WCSLIB: wcshdr.h Source File

WCSLIB 7.3.1

wcshdr.h
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1 /*============================================================================
2 WCSLIB 7.3 - an implementation of the FITS WCS standard.
3 Copyright (C) 1995-2020, Mark Calabretta
4
5 This file is part of WCSLIB.
6
7 WCSLIB is free software: you can redistribute it and/or modify it under the
8 terms of the GNU Lesser General Public License as published by the Free
9 Software Foundation, either version 3 of the License, or (at your option)
10 any later version.
11
12 WCSLIB is distributed in the hope that it will be useful, but WITHOUT ANY
13 WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
14 FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for
15 more details.
16
17 You should have received a copy of the GNU Lesser General Public License
18 along with WCSLIB. If not, see http://www.gnu.org/licenses.
19
20 Direct correspondence concerning WCSLIB to mark@calabretta.id.au
21
22 Author: Mark Calabretta, Australia Telescope National Facility, CSIRO.
23 http://www.atnf.csiro.au/people/Mark.Calabretta
24 $Id: wcshdr.h,v 7.3.1.2 2020/08/17 11:19:09 mcalabre Exp mcalabre $
25 *=============================================================================
26 *
27 * WCSLIB 7.3 - C routines that implement the FITS World Coordinate System
28 * (WCS) standard. Refer to the README file provided with WCSLIB for an
29 * overview of the library.
30 *
31 *
32 * Summary of the wcshdr routines
33 * ------------------------------
34 * Routines in this suite are aimed at extracting WCS information from a FITS
35 * file. The information is encoded via keywords defined in
36 *
37 = "Representations of world coordinates in FITS",
38 = Greisen, E.W., & Calabretta, M.R. 2002, A&A, 395, 1061 (WCS Paper I)
39 =
40 = "Representations of celestial coordinates in FITS",
41 = Calabretta, M.R., & Greisen, E.W. 2002, A&A, 395, 1077 (WCS Paper II)
42 =
43 = "Representations of spectral coordinates in FITS",
44 = Greisen, E.W., Calabretta, M.R., Valdes, F.G., & Allen, S.L.
45 = 2006, A&A, 446, 747 (WCS Paper III)
46 =
47 = "Representations of distortions in FITS world coordinate systems",
48 = Calabretta, M.R. et al. (WCS Paper IV, draft dated 2004/04/22),
49 = available from http://www.atnf.csiro.au/people/Mark.Calabretta
50 =
51 = "Representations of time coordinates in FITS -
52 = Time and relative dimension in space",
53 = Rots, A.H., Bunclark, P.S., Calabretta, M.R., Allen, S.L.,
54 = Manchester, R.N., & Thompson, W.T. 2015, A&A, 574, A36 (WCS Paper VII)
55 *
56 * These routines provide the high-level interface between the FITS file and
57 * the WCS coordinate transformation routines.
58 *
59 * Additionally, function wcshdo() is provided to write out the contents of a
60 * wcsprm struct as a FITS header.
61 *
62 * Briefly, the anticipated sequence of operations is as follows:
63 *
64 * - 1: Open the FITS file and read the image or binary table header, e.g.
65 * using CFITSIO routine fits_hdr2str().
66 *
67 * - 2: Parse the header using wcspih() or wcsbth(); they will automatically
68 * interpret 'TAB' header keywords using wcstab().
69 *
70 * - 3: Allocate memory for, and read 'TAB' arrays from the binary table
71 * extension, e.g. using CFITSIO routine fits_read_wcstab() - refer to
72 * the prologue of getwcstab.h. wcsset() will automatically take
73 * control of this allocated memory, in particular causing it to be
74 * freed by wcsfree().
75 *
76 * - 4: Translate non-standard WCS usage using wcsfix(), see wcsfix.h.
77 *
78 * - 5: Initialize wcsprm struct(s) using wcsset() and calculate coordinates
79 * using wcsp2s() and/or wcss2p(). Refer to the prologue of wcs.h for a
80 * description of these and other high-level WCS coordinate
81 * transformation routines.
82 *
83 * - 6: Clean up by freeing memory with wcsvfree().
84 *
85 * In detail:
86 *
87 * - wcspih() is a high-level FITS WCS routine that parses an image header. It
88 * returns an array of up to 27 wcsprm structs on each of which it invokes
89 * wcstab().
90 *
91 * - wcsbth() is the analogue of wcspih() for use with binary tables; it
92 * handles image array and pixel list keywords. As an extension of the FITS
93 * WCS standard, it also recognizes image header keywords which may be used
94 * to provide default values via an inheritance mechanism.
95 *
96 * - wcstab() assists in filling in members of the wcsprm struct associated
97 * with coordinate lookup tables ('TAB'). These are based on arrays stored
98 * in a FITS binary table extension (BINTABLE) that are located by PVi_ma
99 * keywords in the image header.
100 *
101 * - wcsidx() and wcsbdx() are utility routines that return the index for a
102 * specified alternate coordinate descriptor in the array of wcsprm structs
103 * returned by wcspih() or wcsbth().
104 *
105 * - wcsvfree() deallocates memory for an array of wcsprm structs, such as
106 * returned by wcspih() or wcsbth().
107 *
108 * - wcshdo() writes out a wcsprm struct as a FITS header.
109 *
110 *
111 * wcspih() - FITS WCS parser routine for image headers
112 * ----------------------------------------------------
113 * wcspih() is a high-level FITS WCS routine that parses an image header,
114 * either that of a primary HDU or of an image extension. All WCS keywords
115 * defined in Papers I, II, III, IV, and VII are recognized, and also those
116 * used by the AIPS convention and certain other keywords that existed in early
117 * drafts of the WCS papers as explained in wcsbth() note 5. wcspih() also
118 * handles keywords associated with non-standard distortion functions described
119 * in the prologue of dis.h.
120 *
121 * Given a character array containing a FITS image header, wcspih() identifies
122 * and reads all WCS keywords for the primary coordinate representation and up
123 * to 26 alternate representations. It returns this information as an array of
124 * wcsprm structs.
125 *
126 * wcspih() invokes wcstab() on each of the wcsprm structs that it returns.
127 *
128 * Use wcsbth() in preference to wcspih() for FITS headers of unknown type;
129 * wcsbth() can parse image headers as well as binary table and pixel list
130 * headers, although it cannot handle keywords relating to distortion
131 * functions, which may only exist in a primary image header.
132 *
133 * Given and returned:
134 * header char[] Character array containing the (entire) FITS image
135 * header from which to identify and construct the
136 * coordinate representations, for example, as might be
137 * obtained conveniently via the CFITSIO routine
138 * fits_hdr2str().
139 *
140 * Each header "keyrecord" (formerly "card image")
141 * consists of exactly 80 7-bit ASCII printing characters
142 * in the range 0x20 to 0x7e (which excludes NUL, BS,
143 * TAB, LF, FF and CR) especially noting that the
144 * keyrecords are NOT null-terminated.
145 *
146 * For negative values of ctrl (see below), header[] is
147 * modified so that WCS keyrecords processed by wcspih()
148 * are removed from it.
149 *
150 * Given:
151 * nkeyrec int Number of keyrecords in header[].
152 *
153 * relax int Degree of permissiveness:
154 * 0: Recognize only FITS keywords defined by the
155 * published WCS standard.
156 * WCSHDR_all: Admit all recognized informal
157 * extensions of the WCS standard.
158 * Fine-grained control of the degree of permissiveness
159 * is also possible as explained in wcsbth() note 5.
160 *
161 * ctrl int Error reporting and other control options for invalid
162 * WCS and other header keyrecords:
163 * 0: Do not report any rejected header keyrecords.
164 * 1: Produce a one-line message stating the number
165 * of WCS keyrecords rejected (nreject).
166 * 2: Report each rejected keyrecord and the reason
167 * why it was rejected.
168 * 3: As above, but also report all non-WCS
169 * keyrecords that were discarded, and the number
170 * of coordinate representations (nwcs) found.
171 * 4: As above, but also report the accepted WCS
172 * keyrecords, with a summary of the number
173 * accepted as well as rejected.
174 * The report is written to stderr by default, or the
175 * stream set by wcsprintf_set().
