You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: imReadDownSampled3d.m
    path of file: ./repos/matImage/matImage/imStacks
    
    the code of the file until where you have to start completion: function res = imReadDownSampled3d(fileName, ratio)
%IMREADDOWNSAMPLED3D Read a down-sampled version of a 3D image
%

    
function res = imReadDownSampled3d(fileName, ratio)
%IMREADDOWNSAMPLED3D Read a down-sampled version of a 3D image
%
%   img = imReadDownSampled3d(FNAME, K);
%
%   Inputs:
%   FNAME the name of the input file
%   K     the downsampling factor (as integer larger than 1)
%
%   Example
%     img = imReadDownSampled3d('mri.tif', 2);
%     size(img)
%     ans =
%         64    64    14
%
%     % use different down sampling ratio depend