SIFT特征_图像配准_Matlab.rar

function [des,loc]=zoo_sift(im) % This function reads SIFT keypoints of an image. % Input parameters: % pic: gray image. % % Returned: % des: a K-by-128 matrix, where each row gives an invariant % descriptor for one of the K keypoints. The descriptor is a vector % of 128 values normalized to unit length. % loc: K-by-4 matrix, in which each row has the 4 values for a % keypoint location (row, column, scale, orientation). The % orientation is in the range [-PI, PI] radians. [row,col]=size(im); % Convert into PGM imagefile, readable by "keypoints" executable f=fopen('tmp.pgm','w'); if f==-1 error('Could not create file tmp.pgm.'); end fprintf(f, 'P5\n%d\n%d\n255\n', col, row); fwrite(f,im','uint8'); fclose(f); % Call keypoints executable if isunix command = '!./sift '; else command = '!siftWin32 '; end command = [command ' <tmp.pgm >tmp.key']; eval(command); % Open tmp.key and check its header g=fopen('tmp.key','r'); if g==-1 error('Could not open file tmp.key.'); end [header,cnt]=fscanf(g,'%d %d',[1 2]); if cnt~=2 error('Invalid keypoint file beginning.'); end num=header(1); len=header(2); if len~=128 error('Keypoint descriptor length invalid (should be 128).'); end % Creates the two output matrices (use known size for efficiency) loc=double(zeros(num,4)); des=double(zeros(num,128)); for k=1:num [vector,cnt]=fscanf(g, '%f %f %f %f', [1 4]); if cnt~=4 error('Invalid keypoint file format'); end loc(k,:)=vector(1,:); [descrip, count] = fscanf(g, '%d', [1 len]); if (count ~= 128) error('Invalid keypoint file value.'); end descrip = descrip / sqrt(sum(descrip.^2)); des(k, :) = descrip(1, :); end fclose(g); for k=1:size(des,1) des(k,:)=des(k,:)/sum(des(k,:)); end delete tmp.key delete tmp.pgm