1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
|
include <mach.h>
include "../lib/fitsky.h"
define MEDCUT 0.025
# AP_MEDIAN -- Procedure to calculate the median of the sky pixel array.
int procedure ap_median (skypix, coords, wgt, index, nskypix, snx, sny, losigma,
hisigma, rgrow, maxiter, sky_med, sky_sigma, sky_skew, nsky,
nsky_reject)
real skypix[ARB] # unsorted array of sky pixels
int coords[ARB] # coordinate array for regions growing
real wgt[ARB] # array of weights for rejections
int index[ARB] # sky pixel indices in sort order
int nskypix # total number of sky pixels
int snx, sny # dimensions of the sky subraster
real losigma, hisigma # upper and lower sigma for rejection
real rgrow # radius of region growing
int maxiter # maximum number of cycles of rejection
real sky_med # computed sky value
real sky_sigma # the computed sky sigma
real sky_skew # skewness of sky distribution
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 sky_zero, sky_mean, locut, hicut, dmin, dmax
int ap_grow_regions(), apimed()
real apsmed(), apwsmed(), ap_asumr()
begin
# Intialize.
nsky = nskypix
nsky_reject = 0
sky_med = INDEFR
sky_sigma = INDEFR
sky_skew = INDEFR
if (nskypix <= 0)
return (AP_NOSKYAREA)
# Sort the sky pixels and compute the median, mean, sigma and skew.
# MEDCUT tries to correct for quantization effects
call ap_ialimr (skypix, index, nskypix, dmin, dmax)
sky_zero = ap_asumr (skypix, index, nskypix) / nskypix
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 (maxiter < 1 || (IS_INDEFR(losigma) && IS_INDEFR(hisigma)) ||
sky_sigma <= 0.0)
return (AP_OK)
#call printf (
#"mean=%g med=%g sigma=%g nsky=%d nrej=%d dmin=%g dmax=%g\n")
#call pargr (sky_mean)
#call pargr (sky_med)
#call pargr (sky_sigma)
#call pargi (nsky)
#call pargi (nsky_reject)
#call pargr (dmin)
#call pargr (dmax)
# Reject points outside losigma * sky_sigma and hisigma * sky_sigma
# of the median.
ilo = 1
ihi = nskypix
do i = 1, maxiter {
# Compute the new rejection limits.
if (IS_INDEFR(losigma))
locut = max (-MAX_REAL, dmin)
else if (i == 1)
locut = sky_med - min (sky_med - dmin, dmax - sky_med,
losigma * sky_sigma)
else
locut = sky_med - losigma * sky_sigma
if (IS_INDEFR(hisigma))
hicut = min (MAX_REAL, dmax)
else if (i == 1)
hicut = sky_med + min (dmax - sky_med, sky_med - dmin,
hisigma * sky_sigma)
else
hicut = sky_med + hisigma * sky_sigma
#call printf (" locut=%g hicut=%g\n")
#call pargr (locut)
#call pargr (hicut)
# Detect pixels to be rejected.
for (il = ilo; il <= nskypix; il = il + 1) {
if (skypix[index[il]] >= locut)
break
}
for (ih = ihi; ih >= 1; ih = ih - 1) {
if (skypix[index[ih]] <= hicut)
break
}
if (il == ilo && ih == ihi)
break
# Reject pixels with optional region growing.
if (rgrow > 0.0) {
# Reject low side 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 high side 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)
# Recompute the median.
# and the median pixel
nsky = nskypix - nsky_reject
med = apimed (wgt, index, il, ih, (nsky + 1) / 2)
} else {
# Recompute the number of sky pixels, the number of rejected
# pixels and median pixel
nsky_reject = nsky_reject + (il - ilo) + (ihi - ih)
nsky = nskypix - nsky_reject
med = (ih + il) / 2
# Reject pixels on the low side.
do j = ilo, il - 1 {
dsky = skypix[index[j]] - sky_zero
sumpx = sumpx - dsky
sumsqpx = sumsqpx - dsky ** 2
sumcbpx = sumcbpx - dsky ** 3
}
# Reject pixels on the high side.
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 the median, 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))
#call printf (
#" mean=%g med=%g sigma=%g nsky=%d nrej=%d dmin=%g dmax=%g\n")
#call pargr (sky_mean)
#call pargr (sky_med)
#call pargr (sky_sigma)
#call pargi (nsky)
#call pargi (nsky_reject)
#call pargr (dmin)
#call pargr (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_med = INDEFR
sky_sigma = INDEFR
sky_skew = INDEFR
return (AP_NSKY_TOO_SMALL)
} else
return (AP_OK)
end
|
