MATLAB: How to make a video out of sequenced images in order

image-videoimage2videoMATLAB and Simulink Student Suitematlab coderMATLAB Compilernatural filename sorting

I have this code to make video file from a set of images. I have a folder with 1240 images numbered in order from 1 to 1240. But the video from the code does not start from the image1 but from the image numbered 1000 and goes till 1240 and starts from 1 to 999 again. I know that the reading of images from folder to matlab is going wrong somehow, but how to correct that?
What should I change in order for the video to start from image1 and go till the end. Appreciate the help.
if true
  % % Make an avi movie from a collection of PNG images in a folder.
% Specify the folder.
myFolder = 'H:\My Documents\windowbanktests\tudMAT50M\images';
if ~isdir(myFolder)
  errorMessage = sprintf('Error: The following folder does not exist:\n%s', myFolder);
  uiwait(warndlg(errorMessage));
  return;
end
% Get a directory listing.
filePattern = fullfile(myFolder, '*.PNG');
pngFiles = dir(filePattern);
% Open the video writer object.
writerObj = VideoWriter('YourAVI.avi');
writerObj.FrameRate = 10;
open(writerObj);
% Go through image by image writing it out to the AVI file.
for frameNumber = 1 : length(pngFiles)
  % Construct the full filename.
  baseFileName = pngFiles(frameNumber).name;
  fullFileName = fullfile(myFolder, baseFileName);
  % Display image name in the command window.
  fprintf(1, 'Now reading %s\n', fullFileName);
  % Display image in an axes control.
  thisimage = imread(fullFileName);
  imshow(thisimage);  % Display image.
  drawnow; % Force display to update immediately.
  % Write this frame out to the AVI file.
  writeVideo(writerObj, thisimage);
end
% Close down the video writer object to finish the file.
close(writerObj);
end
Related Question