function out = dh_lsb(block, I)
%function out = dh_lsb(block, I)
%block:the minimal ceil to dehide
%I:stegoed image
si = size(I);
%將圖像劃分為M*N個小塊
N = floor(si(2) / block(2));
M = floor(si(1) / block(1));
out = [];
%計算比特1判決閾值：即每小塊半數以上元素隱藏的是比特1時，判決該小塊嵌入的信息為1
thr = ceil((block(1) * block(2) + 1) / 2);
idx = 0;
for i = 0 : M - 1
%計算每小塊垂直方向起止位置
    rst = i * block(1) + 1;
    red = (i + 1) * block(1);
for j = 0 : N - 1
%計算每小塊將要數據的秘密信息的序號
        idx = i * N + j + 1;
%計算每小塊水平方向起止位置
        cst = j * block(2) + 1;
        ced = (j + 1) * block(2);
%提取小塊最低位平面，統計1比特個數，判決輸出秘密信息
        tmp = sum(sum(bitget(I(rst:red, cst:ced), 1)));
        if(tmp >= thr)
            out(idx) = 1;
        else
            out(idx) = 0;
        end;
    end;
end;