Gabor filter code error

Question

Edit: A description of the GABOR FILTER

 
 % gab2d: **2D Gabor filter**

 % The Gabor filter is basically a Gaussian, modulated by a complex sinusoid
 % G = gab2d(I,Sx,Sy,f,theta,FUN)


 % Input and output arguments ([]'s are optional):
 % I (matrix) of size NxM: Input Image of size NxM. 
 gamma (scalar): The spatial aspect ratio, x to y.
 lambda(scalar): The wavelength of the sinusoidal function. 
 b (scalar): The spatial frequency band-width (in octaves)
 theta (scalar): The orientation of the gabor filter.
 % phi (scalar): The phase offset. 0 is real part of Gabor filter or
 % even-symmetric, pi/2 is imaginary part of Gabor filter or
 % odd-symmetric.

 % **Note**:

 sigma (scalar): The spread of Gabor filter or the standard
 % deviation of Gaussian is automatically computed from lambda and b.
 % [shape] (strings): Shape for conv2. See help conv2. Default is 'same'.
 % % GO (matrix) of size NxM: Output images which was applied Gabor
 % filters. This is the magnitude response.
 % [GF] (matrix) of size (2Sx+1)x(2Sy+1): Gabor filter.

function [GO, GF] = gab2d(I, gamma, lambda, b, theta, phi, shape)

I=imread('C:\Users\Vinay\Documents\MATLAB\textureflawimages\text9.png');

gamma = 1; b = 1; theta = 0:pi/6:pi-pi/6; phi = 0; shape = 'valid'; lambda=8;

if nargin < 7, shape = 'same'; end;

if isa(I, 'double') ~= 1, I = double(I); end

sigma = (1 / pi) * sqrt(log(2)/2) * (2^b+1) / (2^b-1) * lambda;

Sy = sigma * gamma;

for x = -fix(sigma):fix(sigma)

    for y = -fix(Sy):fix(Sy)

        xp = x * cos(theta) + y * sin(theta);

        yp = y * cos(theta) - x * sin(theta);

        GF(fix(Sy)+y+1,fix(sigma)+x+1) = ...

        exp(-.5*(xp^2+gamma^2*yp^2)/sigma^2) * cos(2*pi*xp/lambda+phi) ...

        ; %/ (2*pi*(sigma^2/gamma));

        % Normalize if you use different sigma (lambda or b)
    end
end
GO = conv2(I, double(GF), shape);

Error:

??? Error using ==> mpower Matrix must be square.

Error in ==> gab2d at 36 GF(fix(Sy)+y+1,fix(sigma)+x+1) = ...

I am somehow not able to rectify this problem ..

Please help

What language is that? Also, is it possible to tidy up the formatting to make it more readable? — FrustratedWithFormsDesigner

Jonas Jonas · Accepted Answer · 2012-01-19T16:28:44

theta is an array. Thus, e.g. xp is an array as well. If you want to square each element of xp, then you need to use element-wise operators, such as .^ for power, or .* for multiplication.

In order to more quickly find out what's wrong, set the debugger to stop whenever there's an error by typing dbstop if error at the command line. This allows you to inspect all variables in the editor by hovering over them with the mouse, and to evaluate small bits of your complicated expression to narrow down your error.

Gabor filter code error

1 Answers