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
|
# APSMED -- Compute the averaged median given a sorted array and an averaging
# half width.
real procedure apsmed (pix, index, npts, medcut)
real pix[ARB] # array of sky pixels
int index[ARB] # sorted index array
int npts # number of pixels
int medcut # averaging half width
int med, j, nmed, medlo, medhi
real sumed
begin
med = (npts + 1) / 2
if (mod (med, 2) == 1) {
medlo = max (1, med - medcut)
medhi = min (npts, med + medcut)
} else {
medlo = max (1, med - medcut)
medhi = min (npts, med + medcut + 1)
}
sumed = 0.0
nmed = 0
do j = medlo, medhi {
sumed = sumed + pix[index[j]]
nmed = nmed + 1
}
return (sumed / nmed)
end
# APIMED -- Compute the index of new median value. Weight is an arbitrary
# weight array which is assumed to be zero if the pixels has been rejected
# and is positive otherwise.
int procedure apimed (weight, index, lo, hi, nmed)
real weight[ARB] # array of weights
int index[ARB] # array of sorted indices
int lo, hi # ranges of weights
int nmed # number of good sky pixels
int npts, med
begin
npts = 0
for (med = lo; med <= hi && npts < nmed; med = med + 1) {
if (weight[index[med]] > 0.0)
npts = npts + 1
}
if (npts == 0)
return (0)
else
return (med)
end
# APWSMED -- Compute the new averaged median given a sorted input array,
# an averaging half-width, and assuming that there has been pixel rejection.
real procedure apwsmed (pix, index, weight, npix, med, medcut)
real pix[ARB] # pixel values array
int index[ARB] # sorted indices array
real weight[ARB] # the weights array
int npix # number of pixels
int med # index of median value
int medcut # of median cut
int j, nmed, maxmed
real sumed
begin
sumed = pix[index[med]]
if (mod (med, 2) == 1)
maxmed = 2 * medcut + 1
else
maxmed = 2 * medcut + 2
nmed = 1
for (j = med - 1; j >= 1; j = j - 1) {
if (nmed >= medcut + 1)
break
if (weight[index[j]] > 0.0) {
sumed = sumed + pix[index[j]]
nmed = nmed + 1
}
}
for (j = med + 1; j <= npix; j = j + 1) {
if (nmed >= maxmed)
break
if (weight[index[j]] > 0.0) {
sumed = sumed + pix[index[j]]
nmed = nmed + 1
}
}
return (sumed / nmed)
end
# APMEDR -- Vector median selection. The selection is carried out in a temporary
# array, leaving the input vector unmodified. Especially demanding applications
# may wish to call the asok routine directory to avoid the call to the memory
# allocator.
real procedure apmedr (a, index, npix)
real a[ARB] # input array of values
int index[ARB] # sorted index array
int npix # number of pixels
int i
pointer sp, aa
real median
real asokr() # select the Kth smallest element from A
begin
switch (npix) {
case 1, 2:
return (a[1])
case 3:
if (a[1] < a[2]) {
if (a[2] < a[3])
return (a[2])
else if (a[1] < a[3])
return (a[3])
else
return (a[1])
} else {
if (a[2] > a[3])
return (a[2])
else if (a[1] < a[3])
return (a[1])
else
return (a[3])
}
default:
call smark (sp)
call salloc (aa, npix, TY_REAL)
do i = 1, npix
Memr[aa+i-1] = a[index[i]]
median = asokr (Memr[aa], npix, (npix + 1) / 2)
call sfree (sp)
return (median)
}
end
|
