How to make frame size same for subplots run in loop to make video using videowriter?

Hi friends,

I have written a code to make movie using videowriter command. But I am getting error.

close all
clear all
clc

theta=0:0.1:2*pi;
vidObj = VideoWriter('testMovie.avi');
open(vidObj);
for ii=1:100
    ii
    subplot(1,2,1)
    plot(theta,sin(theta));
    subplot(1,2,2)
    plot(theta,cos(theta));
    currFrame=getframe;
    writeVideo(vidObj,currFrame);
    close all
end
  close(vidObj); 

The error is saying frame is not matching with the previous figure.

Thanks in advance.

Answer 1

[Walter Roberson]

yes that can happen . plot() inside an axes can end up rendered slightly different sizes.

probably the easiest way to fix this is to imresize the result of getframe to a consistent size.

It is possible that you might notice the axes positions shifting slightly from frame to frame and it could even be the case that what should be the same curves move slightly depending upon the labels associated with the data. If you need the boxes to be exactly aligned frame to frame then you might need further precautions .

[Raj Kishor]

Can you tell me where and how I should use imresize?

[Walter Roberson]

After

currFrame=getframe;

use

if ii == 1
    framesize = [size(currFrame, 1), size(currFrame,2)];
else
    currFrame = imresize(currFrame, framesize);
end

This will make all frames the same size as the first frame, whatever size that turns out to be.

[Raj Kishor]

Thanks walter

It worked after small modification.

if rr == 1

framesize = [size(currFrame.cdata, 1), size(currFrame.cdata,2 )];

else

currFrame = imresize(currFrame.cdata, framesize );

end

[Walter Roberson]

Makes sense, yes.