Error while saving image in MATLAB cloud

The error message is the following:

Error using matlab.internal.imagesci.pngwritec
PNG library failed: Write Error.

Error in writepng (line 316)
matlab.internal.imagesci.pngwritec(data, map, filename, colortype, bitdepth, ...
    
Error in imwrite (line 566)
feval(fmt_s.write, data, map, filename, paramPairs{:});

Error in Videos_guapos_orden_4>generate_image (line 332)
imwrite(imind,map,fulldestination);

Error in Videos_guapos_orden_4 (line 124)
generate_image(x,z,tstep,u2,A,fig,destdirectory);

And the generate_image function is

function generate_image(x,z,tstep,u2,A,fig,destdirectory)

    imagen = [flip(u2(3:end-3,:)); u2(3:end-2,:); flip(u2(4:end-3,:)); u2(3:end-2,:); flip(u2(4:end-3,:)); u2(3:end-2,:)];

    imagesc(x,z,imagen, [0 A^2]);        % draw image and scale colormap to values range
    colorbar; % set colorbar

    set(gca,'FontSize',20)

    Z = length(z)-1;
    yticks([0 z(floor(Z/6)) z(floor(Z/3)) z(floor(Z/2)) z(floor(2*Z/3)) z(floor(5*Z/6)) z(Z)])
    yticklabels({'-3/2 d','- d','-1/2 d','0','1/2 d','d','3/2 d'})
    
    X = length(x)-1;
    xticks([x(1) x(floor(X/4)) x(floor(X/2)) x(floor(3*X/4)) x(X)])
    xticklabels({'0','1/4 Z_T','1/2 Z_T','3/4 Z_T','Z_T'})

    drawnow
    frame = getframe(fig);
    im = frame2im(frame);
    [imind,map] = rgb2ind(im,256);
    thisimage = ['img_',num2str(tstep),'.png'];
    fulldestination = fullfile(destdirectory,thisimage);
    imwrite(imind,map,fulldestination); % The error occurs HERE
end

The weird thing is that I only get the error in the cloud version of MATLAB. If I run the same code in my desktop, everything goes smoothly.

Anyone has any idea about where I'm messing up the code?

Thanks!

[Walter Roberson]

What is the value of destdirectory?

Side question: why do you both to convert to indexed image form and write out the indexed form (with colormap). Is there a reason why you are not just writing out the rgb directly? Is this a context that needs the image quantized to 256 colors specifically?

[Gabriel]

Yeah... So I had messed up the value of destdirectory... It had many more '/' than needed and I created the following:

I don't know why it solved the issue. Thank you!

Side question: Bassically, I made that bit of the code a long time ago, when I had never used MATLAB before. I guess I googled how to save a plot to jpg in MATLAB and copied what I've found. As it worked, I've never changed. But yeah, I just realised it was pretty much unnecesary work.

Thank you for the response Walter!

[Walter Roberson]

It would have been better to not have the \ as part of the folder name. That is permitted on Unix but causes interoperability problems.

[Gabriel]

Yeah... It was a badly crafted directory.

Answer 1

[Gabriel]

I messed up the value of destdirectory by entering too many '/'. Fixing it solved the problem.