error in saving overwritten images

I am doing image analysis of particle tracking in a fluidized bed. Part of my code is to produce the figure of particle trajectory then save it as png and then finding the covered area. In order to avoid opening too many windows I invisibled the figure and overwrite the saved png images. But after about 900 iteration and images i get this error:

Error using name (line 102)
Cannot create output file '.\fig.png'.

Error in print (line 71)
pj = name( pj );

Error in saveas (line 168)
        print( h, name, ['-d' dev{i}] )

Error in particle_centriod_mark4 (line 61)
saveas(f,'fig.png');

The part of the code which makes the images is a as below:

       f = figure('visible','off');
      plot(part_cen_x(1:i),part_cen_y(1:i),'k-o','LineWidth', 14)
  xlim([30 440]);
  ylim([30 640]);
  axis off
  ax = gca;
  outerpos = ax.OuterPosition;
  ti = ax.TightInset; 
  left = outerpos(1) + ti(1);
  bottom = outerpos(2) + ti(2);
  ax_width = outerpos(3) - ti(1) - ti(3);
  ax_height = outerpos(4) - ti(2) - ti(4);
  ax.Position = [left bottom ax_width ax_height];

saveas(f,'fig.png');

Answer 1

[Walter Roberson]

As a test, try changing

saveas(f,'fig.png');

to

   try
     saveas(f,'fig.png');
   catch ME
     fprintf('There was a problem saving the file.\n');
     fprintf('List of open files is:\n')
     fopen('all')
     fprintf('End of list of open files\n');
     rethrow(ME)
   end

This tests the possibility that MATLAB might be failing to close files, and shows a list of all of the open files. If there are more than a very small number of files listed then MATLAB might be "leaking" files.

[hamed]

It didn't work and the simulation even crashed (but maybe due to my computer issues)

[Walter Roberson]

When you say "didn't work" do you mean that nothing changed, or that you received the "There was a problem saving the file" message?

[hamed]

Actually I couldn't see any error message as the whole Matlab window turned black. I think my computer also has some issues. I tried to use close(f) after saveas and the simulation is still running. let's see how this goes:

   f = figure('visible','off');

      plot(part_cen_x(1:i),part_cen_y(1:i),'k-o','LineWidth', 14)
  xlim([30 440]);
  ylim([30 640]);
  axis off
  ax = gca;
  outerpos = ax.OuterPosition;
  ti = ax.TightInset; 
  left = outerpos(1) + ti(1);
  bottom = outerpos(2) + ti(2);
  ax_width = outerpos(3) - ti(1) - ti(3);
  ax_height = outerpos(4) - ti(2) - ti(4);
  ax.Position = [left bottom ax_width ax_height];

   saveas(f,'fig.png');
   close(f)

[hamed]

still problem exists. However, this time progresses more up to 2750 iterations. I terminated the program using Ctrl+c as it took so long and seems not moving forward. This is the error:

MATLAB has experienced a low-level graphics error, and may not have drawn correctly.
Read about what you can do to prevent this issue at Resolving Low-Level Graphics Issues then restart MATLAB.
To share details of this issue with MathWorks technical support,
please include this file with your service request.
Operation terminated by user during alternatePrintPath

In alternatePrintPath

In print (line 82)
pj = alternatePrintPath(pj);

In saveas (line 168)
        print( h, name, ['-d' dev{i}] )

In particle_centriod_mark4 (line 64)
 saveas(f,'fig.png');

[hamed]

this is the code that finally gives the area fraction of colored area to white area:

       f = figure('visible','off');

      plot(part_cen_x(1:i),part_cen_y(1:i),'k-o','LineWidth', 14)
  xlim([30 440]);
  ylim([30 640]);
  axis off
  ax = gca;
  outerpos = ax.OuterPosition;
  ti = ax.TightInset; 
  left = outerpos(1) + ti(1);
  bottom = outerpos(2) + ti(2);
  ax_width = outerpos(3) - ti(1) - ti(3);
  ax_height = outerpos(4) - ti(2) - ti(4);
  ax.Position = [left bottom ax_width ax_height];

   saveas(f,'fig.png');
   close(f)
  % try
  %      saveas(f,'fig.png');
  %    catch ME
  %      fprintf('There was a problem saving the file.\n');
  %      fprintf('List of open files is:\n')
  %      fopen('all')
  %      fprintf('End of list of open files\n');
  %      rethrow(ME)
  % end
  I=imread('fig.png');
  I=rgb2gray(I);
  BW = imbinarize(I);
  no_white_pixels=bwarea(BW);
  numberOfPixels = numel(I);
  Area_fraction2(i,1)=1-no_white_pixels/numberOfPixels;

Answer 2

[Image Analyst]

I wonder if your axes are just getting really overstuffed with content. Can you try to do this before you plot to each one:

axes(whateverHandle); % Switch to the axes you want to plot new stuff in.
hold off;
cla reset
% plot() or imshow()....

[hamed]

Undefined function or variable 'whateverHandle'.

Error in particle_centriod_mark4 (line 49)
axes(whateverHandle); % Switch to the axes you want to plot new stuff in.

[hamed]

I'm using MATLAB R2017a academic use.

[Walter Roberson]

Change whateverHandle to the handle of the axis you are plotting in.

[hamed]

What's exactly the command for that?

[Walter Roberson]

whateverHandle = ax;

[Image Analyst]

Let's say you're using GUIDE and you have two axes, one called axes1 and the other called axes2. Let's say you want to make the plots in axes2, so you'd do

axes(handles.axes2);

This will make sure that everything (plots, title, axis labels, etc.) takes place in axes2, not axes1. If you have only one plot/axes, then just use gca, or get rid of the axes() call altogether.

[hamed]

I used handle(axes) and it's still running let's see how this goes.

[Image Analyst]

That won't work. Note, I did not do that. handles is a structure, not an structure array, and axes is the name of a built-in function. So calling handles(axes) will throw all kinds of errors.

[hamed]

non of above mentioned code worked as Matlab didn't recognize the function or command:

whateverHandle = ax;

axes(handles.axes2);