LDP算子 用于人脸识别（）得到特征向量用于识别）

<span style="font-size:18px;">I=imread('E:6.jpg');
I=rgb2gray(I);
[a b]=LDP(I,[1 1],2);</span>

<span style="font-size:18px;">% [HIST, LDPIM] = LDP(IMAGE, SUBSZ, ORDER) 
% Calculates the LDP images and histogram of IMAGE. The concatenation 
% of the LDP histograms of each subblock (of size SUBSZ) in the image
% is returned in HIST, and the LDP code images are returned in LDPIM.
% The LDP order is specified by ORDER.
% This code is based on B Zhang, Y Gao, S Zhao & J Liu, "Local Derivative Pattern Versus Local Binary Pattern: Face Recognition With High-Order Local Pattern Descriptor," Image Processing, IEEE Transactions on, vol.19, no.2, pp.533,544, Feb. 2010
function [hout,ldpim]=LDP(im, subsz, order)
numBinsPerBlock = 32;       % number of bins per direction per block

assert(order >=2 && order <= 10);
assert(all(floor(size(im) ./ subsz(:)') == (size(im) ./ subsz(:)')));

im = double(im);
der0 = im;
der45 = im;
der90 = im;
der135 = im;

% calc derivative image of appropriate order
for ii=2:order
    der0 = [der0(:, 1:end-1)-der0(:, 2:end) zeros(size(der0,1),1)];    % subtract right在最后一列不上0
    der45 = [zeros(1,size(der45,2)); der45(2:end, 1:end-1)-der45(1:end-1, 2:end) zeros(size(der45,1)-1,1)];    % subtract above-right
    der90 = [zeros(1,size(der90,2)); der90(2:end, :)-der90(1:end-1, :)];    % subtract above
    der135 = [zeros(1,size(der135,2)); zeros(size(der135,1)-1,1) der135(2:end, 2:end)-der135(1:end-1, 1:end-1)];    % subtract above-left
end

% calc LDP code using sign(dot product), combine adjacent codes to get 32 codes/bins
div = 256 / numBinsPerBlock;% 分为多少分
codes0 = floor(doDotProdCode(der0) / div);
codes45 = floor(doDotProdCode(der45) / div);
codes90 = floor(doDotProdCode(der90) / div);
codes135 = floor(doDotProdCode(der135) / div);

% make histograms for each subimage (block) within the code images
bins = 0:numBinsPerBlock-1;
hout = zeros(numBinsPerBlock * 4, prod(size(im) ./ subsz));
hidx = 1;
for ii=0:size(im,1)/subsz(1)-1
    bii = ii*subsz(1) + (1:subsz(1));
    for jj=0:size(im,2)/subsz(2)-1
        bjj = jj*subsz(2) + (1:subsz(2));
        block0 = codes0(bii, bjj);
        block45 = codes45(bii, bjj);
        block90 = codes90(bii, bjj);
        block135 = codes135(bii, bjj);
        
        hout(:, hidx) = [intHist(block0(:), bins) intHist(block45(:), bins) intHist(block90(:), bins) intHist(block135(:), bins)]';
%         hout(:, hidx) = [hist(block0(:), bins) hist(block45(:), bins) hist(block90(:), bins) hist(block135(:), bins)]';
        
        hidx = hidx + 1;
    end
end

hout = hout(:);

if nargout > 1
	ldpim.b0 = block0;
	ldpim.b45 = block45;
	ldpim.b90 = block90;
	ldpim.b135 = block135;
end

figure(1)		% show the derivative images
subplot(221), imshow(der0,[]);
subplot(222), imshow(der45,[]);
subplot(223), imshow(der90,[]);
subplot(224), imshow(der135,[]);

figure(2)		% show
subplot(221), imshow(codes0,[]);
subplot(222), imshow(codes45,[]);
subplot(223), imshow(codes90,[]);
subplot(224), imshow(codes135,[]);

end

function yim=doDotProdCode(im)
[m,n] = size(im);
shim = zeros(m+2,n+2);
shim(2:end-1, 2:end-1) = im;    % zero-pad im
%与八个方向的乘积
dp1 = (shim(1:end-2,1:end-2) .* im) <= 0;   % Z1 . Z0
dp2 = (shim(1:end-2,2:end-1) .* im) <= 0;   % Z2 . Z0
dp3 = (shim(1:end-2,3:end) .* im) <= 0;     % Z3 . Z0
dp4 = (shim(2:end-1,3:end) .* im) <= 0;     % Z4 . Z0
dp5 = (shim(3:end,3:end) .* im) <= 0;       % Z5 . Z0
dp6 = (shim(3:end,2:end-1) .* im) <= 0;     % Z6 . Z0
dp7 = (shim(3:end,1:end-2) .* im) <= 0;     % Z7 . Z0
dp8 = (shim(2:end-1,1:end-2) .* im) <= 0;   % Z8 . Z0

yim = 1*dp1 + 2*dp2 + 4*dp3 + 8*dp4 + 16*dp5 + 32*dp6 + 64*dp7 + 128*dp8;
end

% note that all entries must belong to a value in bins, or it won't be
% counted
function ho=intHist(v, bins)
ho = zeros(1,length(bins));
for ii=1:length(bins)
    ho(ii) = sum(v == bins(ii));
end
end</span>