+
+//----------------------------------------------------------------------//
+// USER SYMBOLS //
+//----------------------------------------------------------------------//
+
+// Filter types
+static const char O_FILTER_ABS_BANDLIMIT_STR[]= "abs_bandlimit";
+static const char O_FILTER_ABS_SINC_STR[]= "abs_sinc";
+static const char O_FILTER_ABS_COS_STR[]= "abs_cos";
+static const char O_FILTER_ABS_HAMMING_STR[]= "abs_hamming";
+static const char O_FILTER_SHEPP_STR[]= "shepp";
+static const char O_FILTER_BANDLIMIT_STR[]= "bandlimit";
+static const char O_FILTER_SINC_STR[]= "sinc";
+static const char O_FILTER_COS_STR[]= "cos";
+static const char O_FILTER_HAMMING_STR[]= "hamming";
+static const char O_FILTER_TRIANGLE_STR[]= "triangle";
+
+typedef enum {
+ FILTER_BANDLIMIT,
+ FILTER_SINC,
+ FILTER_G_HAMMING,
+ FILTER_COSINE,
+ FILTER_TRIANGLE,
+ FILTER_ABS_BANDLIMIT, // filter times |x|
+ FILTER_ABS_SINC,
+ FILTER_ABS_G_HAMMING,
+ FILTER_ABS_COSINE,
+ FILTER_SHEPP
+} FilterType;
+
+
+// Function domains
+static const char D_FREQ_STR[]= "freq";
+static const char D_SPATIAL_STR[]= "spatial";
+
+typedef enum {
+ D_FREQ = 1,
+ D_SPATIAL
+} DomainType;
+
+
+/* interpolation methods */
+static const char O_INTERP_NEAREST_STR[]= "nearest";
+static const char O_INTERP_LINEAR_STR[]= "linear";
+static const char O_INTERP_BSPLINE_STR[]= "bspline";
+
+#undef HAVE_BSPLINE_INTERP
+typedef enum { // Interpolation methods
+ I_NEAREST = 1, // Nearest neighbor
+#if HAVE_BSPLINE_INTERP
+ I_BSPLINE,
+ I_1BSPLINE, // 1st order B-Spline
+ I_2BSPLINE,
+ I_3BSPLINE,
+#endif
+ I_LINEAR // Linear interpolation
+} InterpolationType;
+
+
+// Trace levels
+static const char O_TRACE_NONE_STR[]= "none";
+static const char O_TRACE_TEXT_STR[]= "text";
+static const char O_TRACE_PHM_STR[]= "phm";
+static const char O_TRACE_RAYS_STR[]= "rays";
+static const char O_TRACE_PLOT_STR[]= "plot";
+static const char O_TRACE_CLIPPING_STR[]= "clipping";
+
+enum {
+ TRACE_NONE, /* No tracing */
+ TRACE_TEXT, /* Minimal status */
+ TRACE_PHM, /* Show phantom */
+ TRACE_RAYS, /* Show all rays */
+ TRACE_PLOT, /* Plot raysums */
+ TRACE_CLIPPING /* Plot clipping */
+};
+
+// Standard phantomsa
+static const char O_PHM_HERMAN_STR[]= "herman";
+static const char O_PHM_ROWLAND_STR[]= "rowland";
+static const char O_PHM_BROWLAND_STR[]= "browland";
+static const char O_PHM_UNITPULSE_STR[]= "unitpulse";
+typedef enum {
+ O_PHM_HERMAN, /* Herman head phantom */
+ O_PHM_ROWLAND, /* Rowland head phantom */
+ O_PHM_BROWLAND, /* Bordered Rowland head phantom */
+ O_PHM_UNITPULSE /* Unit pulse phantom */
+} PhantomType;
+
+// Backproject types
+static const char O_BPROJ_TRIG_STR[]= "trig";
+static const char O_BPROJ_TABLE_STR[]= "table";
+static const char O_BPROJ_DIFF_STR[]= "diff";
+static const char O_BPROJ_DIFF2_STR[]= "diff2";
+static const char O_BPROJ_IDIFF2_STR[]= "idiff2";
+
+typedef enum {
+ O_BPROJ_TRIG,
+ O_BPROJ_TABLE,
+ O_BPROJ_DIFF,
+ O_BPROJ_DIFF2,
+ O_BPROJ_IDIFF2
+} BackprojType;
+
+// Convolution symmetries
+typedef enum {
+ FUNC_EVEN = 1, // function types, f[-n] = f[n]
+ FUNC_ODD, // f[-n] = -f[n]
+ FUNC_BOTH // function has both odd & even components
+} FunctionSymmetry;
+
+
+