Partitioning.m

function  [Patches, BlX, BlY, PadX, PadY, r, c]  = Partitioning(Im, P, q)
%% References 
% (1) M. Ghahremani, and H. Ghassemian, "Nonlinear IHS: A promising method for pan-sharpening," 
%        IEEE Geoscience and Remote Sensing Letters, vol. 13, no. 11, pp. 1606-1610, 2016.
% (2) A. Azarang, H. E. Manoochehri and N. Kehtarnavaz, "Convolutional Autoencoder-Based Multispectral Image Fusion," 
%        IEEE Access, vol. 7, pp. 35673-35683, 2019.
%% Input parameters
%    Im: a 2D image
%    P : the size of patch
%    q : the size of overlap
%    Outputs
%    Patches    an array of patches
%    BlX        the number of blocks in the direction of X
%    BlY        the number of blocks in the direction of Y
%    PadX       the number of pads required in the direction of X
%    PadY       the number of pads required in the direction of Y

% Description
%   This function partitions the input 2D image into P*P blocks with 'q'
%   overlap between any adjacent blocks


% see Tiling.m


if q > 0.8*P
    disp('Warning! the maximum size of overlapping is 50%.');
    return   
end

[r,c] = size(Im);
%% determining Bl and Pad     
% Bl = the number of patches   
% Pad = the amount of padding

posiX = 1:P-q:c; % column position
posiY = 1:P-q:r; % raw position

% remove extra positions
while  c - posiX(end) <= (q-1)
    posiX = posiX(1:end-1);
end
while r - posiY(end) <= (q-1)
    posiY = posiY(1:end-1);
end

BlX = numel(posiX); % horizontal patches
BlY = numel(posiY); % vertical patches
% [BlY, BlX]

PadX = P - (c - (BlX-1)*(P-q)); % horizontal pads
PadY = P - (r - (BlY-1)*(P-q)); % vertical pads
% [PadY, PadX]

ll = BlX*BlY;
Patches = zeros(P, P, ll);

% Padding ================================================================
ImPad = padarray(Im,[PadY PadX],'symmetric','post');
%% Partioning ==============================================================
counter = 1;


for i = 1:BlY
    for j = 1:BlX
        ii = posiY(i);
        jj = posiX(j);
        %         fprintf('[%d:%d, %d:%d]\n',ii,ii+P-1,jj,jj+P-1)   % the positions of arrays
        Patches(:, :, counter) =  ImPad(ii:(ii+P-1), jj:(jj+P-1), : );
        counter = counter + 1;
    end
end

Patches = reshape(Patches, [P*P BlX*BlY]);
end