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
|
# Copyright(c) 1986 Association of Universities for Research in Astronomy Inc.
include <gio.h>
# GGSCALE -- Get the WCS scale in world coords per NDC at the point (x,y).
# Used to convert offsets or sizes in NDC coordinates into world coordinates,
# and vice versa. If log scaling is in use we can only locally approximate
# the scale.
procedure ggscale (gp, x, y, dx, dy)
pointer gp # graphics descriptor
real x, y # point for which scale is desired
real dx, dy # scale wcs/nds (output)
pointer w
real x1, x2, y1, y2, xs, ys, elog_scale
real log10e, elogr()
data log10e /0.434294482/
begin
w = GP_WCSPTR(gp,GP_WCS(gp))
x1 = WCS_WX1(w)
x2 = WCS_WX2(w)
y1 = WCS_WY1(w)
y2 = WCS_WY2(w)
xs = WCS_SX2(w) - WCS_SX1(w)
ys = WCS_SY2(w) - WCS_SY1(w)
switch (WCS_XTRAN(w)) {
case LOG:
dx = (x / log10e) * log10 (x2 / x1) / xs
case ELOG:
# The following is an approximation.
elog_scale = (elogr(x2) - elogr(x1)) / xs
if (x < 10.0)
dx = (-x / log10e) * elog_scale
else if (x > 10.0)
dx = (x / log10e) * elog_scale
else
dx = (10. / log10e) * elog_scale
default:
# LINEAR
dx = (x2 - x1) / xs
}
switch (WCS_YTRAN(w)) {
case LOG:
dy = (y / log10e) * log10 (y2 / y1) / ys
case ELOG:
# The following is an approximation.
elog_scale = (elogr(y2) - elogr(y1)) / ys
if (y < 10.0)
dy = (-y / log10e) * elog_scale
else if (y > 10.0)
dy = (y / log10e) * elog_scale
else
dy = (10. / log10e) * elog_scale
default:
# LINEAR
dy = (y2 - y1) / ys
}
end
|