176 *
177 * For ctrl < 0, WCS keyrecords processed by wcspih()
178 * are removed from header[]:
179 * -1: Remove only valid WCS keyrecords whose values
180 * were successfully extracted, nothing is
181 * reported.
182 * -2: As above, but also remove WCS keyrecords that
183 * were rejected, reporting each one and the
184 * reason that it was rejected.
185 * -3: As above, and also report the number of
186 * coordinate representations (nwcs) found.
187 * -11: Same as -1 but preserving global WCS-related
188 * keywords such as '{DATE,MJD}-{OBS,BEG,AVG,END}'
189 * and the other basic time-related keywords, and
190 * 'OBSGEO-{X,Y,Z,L,B,H}'.
191 * If any keyrecords are removed from header[] it will
192 * be null-terminated (NUL not being a legal FITS header
193 * character), otherwise it will contain its original
194 * complement of nkeyrec keyrecords and possibly not be
195 * null-terminated.
196 *
197 * Returned:
198 * nreject int* Number of WCS keywords rejected for syntax errors,
199 * illegal values, etc. Keywords not recognized as WCS
200 * keywords are simply ignored. Refer also to wcsbth()
201 * note 5.
202 *
203 * nwcs int* Number of coordinate representations found.
204 *
205 * wcs struct wcsprm**
206 * Pointer to an array of wcsprm structs containing up to
207 * 27 coordinate representations.
208 *
209 * Memory for the array is allocated by wcspih() which
210 * also invokes wcsini() for each struct to allocate
211 * memory for internal arrays and initialize their
212 * members to default values. Refer also to wcsbth()
213 * note 8. Note that wcsset() is not invoked on these
214 * structs.
215 *
216 * This allocated memory must be freed by the user, first
217 * by invoking wcsfree() for each struct, and then by
218 * freeing the array itself. A routine, wcsvfree(), is
219 * provided to do this (see below).
220 *
221 * Function return value:
222 * int Status return value:
223 * 0: Success.
224 * 1: Null wcsprm pointer passed.
225 * 2: Memory allocation failed.
226 * 4: Fatal error returned by Flex parser.
227 *
228 * Notes:
229 * Refer to wcsbth() notes 1, 2, 3, 5, 7, and 8.
230 *
231 *
232 * wcsbth() - FITS WCS parser routine for binary table and image headers
233 * ---------------------------------------------------------------------
234 * wcsbth() is a high-level FITS WCS routine that parses a binary table header.
235 * It handles image array and pixel list WCS keywords which may be present
236 * together in one header.
237 *
238 * As an extension of the FITS WCS standard, wcsbth() also recognizes image
239 * header keywords in a binary table header. These may be used to provide
240 * default values via an inheritance mechanism discussed in note 5 (c.f.
241 * WCSHDR_AUXIMG and WCSHDR_ALLIMG), or may instead result in wcsprm structs
242 * that are not associated with any particular column. Thus wcsbth() can
243 * handle primary image and image extension headers in addition to binary table
244 * headers (it ignores NAXIS and does not rely on the presence of the TFIELDS
245 * keyword).
246 *
247 * All WCS keywords defined in Papers I, II, III, and VII are recognized, and
248 * also those used by the AIPS convention and certain other keywords that
249 * existed in early drafts of the WCS papers as explained in note 5 below.
250 *
251 * wcsbth() sets the colnum or colax[] members of the wcsprm structs that it
252 * returns with the column number of an image array or the column numbers
253 * associated with each pixel coordinate element in a pixel list. wcsprm
254 * structs that are not associated with any particular column, as may be
255 * derived from image header keywords, have colnum == 0.
256 *
257 * Note 6 below discusses the number of wcsprm structs returned by wcsbth(),
258 * and the circumstances in which image header keywords cause a struct to be
259 * created. See also note 9 concerning the number of separate images that may
260 * be stored in a pixel list.
261 *
262 * The API to wcsbth() is similar to that of wcspih() except for the addition
263 * of extra arguments that may be used to restrict its operation. Like
264 * wcspih(), wcsbth() invokes wcstab() on each of the wcsprm structs that it
265 * returns.
266 *
267 * Given and returned:
268 * header char[] Character array containing the (entire) FITS binary
269 * table, primary image, or image extension header from
270 * which to identify and construct the coordinate
271 * representations, for example, as might be obtained
272 * conveniently via the CFITSIO routine fits_hdr2str().
273 *
274 * Each header "keyrecord" (formerly "card image")
275 * consists of exactly 80 7-bit ASCII printing
276 * characters in the range 0x20 to 0x7e (which excludes
277 * NUL, BS, TAB, LF, FF and CR) especially noting that
278 * the keyrecords are NOT null-terminated.
279 *
280 * For negative values of ctrl (see below), header[] is
281 * modified so that WCS keyrecords processed by wcsbth()
282 * are removed from it.
283 *
284 * Given:
285 * nkeyrec int Number of keyrecords in header[].
286 *
287 * relax int Degree of permissiveness:
288 * 0: Recognize only FITS keywords defined by the
289 * published WCS standard.
290 * WCSHDR_all: Admit all recognized informal
291 * extensions of the WCS standard.
292 * Fine-grained control of the degree of permissiveness
293 * is also possible, as explained in note 5 below.
294 *
295 * ctrl int Error reporting and other control options for invalid
296 * WCS and other header keyrecords:
297 * 0: Do not report any rejected header keyrecords.
298 * 1: Produce a one-line message stating the number
299 * of WCS keyrecords rejected (nreject).
300 * 2: Report each rejected keyrecord and the reason
301 * why it was rejected.
302 * 3: As above, but also report all non-WCS
303 * keyrecords that were discarded, and the number
304 * of coordinate representations (nwcs) found.
305 * 4: As above, but also report the accepted WCS
306 * keyrecords, with a summary of the number
307 * accepted as well as rejected.
308 * The report is written to stderr by default, or the
309 * stream set by wcsprintf_set().
310 *
311 * For ctrl < 0, WCS keyrecords processed by wcsbth()
312 * are removed from header[]:
313 * -1: Remove only valid WCS keyrecords whose values
314 * were successfully extracted, nothing is
315 * reported.
316 * -2: Also remove WCS keyrecords that were rejected,
317 * reporting each one and the reason that it was
318 * rejected.
319 * -3: As above, and also report the number of
320 * coordinate representations (nwcs) found.
321 * -11: Same as -1 but preserving global WCS-related
322 * keywords such as '{DATE,MJD}-{OBS,BEG,AVG,END}'
323 * and the other basic time-related keywords, and
324 * 'OBSGEO-{X,Y,Z,L,B,H}'.
325 * If any keyrecords are removed from header[] it will
326 * be null-terminated (NUL not being a legal FITS header
327 * character), otherwise it will contain its original
328 * complement of nkeyrec keyrecords and possibly not be
329 * null-terminated.
330 *
331 * keysel int Vector of flag bits that may be used to restrict the
332 * keyword types considered:
333 * WCSHDR_IMGHEAD: Image header keywords.
334 * WCSHDR_BIMGARR: Binary table image array.
335 * WCSHDR_PIXLIST: Pixel list keywords.
336 * If zero, there is no restriction.
337 *
338 * Keywords such as EQUIna or RFRQna that are common to
339 * binary table image arrays and pixel lists (including
340 * WCSNna and TWCSna, as explained in note 4 below) are
341 * selected by both WCSHDR_BIMGARR and WCSHDR_PIXLIST.
342 * Thus if inheritance via WCSHDR_ALLIMG is enabled as
343 * discussed in note 5 and one of these shared keywords
344 * is present, then WCSHDR_IMGHEAD and WCSHDR_PIXLIST
345 * alone may be sufficient to cause the construction of
346 * coordinate descriptions for binary table image arrays.
347 *
348 * colsel int* Pointer to an array of table column numbers used to
349 * restrict the keywords considered by wcsbth().
350 *
351 * A null pointer may be specified to indicate that there
352 * is no restriction. Otherwise, the magnitude of
353 * cols[0] specifies the length of the array:
354 * cols[0] > 0: the columns are included,
355 * cols[0] < 0: the columns are excluded.
