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include <mach.h>
include "../lib/fitsky.h"
# AP_CENTROID -- Procedure to find the mode, width and skew of the sky
# distribution by computing the moments of the histogram.
int procedure ap_centroid (skypix, coords, wgt, index, nskypix, snx, sny, k1,
hwidth, binsize, smooth, losigma, hisigma, rgrow, maxiter, sky_mode,
sky_sigma, sky_skew, nsky, nsky_reject)
real skypix[ARB] # array of sky pixels
int coords[ARB] # array of coordinates for regions growing
real wgt[ARB] # array of weights for rejection
int index[ARB] # array of sorted indices
int nskypix # the number of sky pixels
int snx, sny # the maximum dimensions of sky raster
real k1 # extent of the histogram in skysigma
real hwidth # width of the histogram
real binsize # the size of the histogram in sky sigma
int smooth # smooth the histogram before fitting
real losigma, hisigma # upper and lower k-sigma rejection limits
real rgrow # region growing radius in pixels
int maxiter # maximum number of rejection cycles
real sky_mode # computed sky value
real sky_sigma # computed sigma of the sky pixels
real sky_skew # skew of sky pixels
int nsky # number of sky pixels used in fit
int nsky_reject # number of sky pixels rejected
double dsky, sumpx, sumsqpx, sumcbpx
int nreject, nbins, nker, ier, i, j
pointer sp, hgm, shgm
real dmin, dmax, sky_mean, hmin, hmax, dh, locut, hicut, cut
real sky_zero
int ap_grow_hist2(), aphigmr()
real ap_asumr(), apmedr()
begin
# Intialize.
nsky = nskypix
nsky_reject = 0
sky_mode = INDEFR
sky_sigma = INDEFR
sky_skew = INDEFR
if (nskypix <= 0)
return (AP_NOSKYAREA)
# Compute the histogram width and binsize.
sky_zero = ap_asumr (skypix, index, nskypix) / nskypix
call ap_ialimr (skypix, index, nskypix, dmin, dmax)
call apfimoments (skypix, index, nskypix, sky_zero, sumpx, sumsqpx,
sumcbpx, sky_mean, sky_sigma, sky_skew)
sky_mean = apmedr (skypix, index, nskypix)
sky_mean = max (dmin, min (sky_mean, dmax))
if (! IS_INDEFR(hwidth) && hwidth > 0.0) {
hmin = sky_mean - k1 * hwidth
hmax = sky_mean + k1 * hwidth
dh = binsize * hwidth
} else {
cut = min (sky_mean - dmin, dmax - sky_mean, k1 * sky_sigma)
hmin = sky_mean - cut
hmax = sky_mean + cut
dh = binsize * cut / k1
}
# Compute the number of histogram bins and the histogram resolution.
if (dh <= 0.0) {
nbins = 1
dh = 0.0
} else {
nbins = 2 * nint ((hmax - sky_mean) / dh) + 1
dh = (hmax - hmin) / (nbins - 1)
}
# Check for a valid histogram.
if (nbins < 2 || k1 <= 0.0 || sky_sigma < dh || dh <= 0.0 ||
sky_sigma <= 0.0) {
sky_mode = sky_mean
sky_sigma = 0.0
sky_skew = 0.0
return (AP_NOHISTOGRAM)
}
# Allocate temporary space.
call smark (sp)
call salloc (hgm, nbins, TY_REAL)
call salloc (shgm, nbins, TY_REAL)
# Accumulate the histogram.
call aclrr (Memr[hgm], nbins)
nsky_reject = nsky_reject + aphigmr (skypix, wgt, index, nskypix,
Memr[hgm], nbins, hmin, hmax)
nsky = nskypix - nsky_reject
# Do the initial rejection.
if (nsky_reject > 0) {
do i = 1, nskypix {
if (wgt[index[i]] <= 0.0) {
dsky = skypix[index[i]] - sky_zero
sumpx = sumpx - dsky
sumsqpx = sumsqpx - dsky ** 2
sumcbpx = sumcbpx - dsky ** 3
}
}
call apmoments (sumpx, sumsqpx, sumcbpx, nsky, sky_zero, sky_mean,
sky_sigma, sky_skew)
