source: trunk/MagicSoft/slalib/pcd.c@ 11169

Last change on this file since 11169 was 731, checked in by tbretz, 24 years ago
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1#include "slalib.h"
2#include "slamac.h"
3void slaPcd ( double disco, double *x, double *y )
4/*
5** - - - - - - -
6** s l a P c d
7** - - - - - - -
8**
9** Apply pincushion/barrel distortion to a tangent-plane [x,y].
10**
11** Given:
12** disco double pincushion/barrel distortion coefficient
13** x,y double tangent-plane coordinates
14**
15** Returned:
16** *x,*y double distorted coordinates
17**
18** Notes:
19**
20** 1) The distortion is of the form rp = r*(1 + c*r**2), where r is
21** the radial distance from the tangent point, c is the disco
22** argument, and rp is the radial distance in the presence of
23** the distortion.
24**
25** 2) For pincushion distortion, c is +ve;
26** For barrel distortion, c is -ve.
27**
28** 3) For x,y in units of one projection radius (in the case of
29** a photographic plate, the focal length), the following
30** disco values apply:
31**
32** geometry disco
33**
34** astrograph 0.0
35** schmidt -0.3333
36** AAT pf doublet +147.069
37** AAT pf triplet +178.585
38** AAT f/8 +21.20
39** JKT f/8 +13.32
40**
41** 4) There is a companion routine, slaUnpcd, which performs
42** an approximately inverse operation.
43**
44** Last revision: 15 July 1993
45**
46** Copyright P.T.Wallace. All rights reserved.
47*/
48{
49 double f;
50
51 f = 1.0 + disco * ( *x * *x + *y * *y );
52 *x *= f;
53 *y *= f;
54}
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