Error creating an animated GIF in Matlab

Hello everyone,

I am trying to create a GIF showing the evolution of a height field (variable noted "h_reel") through time.

Unfortunately, I am encoutering an error and I am unable to performe what I am attempting to do... Here is my script :

p = figure(21);
filename = 'test.gif';

for i = index_intersection:nfichier
    imagesc(h_reel(:,:,i));
    [X, Y] = meshgrid([1:2048]*echelle,[1:2048]*echelle);
    surf(X,Y,h_reel(:,:,i));

    caxis([min(h_reel,[],'all') max(h_reel,[],'all')])

    title(num2str(i))
    shading interp;
    %pause 0.25;

    frame = getframe(p);
    im = frame2im(frame);
    [imind,cm] = rgb2ind(im,256);

    if i == 1
        imwrite(imind,cm,filename,'gif','LoopCount',inf);
    else
        imwrite(imind,cm,filename,'gif','WriteMode','append');
    end
end

Obtaining this error :

Error using matlab.internal.imagesci.wgifc
Can only append to GIF89a format GIFs.

Error in writegif (line 306)
matlab.internal.imagesci.wgifc(mat, map, filename,writemode,disposalmethod,delaytime,...

Error in imwrite (line 566)
        feval(fmt_s.write, data, map, filename, paramPairs{:});

Could someone help me to solve this problem please ?

Thank you in advance.

Sincerely,

Answer 1

[DGM]

This problem happens when you try to append to a file that doesn't already exist.

for i = index_intersection:nfichier
    % ...
end

If index_intersection is not 1, then the case for writing the first frame won't happen.

You can try something like this.

indices = index_intersection:nfichier;
for framenum = 1:numel(indices)
    imagesc(h_reel(:,:,framenum));
    [X, Y] = meshgrid([1:2048]*echelle,[1:2048]*echelle);
    surf(X,Y,h_reel(:,:,framenum));
    caxis([min(h_reel,[],'all') max(h_reel,[],'all')])
    title(num2str(framenum))
    shading interp;
    %pause 0.25;
    frame = getframe(p);
    im = frame2im(frame);
    [imind,cm] = rgb2ind(im,256);
    if framenum == 1
        imwrite(imind,cm,filename,'gif','LoopCount',inf);
    else
        imwrite(imind,cm,filename,'gif','WriteMode','append');
    end
end

Answer 2

[yanqi liu]

yes，sir，may be add some check flag，such as

p = figure(21);
filename = 'test.gif';
check_flag = 0;
for i = index_intersection:nfichier
    imagesc(h_reel(:,:,i));
    [X, Y] = meshgrid([1:2048]*echelle,[1:2048]*echelle);
    surf(X,Y,h_reel(:,:,i));
    
    caxis([min(h_reel,[],'all') max(h_reel,[],'all')])
    
    title(num2str(i))
    shading interp;
    %pause 0.25;
    
    frame = getframe(p);
    im = frame2im(frame);
    [imind,cm] = rgb2ind(im,256);
    
    % use check
    if check_flag == 0
        imwrite(imind,cm,filename,'gif','LoopCount',inf,'DelayTime',0.2);
        check_flag = 1;
    else
        imwrite(imind,cm,filename,'gif','WriteMode','append','DelayTime',0.2);
    end
end

Answer 3

[Wissem]

Thank you all for your help : now it works. I totally forgot about this line so thanks for your intervention.

Sincerely,