stats.c

/* $Id$
 *
 *  (C) 2003-2007, Friedrich Woeger <woeger@kis.uni-freiburg.de>,
 *  Kiepenheuer-Institut für Sonnenphysik, Freiburg (Breisgau), Germany
 *  All rights reserved.
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/* =====================================================================
**
**	Supplementary speckle math routines
**
** =====================================================================
**
**	    uses fftw3 library (http://www.fftw.org)
**	    Library for fast fourier transform
**
** =====================================================================
**
** Author:  F. Woeger
**   Kiepenheuer-Institut fuer Sonnenphysik
**   Freiburg, Germany
**
** Written 17. 06. 2003
**
** =====================================================================
*/


#include "speckle_math.h"


void mean(float *in, int nx, int ny, int nfr, float *out)
{
    // Declare helper variables
    long i, l;
    long N = nx * ny;
    // set resultant matrix to zero!
    memset(out, 0.0, N * sizeof(float));

    // calculate the mean image
    for (i = 0; i < N; i++) {
		for (l = 0; l < nfr; l++) {
			out[i] += in[i + l * N];
		}
	out[i] /= (float) nfr;
    }
}


void stats(float *in, long N, float thres, double *out1, double *out2)
{
    /* Declare helper variable */
    long i, t, c = 0;

    if (out2 != NULL) {
	*out1 = 0;
	*out2 = 0;
	for (i = 0; i < N; i++) {
	    *out1 += in[i];
	    *out2 += in[i] * in[i];
	}
	/* calculate the mean value of image */
	*out1 /= N;
	/* calculate the variance of image */
	*out2 = *out2 / N - (*out1) * (*out1);
    } else {
	*out1 = 0;
	for (i = 0; i < N; i++) {
	    *out1 += in[i];
	}
	/* calculate the mean value of image */
	*out1 /= N;
    }
    /*
     *  if thres greater zero then compute mean only from pixels that are
     *  greater than thres percent of overall mean
     */
    if (thres > 0) {
	t = thres * (*out1);
	*out1 = 0;
	for (i = 0; i < N; i++) {
	    if (in[i] > t) {
		*out1 += in[i];
		c++;
	    }
	}
	*out1 /= c;
    }
}