356 *
357 * For the pixel list keywords TPn_ka and TCn_ka (and
358 * TPCn_ka and TCDn_ka if WCSHDR_LONGKEY is enabled), it
359 * is an error for one column to be selected but not the
360 * other. This is unlike the situation with invalid
361 * keyrecords, which are simply rejected, because the
362 * error is not intrinsic to the header itself but
363 * arises in the way that it is processed.
364 *
365 * Returned:
366 * nreject int* Number of WCS keywords rejected for syntax errors,
367 * illegal values, etc. Keywords not recognized as WCS
368 * keywords are simply ignored, refer also to note 5
369 * below.
370 *
371 * nwcs int* Number of coordinate representations found.
372 *
373 * wcs struct wcsprm**
374 * Pointer to an array of wcsprm structs containing up
375 * to 27027 coordinate representations, refer to note 6
376 * below.
377 *
378 * Memory for the array is allocated by wcsbth() which
379 * also invokes wcsini() for each struct to allocate
380 * memory for internal arrays and initialize their
381 * members to default values. Refer also to note 8
382 * below. Note that wcsset() is not invoked on these
383 * structs.
384 *
385 * This allocated memory must be freed by the user, first
386 * by invoking wcsfree() for each struct, and then by
387 * freeing the array itself. A routine, wcsvfree(), is
388 * provided to do this (see below).
389 *
390 * Function return value:
391 * int Status return value:
392 * 0: Success.
393 * 1: Null wcsprm pointer passed.
394 * 2: Memory allocation failed.
395 * 3: Invalid column selection.
396 * 4: Fatal error returned by Flex parser.
397 *
398 * Notes:
399 * 1: wcspih() determines the number of coordinate axes independently for
400 * each alternate coordinate representation (denoted by the "a" value in
401 * keywords like CTYPEia) from the higher of
402 *
403 * a: NAXIS,
404 * b: WCSAXESa,
405 * c: The highest axis number in any parameterized WCS keyword. The
406 * keyvalue, as well as the keyword, must be syntactically valid
407 * otherwise it will not be considered.
408 *
409 * If none of these keyword types is present, i.e. if the header only
410 * contains auxiliary WCS keywords for a particular coordinate
411 * representation, then no coordinate description is constructed for it.
412 *
413 * wcsbth() is similar except that it ignores the NAXIS keyword if given
414 * an image header to process.
415 *
416 * The number of axes, which is returned as a member of the wcsprm
417 * struct, may differ for different coordinate representations of the
418 * same image.
419 *
420 * 2: wcspih() and wcsbth() enforce correct FITS "keyword = value" syntax
421 * with regard to "= " occurring in columns 9 and 10.
422 *
423 * However, they do recognize free-format character (NOST 100-2.0,
424 * Sect. 5.2.1), integer (Sect. 5.2.3), and floating-point values
425 * (Sect. 5.2.4) for all keywords.
426 *
427 * 3: Where CROTAn, CDi_ja, and PCi_ja occur together in one header wcspih()
428 * and wcsbth() treat them as described in the prologue to wcs.h.
429 *
430 * 4: WCS Paper I mistakenly defined the pixel list form of WCSNAMEa as
431 * TWCSna instead of WCSNna; the 'T' is meant to substitute for the axis
432 * number in the binary table form of the keyword - note that keywords
433 * defined in WCS Papers II, III, and VII that are not parameterized by
434 * axis number have identical forms for binary tables and pixel lists.
435 * Consequently wcsbth() always treats WCSNna and TWCSna as equivalent.
436 *
437 * 5: wcspih() and wcsbth() interpret the "relax" argument as a vector of
438 * flag bits to provide fine-grained control over what non-standard WCS
439 * keywords to accept. The flag bits are subject to change in future and
440 * should be set by using the preprocessor macros (see below) for the
441 * purpose.
442 *
443 * - WCSHDR_none: Don't accept any extensions (not even those in the
444 * errata). Treat non-conformant keywords in the same way as
445 * non-WCS keywords in the header, i.e. simply ignore them.
446 *
447 * - WCSHDR_all: Accept all extensions recognized by the parser.
448 *
449 * - WCSHDR_reject: Reject non-standard keyrecords (that are not otherwise
450 * explicitly accepted by one of the flags below). A message will
451 * optionally be printed on stderr by default, or the stream set
452 * by wcsprintf_set(), as determined by the ctrl argument, and
453 * nreject will be incremented.
454 *
455 * This flag may be used to signal the presence of non-standard
456 * keywords, otherwise they are simply passed over as though they
457 * did not exist in the header. It is mainly intended for testing
458 * conformance of a FITS header to the WCS standard.
459 *
460 * Keyrecords may be non-standard in several ways:
461 *
462 * - The keyword may be syntactically valid but with keyvalue of
463 * incorrect type or invalid syntax, or the keycomment may be
464 * malformed.
465 *
466 * - The keyword may strongly resemble a WCS keyword but not, in
467 * fact, be one because it does not conform to the standard.
468 * For example, "CRPIX01" looks like a CRPIXja keyword, but in
469 * fact the leading zero on the axis number violates the basic
470 * FITS standard. Likewise, "LONPOLE2" is not a valid
471 * LONPOLEa keyword in the WCS standard, and indeed there is
472 * nothing the parser can sensibly do with it.
473 *
474 * - Use of the keyword may be deprecated by the standard. Such
475 * will be rejected if not explicitly accepted via one of the
476 * flags below.
477 *
478 * - WCSHDR_strict: As for WCSHDR_reject, but also reject AIPS-convention
479 * keywords and all other deprecated usage that is not explicitly
480 * accepted.
481 *
482 * - WCSHDR_CROTAia: Accept CROTAia (wcspih()),
483 * iCROTna (wcsbth()),
484 * TCROTna (wcsbth()).
485 * - WCSHDR_VELREFa: Accept VELREFa.
486 * wcspih() always recognizes the AIPS-convention keywords,
487 * CROTAn, EPOCH, and VELREF for the primary representation
488 * (a = ' ') but alternates are non-standard.
489 *
490 * wcsbth() accepts EPOCHa and VELREFa only if WCSHDR_AUXIMG is
491 * also enabled.
492 *
493 * - WCSHDR_CD00i00j: Accept CD00i00j (wcspih()).
494 * - WCSHDR_PC00i00j: Accept PC00i00j (wcspih()).
495 * - WCSHDR_PROJPn: Accept PROJPn (wcspih()).
496 * These appeared in early drafts of WCS Paper I+II (before they
497 * were split) and are equivalent to CDi_ja, PCi_ja, and PVi_ma
498 * for the primary representation (a = ' '). PROJPn is
499 * equivalent to PVi_ma with m = n <= 9, and is associated
500 * exclusively with the latitude axis.
501 *
502 * - WCSHDR_CD0i_0ja: Accept CD0i_0ja (wcspih()).
503 * - WCSHDR_PC0i_0ja: Accept PC0i_0ja (wcspih()).
504 * - WCSHDR_PV0i_0ma: Accept PV0i_0ja (wcspih()).
505 * - WCSHDR_PS0i_0ma: Accept PS0i_0ja (wcspih()).
506 * Allow the numerical index to have a leading zero in doubly-
507 * parameterized keywords, for example, PC01_01. WCS Paper I
508 * (Sects 2.1.2 & 2.1.4) explicitly disallows leading zeroes.
509 * The FITS 3.0 standard document (Sect. 4.1.2.1) states that the
510 * index in singly-parameterized keywords (e.g. CTYPEia) "shall
511 * not have leading zeroes", and later in Sect. 8.1 that "leading
512 * zeroes must not be used" on PVi_ma and PSi_ma. However, by an
513 * oversight, it is silent on PCi_ja and CDi_ja.
514 *
515 * - WCSHDR_DOBSn (wcsbth() only): Allow DOBSn, the column-specific
516 * analogue of DATE-OBS. By an oversight this was never formally
517 * defined in the standard.
518 *
519 * - WCSHDR_OBSGLBHn (wcsbth() only): Allow OBSGLn, OBSGBn, and OBSGHn,
520 * the column-specific analogues of OBSGEO-L, OBSGEO-B, and
521 * OBSGEO-H. By an oversight these were never formally defined in
522 * the standard.
