gabor.cpp

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00042 
00043 #include "precomp.hpp"
00044 
00045 /*
00046  Gabor filters and such. To be greatly extended to have full texture analysis.
00047  For the formulas and the explanation of the parameters see:
00048  http://en.wikipedia.org/wiki/Gabor_filter
00049 */
00050 
00051 cv::Mat cv::getGaborKernel( Size ksize, double sigma, double theta,
00052                             double lambd, double gamma, double psi, int ktype )
00053 {
00054     double sigma_x = sigma;
00055     double sigma_y = sigma/gamma;
00056     int nstds = 3;
00057     int xmin, xmax, ymin, ymax;
00058     double c = cos(theta), s = sin(theta);
00059 
00060     if( ksize.width > 0 )
00061         xmax = ksize.width/2;
00062     else
00063         xmax = cvRound(std::max(fabs(nstds*sigma_x*c), fabs(nstds*sigma_y*s)));
00064 
00065     if( ksize.height > 0 )
00066         ymax = ksize.height/2;
00067     else
00068         ymax = cvRound(std::max(fabs(nstds*sigma_x*s), fabs(nstds*sigma_y*c)));
00069 
00070     xmin = -xmax;
00071     ymin = -ymax;
00072 
00073     CV_Assert( ktype == CV_32F || ktype == CV_64F );
00074 
00075     Mat kernel(ymax - ymin + 1, xmax - xmin + 1, ktype);
00076     double scale = 1;
00077     double ex = -0.5/(sigma_x*sigma_x);
00078     double ey = -0.5/(sigma_y*sigma_y);
00079     double cscale = CV_PI*2/lambd;
00080 
00081     for( int y = ymin; y <= ymax; y++ )
00082         for( int x = xmin; x <= xmax; x++ )
00083         {
00084             double xr = x*c + y*s;
00085             double yr = -x*s + y*c;
00086 
00087             double v = scale*std::exp(ex*xr*xr + ey*yr*yr)*cos(cscale*xr + psi);
00088             if( ktype == CV_32F )
00089                 kernel.at<float>(ymax - y, xmax - x) = (float)v;
00090             else
00091                 kernel.at<double>(ymax - y, xmax - x) = v;
00092         }
00093 
00094     return kernel;
00095 }
00096 
00097 
00098 /* End of file. */
00099