getusan.m

一个好用的角点检测程序

%function U = getUSAN(A,maxInt,sigma,thresh,width)
%
% Returns the USAN response of a greysale image
%
% INPUT:
%       A - the image. Intensity must be quantized as integers with a minimum
%             intensity 0 to a maximum maxInt
%       maxInt- the maximum intensity
%       sigma - the guassian mask coefficient
%       thresh - the maximum allowed difference between intensity values
%       width(optional) - the width of the mask, which must be odd.
%
% OUTPUT:
%       U - the normalized USAN response

function U = getUSAN(A,maxInt,sigma,thresh,width)

if(nargin == 4)
    width = 2*ceil(sigma)+1;
end

%prepare A
A = double(A);
if(isrgb(A))
    A = rgb2gray(A);
end

%create the guassian mask
halfWidth = (width-1)/2;
mask = meshgrid(-halfWidth:halfWidth,-halfWidth:halfWidth)/(sqrt(2)*sigma);
mask = exp(-mask.^2 - (mask').^2);
maxResponse = sum(mask(:));

%make the lookup table
table = [exp(-([maxInt:-1:0]/thresh).^6) exp(-([1:maxInt]/thresh).^6)];

%pass it to the nonlinear filter
U = nlDiffFilter(A,table,mask)/maxResponse;