523 *
524 * - WCSHDR_RADECSYS: Accept RADECSYS. This appeared in early drafts of
525 * WCS Paper I+II and was subsequently replaced by RADESYSa.
526 *
527 * wcsbth() accepts RADECSYS only if WCSHDR_AUXIMG is also
528 * enabled.
529 *
530 * - WCSHDR_EPOCHa: Accept EPOCHa.
531 *
532 * - WCSHDR_VSOURCE: Accept VSOURCEa or VSOUna (wcsbth()). This appeared
533 * in early drafts of WCS Paper III and was subsequently dropped
534 * in favour of ZSOURCEa and ZSOUna.
535 *
536 * wcsbth() accepts VSOURCEa only if WCSHDR_AUXIMG is also
537 * enabled.
538 *
539 * - WCSHDR_DATEREF: Accept DATE-REF, MJD-REF, MJD-REFI, MJD-REFF, JDREF,
540 * JD-REFI, and JD-REFF as synonyms for the standard keywords,
541 * DATEREF, MJDREF, MJDREFI, MJDREFF, JDREF, JDREFI, and JDREFF.
542 * The latter buck the pattern set by the other date keywords
543 * ({DATE,MJD}-{OBS,BEG,AVG,END}), thereby increasing the
544 * potential for confusion and error.
545 *
546 * - WCSHDR_LONGKEY (wcsbth() only): Accept long forms of the alternate
547 * binary table and pixel list WCS keywords, i.e. with "a" non-
548 * blank. Specifically
549 *
550 # jCRPXna TCRPXna : jCRPXn jCRPna TCRPXn TCRPna CRPIXja
551 # - TPCn_ka : - ijPCna - TPn_ka PCi_ja
552 # - TCDn_ka : - ijCDna - TCn_ka CDi_ja
553 # iCDLTna TCDLTna : iCDLTn iCDEna TCDLTn TCDEna CDELTia
554 # iCUNIna TCUNIna : iCUNIn iCUNna TCUNIn TCUNna CUNITia
555 # iCTYPna TCTYPna : iCTYPn iCTYna TCTYPn TCTYna CTYPEia
556 # iCRVLna TCRVLna : iCRVLn iCRVna TCRVLn TCRVna CRVALia
557 # iPVn_ma TPVn_ma : - iVn_ma - TVn_ma PVi_ma
558 # iPSn_ma TPSn_ma : - iSn_ma - TSn_ma PSi_ma
559 *
560 * where the primary and standard alternate forms together with
561 * the image-header equivalent are shown rightwards of the colon.
562 *
563 * The long form of these keywords could be described as quasi-
564 * standard. TPCn_ka, iPVn_ma, and TPVn_ma appeared by mistake
565 * in the examples in WCS Paper II and subsequently these and
566 * also TCDn_ka, iPSn_ma and TPSn_ma were legitimized by the
567 * errata to the WCS papers.
568 *
569 * Strictly speaking, the other long forms are non-standard and
570 * in fact have never appeared in any draft of the WCS papers nor
571 * in the errata. However, as natural extensions of the primary
572 * form they are unlikely to be written with any other intention.
573 * Thus it should be safe to accept them provided, of course,
574 * that the resulting keyword does not exceed the 8-character
575 * limit.
576 *
577 * If WCSHDR_CNAMn is enabled then also accept
578 *
579 # iCNAMna TCNAMna : --- iCNAna --- TCNAna CNAMEia
580 # iCRDEna TCRDEna : --- iCRDna --- TCRDna CRDERia
581 # iCSYEna TCSYEna : --- iCSYna --- TCSYna CSYERia
582 # iCZPHna TCZPHna : --- iCZPna --- TCZPna CZPHSia
583 # iCPERna TCPERna : --- iCPRna --- TCPRna CPERIia
584 *
585 * Note that CNAMEia, CRDERia, CSYERia, CZPHSia, CPERIia, and
586 * their variants are not used by WCSLIB but are stored in the
587 * wcsprm struct as auxiliary information.
588 *
589 * - WCSHDR_CNAMn (wcsbth() only): Accept iCNAMn, iCRDEn, iCSYEn, iCZPHn,
590 * iCPERn, TCNAMn, TCRDEn, TCSYEn, TCZPHn, and TCPERn, i.e. with
591 * "a" blank. While non-standard, these are the obvious analogues
592 * of iCTYPn, TCTYPn, etc.
593 *
594 * - WCSHDR_AUXIMG (wcsbth() only): Allow the image-header form of an
595 * auxiliary WCS keyword with representation-wide scope to
596 * provide a default value for all images. This default may be
597 * overridden by the column-specific form of the keyword.
598 *
599 * For example, a keyword like EQUINOXa would apply to all image
600 * arrays in a binary table, or all pixel list columns with
601 * alternate representation "a" unless overridden by EQUIna.
602 *
603 * Specifically the keywords are:
604 *
605 # LONPOLEa for LONPna
606 # LATPOLEa for LATPna
607 # VELREF - ... (No column-specific form.)
608 # VELREFa - ... Only if WCSHDR_VELREFa is set.
609 *
610 * whose keyvalues are actually used by WCSLIB, and also keywords
611 * providing auxiliary information that is simply stored in the
612 * wcsprm struct:
613 *
614 # WCSNAMEa for WCSNna ... Or TWCSna (see below).
615 #
616 # DATE-OBS for DOBSn
617 # MJD-OBS for MJDOBn
618 #
619 # RADESYSa for RADEna
620 # RADECSYS for RADEna ... Only if WCSHDR_RADECSYS is set.
621 # EPOCH - ... (No column-specific form.)
622 # EPOCHa - ... Only if WCSHDR_EPOCHa is set.
623 # EQUINOXa for EQUIna
624 *
625 * where the image-header keywords on the left provide default
626 * values for the column specific keywords on the right.
627 *
628 * Note that, according to Sect. 8.1 of WCS Paper III, and
629 * Sect. 5.2 of WCS Paper VII, the following are always inherited:
630 *
631 # RESTFREQ for RFRQna
632 # RESTFRQa for RFRQna
633 # RESTWAVa for RWAVna
634 *
635 * being those actually used by WCSLIB, together with the
636 * following auxiliary keywords, many of which do not have binary
637 * table equivalents and therefore can only be inherited:
638 *
639 # TIMESYS -
640 # TREFPOS for TRPOSn
641 # TREFDIR for TRDIRn
642 # PLEPHEM -
643 # TIMEUNIT -
644 # DATEREF -
645 # MJDREF -
646 # MJDREFI -
647 # MJDREFF -
648 # JDREF -
649 # JDREFI -
650 # JDREFF -
651 # TIMEOFFS -
652 #
653 # DATE-BEG -
654 # DATE-AVG for DAVGn
655 # DATE-END -
656 # MJD-BEG -
657 # MJD-AVG for MJDAn
658 # MJD-END -
659 # JEPOCH -
660 # BEPOCH -
661 # TSTART -
662 # TSTOP -
663 # XPOSURE -
664 # TELAPSE -
665 #
666 # TIMSYER -
667 # TIMRDER -
668 # TIMEDEL -
669 # TIMEPIXR -
670 #
671 # OBSGEO-X for OBSGXn
672 # OBSGEO-Y for OBSGYn
673 # OBSGEO-Z for OBSGZn
674 # OBSGEO-L for OBSGLn
675 # OBSGEO-B for OBSGBn
676 # OBSGEO-H for OBSGHn
677 # OBSORBIT -
678 #
679 # SPECSYSa for SPECna
680 # SSYSOBSa for SOBSna
681 # VELOSYSa for VSYSna
682 # VSOURCEa for VSOUna ... Only if WCSHDR_VSOURCE is set.
683 # ZSOURCEa for ZSOUna
684 # SSYSSRCa for SSRCna
685 # VELANGLa for VANGna
686 *
687 * Global image-header keywords, such as MJD-OBS, apply to all
688 * alternate representations, and would therefore provide a
689 * default value for all images in the header.