}
# Fit the mode, sigma an skew of the histogram.
if (smooth == YES) {
nker = max (1, nint (sky_sigma / dh))
#call ap_lucy_smooth (Memr[hgm], Memr[shgm], nbins, nker, 2)
call ap_bsmooth (Memr[hgm], Memr[shgm], nbins, nker, 2)
call ap_imode (Memr[shgm], nbins, hmin, hmax, YES, sky_mode, ier)
} else
call ap_imode (Memr[hgm], nbins, hmin, hmax, NO, sky_mode, ier)
sky_mode = max (dmin, min (sky_mode, dmax))
if ((IS_INDEFR(losigma) && IS_INDEFR(hisigma)) || (sky_sigma < dh) ||
maxiter < 1) {
call sfree (sp)
return (AP_OK)
}
# Fit histogram with pixel rejection and optional region growing.
do i = 1, maxiter {
# Compute new histogram limits.
if (IS_INDEFR(losigma))
locut = -MAX_REAL
else
locut = sky_mode - losigma * sky_sigma
if (IS_INDEFR(hisigma))
hicut = MAX_REAL
else
hicut = sky_mode + hisigma * sky_sigma
# Reject pixels.
nreject = 0
do j = 1, nskypix {
if (skypix[index[j]] >= locut && skypix[index[j]] <= hicut)
next
if (rgrow > 0.0)
nreject = nreject + ap_grow_hist2 (skypix, coords,
wgt, nskypix, sky_zero, index[j], snx, sny, Memr[hgm],
nbins, hmin, hmax, rgrow, sumpx, sumsqpx, sumcbpx)
else if (wgt[index[j]] > 0.0) {
call ap_hgmsub2 (Memr[hgm], nbins, hmin, hmax,
skypix[index[j]], sky_zero, sumpx, sumsqpx, sumcbpx)
wgt[index[j]] = 0.0
nreject = nreject + 1
}
}
if (nreject == 0)
break
nsky_reject = nsky_reject + nreject
nsky = nskypix - nsky_reject
if (nsky <= 0)
break
# Recompute the moments.
call apmoments (sumpx, sumsqpx, sumcbpx, nsky, sky_zero, sky_mean,
sky_sigma, sky_skew)
# Recompute the histogram peak.
if (smooth == YES) {
nker = max (1, nint (sky_sigma / dh))
#call ap_lucy_smooth (Memr[hgm], Memr[shgm], nbins, nker, 2)
call ap_bsmooth (Memr[hgm], Memr[shgm], nbins, nker, 2)
call ap_imode (Memr[shgm], nbins, hmin, hmax, YES, sky_mode,
ier)
} else
call ap_imode (Memr[hgm], nbins, hmin, hmax, NO, sky_mode, ier)
sky_mode = max (dmin, min (sky_mode, dmax))
if (sky_sigma <= dh || ier != AP_OK)
break
}
# Return the error codes.
call sfree (sp)
if (nsky == 0 || nsky_reject == nskypix || ier == AP_NOHISTOGRAM) {
nsky = 0
nsky_reject = nskypix
sky_mode = INDEFR
sky_sigma = INDEFR
sky_skew = INDEFR
return (AP_NSKY_TOO_SMALL)
} else
return (AP_OK)
end
# AP_IMODE -- Procedure to compute the 1st, 2nd and third moments of the
# histogram of sky pixels.
procedure ap_imode (hgm, nbins, z1, z2, smooth, sky_mode, ier)
real hgm[ARB] # histogram
int nbins # number of bins
real z1, z2 # min and max of the histogram
int smooth # is the histogram smoothed
real sky_mode # mode of histogram
int ier # error code
int i, noccup
double sumi, sumix, x, dh
real hmean, dz
real asumr()
begin
# Initialize the sums.
sumi = 0.0
sumix = 0.0
# Compute a continuum level.
if (smooth == NO)
hmean = asumr (hgm, nbins) / nbins
else {
call alimr (hgm, nbins, dz, hmean)
hmean = 2.0 * hmean / 3.0
}
# Accumulate the sums.
noccup = 1
dz = (z2 - z1) / (nbins - 1)
x = z1 + 0.5 * dz
do i = 1, nbins {
dh = hgm[i] - hmean
if (dh > 0.0d0) {
sumi = sumi + dh
sumix = sumix + dh * x
noccup = noccup + 1
}
x = x + dz
}
# Compute the sky mode, sigma and skew.
if (sumi > 0.0) {
sky_mode = sumix / sumi
ier = AP_OK
} else {
sky_mode = INDEFR
ier = AP_NOHISTOGRAM
}
end
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