--- /dev/null
+#!/usr/bin/python
+from opencv.cv import *
+from opencv.highgui import *
+import sys
+
+# Rearrange the quadrants of Fourier image so that the origin is at
+# the image center
+# src & dst arrays of equal size & type
+def cvShiftDFT(src_arr, dst_arr ):
+
+ size = cvGetSize(src_arr)
+ dst_size = cvGetSize(dst_arr)
+
+ if(dst_size.width != size.width or
+ dst_size.height != size.height) :
+ cvError( CV_StsUnmatchedSizes, "cvShiftDFT", "Source and Destination arrays must have equal sizes", __FILE__, __LINE__ )
+
+ if(src_arr is dst_arr):
+ tmp = cvCreateMat(size.height/2, size.width/2, cvGetElemType(src_arr))
+
+ cx = size.width/2
+ cy = size.height/2 # image center
+
+ q1 = cvGetSubRect( src_arr, cvRect(0,0,cx, cy) )
+ q2 = cvGetSubRect( src_arr, cvRect(cx,0,cx,cy) )
+ q3 = cvGetSubRect( src_arr, cvRect(cx,cy,cx,cy) )
+ q4 = cvGetSubRect( src_arr, cvRect(0,cy,cx,cy) )
+ d1 = cvGetSubRect( src_arr, cvRect(0,0,cx,cy) )
+ d2 = cvGetSubRect( src_arr, cvRect(cx,0,cx,cy) )
+ d3 = cvGetSubRect( src_arr, cvRect(cx,cy,cx,cy) )
+ d4 = cvGetSubRect( src_arr, cvRect(0,cy,cx,cy) )
+
+ if(src_arr is not dst_arr):
+ if( not CV_ARE_TYPES_EQ( q1, d1 )):
+ cvError( CV_StsUnmatchedFormats, "cvShiftDFT", "Source and Destination arrays must have the same format", __FILE__, __LINE__ )
+
+ cvCopy(q3, d1)
+ cvCopy(q4, d2)
+ cvCopy(q1, d3)
+ cvCopy(q2, d4)
+
+ else:
+ cvCopy(q3, tmp)
+ cvCopy(q1, q3)
+ cvCopy(tmp, q1)
+ cvCopy(q4, tmp)
+ cvCopy(q2, q4)
+ cvCopy(tmp, q2)
+
+if __name__ == "__main__":
+
+ im = cvLoadImage( sys.argv[1], CV_LOAD_IMAGE_GRAYSCALE)
+
+ realInput = cvCreateImage( cvGetSize(im), IPL_DEPTH_64F, 1)
+ imaginaryInput = cvCreateImage( cvGetSize(im), IPL_DEPTH_64F, 1)
+ complexInput = cvCreateImage( cvGetSize(im), IPL_DEPTH_64F, 2)
+
+ cvScale(im, realInput, 1.0, 0.0)
+ cvZero(imaginaryInput)
+ cvMerge(realInput, imaginaryInput, None, None, complexInput)
+
+ dft_M = cvGetOptimalDFTSize( im.height - 1 )
+ dft_N = cvGetOptimalDFTSize( im.width - 1 )
+
+ dft_A = cvCreateMat( dft_M, dft_N, CV_64FC2 )
+ image_Re = cvCreateImage( cvSize(dft_N, dft_M), IPL_DEPTH_64F, 1)
+ image_Im = cvCreateImage( cvSize(dft_N, dft_M), IPL_DEPTH_64F, 1)
+
+ # copy A to dft_A and pad dft_A with zeros
+ tmp = cvGetSubRect( dft_A, cvRect(0,0, im.width, im.height))
+ cvCopy( complexInput, tmp, None )
+ if(dft_A.width > im.width):
+ tmp = cvGetSubRect( dft_A, cvRect(im.width,0, dft_N - im.width, im.height))
+ cvZero( tmp )
+
+ # no need to pad bottom part of dft_A with zeros because of
+ # use nonzero_rows parameter in cvDFT() call below
+
+ cvDFT( dft_A, dft_A, CV_DXT_FORWARD, complexInput.height )
+
+ cvNamedWindow("win", 0)
+ cvNamedWindow("magnitude", 0)
+ cvShowImage("win", im)
+
+ # Split Fourier in real and imaginary parts
+ cvSplit( dft_A, image_Re, image_Im, None, None )
+
+ # Compute the magnitude of the spectrum Mag = sqrt(Re^2 + Im^2)
+ cvPow( image_Re, image_Re, 2.0)
+ cvPow( image_Im, image_Im, 2.0)
+ cvAdd( image_Re, image_Im, image_Re, None)
+ cvPow( image_Re, image_Re, 0.5 )
+
+ # Compute log(1 + Mag)
+ cvAddS( image_Re, cvScalarAll(1.0), image_Re, None ) # 1 + Mag
+ cvLog( image_Re, image_Re ) # log(1 + Mag)
+
+
+ # Rearrange the quadrants of Fourier image so that the origin is at
+ # the image center
+ cvShiftDFT( image_Re, image_Re )
+
+ min, max, pt1, pt2 = cvMinMaxLoc(image_Re)
+ cvScale(image_Re, image_Re, 1.0/(max-min), 1.0*(-min)/(max-min))
+ cvShowImage("magnitude", image_Re)
+
+ cvWaitKey(0)