690 *
691 * This auxiliary inheritance mechanism applies to binary table
692 * image arrays and pixel lists alike. Most of these keywords
693 * have no default value, the exceptions being LONPOLEa and
694 * LATPOLEa, and also RADESYSa and EQUINOXa which provide
695 * defaults for each other. Thus one potential difficulty in
696 * using WCSHDR_AUXIMG is that of erroneously inheriting one of
697 * these four keywords.
698 *
699 * Also, beware of potential inconsistencies that may arise where,
700 * for example, DATE-OBS is inherited, but MJD-OBS is overridden
701 * by MJDOBn and specifies a different time. Pairs in this
702 * category are:
703 *
704 = DATE-OBS/DOBSn versus MJD-OBS/MJDOBn
705 = DATE-AVG/DAVGn versus MJD-AVG/MJDAn
706 = RESTFRQa/RFRQna versus RESTWAVa/RWAVna
707 = OBSGEO-[XYZ]/OBSG[XYZ]n versus OBSGEO-[LBH]/OBSG[LBH]n
708 *
709 * The wcsfixi() routines datfix() and obsfix() are provided to
710 * check the consistency of these and other such pairs of
711 * keywords.
712 *
713 * Unlike WCSHDR_ALLIMG, the existence of one (or all) of these
714 * auxiliary WCS image header keywords will not by itself cause a
715 * wcsprm struct to be created for alternate representation "a".
716 * This is because they do not provide sufficient information to
717 * create a non-trivial coordinate representation when used in
718 * conjunction with the default values of those keywords that are
719 * parameterized by axis number, such as CTYPEia.
720 *
721 * - WCSHDR_ALLIMG (wcsbth() only): Allow the image-header form of *all*
722 * image header WCS keywords to provide a default value for all
723 * image arrays in a binary table (n.b. not pixel list). This
724 * default may be overridden by the column-specific form of the
725 * keyword.
726 *
727 * For example, a keyword like CRPIXja would apply to all image
728 * arrays in a binary table with alternate representation "a"
729 * unless overridden by jCRPna.
730 *
731 * Specifically the keywords are those listed above for
732 * WCSHDR_AUXIMG plus
733 *
734 # WCSAXESa for WCAXna
735 *
736 * which defines the coordinate dimensionality, and the following
737 * keywords that are parameterized by axis number:
738 *
739 # CRPIXja for jCRPna
740 # PCi_ja for ijPCna
741 # CDi_ja for ijCDna
742 # CDELTia for iCDEna
743 # CROTAi for iCROTn
744 # CROTAia - ... Only if WCSHDR_CROTAia is set.
745 # CUNITia for iCUNna
746 # CTYPEia for iCTYna
747 # CRVALia for iCRVna
748 # PVi_ma for iVn_ma
749 # PSi_ma for iSn_ma
750 #
751 # CNAMEia for iCNAna
752 # CRDERia for iCRDna
753 # CSYERia for iCSYna
754 # CZPHSia for iCZPna
755 # CPERIia for iCPRna
756 *
757 * where the image-header keywords on the left provide default
758 * values for the column specific keywords on the right.
759 *
760 * This full inheritance mechanism only applies to binary table
761 * image arrays, not pixel lists, because in the latter case
762 * there is no well-defined association between coordinate axis
763 * number and column number (see note 9 below).
764 *
765 * Note that CNAMEia, CRDERia, CSYERia, and their variants are
766 * not used by WCSLIB but are stored in the wcsprm struct as
767 * auxiliary information.
768 *
769 * Note especially that at least one wcsprm struct will be
770 * returned for each "a" found in one of the image header
771 * keywords listed above:
772 *
773 * - If the image header keywords for "a" ARE NOT inherited by a
774 * binary table, then the struct will not be associated with
775 * any particular table column number and it is up to the user
776 * to provide an association.
777 *
778 * - If the image header keywords for "a" ARE inherited by a
779 * binary table image array, then those keywords are considered
780 * to be "exhausted" and do not result in a separate wcsprm
781 * struct.
782 *
783 * For example, to accept CD00i00j and PC00i00j and reject all other
784 * extensions, use
785 *
786 = relax = WCSHDR_reject | WCSHDR_CD00i00j | WCSHDR_PC00i00j;
787 *
788 * The parser always treats EPOCH as subordinate to EQUINOXa if both are
789 * present, and VSOURCEa is always subordinate to ZSOURCEa.
790 *
791 * Likewise, VELREF is subordinate to the formalism of WCS Paper III, see
792 * spcaips().
793 *
794 * Neither wcspih() nor wcsbth() currently recognize the AIPS-convention
795 * keywords ALTRPIX or ALTRVAL which effectively define an alternative
796 * representation for a spectral axis.
797 *
798 * 6: Depending on what flags have been set in its "relax" argument,
799 * wcsbth() could return as many as 27027 wcsprm structs:
800 *
801 * - Up to 27 unattached representations derived from image header
802 * keywords.
803 *
804 * - Up to 27 structs for each of up to 999 columns containing an image
805 * arrays.
806 *
807 * - Up to 27 structs for a pixel list.
808 *
809 * Note that it is considered legitimate for a column to contain an image
810 * array and also form part of a pixel list, and in particular that
811 * wcsbth() does not check the TFORM keyword for a pixel list column to
812 * check that it is scalar.
813 *
814 * In practice, of course, a realistic binary table header is unlikely to
815 * contain more than a handful of images.
816 *
817 * In order for wcsbth() to create a wcsprm struct for a particular
818 * coordinate representation, at least one WCS keyword that defines an
819 * axis number must be present, either directly or by inheritance if
820 * WCSHDR_ALLIMG is set.
821 *
822 * When the image header keywords for an alternate representation are
823 * inherited by a binary table image array via WCSHDR_ALLIMG, those
824 * keywords are considered to be "exhausted" and do not result in a
825 * separate wcsprm struct. Otherwise they do.
826 *
827 * 7: Neither wcspih() nor wcsbth() check for duplicated keywords, in most
828 * cases they accept the last encountered.
829 *
830 * 8: wcspih() and wcsbth() use wcsnpv() and wcsnps() (refer to the prologue
831 * of wcs.h) to match the size of the pv[] and ps[] arrays in the wcsprm
832 * structs to the number in the header. Consequently there are no unused
833 * elements in the pv[] and ps[] arrays, indeed they will often be of
834 * zero length.
835 *
836 * 9: The FITS WCS standard for pixel lists assumes that a pixel list
837 * defines one and only one image, i.e. that each row of the binary table
838 * refers to just one event, e.g. the detection of a single photon or
839 * neutrino, for which the device "pixel" coordinates are stored in
840 * separate scalar columns of the table.
841 *
842 * In the absence of a standard for pixel lists - or even an informal
843 * description! - let alone a formal mechanism for identifying the columns
844 * containing pixel coordinates (as opposed to pixel values or metadata
845 * recorded at the time the photon or neutrino was detected), WCS Paper I
846 * discusses how the WCS keywords themselves may be used to identify them.
847 *
848 * In practice, however, pixel lists have been used to store multiple
849 * images. Besides not specifying how to identify columns, the pixel list
850 * convention is also silent on the method to be used to associate table
851 * columns with image axes.
852 *
853 * An additional shortcoming is the absence of a formal method for
854 * associating global binary-table WCS keywords, such as WCSNna or MJDOBn,
855 * with a pixel list image, whether one or several.
856 *
857 * In light of these uncertainties, wcsbth() simply collects all WCS
858 * keywords for a particular pixel list coordinate representation (i.e.
859 * the "a" value in TCTYna) into one wcsprm struct. However, these
860 * alternates need not be associated with the same table columns and this
861 * allows a pixel list to contain up to 27 separate images. As usual, if
862 * one of these representations happened to contain more than two
863 * celestial axes, for example, then an error would result when wcsset()
864 * is invoked on it. In this case the "colsel" argument could be used to
865 * restrict the columns used to construct the representation so that it
866 * only contained one pair of celestial axes.
