sift-matlab.zip_lowe_matlab sift_sift_sift matlab_sift matlab

% [image, descriptors, locs] = sift(imageFile) % % This function reads an image and returns its SIFT keypoints. % Input parameters: % imageFile: the file name for the image. % % Returned: % image: the image array in double format % descriptors: 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. % locs: 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. % % Credits: Thanks for initial version of this program to D. Alvaro and % J.J. Guerrero, Universidad de Zaragoza (modified by D. Lowe) function [image, descriptors, locs] = sift(imageFile) % Load image image = imread(imageFile); % If you have the Image Processing Toolbox, you can uncomment the following % lines to allow input of color images, which will be converted to grayscale. if isrgb(image) image = rgb2gray(image); end [rows, cols] = size(image); % 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', cols, rows); fwrite(f, image', 'uint8');% transposed matrix of image fclose(f); % Call keypoints executable if isunix % code to run on Linux plaform command = '!./sift '; else command = '!siftWin32 '; end command = [command ' <tmp.pgm >tmp.key']; eval(command); % excute siftWin32.exe; input tmp.pgm, output tmp.key(keypoints) % Open tmp.key and check its header g = fopen('tmp.key', 'r'); if g == -1 error('Could not open file tmp.key.'); end [header, count] = fscanf(g, '%d %d', [1 2]); %read data from tmp.key file 1 rows 2 column if count ~= 2 error('Invalid keypoint file beginning.'); end num = header(1);% the number of keypoints len = header(2); % The descriptor is a vector of 128 values normalized to unit length. if len ~= 128 error('Keypoint descriptor length invalid (should be 128).'); end % Creates the two output matrices (use known size for efficiency) locs = double(zeros(num, 4));% row, column, scale, orientation descriptors = double(zeros(num, 128)); % Parse tmp.key for i = 1:num [vector, count] = fscanf(g, '%f %f %f %f', [1 4]); %row col scale ori if count ~= 4 error('Invalid keypoint file format'); end locs(i, :) = vector(1, :); [descrip, count] = fscanf(g, '%d', [1 len]); if (count ~= 128) error('Invalid keypoint file value.'); end % Normalize each input vector to unit length descrip = descrip / sqrt(sum(descrip.^2)); descriptors(i, :) = descrip(1, :); end fclose(g);