Saving a montage image

I created a montage of an RGB and logical image and stored t into a variable 'h'. The content of the variable 'h' is of the type 'image'. I would like to save 'h' into a folder. I have tried to use saveas and imwrite but I am unable to do so. My code and the resulting errors are as follows. How can I save the image in variable 'h'?

    ImFileOut = fullfile(ImOutFolder, ImName)
    ImCell = {RGBIm, LogicalIm};
    h = montage(ImCell); %file type is '1x1 Image'
    saveas(h,ImFileOut);
    % Error using saveas 
    % Invalid handle.
    
    imwrite(h,ImFileOut);
    %Error using imwrite (line 427)
    %Expected DATA to be one of these types:

    %numeric, logical

    %Instead its type was matlab.graphics.primitive.Image.

Answer 1

[Rik]

There is a difference between an image and an image object. The latter is a graphics object that is shown in the axes. It does contain the data required to write the montage to an image. The code below generates some example data and then writes a montage to a file. You can adapt it to suit your specific needs.

%generate required variables
ImOutFolder=pwd;
ImName='example_montage.png';
RGBIm=randi(127,100,100,3,'uint8');
LogicalIm=logical(randi([0 1],100,100));

%compose inputs
ImFileOut = fullfile(ImOutFolder, ImName);
ImCell = {RGBIm, LogicalIm};

%create montage and extract color data from the image object
figure(1),clf(1)%create a clean figure (use clf only in debugging)
h=montage(ImCell);
montage_IM=h.CData;

%write to file
imwrite(montage_IM,ImFileOut);

[Rik]

Did this suggestion solve your problem? If so, please consider marking it as accepted answer. It will make it easier for other people with the same question to find an answer. If this didn't solve your question, please comment with what problems you are still having.

[Sandy Woo]

I could recommend adding the CData properties into the help doc on the website, as the montage images could be very helpful when writing a paper. I failed to save the montage image until I noticed this answer. Meanwhile, when I'm doing the batch processing, I would not hope the figure window to jump out frequently. So I will search for a method to hide the window and save the montage image.

[Rik]

The CData property is in the doc: on the page with properties of image objects.

If you want to hide things in a loop you have two options: open a figure at the beginning and set Visible to off. Then use explicit handles when calling montage. The other option is to reimplement montage yourself, which is what I did myself.

[Koosha]

Thank u soooo much.