source/libtomo/recon/osem.c
// Copyright (c) 2015, UChicago Argonne, LLC. All rights reserved.
// Copyright 2015. UChicago Argonne, LLC. This software was produced
// under U.S. Government contract DE-AC02-06CH11357 for Argonne National
// Laboratory (ANL), which is operated by UChicago Argonne, LLC for the
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#include <string.h>
#include "libtomo/recon.h"
#include "utils.h"
void
osem(const float* data, int dy, int dt, int dx, const float* center, const float* theta,
float* recon, int ngridx, int ngridy, int num_iter, int num_block,
const int* ind_block)
{
if(dy == 0 || dt == 0 || dx == 0)
return;
float* gridx = (float*) malloc((ngridx + 1) * sizeof(float));
float* gridy = (float*) malloc((ngridy + 1) * sizeof(float));
float* coordx = (float*) malloc((ngridy + 1) * sizeof(float));
float* coordy = (float*) malloc((ngridx + 1) * sizeof(float));
float* ax = (float*) malloc((ngridx + ngridy) * sizeof(float));
float* ay = (float*) malloc((ngridx + ngridy) * sizeof(float));
float* bx = (float*) malloc((ngridx + ngridy) * sizeof(float));
float* by = (float*) malloc((ngridx + ngridy) * sizeof(float));
float* coorx = (float*) malloc((ngridx + ngridy) * sizeof(float));
float* coory = (float*) malloc((ngridx + ngridy) * sizeof(float));
float* dist = (float*) malloc((ngridx + ngridy) * sizeof(float));
int* indi = (int*) malloc((ngridx + ngridy) * sizeof(int));
float* simdata = (float*) malloc((dy * dt * dx) * sizeof(float));
float* sum_dist = (float*) malloc((ngridx * ngridy) * sizeof(float));
float* update = (float*) malloc((ngridx * ngridy) * sizeof(float));
assert(coordx != NULL && coordy != NULL && ax != NULL && ay != NULL && by != NULL &&
bx != NULL && coorx != NULL && coory != NULL && dist != NULL && indi != NULL &&
simdata != NULL && sum_dist != NULL && update != NULL);
int s, q, p, d, i, m, n, os;
int quadrant;
float theta_p, sin_p, cos_p;
float mov, xi, yi;
int asize, bsize, csize;
float upd;
int ind_data, ind_recon;
float sum_dist2;
const int blocksize = dt / num_block;
const int remainder = dt % num_block;
for(i = 0; i < num_iter; i++)
{
// initialize simdata to zero
memset(simdata, 0, dy * dt * dx * sizeof(float));
// For each slice
for(s = 0; s < dy; s++)
{
preprocessing(ngridx, ngridy, dx, center[s], &mov, gridx,
gridy); // Outputs: mov, gridx, gridy
// For each ordered-subset num_subset
int subset_end = 0;
for(os = 0; os < num_block; os++)
{
const int subset_start = subset_end;
subset_end = subset_start + blocksize + ((os < remainder) ? 1 : 0);
assert(subset_end < dt);
// initialize sum_dist and update to zero
memset(sum_dist, 0, (ngridx * ngridy) * sizeof(float));
memset(update, 0, (ngridx * ngridy) * sizeof(float));
// For each projection angle
for(int q = subset_start; q < subset_end; q++)
{
const int p = (num_block == 1) ? q : ind_block[q];
// Calculate the sin and cos values
// of the projection angle and find
// at which quadrant on the cartesian grid.
theta_p = fmodf(theta[p], 2.0f * (float) M_PI);
quadrant = calc_quadrant(theta_p);
sin_p = sinf(theta_p);
cos_p = cosf(theta_p);
// For each detector pixel
for(d = 0; d < dx; d++)
{
// Calculate coordinates
xi = -ngridx - ngridy;
yi = 0.5f * (1 - dx) + d + mov;
calc_coords(ngridx, ngridy, xi, yi, sin_p, cos_p, gridx, gridy,
coordx, coordy);
// Merge the (coordx, gridy) and (gridx, coordy)
trim_coords(ngridx, ngridy, coordx, coordy, gridx, gridy, &asize,
ax, ay, &bsize, bx, by);
// Sort the array of intersection points (ax, ay) and
// (bx, by). The new sorted intersection points are
// stored in (coorx, coory). Total number of points
// are csize.
sort_intersections(quadrant, asize, ax, ay, bsize, bx, by, &csize,
coorx, coory);
// Calculate the distances (dist) between the
// intersection points (coorx, coory). Find the
// indices of the pixels on the reconstruction grid.
calc_dist(ngridx, ngridy, csize, coorx, coory, indi, dist);
// Calculate simdata
calc_simdata(s, p, d, ngridx, ngridy, dt, dx, csize, indi, dist,
recon,
simdata); // Output: simdata
// Calculate dist*dist
sum_dist2 = 0.0f;
for(n = 0; n < csize - 1; n++)
{
sum_dist2 += dist[n] * dist[n];
sum_dist[indi[n]] += dist[n];
}
// Update
if(sum_dist2 != 0.0f)
{
ind_data = d + p * dx + s * dt * dx;
upd = data[ind_data] / simdata[ind_data];
for(n = 0; n < csize - 1; n++)
{
update[indi[n]] += upd * dist[n];
}
}
}
}
m = 0;
for(n = 0; n < ngridx * ngridy; n++)
{
if(sum_dist[n] != 0.0f)
{
ind_recon = s * ngridx * ngridy;
recon[m + ind_recon] *= update[m] / sum_dist[n];
}
m++;
}
}
}
}
free(gridx);
free(gridy);
free(coordx);
free(coordy);
free(ax);
free(ay);
free(bx);
free(by);
free(coorx);
free(coory);
free(dist);
free(indi);
free(simdata);
free(sum_dist);
free(update);
}