change comments

Base/Math/FourierTransform.h

@@ -23,15 +23,6 @@
 #include <vector>
 
 //! Fourier transform of vectors (in 1D or 2D) using Fast Fourier Transform (fftw package).
-//!
-//! Usage:
-//! std::vector<double> signal, result;
-//! FourierTransform ft;
-//! ft.fft(signal, result)
-//!
-//! Given code rely on code from Jeremy Fix page, http://jeremy.fix.free.fr/spip.php?article15,
-//! see also "Efficient convolution using the Fast Fourier Transform, Application in C++"
-//! by Jeremy Fix, May 30, 2011
 class FourierTransform {
 public:
     // 1D and 2D vectors
@@ -42,29 +33,31 @@ public:
 
     FourierTransform();
 
-    //! FT in 1D
+    // forward transform
     void rfft(const double1d_t& source, complex1d_t& result);
-    void irfft(const complex1d_t& source, double1d_t& result, int w_src);
-    void ramplitude(const double1d_t& source, double1d_t& result);
-
-    //! Shift low frequency to the center of 1D FT array
-    static void fftshift(double1d_t& result);
-    static void fftshift(complex1d_t& result);
+    void rfft(const double2d_t& source, complex2d_t& result);
 
-    //! Shift low frequency to the edges of 1D FT array
-    static void ifftshift(double1d_t& result);
-    static void ifftshift(complex1d_t& result);
+    // forward transform with real-valued amplitudes in output
+    void ramplitude(const double1d_t& source, double1d_t& result);
+    void ramplitude(const double2d_t& source, double2d_t& result);
 
-    //! FT in 2D
-    void rfft(const double2d_t& source, complex2d_t& result);
+    // backward transform
+    void irfft(const complex1d_t& source, double1d_t& result, int w_src);
     void irfft(const complex2d_t& source, double2d_t& result, int w_real);
-    void ramplitude(const double2d_t& source, double2d_t& result);
 
-    //! Shift low frequency to the center of 2D FT array
+    // Frequency shifts are useful for providing different representations of spectrum: with lowest
+    // frequency at edges of array (default output of fft) or with lowest frequency in center of
+    // array
+
+    // shift low frequency from corners to center
+    static void fftshift(double1d_t& result);
+    static void fftshift(complex1d_t& result);
     static void fftshift(double2d_t& result);
     static void fftshift(complex2d_t& result);
 
-    //! Shift low frequency to the corners of 2D FT array
+    // shift low frequency from center to corners
+    static void ifftshift(double1d_t& result);
+    static void ifftshift(complex1d_t& result);
     static void ifftshift(double2d_t& result);
     static void ifftshift(complex2d_t& result);