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include <math.h>
include "../lib/fitpsf.h"
define NPARAMETERS 7
# APSFMOMENTS -- Procedure to compute the 0, 1st and second moments of an
# image and estimate the x,y center, the ellipticity and the position angle.
int procedure apsfmoments (ctrpix, nx, ny, lthreshold, uthreshold, positive,
par, perr, npar)
real ctrpix[nx, ny] # object to be centered
int nx, ny # dimensions of subarray
real lthreshold # lower threshold for moment computation
real uthreshold # upper threshold for moment computation
int positive # emission feature
real par[ARB] # parameters
real perr[ARB] # errors in parameters
int npar # number of parameters
int i, j
real temp, sumi, sumxi, sumyi, sumx2i, sumy2i, sumxyi, r2, varx, vary, varxy
bool fp_equalr()
begin
# Initialize the sums.
sumi = 0.0
sumxi = 0.0
sumyi = 0.0
sumxyi = 0.0
sumx2i = 0.0
sumy2i = 0.0
# Accumulate the moments.
if (positive == YES) {
do j = 1, ny {
do i = 1, nx {
if (ctrpix[i,j] > uthreshold)
next
temp = ctrpix[i,j] - lthreshold
if (temp <= 0.0)
next
sumi = sumi + temp
sumxi = sumxi + i * temp
sumyi = sumyi + j * temp
sumxyi = sumxyi + i * j * temp
sumx2i = sumx2i + i * i * temp
sumy2i = sumy2i + j * j * temp
}
}
} else {
do j = 1, ny {
do i = 1, nx {
if (ctrpix[i,j] < uthreshold)
next
temp = lthreshold - ctrpix[i,j]
if (temp <= 0.0)
next
sumi = sumi + temp
sumxi = sumxi + i * temp
sumyi = sumyi + j * temp
sumxyi = sumxyi + i * j * temp
sumx2i = sumx2i + i * i * temp
sumy2i = sumy2i + j * j * temp
}
}
}
# Compute the parameters.
if (fp_equalr (sumi, 0.0)) {
par[1] = 0.0
par[2] = (1 + nx) / 2.0
par[3] = (1 + ny) / 2.0
par[4] = 0.0
par[5] = 0.0
par[6] = 0.0
par[7] = lthreshold
} else {
par[1] = sumi
par[2] = sumxi / sumi
par[3] = sumyi / sumi
varx = max (0.0, sumx2i / sumi - par[2] ** 2)
vary = max (0.0, sumy2i / sumi - par[3] ** 2)
r2 = varx + vary
if (r2 <= 0.0) {
par[4] = 0.0
par[5] = 0.0
par[6] = 0.0
} else {
par[4] = sqrt (r2)
varxy = sumxyi / sumi - par[2] * par[3]
par[5] = sqrt ((varx - vary) ** 2 + 4.0 * varxy ** 2) / r2
par[6] = (0.5 * r2 * (1.0 + par[5]) - vary)
if (fp_equalr (par[6], 0.0))
par[6] = 90.0
else
par[6] = RADTODEG (atan (varxy / par[6]))
}
par[7] = lthreshold
}
# Compute the errors.
npar = NPARAMETERS
call amovkr (0.0, perr, NPARAMETERS)
return (AP_OK)
end
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