Creating a movie sequence from rgb images

Dear All,

Given a 3D array of grayscale images (M by N by K - where k is the number of images), and a 3D array of binary masks; I would like first of all to produce a series of images where the boundary of each mask (i.e. boundary = edge(mask)) has been drawn on to the corresponding image in red; then I would like to create a new array of these truecolor images and display it as a movie.

The problem is in creating the new array of truecolor images. I tried this code:

 new_sequence(:,:,3,frame_idx) = imoverlay(image, boundary, [1 0 0]);

but it produced a subscripted assignment dimension mismatch error.

So then I tried the following solution:

for frame_idx = start_frame:end_frame

     image = dataset(:,:,frame_idx);
     msk = mask_stack(:,:,frame_idx);
     boundary = edge(msk, 'canny'); 
     rgb = imoverlay(image, boundary, [1 0 0]);
     [X(:,:,1,frame_idx), map] = rgb2ind(rgb, 3);

end

 mov = immovie(X,map);
 implay(mov);

But the resulting colormap of the movie was not what I expected; I would like the frames the movie to be grayscale (i.e. unchanged) with the boundaries drawn in red - however this code produces a movie with something like a grayscale colormap but the boundary also in gray.

If anyone can help - it would be much appreciated!

-n

Answer 1

[Chaowei Chen]

for frame_idx = start_frame:end_frame

       image = dataset(:,:,frame_idx);
       msk = mask_stack(:,:,frame_idx);
       boundary = edge(msk, 'canny'); 
       rgb = repmat(image,[1 1 3]);
       rgb(:,:,1)=max(boundary,image);
       rgbf(:,:,:,frame_idx)=rgb;
  end
  mov = immovie(rgbf); implay(mov);

[noam Y]

is it possible to simply write the RGB image to the rgbf array without code lines 2-5?

[Walter Roberson]

The original question involved having a sequence of masks that needed to be overlayed into the frames. Do you have that requirement as well? If not then you could use

rbgf = dataset(:, :, start_frame : end_frame );
rgbf = repmat( permute(rgbf, [1 2 4 3]), 1, 1, 3, 1);

This code assumes you are moving from grayscale frames to RGB with equal R, G, and B components, for further processing. If you are only intending to write the frames as movies from there, then you would be better off leaving it as grayscale:

rgbf = permute(dataset(:, :, start_frame : end_frame ), [1 2 4 3]);