how can i understand Local Binary code better?

Question

bkshn 2013-7-8

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/81409-how-can-i-understand-local-binary-code-better

hello i have this code for implementation Local binary pattern

function result = lbp(varargin) % image,radius,neighbors,mapping,mode) % Version 0.3.2 % Authors: Marko Heikkilä and Timo Ahonen

% Changelog % Version 0.3.2: A bug fix to enable using mappings together with a % predefined spoints array % Version 0.3.1: Changed MAPPING input to be a struct containing the mapping % table and the number of bins to make the function run faster with high number % of sampling points. Lauge Sorensen is acknowledged for spotting this problem.

% Check number of input arguments.

error(nargchk(1,5,nargin));

image=varargin{1}; d_image=double(image);

if nargin==1 spoints=[-1 -1; -1 0; -1 1; 0 -1; -0 1; 1 -1; 1 0; 1 1]; neighbors=8; mapping=0; mode='h'; end

if (nargin == 2) && (length(varargin{2}) == 1) error('Input arguments'); end

if (nargin > 2) && (length(varargin{2}) == 1) radius=varargin{2}; neighbors=varargin{3};

    spoints=zeros(neighbors,2);
    % Angle step.
    a = 2*pi/neighbors;
    for i = 1:neighbors
        spoints(i,1) = -radius*sin((i-1)*a);
        spoints(i,2) = radius*cos((i-1)*a);
    end
    if(nargin >= 4)
        mapping=varargin{4};
        if(isstruct(mapping) && mapping.samples ~= neighbors)
            error('Incompatible mapping');
        end
    else
        mapping=0;
    end
    if(nargin >= 5)
        mode=varargin{5};
    else
        mode='h';
    end
end

if (nargin > 1) && (length(varargin{2}) > 1) spoints=varargin{2}; neighbors=size(spoints,1);

    if(nargin >= 3)
        mapping=varargin{3};
        if(isstruct(mapping) && mapping.samples ~= neighbors)
            error('Incompatible mapping');
        end
    else
        mapping=0;
    end
    if(nargin >= 4)
        mode=varargin{4};
    else
        mode='h';
    end   
end

% Determine the dimensions of the input image. [ysize xsize] = size(image);

miny=min(spoints(:,1)); maxy=max(spoints(:,1)); minx=min(spoints(:,2)); maxx=max(spoints(:,2));

% Block size, each LBP code is computed within a block of size bsizey*bsizex bsizey=ceil(max(maxy,0))-floor(min(miny,0))+1; bsizex=ceil(max(maxx,0))-floor(min(minx,0))+1;

% Coordinates of origin (0,0) in the block origy=1-floor(min(miny,0)); origx=1-floor(min(minx,0));

% Minimum allowed size for the input image depends % on the radius of the used LBP operator. if(xsize < bsizex ysize < bsizey) error('Too small input image. Should be at least (2*radius+1) x (2*radius+1)'); end

Calculate dx and dy; dx = xsize - bsizex; dy = ysize - bsizey;>>>*

% Fill the center pixel matrix C. C = image(origy:origy+dy,origx:origx+dx); d_C = double(C);

bins = 2^neighbors;

% Initialize the result matrix with zeros. result=zeros(dy+1,dx+1);

%Compute the LBP code image

for i = 1:neighbors y = spoints(i,1)+origy; x = spoints(i,2)+origx; % Calculate floors, ceils and rounds for the x and y. fy = floor(y); cy = ceil(y); ry = round(y); fx = floor(x); cx = ceil(x); rx = round(x); % Check if interpolation is needed. if (abs(x - rx) < 1e-6) && (abs(y - ry) < 1e-6) % Interpolation is not needed, use original datatypes N = image(ry:ry+dy,rx:rx+dx); D = N >= C; else % Interpolation needed, use double type images ty = y - fy; tx = x - fx;

   * % Calculate the interpolation weights.
    w1 = (1 - tx) * (1 - ty);
    w2 =      tx  * (1 - ty);
    w3 = (1 - tx) *      ty ;
    w4 =      tx  *      ty ;*
    % Compute interpolated pixel values
    N = w1*d_image(fy:fy+dy,fx:fx+dx) + w2*d_image(fy:fy+dy,cx:cx+dx) + ...
        w3*d_image(cy:cy+dy,fx:fx+dx) + w4*d_image(cy:cy+dy,cx:cx+dx);
    D = N >= d_C; 
  end  
  % Update the result matrix.
  v = 2^(i-1);
  result = result + v*D;
end

%Apply mapping if it is defined if isstruct(mapping) bins = mapping.num; for i = 1:size(result,1) for j = 1:size(result,2) result(i,j) = mapping.table(result(i,j)+1); end end end

if (strcmp(mode,'h') strcmp(mode,'hist') strcmp(mode,'nh')) % Return with LBP histogram if mode equals 'hist'. result=hist(result(:),0:(bins-1)); if (strcmp(mode,'nh')) result=result/sum(result); end else %Otherwise return a matrix of unsigned integers if ((bins-1)<=intmax('uint8')) result=uint8(result); elseif ((bins-1)<=intmax('uint16')) result=uint16(result); else result=uint32(result); end if true % code endend

end

but idon't understand bold line , is there anyone that know about LBP? or is there any suggestion? Thanks alot