Contents

Convert Between Image Sequences and Video

This example shows how to convert between video files and sequences of image files using VideoReader and VideoWriter.

The sample file named shuttle.avi contains 121 frames. Convert the frames to image files using VideoReader and the imwrite function. Then, convert the image files to an AVI file using VideoWriter.

Setup

Create a temporary working folder to store the image sequence.

workingDir = tempname;
mkdir(workingDir)
mkdir(workingDir,'images')

Create VideoReader

Create a VideoReader to use for reading frames from the file.

shuttleVideo = VideoReader('shuttle.avi');

Create the Image Sequence

Loop through the video, reading each frame into a width-by-height-by-3 array named img. Write out each image to a JPEG file with a name in the form imgN.jpg, where N is the frame number.

      img001.jpg
      img002.jpg
      ...
      img121.jpg
ii = 1;

while hasFrame(shuttleVideo)
   img = readFrame(shuttleVideo);
   filename = [sprintf('%03d',ii) '.jpg'];
   fullname = fullfile(workingDir,'images',filename);
   imwrite(img,fullname)    % Write out to a JPEG file (img1.jpg, img2.jpg, etc.)
   ii = ii+1;
end

Find Image File Names

Find all the JPEG file names in the images folder. Convert the set of image names to a cell array.

imageNames = dir(fullfile(workingDir,'images','*.jpg'));
imageNames = {imageNames.name}';

Create New Video with the Image Sequence

Construct a VideoWriter object, which creates a Motion-JPEG AVI file by default.

outputVideo = VideoWriter(fullfile(workingDir,'shuttle_out.avi'));
outputVideo.FrameRate = shuttleVideo.FrameRate;
open(outputVideo)

Loop through the image sequence, load each image, and then write it to the video.

for ii = 1:length(imageNames)
   img = imread(fullfile(workingDir,'images',imageNames{ii}));
   writeVideo(outputVideo,img)
end

Finalize the video file.

close(outputVideo)

View the Final Video

Construct a reader object.

shuttleAvi = VideoReader(fullfile(workingDir,'shuttle_out.avi'));

Create a MATLAB movie struct from the video frames.

ii = 1;
while hasFrame(shuttleAvi)
   mov(ii) = im2frame(readFrame(shuttleAvi));
   ii = ii+1;
end

Resize the current figure and axes based on the video's width and height, and view the first frame of the movie.

f = figure;
f.Position = [150 150 shuttleAvi.Width shuttleAvi.Height];

ax = gca;
ax.Units = 'pixels';
ax.Position = [0 0 shuttleAvi.Width shuttleAvi.Height];

image(mov(1).cdata,'Parent',ax)
axis off

Play back the movie once at the video's frame rate.

movie(mov,1,shuttleAvi.FrameRate)

Credits

Video of the Space Shuttle courtesy of NASA.

Was this topic helpful?