# How to make a gif of an already animated figure

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Maarten el 21 de En. de 2016
Hello,
I have been looking around for a bit but I cannot seem to find a solution which works for me.
So a colleague of mine send me a code which explains a proposal he made. This explaination is done by updating a figure using a loop, thus animating it. I would like to save this as animation as a .gif file, but I cannot get it to work. As soon as I open the file, I see the first frame and then the gif turns black.
So this is the code:
clear all
close all
C=double(C);
%[x,y]=ndgrid(1:128);
%[X,Y]=ndgrid(28+(1:100));
% cut image to 100 by 100 pixels
Ctx=C(29:128,29:128);
clear x y X Y
Cmax=max(Ctx(:));
Cmin=min(log10(Ctx(:)/Cmax));
figure(1)
image(255*(1-log10(Ctx/Cmax)/Cmin))
axis equal
colormap bone(256)
% Ftx is the 2D Fourier transform of the original image Ctx
Ftx=fftshift(fft2(Ctx));
Fmax=max(20*log10(abs(Ftx(:)+1)));
Fscale=255/Fmax;
figure(2)
image(Fscale*20*log10(abs(Ftx+1)))
axis equal
colormap bone(256)
% Acc1-3 are the resulting (integrated) CCD images of the 3 succesive camera's
Acc1=zeros(size(Ctx));
Acc2=zeros(size(Ctx));
Acc3=zeros(size(Ctx));
% per timestep Ftx shifts along the 3 camera postions with aperture stops
% in between. The sweep is performed from the bottom to the top.
for timestep=1:460 % in ns at 10 Mfps
% LB is the total plane in front of the lens bank
% 3 x (100x100) plus aperture stops of 3 x (20x100)
LB=zeros(360,100);
% in principle 1 tot 100
Start_Row_Index=1;
End_Row_Index=100;
% exception at begin and end
if timestep < 100
End_Row_Index=timestep;
elseif timestep > 360
Start_Row_Index=timestep-359;
end
% let Ftx shift over the entrance of the lens bank
Row_Index=Start_Row_Index:End_Row_Index;
LB(360-timestep+Row_Index,:)=Ftx(Row_Index,:);
% devide LB over 3 camera channels
N1=LB(241:340,:);
N2=LB(121:220,:);
N3=LB(1:100,:);
% get image from each Fourier transform
B_blind=zeros(20,100); % the aperture stop
B1=abs(ifft2(N1));
B2=abs(ifft2(N2));
B3=abs(ifft2(N3));
% assemble the total image at the image plane (the CCD camera's)
B=cat(1,B3,B_blind,B2,B_blind,B1, B_blind);
% determine the integrated image on the CCD's per frame
Acc1=Acc1+B1/100;
Acc2=Acc2+B2/100;
Acc3=Acc3+B3/100;
% image on the CCD's
Acc=cat(1,Acc3,B_blind,Acc2,B_blind,Acc1,B_blind);
figure(3)
% plot
% left row: sweep of the Fourier transform
% middle row: resulting image on the plane of the CCD camera's
% right row: integrated pixel values on the CCD's
subplot(1,3,1)
image(Fscale*20*log10(abs(LB)+1))
axis equal
axis([0 100 0 360])
subplot(1,3,2)
image(B)
axis equal
axis([0 100 0 360])
subplot(1,3,3)
image(Acc)
axis equal
axis([0 100 0 360])
colormap bone(256)
drawnow
pause(.1)
end
% normalization of the images in column 3
subplot(1,3,3)
AccMax=max(Acc(:));
AccMin=min(Acc(:));
image(255*(Acc/AccMax))
axis equal
axis([0 100 0 360])
colormap bone(256)
The code requires the following image
f = getframe(figure(3));
[im,map] = rgb2ind(f.cdata,256,'nodither');;
im(:,:,1,timestep) = rgb2ind(f.cdata,map,'nodither');
in the loop followed by
imwrite(im,map,'Fourier.gif','gif','LoopCount',Inf,'DelayTime',1);
but this gave me the one-frame followed by black gif
I want the gif to be an animated image of the full figure with timestep (from 1 to 460).
Could anyone help me to a solution?
Thanks, Maarten
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Mike Garrity el 21 de En. de 2016
You also need WriteMode=append or the imwrite keeps creating a new file.
See the example at the end of this blog post .
##### 1 comentarioMostrar NingunoOcultar Ninguno
Adam Danz el 23 de Mzo. de 2022
Starting in Matlab R2022a, another option is to use exportgraphics with append=true. See this Community Highlight for an example.

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