imout=gen_shift_downsample_image(image,ds,sh)

function imout=gen_shift_downsample_image(image,ds,sh)

image=image(1:floor(size(image,1)/ds)*ds,1:floor(size(image,2)/ds)*ds);

% if sh(1)>0 % pad above
%     image=[repmat(image(1,:),[sh(1),1]); image];
%     image(size(image,1)-sh(1)+1:size(image,1),:)=[];
% elseif sh(1)<0 % pad below
%     image=[image; repmat(image(size(image,1),:),[-sh(1),1])];
%     image(1:-sh(1),:)=[];
% end
% 
% if sh(2)>0 % pad left
%     image=[repmat(image(:,1),[1,sh(2)]), image];
%     image(:,size(image,2)-sh(2)+1:size(image,2))=[];
% elseif sh(2)<0 % pad right
%     image=[image, repmat(image(:,size(image,2)),[1,-sh(2)])];
%     image(:,1:-sh(2))=[];
% end

image=shift_image(image,sh);

imouts=floor(size(image)/ds);

imout=zeros(imouts);
for id=1:ds
    for jd=1:ds
        imout=imout+image(id:ds:size(image,1),jd:ds:size(image,2));
    end
end
imout=imout/ds/ds;