Convert Between Image Sequences and Video
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.
figure imshow(mov(1).cdata, 'Border', 'tight')
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.