MATLAB: Convert image into 3XN matrix

image processingmatrix manipulation

I have a dem data(an image of 6000X5200). I need to convert the data and create a 3XN matrix with row number, coloum number and Z value (pixel value of the image represent the Z value).
    orgim = imread('dem');   % read DEM data
    nentry = 0;
        for ii = 1:size(orgim,2)
          for jj = 1:size(orgim,1)
                nentry = nentry +1;
                mydata(nentry, :) = [ii, jj, orgim(jj,ii)];
                clear X Y Z;
        end
      end
This works but takes time. Is there any optimum way to convert the multi-dimentional 6000X 5200 matrix as 3XN matrix, without loop

Best Answer

[x,y] = ndgrid(1:size(orgim,1),1:size(orgim,2));
mydata = [y(:),x(:),orgim(:)];
or
mydata = [fliplr(fullfact(size(orgim))), orgim(:)];
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