I, but it says "there are too many output arguments"

which is why I can't seem to save the image that's generated

[Abolfazl Chaman Motlagh]

if you have access to imagegenerator function, just add output wich is final generated image.

you should find image variable in the function file and write it's name as output.

function I=imagegenerator(volume,location)
%%%%%%
% function Content
%%%%%%
end

[Rachel Dawn]

Thank you!

Last question: this is the code that I think is generating the image within imagegenerator function:

% PLOT DENSITIES

colormap(gray); imagesc(-x); axis equal; axis tight; axis off;pause(1e-6);

Which part of this code would I call as "=I"?

Thanks!

[Rachel Dawn]

I did this in the imagegenerator code:

function image=imagegenerator(volume,location)
....
image=x
 colormap(gray); imagesc(-x); axis equal; axis tight; axis off;pause(1e-6);

And then in the script within the for loop, I wrote this:

 image=imagegenerator(volume,location);
  
   %saving image + inputs
    Name=['att6image_' num2str(numdesigns)];
    save([Name '.mat'],'volfrac');
    imwrite(image,[Name '.jpg'])

The images are saving, but they are coming out VERY very tiny + are inverted (black and white colors inverted). How can I fix this?

[Rachel Dawn]

Also, I looked into datastore as you suggested but am still confused on how I would apply it in this case. Would all the images generated from this for loop be saved in some folder? then would I later call these images for machine learning algorithm?

[Abolfazl Chaman Motlagh]

about first question : the image is tiny propobly because the size itself . i don't know this related or not , just guessing. but use size(I) if you don't know the size already.

about inverted image. as you can see argument in imagesc is -x. thats why you see an image but the inverted is saving as image. you can use this transform :

image=-image; % invert the image
% because the values are less than 0 if you save it and read it again you'll see the image corrupted 
% so need to sacle it to be between 0 to 1
I=(image-min(image,[],'all'))/(max(image,[],'all')-min(image,[],'all'))
 % then save I as an image

this will scale up your image for reading.

[Abolfazl Chaman Motlagh]

imageDatastore is a class for saving image addresses. you should have a cell that every cell include path to an image . then write this :

imds=imageDatastore(paths)

for many of application in matlab imageDatastore is supported as Train (Test or validation) of ML or deep learning training process.

every time you use read on your datastore , an image come out as an output.

also Labels of train dataset can be saved in this object.

see:

imagedatastore

it doesnt need read function for this class.

if you use special dataset you can use datastore

datastore (example : use .mat file as a dataset)

but in most cases you should write read_function yourself.

for example this function that train a Network need imagedatastore as first argument.

net = trainNetwork(imds,layers,options)

Answer 2

[S. Walter]

You can print the image:

print('filename','-dpng','-r300')

where '-dpng' can be set to whatever format you want (check out the help file) and '-r300' is the resolution ('-r0' is screen resolution).

To change the filename to image 1 etc you can add the following to your for loop

f_name = ['image ' num2str(i)];
print(f_name,'-dpng','-r300')

Make sure you close your figures after you're done printing them.

Edit: In terms of saving the data, you can just use

save('filename','volume','location')

That will save it as a Matlab .mat file. If you want to write it to file, you should check out "writematrix" or "fprintf".

[Rachel Dawn]

Thank you!

Okay, so the imagegenerator generates an image but in order to print this image don't I have to call it something like

A=imagegenerator(volume,location)

and then print that image A?

When i try this it says there are too many outputs

[S. Walter]

It depends on what the function imagegenerator() allows for output.

Function syntax is:

function [x,y] = FunctionName(a,b)

where x and y are the outputs and a and b are the inputs. If the syntax for imagegenerator is:

function imagegenerator(volume,location)

then the function is not set up to give an output. In this case, you would have to add a line somewhere inside the function to grab the figure handle and output that to A:

function A = imagegenerator(volume,location)
    A = figure;
    plot(volume,location)
end

Then you could change your original loop to:

for i=1:20
    volume=randi([2 10], 1,1)
    location=randi([10 100], 1, 1)
    % Save the image handle
    A = imagegenerator(volume,location);
    % Make a file name
    f_name = ['image ' num2str(i)];
    % Save the figure
    print(A,f_name,'-dpng','-r150')
    % Close the figure
    close(A)
    % Save the variables to a .mat file
    save(f_name,'volume','location')
end

[Rachel Dawn]

You're so so helpful, thank you!

Last question: this is the code that I think is generating the image within imagegenerator function:

% PLOT DENSITIES

colormap(gray); imagesc(-x); axis equal; axis tight; axis off;pause(1e-6);

Which part of this code would I call as "A="?

Thanks!

[S. Walter]

You can either try

A = gcf

at the end of that snippet of code (gcf = "get current figure"). This stores the figure handle in A.

Or you can do it before:

% PLOT DENSITIES  
% Open a new figure window
A = figure;
% Add a colormap
colormap(gray);
% Display the image - store the handle in A
imagesc(-x);
% Make the axis equal and tight
axis equal; 
axis tight;
% Turn the axis off
axis off;
% Pause for a moment
pause(1e-6);

[Rachel Dawn]

Very helpful. Thank you!