867 *
868 * Global, binary-table WCS keywords are considered to apply to the pixel
869 * list image with matching alternate (e.g. the "a" value in LONPna or
870 * EQUIna), regardless of the table columns the image occupies. In other
871 * words, the column number is ignored (the "n" value in LONPna or
872 * EQUIna). This also applies for global, binary-table WCS keywords that
873 * have no alternates, such as MJDOBn and OBSGXn, which match all images
874 * in a pixel list. Take heed that this may lead to counterintuitive
875 * behaviour, especially where such a keyword references a column that
876 * does not store pixel coordinates, and moreso where the pixel list
877 * stores only a single image. In fact, as the column number, n, is
878 * ignored for such keywords, it would make no difference even if they
879 * referenced non-existent columns. Moreover, there is no requirement for
880 * consistency in the column numbers used for such keywords, even for
881 * OBSGXn, OBSGYn, and OBSGZn which are meant to define the elements of a
882 * coordinate vector. Although it would surely be perverse to construct a
883 * pixel list like this, such a situation may still arise in practice
884 * where columns are deleted from a binary table.
885 *
886 * The situation with global, binary-table WCS keywords becomes
887 * potentially even more confusing when image arrays and pixel list images
888 * coexist in one binary table. In that case, a keyword such as MJDOBn
889 * may legitimately appear multiple times with n referencing different
890 * image arrays. Which then is the one that applies to the pixel list
891 * images? In this implementation, it is the last instance that appears
892 * in the header, whether or not it is also associated with an image
893 * array.
894 *
895 *
896 * wcstab() - Tabular construction routine
897 * ---------------------------------------
898 * wcstab() assists in filling in the information in the wcsprm struct relating
899 * to coordinate lookup tables.
900 *
901 * Tabular coordinates ('TAB') present certain difficulties in that the main
902 * components of the lookup table - the multidimensional coordinate array plus
903 * an index vector for each dimension - are stored in a FITS binary table
904 * extension (BINTABLE). Information required to locate these arrays is stored
905 * in PVi_ma and PSi_ma keywords in the image header.
906 *
907 * wcstab() parses the PVi_ma and PSi_ma keywords associated with each 'TAB'
908 * axis and allocates memory in the wcsprm struct for the required number of
909 * tabprm structs. It sets as much of the tabprm struct as can be gleaned from
910 * the image header, and also sets up an array of wtbarr structs (described in
911 * the prologue of wtbarr.h) to assist in extracting the required arrays from
912 * the BINTABLE extension(s).
913 *
914 * It is then up to the user to allocate memory for, and copy arrays from the
915 * BINTABLE extension(s) into the tabprm structs. A CFITSIO routine,
916 * fits_read_wcstab(), has been provided for this purpose, see getwcstab.h.
917 * wcsset() will automatically take control of this allocated memory, in
918 * particular causing it to be freed by wcsfree(); the user must not attempt
919 * to free it after wcsset() has been called.
920 *
921 * Note that wcspih() and wcsbth() automatically invoke wcstab() on each of the
922 * wcsprm structs that they return.
923 *
924 * Given and returned:
925 * wcs struct wcsprm*
926 * Coordinate transformation parameters (see below).
927 *
928 * wcstab() sets ntab, tab, nwtb and wtb, allocating
929 * memory for the tab and wtb arrays. This allocated
930 * memory will be freed automatically by wcsfree().
931 *
932 * Function return value:
933 * int Status return value:
934 * 0: Success.
935 * 1: Null wcsprm pointer passed.
936 * 2: Memory allocation failed.
937 * 3: Invalid tabular parameters.
938 *
939 * For returns > 1, a detailed error message is set in
940 * wcsprm::err if enabled, see wcserr_enable().
941 *
942 *
943 * wcsidx() - Index alternate coordinate representations
944 * -----------------------------------------------------
945 * wcsidx() returns an array of 27 indices for the alternate coordinate
946 * representations in the array of wcsprm structs returned by wcspih(). For
947 * the array returned by wcsbth() it returns indices for the unattached
948 * (colnum == 0) representations derived from image header keywords - use
949 * wcsbdx() for those derived from binary table image arrays or pixel lists
950 * keywords.
951 *
952 * Given:
953 * nwcs int Number of coordinate representations in the array.
954 *
955 * wcs const struct wcsprm**
956 * Pointer to an array of wcsprm structs returned by
957 * wcspih() or wcsbth().
958 *
959 * Returned:
960 * alts int[27] Index of each alternate coordinate representation in
961 * the array: alts[0] for the primary, alts[1] for 'A',
962 * etc., set to -1 if not present.
963 *
964 * For example, if there was no 'P' representation then
965 *
966 = alts['P'-'A'+1] == -1;
967 *
968 * Otherwise, the address of its wcsprm struct would be
969 *
970 = wcs + alts['P'-'A'+1];
971 *
972 * Function return value:
973 * int Status return value:
974 * 0: Success.
975 * 1: Null wcsprm pointer passed.
976 *
977 *
978 * wcsbdx() - Index alternate coordinate representions
979 * ---------------------------------------------------
980 * wcsbdx() returns an array of 999 x 27 indices for the alternate coordinate
981 * representions for binary table image arrays xor pixel lists in the array of
982 * wcsprm structs returned by wcsbth(). Use wcsidx() for the unattached
983 * representations derived from image header keywords.
984 *
985 * Given:
986 * nwcs int Number of coordinate representations in the array.
987 *
988 * wcs const struct wcsprm**
989 * Pointer to an array of wcsprm structs returned by
990 * wcsbth().
991 *
992 * type int Select the type of coordinate representation:
993 * 0: binary table image arrays,
994 * 1: pixel lists.
995 *
996 * Returned:
997 * alts short[1000][28]
998 * Index of each alternate coordinate represention in the
999 * array: alts[col][0] for the primary, alts[col][1] for
1000 * 'A', to alts[col][26] for 'Z', where col is the
1001 * 1-relative column number, and col == 0 is used for
1002 * unattached image headers. Set to -1 if not present.
1003 *
1004 * alts[col][27] counts the number of coordinate
1005 * representations of the chosen type for each column.
1006 *
1007 * For example, if there was no 'P' represention for
1008 * column 13 then
1009 *
1010 = alts[13]['P'-'A'+1] == -1;
1011 *
1012 * Otherwise, the address of its wcsprm struct would be
1013 *
1014 = wcs + alts[13]['P'-'A'+1];
1015 *
1016 * Function return value:
1017 * int Status return value:
1018 * 0: Success.
1019 * 1: Null wcsprm pointer passed.
1020 *
1021 *
1022 * wcsvfree() - Free the array of wcsprm structs
1023 * ---------------------------------------------
1024 * wcsvfree() frees the memory allocated by wcspih() or wcsbth() for the array
1025 * of wcsprm structs, first invoking wcsfree() on each of the array members.
1026 *
1027 * Given and returned:
1028 * nwcs int* Number of coordinate representations found; set to 0
1029 * on return.
1030 *
1031 * wcs struct wcsprm**
1032 * Pointer to the array of wcsprm structs; set to 0x0 on
1033 * return.
1034 *
1035 * Function return value:
1036 * int Status return value:
1037 * 0: Success.
1038 * 1: Null wcsprm pointer passed.
1039 *
1040 *
1041 * wcshdo() - Write out a wcsprm struct as a FITS header
1042 * -----------------------------------------------------
1043 * wcshdo() translates a wcsprm struct into a FITS header. If the colnum
1044 * member of the struct is non-zero then a binary table image array header will
1045 * be produced. Otherwise, if the colax[] member of the struct is set non-zero
1046 * then a pixel list header will be produced. Otherwise, a primary image or
1047 * image extension header will be produced.
1048 *
1049 * If the struct was originally constructed from a header, e.g. by wcspih(),
1050 * the output header will almost certainly differ in a number of respects:
1051 *
1052 * - The output header only contains WCS-related keywords. In particular, it
1053 * does not contain syntactically-required keywords such as SIMPLE, NAXIS,
1054 * BITPIX, or END.
1055 *
1056 * - Elements of the PCi_ja matrix will be written if and only if they differ
1057 * from the unit matrix. Thus, if the matrix is unity then no elements
1058 * will be written.
1059 *
1060 * - The redundant keywords MJDREF, JDREF, JDREFI, JDREFF, all of which
1061 * duplicate MJDREFI + MJDREFF, are never written. OBSGEO-[LBH] are not
1062 * written if OBSGEO-[XYZ] are defined.
