How to write a video from png files and/or matlab figures

Hello,

I've been trying to write a simple code that takes a sequence of images and makes a video from them. However, the video file always ends up empty or unreadable, and I have no idea why the code isn't working. This is the code :

video23 = VideoWriter('video23.avi');
%video23.FrameRate = 1;
open(video23);
 
baseN = 'VectorOverlay';
d = '_';
e = 'Individual.png';
f = '-';
 
for i = 1:87
    file_name = [baseN,d,num2str(i),f,num2str(i+1),d,e];
    %VectorOverlay_1-2_Individual.png from PIV analysis
    im = imread(file_name);
    figure(1)
    image(im)
    writeVideo(video23, im);
    
end
close(video23)    
implay(video23);
 

Can someone help me? I also have the images saved as Matlab figures, but matlab won't recognize the file format when I try and get it to read the files.

[Ameer Hamza]

Have you tried without Archival option?

[Anna Clouvel-Gervaiseau]

yes, still doesn't work

Answer 1

[Bjorn Gustavsson]

Try modifying your call to writeVideo to this:

       currFrame = getframe(gcf);
       writeVideo(vidObj,currFrame);

HTH

[Anna Clouvel-Gervaiseau]

Thanks for the answer! I get the following error message :

"Error using VideoWriter/writeVideo (line 368)

Frame must be 1120 by 840"

Also, for some reason the currFrame cdata has dimensions of 840x1120x3, and that seems strange - its been the same whenever I read the images previously.

[Bjorn Gustavsson]

That is strange. (unless you happened to resize your figure-window, since in this version the getframe call captures the entire figure and then you try to write that frame to the avi-file. That must not change size from frame to frame...)

You can try to simply check the sizes of all frames:

for i1 = 1:87
    file_name = [baseN,d,num2str(i1),f,num2str(i1+1),d,e];
    %VectorOverlay_1-2_Individual.png from PIV analysis
    im = imread(file_name);
    figure(1)
    image(im)
    currFrame = getframe(gcf);
    % writeVideo(vidObj,currFrame);
    szCF = size(currFrame);
    frame_sz(i1,1:numel(szCF)) = szCF;
end

Then you can check that the frame-size doesn't change through the loop.

HTH