3D matrix to Video

Hello all, I have been having a lot of trouble trying to export a video from Matlab from a 3D matrix. The matrix dimensions indicate frame height, width and frame number. The element values are what is being used to form images with commands such as imagesc or imshow. I can create a video in Matlab by putting the imshow or imagesc command in a for loop but I want to extract something equivalent from Matlab to put in youtube or imbed in a powerpoint or soemthing. Here's an example of the situation:

IM % an mxnxz matrix

for i = 1:size(IM,3);
    imshow(IM(:,:,i))
    pause(.001);
end

Since the matrix has no color information after processing I have run into problems using WriteVideo or im2frame command. Thanks for any help.

Answer 1

[Stephen23]

It is easy to use getframe and videoWriter object. Here is an example from the videoWriter object help:

v = VideoWriter('peaks.avi');
open(v);

Generate initial data and set axes and figure properties.

Z = peaks;
surf(Z); 
axis tight manual 
set(gca,'nextplot','replacechildren');

Create a set of frames and write each frame to the file.

for k = 1:20 
   surf(sin(2*pi*k/20)*Z,Z)
   frame = getframe;
   writeVideo(v,frame);
end

close(v);

[Andrew Chen]

Thanks for the response! Is there some easy way to iterate the VideoWriter command? What I mean by this is that I can see a "video" in Matlab by sequentially showing the frames by useing imshow in a for loop as shown above. The Video Writer has an example where the video object is opened and a .jpeg is written and the video object is closed:

A = imread('peppers.png');

% Create a |VideoWriter| object for a new uncompressed AVI file for RGB24 video.
v = VideoWriter('newfile.avi','Uncompressed AVI');

% Open the file for writing.
open(v)

% Write the image in |A| to the video file.
writeVideo(v,A)

% Close the file.
close(v)

Is it as easy as opening and closing the video pbject in the for loop I wrote above? Would I close the video object after the for loop is completed? Thanks for your time.

[Andrew Chen]

I Just saw your edits, I'll give it a try! Thanks!

[Andrew Chen]

Thanks! It worked!

Answer 2

[Guangxu Li]

Video to 3D image (single channel)

filename="./*.avi";

obj = VideoReader(filename);

vid = read(obj);

mImage=obj.Width;

nImage=obj.Height;

frames = obj.NumberOfFrames;

Image3D=zeros(nImage,mImage,frames,'uint8');

for x = 1 : frames

Image3D(:,:,x)=vid(:,:,1,x);

end

niftiwrite(Image3D,filename);

[Melika Bahmanabasdi]

Hi Guangxu Li ,

Thankyou for your answer. I have a question. Why we should use rote90 in Image3D=rot90(Image3D); ?

I can`t understand the reason.

many thanks

[Guangxu Li]

Dear Bahmanabasdi,

I am very sorry. Please ignore the rotation and flipud lines. That is for my case.