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include <mach.h>
include "../lib/fitsky.h"
define MEDCUT 0.025
# AP_MODE -- Procedure to calculate the mode of the sky pixel array.
int procedure ap_mode (skypix, coords, wgt, index, nskypix, snx, sny, losigma,
hisigma, rgrow, maxiter, sky_mode, sky_sigma, sky_skew, nsky,
nsky_reject)
real skypix[ARB] # unsorted array of skypixels
int coords[ARB] # coordinate array for regions growing
real wgt[ARB] # array of weights for rejection
int index[ARB] # indices in sort order
int nskypix # total number of sky pixels
int snx, sny # dimensions of the sky subraster
real losigma, hisigma # number of sky_sigma for rejection
real rgrow # radius of region growing
int maxiter # maximum number of cycles of rejection
real sky_mode # computed sky value
real sky_sigma # the computed sky sigma
real sky_skew # skew of sky pixels
int nsky # the number of sky pixels used
int nsky_reject # the number of sky pixels rejected
double dsky, sumpx, sumsqpx, sumcbpx
int i, j, ilo, ihi, il, ih, med, medcut
real dmin, dmax, locut, hicut, sky_zero, sky_mean, sky_med
int ap_grow_regions(), apimed()
real apsmed(), apwsmed(), ap_asumr()
begin
# Initialize.
nsky = nskypix
nsky_reject = 0
sky_mode = INDEFR
sky_sigma = INDEFR
sky_skew = INDEFR
if (nskypix <= 0)
return (AP_NOSKYAREA)
# Compute the median, sigma, skew and sky mode.
sky_zero = ap_asumr (skypix, index, nskypix) / nskypix
call ap_ialimr (skypix, index, nskypix, dmin, dmax)
medcut = nint (MEDCUT * real (nskypix))
sky_med = apsmed (skypix, index, nskypix, medcut)
sky_med = max (dmin, min (sky_med, dmax))
call apfimoments (skypix, index, nskypix, sky_zero, sumpx, sumsqpx,
sumcbpx, sky_mean, sky_sigma, sky_skew)
sky_mean = max (dmin, min (sky_mean, dmax))
if (sky_mean < sky_med)
sky_mode = sky_mean
else
sky_mode = 3.0 * sky_med - 2.0 * sky_mean
sky_mode = max (dmin, min (sky_mode, dmax))
if (maxiter < 1 || (IS_INDEFR(losigma) && IS_INDEFR(hisigma)) ||
sky_sigma <= 0.0)
return (AP_OK)
# Reject points outside losigma * sky_sigma and hisigma * sky_sigma
# of the mode.
ilo = 1
ihi = nskypix
do i = 1, maxiter {
# Compute the new rejection limits.
if (i == 1) {
if (IS_INDEFR(losigma))
locut = max (-MAX_REAL, dmin)
else
locut = sky_med - min (sky_med - dmin, dmax - sky_med,
losigma * sky_sigma)
if (IS_INDEFR(hisigma))
hicut = min (MAX_REAL, dmax)
else
hicut = sky_med + min (sky_med - dmin, dmax - sky_med,
hisigma * sky_sigma)
} else {
if (IS_INDEFR(losigma))
locut = max (-MAX_REAL, dmin)
else
locut = sky_mode - losigma * sky_sigma
if (IS_INDEFR(hisigma))
hicut = min (MAX_REAL, dmax)
else
hicut = sky_mode + hisigma * sky_sigma
}
#call eprintf ("i=%d mean=%g median=%g mode=%g locut=%g hicut=%g\n")
#call pargi (i)
#call pargr (sky_mean)
#call pargr (sky_med)
#call pargr (sky_mode)
#call pargr (locut)
#call pargr (hicut)
# Perform lower bound pixel rejection.
for (il = ilo; il <= nskypix; il = il + 1) {
if (skypix[index[il]] >= locut)
break
}
# Perform upper bound pixel rejection.
for (ih = ihi; ih >= 1; ih = ih - 1) {
if (skypix[index[ih]] <= hicut)
break
}
if (il == ilo && ih == ihi)
break
# Compute number of rejected pixels with optional region growing.
if (rgrow > 0.0) {
# Reject lower bound pixels with region growing.
do j = ilo, il - 1
nsky_reject = nsky_reject + ap_grow_regions (skypix, coords,
wgt, nskypix, sky_zero, index[j], snx, sny, rgrow,
sumpx, sumsqpx, sumcbpx)
# Reject upper bound pixels with region growing.
do j = ih + 1, ihi
nsky_reject = nsky_reject + ap_grow_regions (skypix, coords,
wgt, nskypix, sky_zero, index[j], snx, sny, rgrow,
sumpx, sumsqpx, sumcbpx)
# Compute the new median.
nsky = nskypix - nsky_reject
med = apimed (wgt, index, il, ihi, (nsky + 1) / 2)
} else {
# Recompute the number of sky pixels, number of rejected
# pixels and the median.
nsky_reject = nsky_reject + (il - ilo) + (ihi - ih)
nsky = nskypix - nsky_reject
med = (ih + il) / 2
# Reject number of lower bound pixels.
do j = ilo, il - 1 {
dsky = skypix[index[j]] - sky_zero
sumpx = sumpx - dsky
sumsqpx = sumsqpx - dsky ** 2
sumcbpx = sumcbpx - dsky ** 3
}
# Reject number of upper bound pixels.
do j = ih + 1, ihi {
dsky = skypix[index[j]] - sky_zero
sumpx = sumpx - dsky
sumsqpx = sumsqpx - dsky ** 2
sumcbpx = sumcbpx - dsky ** 3
}
}
if (nsky <= 0)
break
# Recompute mean, median, mode, sigma and skew.
medcut = nint (MEDCUT * real (nsky))
sky_med = apwsmed (skypix, index, wgt, nskypix, med, medcut)
sky_med = max (dmin, min (sky_med, dmax))
call apmoments (sumpx, sumsqpx, sumcbpx, nsky, sky_zero,
sky_mean, sky_sigma, sky_skew)
sky_mean = max (dmin, min (sky_mean, dmax))
if (sky_mean < sky_med)
sky_mode = sky_mean
else
sky_mode = 3.0 * sky_med - 2.0 * sky_mean
sky_mode = max (dmin, min (sky_mode, dmax))
if (sky_sigma <= 0.0)
break
ilo = il
ihi = ih
}
# Return an appropriate error code.
if (nsky == 0 || nsky_reject == nskypix) {
nsky = 0
nsky_reject = nskypix
sky_mode = INDEFR
sky_sigma = INDEFR
sky_skew = INDEFR
return (AP_NSKY_TOO_SMALL)
} else
return (AP_OK)
end
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