what does (:,:,:,x) mean in matlab?

Question

Sneheet 2014-3-20

回答： Frank 2014-3-20

obj = mmreader('rhinos.avi');

vid = read(obj);

frames = obj.NumberOfFrames;

ST='.jpg';

 for x = 1:frames
      Sx=num2str(x);
      Strc=strcat(Sx,ST);
      Vid=vid(:,:,:,x)
      imwrite(Vid,Strc);
 end

In the above code what does vid(:,:,:,x) mean?

Answer 1

Frank 2014-3-20

vid is a four-dimension matrix. vid = vid(:,:,:,:).

And if you specify anyone of the four dimensions, it indicates a 3-dimension matrix.

For example:

a = [1 1 1; 1 1 1; 1 1 1;]

a is a 3*3 matrix, if you specify any of the two dimensions for example a(:,1), then it's a one dimension matrix, i.e. an array [1 1 1]'.