osl_resample_meeg.m

function D = osl_resample_meeg(D,input_nii,output_nii,weighting)
    % Take in a MEEG object, a NIFTI file specifying the voxels for the MEEG channels
    % and an output NII. A new online montage will be computed where the 
    % weight of each output voxel is a linear combination of the input voxels, weighted by
    % a function of distance (default - 1/d)
    %
    % INPUTS
    % D - MEEG object in source space
    % input_nii - NIFTI file with as many nonzero voxels as channels in D. Can also be standard MNI spatial resolution 
    %               (e.g. 8). If the file doesn't exist, try appending the osl standard mask folder
    % output_nii - NIFTI file with new voxel locations. Can also be standard MNI spatial resolution 
    %               (e.g. 8). If the file doesn't exist, try appending the osl standard mask folder
    % weighting - Function handle to convert distance to weight (default - 1/d)
    %
    % Romesh Abeysuriya 2017
    
    fprintf(2,'Output has not been validated yet\n')

    if nargin < 4 || isempty(weighting) 
        weighting = @(d) 1./d;
    end

    if isnumeric(input_nii)
        input_nii = fullfile(osldir,'std_masks',sprintf('MNI152_T1_%dmm_brain.nii.gz',input_nii));
    end

    if ~exist(input_nii)
        input_nii = fullfile(osldir,'std_masks',input_nii);
    end

    if isnumeric(output_nii)
        output_nii = fullfile(osldir,'std_masks',sprintf('MNI152_T1_%dmm_brain.nii.gz',output_nii));
    end

    if ~exist(output_nii)
        output_nii = fullfile(osldir,'std_masks',output_nii);
    end

    our_coordinates = osl_mnimask2mnicoords(input_nii);
    ft_coordinates = osl_mnimask2mnicoords(output_nii);

    for j = 1:size(our_coordinates,1)
        a = our_coordinates(j,:);
        dx = bsxfun(@minus,ft_coordinates,a);
        d = sqrt(sum(dx.^2,2));
        w(:,j) = weighting(d);
    end

    w = bsxfun(@rdivide,w,sum(w));
    D = add_montage(D,w,sprintf('Converted %s to %s',input_nii,output_nii));