X-Git-Url: http://git.kpe.io/?a=blobdiff_plain;f=libctsim%2Fbackprojectors.cpp;h=d3cb2035dc125af3415006a2d204cc61b5cc7907;hb=6850134e4711a842cc7c0a306a9e4243df06b952;hp=0684c16c5c638e95e01eec79a8d5988968b5ed04;hpb=dfa390de2efc04d85b03718a6480f735516df0e8;p=ctsim.git

diff --git a/libctsim/backprojectors.cpp b/libctsim/backprojectors.cpp
index 0684c16..d3cb203 100644
--- a/libctsim/backprojectors.cpp
+++ b/libctsim/backprojectors.cpp
@@ -8,7 +8,7 @@
 **  This is part of the CTSim program
 **  Copyright (C) 1983-2000 Kevin Rosenberg
 **
-**  $Id: backprojectors.cpp,v 1.5 2000/07/07 15:30:59 kevin Exp $
+**  $Id: backprojectors.cpp,v 1.6 2000/07/09 08:16:17 kevin Exp $
 **
 **  This program is free software; you can redistribute it and/or modify
 **  it under the terms of the GNU General Public License (version 2) as
@@ -152,6 +152,8 @@ Backprojector::convertInterpolationNameToID (const char* const interpName)
     interpID = INTERP_NEAREST;
   else if (strcasecmp (interpName, INTERP_LINEAR_STR) == 0)
     interpID = INTERP_LINEAR;
+  else if (strcasecmp (interpName, INTERP_FREQ_PREINTERPOLATE_STR) == 0)
+    interpID = INTERP_FREQ_PREINTERPOLATE;
 #if HAVE_BSPLINE_INTERP
   else if (strcasecmp (interpName, INTERP_BSPLINE_STR) == 0)
     interpID = INTERP_BSPLINE;
@@ -180,6 +182,8 @@ Backprojector::convertInterpolationIDToName (const InterpolationID interpID)
     return (INTERP_NEAREST_STR);
   else if (interpID == INTERP_LINEAR)
     return (INTERP_LINEAR_STR);
+  else if (interpID == INTERP_FREQ_PREINTERPOLATE)
+    return (INTERP_FREQ_PREINTERPOLATE_STR);
 #if HAVE_BSPLINE_INTERP
   else if (interpID == INTERP_BSPLINE)
     return (INTERP_BSPLINE_STR);
@@ -471,12 +475,12 @@ BackprojectIntDiff2::BackprojectView (const double* const filteredProj, const do
 {
   double theta = - view_angle;  // add half PI to view angle to get perpendicular theta angle
 
-  kint32 scale = 1 << 16;
-  double dScale = scale;
-  kint32 halfScale = scale / 2;
+  static const kint32 scale = 1 << 16;
+  static const double dScale = scale;
+  static const kint32 halfScale = scale / 2;
 
-  kint32 det_dx = nearest<kint32> (xInc * sin (theta) / detInc * scale);
-  kint32 det_dy = nearest<kint32> (yInc * cos (theta) / detInc * scale);
+  const kint32 det_dx = nearest<kint32> (xInc * sin (theta) / detInc * scale);
+  const kint32 det_dy = nearest<kint32> (yInc * cos (theta) / detInc * scale);
 
   // calculate L for first point in image (0, 0) 
   kint32 detPosColStart = nearest<kint32> (start_r * cos (theta - start_phi) / detInc * scale);
@@ -524,8 +528,10 @@ BackprojectIntDiff3::BackprojectView (const double* const filteredProj, const do
   double theta = - view_angle;  // add half PI to view angle to get perpendicular theta angle
   static const int scaleShift = 16;
   static const kint32 scale = (1 << scaleShift);
+  static const kint32 scaleBitmask = scale - 1;
   static const double dScale = scale;
   static const kint32 halfScale = scale / 2;
+  static const double dInvScale = 1. / scale;
 
   const kint32 det_dx = nearest<kint32> (xInc * sin (theta) / detInc * scale);
   const kint32 det_dy = nearest<kint32> (yInc * cos (theta) / detInc * scale);
@@ -537,28 +543,26 @@ BackprojectIntDiff3::BackprojectView (const double* const filteredProj, const do
     kint32 curDetPos = detPosColStart;
     ImageFileColumn pImCol = v[ix];
 
-    for (int iy = 0; iy < ny; iy++, curDetPos += det_dy) {
-      if (interpType == Backprojector::INTERP_NEAREST) {
-	int iDetPos = (curDetPos + halfScale) >> scaleShift;
-
-	if (iDetPos < 0 || iDetPos >= nDet)  // check for impossible: index outside of raysum pos 
-	    errorIndexOutsideDetector (ix, iy, theta, curDetPos, iDetPos);
-	else
-	  *pImCol++ += filteredProj[iDetPos];
-      } else if (interpType == Backprojector::INTERP_LINEAR) {
-	kint32 detPosFloor = curDetPos / scale;
-	kint32 detPosRemainder = curDetPos % scale;
-	if (detPosRemainder < 0) {
-	  detPosFloor--;
-	  detPosRemainder += scale;
-	}
-	int iDetPos = iDetCenter + detPosFloor;
-	double frac = detPosRemainder / dScale;
-	if (iDetPos < 0 || iDetPos >= nDet - 1)
-	    errorIndexOutsideDetector (ix, iy, theta, curDetPos, iDetPos);
-	else
-	  *pImCol++ += ((1.-frac) * filteredProj[iDetPos] + frac * filteredProj[iDetPos+1]);
-      }
-    }	// end for y
-  }	// end for x
+    if (interpType == Backprojector::INTERP_NEAREST) {
+      for (int iy = 0; iy < ny; iy++, curDetPos += det_dy) {
+	int iDetPos = (curDetPos + halfScale) >> 16;
+	assert(iDetPos >= 0 && iDetPos < nDet);
+	*pImCol++ += filteredProj[iDetPos];
+      }	// end for iy
+    } else if (interpType == Backprojector::INTERP_LINEAR) {
+      for (int iy = 0; iy < ny; iy++, curDetPos += det_dy) {
+	kint32 iDetPos = curDetPos >> scaleShift;
+	kint32 detRemainder = curDetPos & scaleBitmask;
+#if 0
+	double frac = detRemainder * (1. / 65536.);
+	assert(iDetPos >= 0 && iDetPos < nDet - 1);
+	*pImCol++ += ((1.-frac) * filteredProj[iDetPos]) + (frac * filteredProj[iDetPos+1]);
+#else
+	assert(iDetPos >= 0 && iDetPos < nDet - 1);
+	const double* const detPointer = &filteredProj[iDetPos];
+	*pImCol++ += (((scale-detRemainder) * *detPointer) + (detRemainder * *(detPointer+1))) * dInvScale;
+#endif
+      }	// end for iy
+    } //end linear
+  } // end for ix
 }