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# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include "../icombine.h"
$for (sird)
# IC_MEDIAN -- Median of lines
procedure ic_median$t (d, n, npts, doblank, median)
pointer d[ARB] # Input data line pointers
int n[npts] # Number of good pixels
int npts # Number of output points per line
int doblank # Set blank values?
$if (datatype == sil)
real median[npts] # Median
$else
PIXEL median[npts] # Median
$endif
int i, j, k, j1, j2, n1, lo, up, lo1, up1
bool even
$if (datatype == silx)
real val1, val2, val3
$else
PIXEL val1, val2, val3
$endif
PIXEL temp, wtemp
$if (datatype == x)
real abs_temp
$endif
include "../icombine.com"
begin
# If no data return after possibly setting blank values.
if (dflag == D_NONE) {
if (doblank == YES) {
do i = 1, npts
median[i]= blank
}
return
}
# If the data were previously sorted then directly compute the median.
if (mclip) {
if (dflag == D_ALL) {
n1 = n[1]
even = (mod (n1, 2) == 0)
j1 = n1 / 2 + 1
j2 = n1 / 2
do i = 1, npts {
k = i - 1
if (even) {
val1 = Mem$t[d[j1]+k]
val2 = Mem$t[d[j2]+k]
median[i] = (val1 + val2) / 2.
} else
median[i] = Mem$t[d[j1]+k]
}
} else {
do i = 1, npts {
k = i - 1
n1 = n[i]
if (n1 > 0) {
j1 = n1 / 2 + 1
if (mod (n1, 2) == 0) {
j2 = n1 / 2
val1 = Mem$t[d[j1]+k]
val2 = Mem$t[d[j2]+k]
median[i] = (val1 + val2) / 2.
} else
median[i] = Mem$t[d[j1]+k]
} else if (doblank == YES)
median[i] = blank
}
}
return
}
# Compute the median.
do i = 1, npts {
k = i - 1
n1 = n[i]
# If there are more than 3 points use Wirth algorithm. This
# is the same as vops$amed.gx except for an even number of
# points it selects the middle two and averages.
if (n1 > 3) {
lo = 1
up = n1
j = max (lo, min (up, (up+1)/2))
while (lo < up) {
if (! (lo < up))
break
temp = Mem$t[d[j]+k]; lo1 = lo; up1 = up
$if (datatype == x)
abs_temp = abs (temp)
$endif
repeat {
$if (datatype == x)
while (abs (Mem$t[d[lo1]+k]) < abs_temp)
$else
while (Mem$t[d[lo1]+k] < temp)
$endif
lo1 = lo1 + 1
$if (datatype == x)
while (abs_temp < abs (Mem$t[d[up1]+k]))
$else
while (temp < Mem$t[d[up1]+k])
$endif
up1 = up1 - 1
if (lo1 <= up1) {
wtemp = Mem$t[d[lo1]+k]
Mem$t[d[lo1]+k] = Mem$t[d[up1]+k]
Mem$t[d[up1]+k] = wtemp
lo1 = lo1 + 1; up1 = up1 - 1
}
} until (lo1 > up1)
if (up1 < j)
lo = lo1
if (j < lo1)
up = up1
}
median[i] = Mem$t[d[j]+k]
if (mod (n1,2) == 0) {
lo = 1
up = n1
j = max (lo, min (up, (up+1)/2)+1)
while (lo < up) {
if (! (lo < up))
break
temp = Mem$t[d[j]+k]; lo1 = lo; up1 = up
$if (datatype == x)
abs_temp = abs (temp)
$endif
repeat {
$if (datatype == x)
while (abs (Mem$t[d[lo1]+k]) < abs_temp)
$else
while (Mem$t[d[lo1]+k] < temp)
$endif
lo1 = lo1 + 1
$if (datatype == x)
while (abs_temp < abs (Mem$t[d[up1]+k]))
$else
while (temp < Mem$t[d[up1]+k])
$endif
up1 = up1 - 1
if (lo1 <= up1) {
wtemp = Mem$t[d[lo1]+k]
Mem$t[d[lo1]+k] = Mem$t[d[up1]+k]
Mem$t[d[up1]+k] = wtemp
lo1 = lo1 + 1; up1 = up1 - 1
}
} until (lo1 > up1)
if (up1 < j)
lo = lo1
if (j < lo1)
up = up1
}
median[i] = (median[i] + Mem$t[d[j]+k]) / 2
}
# If 3 points find the median directly.
} else if (n1 == 3) {
$if (datatype == x)
val1 = abs (Mem$t[d[1]+k])
val2 = abs (Mem$t[d[2]+k])
val3 = abs (Mem$t[d[3]+k])
if (val1 < val2) {
if (val2 < val3) # abc
median[i] = Mem$t[d[2]+k]
else if (val1 < val3) # acb
median[i] = Mem$t[d[3]+k]
else # cab
median[i] = Mem$t[d[1]+k]
} else {
if (val2 > val3) # cba
median[i] = Mem$t[d[2]+k]
else if (val1 > val3) # bca
median[i] = Mem$t[d[3]+k]
else # bac
median[i] = Mem$t[d[1]+k]
}
$else
val1 = Mem$t[d[1]+k]
val2 = Mem$t[d[2]+k]
val3 = Mem$t[d[3]+k]
if (val1 < val2) {
if (val2 < val3) # abc
median[i] = val2
else if (val1 < val3) # acb
median[i] = val3
else # cab
median[i] = val1
} else {
if (val2 > val3) # cba
median[i] = val2
else if (val1 > val3) # bca
median[i] = val3
else # bac
median[i] = val1
}
$endif
# If 2 points average.
} else if (n1 == 2) {
val1 = Mem$t[d[1]+k]
val2 = Mem$t[d[2]+k]
median[i] = (val1 + val2) / 2
# If 1 point return the value.
} else if (n1 == 1)
median[i] = Mem$t[d[1]+k]
# If no points return with a possibly blank value.
else if (doblank == YES)
median[i] = blank
}
end
$endfor
|