1063 *
1064 * - Deprecated (e.g. CROTAn, RESTFREQ, VELREF, RADECSYS, EPOCH, VSOURCEa) or
1065 * non-standard usage will be translated to standard (this is partially
1066 * dependent on whether wcsfix() was applied).
1067 *
1068 * - Additional keywords such as WCSAXESa, CUNITia, LONPOLEa and LATPOLEa may
1069 * appear.
1070 *
1071 * - Quantities will be converted to the units used internally, basically SI
1072 * with the addition of degrees.
1073 *
1074 * - Floating-point quantities may be given to a different decimal precision.
1075 *
1076 * - The original keycomments will be lost, although wcshdo() tries hard to
1077 * write meaningful comments.
1078 *
1079 * - Keyword order will almost certainly be changed.
1080 *
1081 * Keywords can be translated between the image array, binary table, and pixel
1082 * lists forms by manipulating the colnum or colax[] members of the wcsprm
1083 * struct.
1084 *
1085 * Given:
1086 * ctrl int Vector of flag bits that controls the degree of
1087 * permissiveness in departing from the published WCS
1088 * standard, and also controls the formatting of
1089 * floating-point keyvalues. Set it to zero to get the
1090 * default behaviour.
1091 *
1092 * Flag bits for the degree of permissiveness:
1093 * WCSHDO_none: Recognize only FITS keywords defined by
1094 * the published WCS standard.
1095 * WCSHDO_all: Admit all recognized informal extensions
1096 * of the WCS standard.
1097 * Fine-grained control of the degree of permissiveness
1098 * is also possible as explained in the notes below.
1099 *
1100 * As for controlling floating-point formatting, by
1101 * default wcshdo() uses "%20.12G" for non-parameterized
1102 * keywords such as LONPOLEa, and attempts to make the
1103 * header more human-readable by using the same "%f"
1104 * format for all values of each of the following
1105 * parameterized keywords: CRPIXja, PCi_ja, and CDELTia
1106 * (n.b. excluding CRVALia). Each has the same field
1107 * width and precision so that the decimal points line
1108 * up. The precision, allowing for up to 15 significant
1109 * digits, is chosen so that there are no excess trailing
1110 * zeroes. A similar formatting scheme applies by
1111 * default for distortion function parameters.
1112 *
1113 * However, where the values of, for example, CDELTia
1114 * differ by many orders of magnitude, the default
1115 * formatting scheme may cause unacceptable loss of
1116 * precision for the lower-valued keyvalues. Thus the
1117 * default behaviour may be overridden:
1118 * WCSHDO_P12: Use "%20.12G" format for all floating-
1119 * point keyvalues (12 significant digits).
1120 * WCSHDO_P13: Use "%21.13G" format for all floating-
1121 * point keyvalues (13 significant digits).
1122 * WCSHDO_P14: Use "%22.14G" format for all floating-
1123 * point keyvalues (14 significant digits).
1124 * WCSHDO_P15: Use "%23.15G" format for all floating-
1125 * point keyvalues (15 significant digits).
1126 * WCSHDO_P16: Use "%24.16G" format for all floating-
1127 * point keyvalues (16 significant digits).
1128 * WCSHDO_P17: Use "%25.17G" format for all floating-
1129 * point keyvalues (17 significant digits).
1130 * If more than one of the above flags are set, the
1131 * highest number of significant digits prevails. In
1132 * addition, there is an anciliary flag:
1133 * WCSHDO_EFMT: Use "%E" format instead of the default
1134 * "%G" format above.
1135 * Note that excess trailing zeroes are stripped off the
1136 * fractional part with "%G" (which never occurs with
1137 * "%E"). Note also that the higher-precision options
1138 * eat into the keycomment area. In this regard,
1139 * WCSHDO_P14 causes minimal disruption with "%G" format,
1140 * while WCSHDO_P13 is appropriate with "%E".
1141 *
1142 * Given and returned:
1143 * wcs struct wcsprm*
1144 * Pointer to a wcsprm struct containing coordinate
1145 * transformation parameters. Will be initialized if
1146 * necessary.
1147 *
1148 * Returned:
1149 * nkeyrec int* Number of FITS header keyrecords returned in the
1150 * "header" array.
1151 *
1152 * header char** Pointer to an array of char holding the header.
1153 * Storage for the array is allocated by wcshdo() in
1154 * blocks of 2880 bytes (32 x 80-character keyrecords)
1155 * and must be freed by the user to avoid memory leaks.
1156 * See wcsdealloc().
1157 *
1158 * Each keyrecord is 80 characters long and is *NOT*
1159 * null-terminated, so the first keyrecord starts at
1160 * (*header)[0], the second at (*header)[80], etc.
1161 *
1162 * Function return value:
1163 * int Status return value (associated with wcs_errmsg[]):
1164 * 0: Success.
1165 * 1: Null wcsprm pointer passed.
1166 * 2: Memory allocation failed.
1167 * 3: Linear transformation matrix is singular.
1168 * 4: Inconsistent or unrecognized coordinate axis
1169 * types.
1170 * 5: Invalid parameter value.
1171 * 6: Invalid coordinate transformation parameters.
1172 * 7: Ill-conditioned coordinate transformation
1173 * parameters.
1174 *
1175 * For returns > 1, a detailed error message is set in
1176 * wcsprm::err if enabled, see wcserr_enable().
1177 *
1178 * Notes:
1179 * wcshdo() interprets the "relax" argument as a vector of flag bits to
1180 * provide fine-grained control over what non-standard WCS keywords to write.
1181 * The flag bits are subject to change in future and should be set by using
1182 * the preprocessor macros (see below) for the purpose.
1183 *
1184 * - WCSHDO_none: Don't use any extensions.
1185 *
1186 * - WCSHDO_all: Write all recognized extensions, equivalent to setting each
1187 * flag bit.
1188 *
1189 * - WCSHDO_safe: Write all extensions that are considered to be safe and
1190 * recommended.
1191 *
1192 * - WCSHDO_DOBSn: Write DOBSn, the column-specific analogue of DATE-OBS for
1193 * use in binary tables and pixel lists. WCS Paper III introduced
1194 * DATE-AVG and DAVGn but by an oversight DOBSn (the obvious analogy)
1195 * was never formally defined by the standard. The alternative to
1196 * using DOBSn is to write DATE-OBS which applies to the whole table.
1197 * This usage is considered to be safe and is recommended.
1198 *
1199 * - WCSHDO_TPCn_ka: WCS Paper I defined
1200 *
1201 * - TPn_ka and TCn_ka for pixel lists
1202 *
1203 * but WCS Paper II uses TPCn_ka in one example and subsequently the
1204 * errata for the WCS papers legitimized the use of
1205 *
1206 * - TPCn_ka and TCDn_ka for pixel lists
1207 *
1208 * provided that the keyword does not exceed eight characters. This
1209 * usage is considered to be safe and is recommended because of the
1210 * non-mnemonic terseness of the shorter forms.
1211 *
1212 * - WCSHDO_PVn_ma: WCS Paper I defined
1213 *
1214 * - iVn_ma and iSn_ma for bintables and
1215 * - TVn_ma and TSn_ma for pixel lists
1216 *
1217 * but WCS Paper II uses iPVn_ma and TPVn_ma in the examples and
1218 * subsequently the errata for the WCS papers legitimized the use of
1219 *
1220 * - iPVn_ma and iPSn_ma for bintables and
1221 * - TPVn_ma and TPSn_ma for pixel lists
1222 *
1223 * provided that the keyword does not exceed eight characters. This
1224 * usage is considered to be safe and is recommended because of the
1225 * non-mnemonic terseness of the shorter forms.
