phasecong3_相位一致性算法_图像提取_

% PHASECONG3 - Computes edge and corner phase congruency in an image. % % This function calculates the PC_2 measure of phase congruency. % This function supersedes PHASECONG2 and PHASECONG being faster and requires % less memory % % There are potentially many arguments, here is the full usage: % % [M m or ft pc EO, T] = phasecong3(im, nscale, norient, minWaveLength, ... % mult, sigmaOnf, k, cutOff, g, noiseMethod) % % However, apart from the image, all parameters have defaults and the % usage can be as simple as: % % M = phasecong3(im); % % Arguments: % Default values Description % % nscale 4 - Number of wavelet scales, try values 3-6 % norient 6 - Number of filter orientations. % minWaveLength 3 - Wavelength of smallest scale filter. % mult 2.1 - Scaling factor between successive filters. % sigmaOnf 0.55 - Ratio of the standard deviation of the Gaussian % describing the log Gabor filter's transfer function % in the frequency domain to the filter center frequency. % k 2.0 - No of standard deviations of the noise energy beyond % the mean at which we set the noise threshold point. % You may want to vary this up to a value of 10 or % 20 for noisy images % cutOff 0.5 - The fractional measure of frequency spread % below which phase congruency values get penalized. % g 10 - Controls the sharpness of the transition in % the sigmoid function used to weight phase % congruency for frequency spread. % noiseMethod -1 - Parameter specifies method used to determine % noise statistics. % -1 use median of smallest scale filter responses % -2 use mode of smallest scale filter responses % 0+ use noiseMethod value as the fixed noise threshold % % Returned values: % M - Maximum moment of phase congruency covariance. % This is used as a indicator of edge strength. % m - Minimum moment of phase congruency covariance. % This is used as a indicator of corner strength. % or - Orientation image in integer degrees 0-180, % positive anticlockwise. % 0 corresponds to a vertical edge, 90 is horizontal. % ft - Local weighted mean phase angle at every point in the % image. A value of pi/2 corresponds to a bright line, 0 % corresponds to a step and -pi/2 is a dark line. % pc - Cell array of phase congruency images (values between 0 and 1) % for each orientation % EO - A 2D cell array of complex valued convolution result % T - Calculated noise threshold (can be useful for % diagnosing noise characteristics of images). Once you know % this you can then specify fixed thresholds and save some % computation time. % % EO{s,o} = convolution result for scale s and orientation o. The real part % is the result of convolving with the even symmetric filter, the imaginary % part is the result from convolution with the odd symmetric filter. % % Hence: % abs(EO{s,o}) returns the magnitude of the convolution over the % image at scale s and orientation o. % angle(EO{s,o}) returns the phase angles. % % Notes on specifying parameters: % % The parameters can be specified as a full list eg. % >> [M m or ft pc EO] = phasecong3(im, 5, 6, 3, 2.5, 0.55, 2.0, 0.4, 10); % % or as a partial list with unspecified parameters taking on default values % >> [M m or ft pc EO] = phasecong3(im, 5, 6, 3); % % or as a partial list of parameters followed by some parameters specified via a % keyword-value pair, remaining parameters are set to defaults, for example: % >> [M m or ft pc EO] = phasecong3(im, 5, 6, 3, 'cutOff', 0.3, 'k', 2.5); % % The convolutions are done via the FFT. Many of the parameters relate to the % specification of the filters in the frequency plane. The values do not seem % to be very critical and the defaults are usually fine. You may want to % experiment with the values of 'nscales' and 'k', the noise compensation factor. % % Notes on filter settings to obtain even coverage of the spectrum % sigmaOnf .85 mult 1.3 % sigmaOnf .75 mult 1.6 (filter bandwidth ~1 octave) % sigmaOnf .65 mult 2.1 % sigmaOnf .55 mult 3 (filter bandwidth ~2 octaves) % % See Also: PHASECONG, PHASECONG2, PHASESYM, GABORCONVOLVE, PLOTGABORFILTERS % References: % % Peter Kovesi, "Image Features From Phase Congruency". Videre: A % Journal of Computer Vision Research. MIT Press. Volume 1, Number 3, % Summer 1999 http://mitpress.mit.edu/e-journals/Videre/001/v13.html % % Peter Kovesi, "Phase Congruency Detects Corners and % Edges". Proceedings DICTA 2003, Sydney Dec 10-12 % April 1996 Original Version written % August 1998 Noise compensation corrected. % October 1998 Noise compensation corrected. - Again!!! % September 1999 Modified to operate on non-square images of arbitrary size. % May 2001 Modified to return feature type image. % July 2003 Altered to calculate 'corner' points. % October 2003 Speed improvements and refinements. % July 2005 Better argument handling, changed order of return values % August 2005 Made Octave compatible % May 2006 Bug in checkargs fixed % Jan 2007 Bug in setting radius to 0 for odd sized images fixed. % April 2009 Scaling of covariance values fixed. (Negligible change to results) % May 2009 Noise compensation simplified reducing memory and % computation overhead. Spread function changed to a cosine, % eliminating parameter dThetaOnSigma and ensuring even % angular coverage. Frequency width measure slightly % improved. % November 2010 Cosine angular spread function corrected (it was 2x as wide % as it should have been) % September 2017 Correction to setting up matrices of frequency values for % odd sized images. % Copyright (c) 1996-2017 Peter Kovesi % Centre for Exploration Targeting % The University of Western Australia % peter.kovesi at uwa edu au % % Permission is hereby granted, free of charge, to any person obtaining a copy % of this software and associated documentation files (the "Software"), to deal % in the Software without restriction, subject to the following conditions: % % The above copyright notice and this permission notice shall be included in % all copies or substantial portions of the Software. % % The Software is provided "as is", without warranty of any kind. function [M, m, or, featType, PC, EO, T, pcSum] = phasecong3(varargin) % Get arguments and/or default values [im, nscale, norient, minWaveLength, mult, sigmaOnf, ... k, cutOff, g, noiseMethod] = checkargs(varargin(:)); epsilon = .0001; % Used to prevent division by zero. [rows,cols] = size(im); imagefft = fft2(im); % Fourier transform of image zero = zeros(rows,cols); EO = cell(nscale, norient); % Array of convolution results. PC = cell(norient,1); covx2 = zero; % Matrices for covariance data covy2 = zero; covxy = zero; EnergyV = zeros(rows,cols,3); % Matrix for accumulating total energy