How can I make a gif using subplots and avoid an error in function wgifc?

Question

David Kaeser 2021-11-10

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https://ww2.mathworks.cn/matlabcentral/answers/1583259-how-can-i-make-a-gif-using-subplots-and-avoid-an-error-in-function-wgifc

评论： David Kaeser 2021-11-17

采纳的回答： Walter Roberson

在 MATLAB Online 中打开

Hi everyone,

I am trying to generate a gif of my results over different timestep using the following procedure:

h = figure;
filename = 'testnew51.gif';
axis tight manual % this ensures that getframe() returns a consistent size
for t=10:10:100  % t is the percent number in the file name
    subplot(121)
    fn = "T_timestep_"+t+"_precent.bin";
    fid = fopen(fn);       % file for t-th step
    nx = fread(fid,1,'int32');
    ny = fread(fid,1,'int32');
    T = reshape(fread(fid,nx*ny,'double'),nx,ny);
    fclose = (fid);
    contourf(T')
    colorbar;
    
    subplot(122)
    fn = "S_timestep_"+t+"_precent.bin";
    fid = fopen(fn);       % file for t-th stepfid = fopen('S.bin');
    nx = fread(fid,1,'int32');
    ny = fread(fid,1,'int32');
    S = reshape(fread(fid,nx*ny,'double'),nx,ny);
    fclose = (fid);
    contourf(S')
    colorbar;
    
    drawnow
    % Capture the plot as an image 
      frame = getframe(h); 
      im = frame2im(frame); 
      [imind,cm] = rgb2ind(im,256); 
      % Write to the GIF File 
      if t == 1 
          imwrite(imind,cm,filename,'gif', 'Loopcount',inf); 
      else 
          imwrite(imind,cm,filename,'gif','WriteMode','append'); 
      end 
    pause(0.2)
end

However I get the error:

Error using wgifc
Can only append to GIF89a format GIFs.
Error in writegif (line 306)
wgifc(mat, map, filename,writemode,disposalmethod,delaytime,...
Error in imwrite (line 566)
        feval(fmt_s.write, data, map, filename, paramPairs{:});
Error in matlab_run (line 34)
          imwrite(imind,cm,filename,'gif','WriteMode','append');
          

How can I resulve that? Or is there a better way to generate a gif?

And also how can I scale the x-axis and y-axis of the subplots in respect of an scaled entity of nx and ny respectively? So that the ratio of the subplots are representing my original grid.

Thanks a lot already in advance for all your help and time.

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Answer 1

Walter Roberson 2021-11-17

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Your t==1 test is never successful because your for loop is t=10:10:100 and so starts with 10 instead of 1

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David Kaeser 2021-11-17

Thank you very much! It works now perfectly fine!

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Answer 2

Jan 2021-11-10

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https://ww2.mathworks.cn/matlabcentral/answers/1583259-how-can-i-make-a-gif-using-subplots-and-avoid-an-error-in-function-wgifc#answer_828304

编辑：Jan 2021-11-10

在 MATLAB Online 中打开

The calling style "subplot(121)" is outdated for over 20 years now. Use subplot(1, 2, 1) instead.

You can simplify:

reshape(fread(fid,nx*ny,'double'),nx,ny)

to

fread(fid, [nx, ny],'double')

This line redefines the command fclose as a variable:

fclose = (fid);

You want this instead:

fclose(fid);

I guess, that the number of unclosed files stops opening a new file, because the number of simultaneously open files is limited by the operating system. The error message would be misleading, if this is true.

Use fclose('all') in the command window to clean up the already open files or restart Matlab.

how can I scale the x-axis and y-axis of the subplots in respect of an scaled entity of nx and ny respectively? So that the ratio of the subplots are representing my original grid.

I'm not sure, what this means. Maybe:

axesH = subplot(1, 2, 1);
axis(axesH, 'equal');

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David Kaeser 2021-11-10

编辑：David Kaeser 2021-11-13

在 MATLAB Online 中打开

Hi thanks foryour help and inputs. I changed the code now accordingly however I still get an error:

Error using wgifc
Can only append to GIF89a format GIFs.
Error in writegif (line 306)
wgifc(mat, map,
filename,writemode,disposalmethod,delaytime,...
Error in imwrite (line 566)
        feval(fmt_s.write, data, map, filename,
        paramPairs{:});
Error in matlab_run (line 34)
          imwrite(imind,cm,filename,'gif','WriteMode','append'); 

The code is now:

h = figure;
filename = 'testnew51.gif';
axis tight manual % this ensures that getframe() returns a consistent size
for t=10:10:100  % t is the percent number in the file name
    subplot(1,2,1)
    fn = "T_timestep_"+t+"_precent.bin";
    fid = fopen(fn);       % file for t-th step
    nx = fread(fid,1,'int32');
    ny = fread(fid,1,'int32');
    T = fread(fid, [nx, ny],'double');
    fclose(fid);
    contourf(T')
    colorbar;
    
    subplot(1,2,2)
    fn = "S_timestep_"+t+"_precent.bin";
    fid = fopen(fn);       % file for t-th stepfid = fopen('S.bin');
    nx = fread(fid,1,'int32');
    ny = fread(fid,1,'int32');
    S = fread(fid, [nx, ny],'double');
    fclose(fid);
    contourf(S')
    colorbar;
    
    drawnow
    % Capture the plot as an image 
      frame = getframe(h); 
      im = frame2im(frame); 
      [imind,cm] = rgb2ind(im,256); 
      % Write to the GIF File 
      if t == 1 
          imwrite(imind,cm,filename,'gif', 'Loopcount',inf); 
      else 
          imwrite(imind,cm,filename,'gif','WriteMode','append'); 
      end 
    pause(0.2)
end

I have also used cose('all') as sujested.

Walter Roberson 2021-11-16

To check: are you doing the isfile() before you do the imwrite 'loopcount' call, or after that call? The file is not expected to exist until after the call.

David Kaeser 2021-11-16

test_case_1.gif

I tired it as statement just after the "loopcount" call in the script and as well outside of the script after an unsucessful run. When I tried as statement in the script the error message already appeared and the statment is not executed. Outside of the script I get a zero value.

I discouvered however something strange now. If I run your code first Walter Roberson and then my code with the same filename the error disaspears. I get then an gif with the results first from the first code and in the same gif the results from my code. How can make sure that I get only my results in the gif?

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