c# - EMGU/OpenCV FFT of image not yielding expected results -

i'm trying visualize fft of image emgu. here's image i'm processing:

here's expected result:

here's get:

here's code:

image<gray, float> image = new image<gray, float>(@"c:\users\me\desktop\sample3.jpg"); intptr compleximage = cvinvoke.cvcreateimage(image.size, emgu.cv.cvenum.ipl_depth.ipl_depth_32f, 2);  cvinvoke.cvsetzero(compleximage); cvinvoke.cvsetimagecoi(compleximage, 1); cvinvoke.cvcopy(image, compleximage, intptr.zero); cvinvoke.cvsetimagecoi(compleximage, 0);  matrix<float> dft = new matrix<float>(image.rows, image.cols, 2); cvinvoke.cvdft(compleximage, dft, emgu.cv.cvenum.cv_dxt.cv_dxt_forward, 0);  matrix<float> outreal = new matrix<float>(image.size); matrix<float> outim = new matrix<float>(image.size); cvinvoke.cvsplit(dft, outreal, outim, intptr.zero, intptr.zero);  image<gray, float> fftimage = new image<gray, float>(outreal.size); cvinvoke.cvcopy(outreal, fftimage, intptr.zero);  picturebox1.image = image.tobitmap(); picturebox2.image = fftimage.log().tobitmap(); 

what mistake making here?

update: per roger rowland's suggestion here's updated code. result looks better i'm not 100% sure it's correct. here's result:

image<gray, float> image = new image<gray, float>(@"c:\users\yytov\desktop\sample3.jpg");         intptr compleximage = cvinvoke.cvcreateimage(image.size, emgu.cv.cvenum.ipl_depth.ipl_depth_32f, 2);          cvinvoke.cvsetzero(compleximage);  // initialize elements 0         cvinvoke.cvsetimagecoi(compleximage, 1);         cvinvoke.cvcopy(image, compleximage, intptr.zero);         cvinvoke.cvsetimagecoi(compleximage, 0);          matrix<float> dft = new matrix<float>(image.rows, image.cols, 2);         cvinvoke.cvdft(compleximage, dft, emgu.cv.cvenum.cv_dxt.cv_dxt_forward, 0);          //the real part of fourier transform         matrix<float> outreal = new matrix<float>(image.size);         //the imaginary part of fourier transform         matrix<float> outim = new matrix<float>(image.size);         cvinvoke.cvsplit(dft, outreal, outim, intptr.zero, intptr.zero);          cvinvoke.cvpow(outreal, outreal, 2.0);         cvinvoke.cvpow(outim, outim, 2.0);          cvinvoke.cvadd(outreal, outim, outreal, intptr.zero);         cvinvoke.cvpow(outreal, outreal, 0.5);          cvinvoke.cvadds(outreal, new mcvscalar(1.0), outreal, intptr.zero); // 1 + mag         cvinvoke.cvlog(outreal, outreal); // log(1 + mag)          // swap quadrants         int cx = outreal.cols / 2;         int cy = outreal.rows / 2;          matrix<float> q0 = outreal.getsubrect(new rectangle(0, 0, cx, cy));         matrix<float> q1 = outreal.getsubrect(new rectangle(cx, 0, cx, cy));         matrix<float> q2 = outreal.getsubrect(new rectangle(0, cy, cx, cy));         matrix<float> q3 = outreal.getsubrect(new rectangle(cx, cy, cx, cy));         matrix<float> tmp = new matrix<float>(q0.size);          q0.copyto(tmp);         q3.copyto(q0);         tmp.copyto(q3);         q1.copyto(tmp);                             q2.copyto(q1);         tmp.copyto(q2);          cvinvoke.cvnormalize(outreal, outreal, 0.0, 255.0, emgu.cv.cvenum.norm_type.cv_minmax, intptr.zero);          image<gray, float> fftimage = new image<gray, float>(outreal.size);         cvinvoke.cvcopy(outreal, fftimage, intptr.zero);          picturebox1.image = image.tobitmap();         picturebox2.image = fftimage.tobitmap();   

i cannot comment on magnitude/intensity of resulting image, can give tip spatial distribution of points in image.

opencv doesn't rearrange quadrants put origin [0,0] center of image. have rearrange quadrants manually.

look @ step 6 @ following page: http://docs.opencv.org/doc/tutorials/core/discrete_fourier_transform/discrete_fourier_transform.html

it's official doc opencv, it's in c++, principle holds.