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2026-09-18 00:09:10 +09:00 · 2026-08-07 15:56:42 +09:00
commit 91ad25aca9
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+/* iradon_c.c: 
+   sub-routine of a modified iradon.m, i.e., the time consuming loop 
+   of this routine in C. 
+ 
+   Compilation from Matlab:
+   mex iradon_c.c
+   maybe a tiny bit faster code is generated by 
+   mex -O COPTIMFLAGS='-O2' LDOPTIMFLAGS='-O2' iradon_c.c
+ 
+   Usage from Matlab:
+   iradon_c( p, theta, x, y );
+ */
+
+#include "mex.h"
+
+#include <math.h> 
+
+
+void mexFunction(int nlhs, mxArray *plhs[],
+                 int nrhs, const mxArray *prhs[])
+{
+  int dim1, dim2, dim1_data;
+  int i, no_of_angles, ctrIdx;
+  double *data, *theta, *xorg, *yorg, *imgorg;
+  
+  /* Check for proper number of arguments. */
+  if (nrhs != 4) 
+    mexErrMsgTxt("Four input arguments required: Data, theta, x and y.");
+  else if (nlhs != 1) 
+    mexErrMsgTxt("One output argument has to be specified.");
+
+  /* Input must be double. */
+  if (mxIsDouble(prhs[0]) != 1)
+    mexErrMsgTxt("Input 1 (data) must be of double precision floating point type.");
+  if (mxIsDouble(prhs[1]) != 1)
+    mexErrMsgTxt("Input 2 (theta) must be of double precision floating point type.");
+  if (mxIsDouble(prhs[2]) != 1)
+    mexErrMsgTxt("Input 3 (x) must be of double precision floating point type.");
+  if (mxIsDouble(prhs[3]) != 1)
+    mexErrMsgTxt("Input 4 (y) must be of double precision floating point type.");
+
+
+  /* get number of different angles */
+  if (mxGetM(prhs[1]) == 1) {
+    no_of_angles = mxGetN(prhs[1]);
+  } else {
+    if (mxGetN(prhs[1]) == 1) {
+      no_of_angles = mxGetM(prhs[1]);
+    } else {
+      mexErrMsgTxt("Theta has to be a vector, not an array.");
+    }
+  }
+  
+  /* get dimensions and check that they are consistent */
+  dim1 = mxGetM(prhs[2]);
+  dim2 = mxGetN(prhs[2]);
+  if ((dim1 != mxGetM(prhs[3])) || (dim1 != mxGetN(prhs[3]))) 
+    mexErrMsgTxt("x and y must have the same dimensions.");
+  if (no_of_angles > mxGetN(prhs[0]))
+    mexErrMsgTxt("The second dimension of data must be at least as large as the number of theta angles.");
+dim1_data = mxGetM(prhs[0]);
+  
+  /* allocate memory for image data, to be returned */
+  plhs[0] = 
+    mxCreateNumericMatrix(dim1, dim2, mxDOUBLE_CLASS, mxREAL);
+  if (plhs[0] == NULL)
+    mexErrMsgTxt("Could not allocate memory for return data.");
+
+  /* get pointers to input and output data */
+  data = mxGetPr(prhs[0]);
+  theta = mxGetPr(prhs[1]);
+  xorg = mxGetPr(prhs[2]);
+  yorg = mxGetPr(prhs[3]);
+  imgorg = mxGetPr(plhs[0]);
+
+  /* index to image center */
+  ctrIdx = ceil(mxGetM(prhs[0]) / 2);
+  
+  for (i=0; i < no_of_angles; i++) {
+    double *x = xorg;
+    double *y = yorg;
+    double *img = imgorg;
+    /* temporary variables */
+    double costheta = cos(*theta);
+    double sintheta = sin(*theta);
+    double *proj = &data[i*dim1_data +1];
+    int j;
+    for (j=0; j < dim2; j++) {
+      int k;
+      for (k=0; k < dim1; k++) {
+        double t = *x * costheta + *y * sintheta;
+        int a = floor(t);
+        *img += (t-a) * proj[a+ctrIdx] + (a+1-t) * proj[a+ctrIdx-1];
+        x++;
+        y++;
+        img++;
+      }
+    }
+    theta++;
+  }
+  return;
+}