There are basically 2 parameters defining the shape of a Gabor filter. One parameter (often denoted with sigma) defines the standard deviation of the Gaussian envelope whereas another parameter (often denoted with omega) represents the wavelength of the sinusoidal plane wave.

The parameters that define a Gabor filter are its frequency, standard deviation and orientation.

Following link may be useful :

http://homepages.inf.ed.ac.uk/rbf/CAVIAR/PAPERS/05-ibpria-features.pdf

hi please go through the following document for more detailed information on Gabor filters

http://stackoverflow.com/questions/20608458/gabor-feature-extraction

http://www.sciencedirect.com/science/article/pii/S0031320304003012

http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=6482091&url=http%3A%2F%2Fieeexplore.ieee.org%2Fxpls%2Fabs_all.jsp%3Farnumber%3D6482091

http://www3.ntu.edu.sg/home/adamskong/publication/PR_Gabor.pdf

http://in.mathworks.com/matlabcentral/answers/65138-what-are-the-features-we-can-extract-using-gabor-filtering-for-images