1226 *
1227 * - WCSHDO_CRPXna: For historical reasons WCS Paper I defined
1228 *
1229 * - jCRPXn, iCDLTn, iCUNIn, iCTYPn, and iCRVLn for bintables and
1230 * - TCRPXn, TCDLTn, TCUNIn, TCTYPn, and TCRVLn for pixel lists
1231 *
1232 * for use without an alternate version specifier. However, because
1233 * of the eight-character keyword constraint, in order to accommodate
1234 * column numbers greater than 99 WCS Paper I also defined
1235 *
1236 * - jCRPna, iCDEna, iCUNna, iCTYna and iCRVna for bintables and
1237 * - TCRPna, TCDEna, TCUNna, TCTYna and TCRVna for pixel lists
1238 *
1239 * for use with an alternate version specifier (the "a"). Like the
1240 * PC, CD, PV, and PS keywords there is an obvious tendency to
1241 * confuse these two forms for column numbers up to 99. It is very
1242 * unlikely that any parser would reject keywords in the first set
1243 * with a non-blank alternate version specifier so this usage is
1244 * considered to be safe and is recommended.
1245 *
1246 * - WCSHDO_CNAMna: WCS Papers I and III defined
1247 *
1248 * - iCNAna, iCRDna, and iCSYna for bintables and
1249 * - TCNAna, TCRDna, and TCSYna for pixel lists
1250 *
1251 * By analogy with the above, the long forms would be
1252 *
1253 * - iCNAMna, iCRDEna, and iCSYEna for bintables and
1254 * - TCNAMna, TCRDEna, and TCSYEna for pixel lists
1255 *
1256 * Note that these keywords provide auxiliary information only, none
1257 * of them are needed to compute world coordinates. This usage is
1258 * potentially unsafe and is not recommended at this time.
1259 *
1260 * - WCSHDO_WCSNna: In light of wcsbth() note 4, write WCSNna instead of
1261 * TWCSna for pixel lists. While wcsbth() treats WCSNna and TWCSna
1262 * as equivalent, other parsers may not. Consequently, this usage
1263 * is potentially unsafe and is not recommended at this time.
1264 *
1265 *
1266 * Global variable: const char *wcshdr_errmsg[] - Status return messages
1267 * ---------------------------------------------------------------------
1268 * Error messages to match the status value returned from each function.
1269 * Use wcs_errmsg[] for status returns from wcshdo().
1270 *
1271 *===========================================================================*/
1272
1273 #ifndef WCSLIB_WCSHDR
1274 #define WCSLIB_WCSHDR
1275
1276 #include "wcs.h"
1277
1278 #ifdef __cplusplus
1279 extern "C" {
1280 #endif
1281
1282 #define WCSHDR_none 0x00000000
1283 #define WCSHDR_all 0x000FFFFF
1284 #define WCSHDR_reject 0x10000000
1285 #define WCSHDR_strict 0x20000000
1286
1287 #define WCSHDR_CROTAia 0x00000001
1288 #define WCSHDR_VELREFa 0x00000002
1289 #define WCSHDR_CD00i00j 0x00000004
1290 #define WCSHDR_PC00i00j 0x00000008
1291 #define WCSHDR_PROJPn 0x00000010
1292 #define WCSHDR_CD0i_0ja 0x00000020
1293 #define WCSHDR_PC0i_0ja 0x00000040
1294 #define WCSHDR_PV0i_0ma 0x00000080
1295 #define WCSHDR_PS0i_0ma 0x00000100
1296 #define WCSHDR_DOBSn 0x00000200
1297 #define WCSHDR_OBSGLBHn 0x00000400
1298 #define WCSHDR_RADECSYS 0x00000800
1299 #define WCSHDR_EPOCHa 0x00001000
1300 #define WCSHDR_VSOURCE 0x00002000
1301 #define WCSHDR_DATEREF 0x00004000
1302 #define WCSHDR_LONGKEY 0x00008000
1303 #define WCSHDR_CNAMn 0x00010000
1304 #define WCSHDR_AUXIMG 0x00020000
1305 #define WCSHDR_ALLIMG 0x00040000
1306
1307 #define WCSHDR_IMGHEAD 0x00100000
1308 #define WCSHDR_BIMGARR 0x00200000
1309 #define WCSHDR_PIXLIST 0x00400000
1310
1311 #define WCSHDO_none 0x00000
1312 #define WCSHDO_all 0x000FF
1313 #define WCSHDO_safe 0x0000F
1314 #define WCSHDO_DOBSn 0x00001
1315 #define WCSHDO_TPCn_ka 0x00002
1316 #define WCSHDO_PVn_ma 0x00004
1317 #define WCSHDO_CRPXna 0x00008
1318 #define WCSHDO_CNAMna 0x00010
1319 #define WCSHDO_WCSNna 0x00020
1320 #define WCSHDO_P12 0x01000
1321 #define WCSHDO_P13 0x02000
1322 #define WCSHDO_P14 0x04000
1323 #define WCSHDO_P15 0x08000
1324 #define WCSHDO_P16 0x10000
1325 #define WCSHDO_P17 0x20000
1326 #define WCSHDO_EFMT 0x40000
1327
1328
1329 extern const char *wcshdr_errmsg[];
1330
1331 enum wcshdr_errmsg_enum {
1332 WCSHDRERR_SUCCESS = 0, // Success.
1333 WCSHDRERR_NULL_POINTER = 1, // Null wcsprm pointer passed.
1334 WCSHDRERR_MEMORY = 2, // Memory allocation failed.
1335 WCSHDRERR_BAD_COLUMN = 3, // Invalid column selection.
1336 WCSHDRERR_PARSER = 4, // Fatal error returned by Flex
1337 // parser.
1338 WCSHDRERR_BAD_TABULAR_PARAMS = 5 // Invalid tabular parameters.
1339 };
1340
1341 int wcspih(char *header, int nkeyrec, int relax, int ctrl, int *nreject,
1342 int *nwcs, struct wcsprm **wcs);
1343
1344 int wcsbth(char *header, int nkeyrec, int relax, int ctrl, int keysel,
1345 int *colsel, int *nreject, int *nwcs, struct wcsprm **wcs);
1346
1347 int wcstab(struct wcsprm *wcs);
1348
1349 int wcsidx(int nwcs, struct wcsprm **wcs, int alts[27]);
1350
1351 int wcsbdx(int nwcs, struct wcsprm **wcs, int type, short alts[1000][28]);
1352
1353 int wcsvfree(int *nwcs, struct wcsprm **wcs);
1354
1355 int wcshdo(int ctrl, struct wcsprm *wcs, int *nkeyrec, char **header);
1356
1357
1358 #ifdef __cplusplus
1359 }
1360 #endif
1361
1362 #endif // WCSLIB_WCSHDR
WCSHDRERR_NULL_POINTER
@ WCSHDRERR_NULL_POINTER
Definition: wcshdr.h:1333
WCSHDRERR_BAD_TABULAR_PARAMS
@ WCSHDRERR_BAD_TABULAR_PARAMS
Definition: wcshdr.h:1338
wcshdr_errmsg
const char * wcshdr_errmsg[]
Status return messages.
wcstab
int wcstab(struct wcsprm *wcs)
Tabular construction routine.
WCSHDRERR_MEMORY
@ WCSHDRERR_MEMORY
Definition: wcshdr.h:1334
wcshdo
int wcshdo(int ctrl, struct wcsprm *wcs, int *nkeyrec, char **header)
Write out a wcsprm struct as a FITS header.
wcsidx
int wcsidx(int nwcs, struct wcsprm **wcs, int alts[27])
Index alternate coordinate representations.
wcsprm
Coordinate transformation parameters.
Definition: wcs.h:1807
WCSHDRERR_SUCCESS
@ WCSHDRERR_SUCCESS
Definition: wcshdr.h:1332
wcsvfree
int wcsvfree(int *nwcs, struct wcsprm **wcs)
Free the array of wcsprm structs.
wcsbth
int wcsbth(char *header, int nkeyrec, int relax, int ctrl, int keysel, int *colsel, int *nreject, int *nwcs, struct wcsprm **wcs)
FITS WCS parser routine for binary table and image headers.
wcs.h
WCSHDRERR_BAD_COLUMN
@ WCSHDRERR_BAD_COLUMN
Definition: wcshdr.h:1335
WCSHDRERR_PARSER
@ WCSHDRERR_PARSER
Definition: wcshdr.h:1336
wcspih
int wcspih(char *header, int nkeyrec, int relax, int ctrl, int *nreject, int *nwcs, struct wcsprm **wcs)
FITS WCS parser routine for image headers.
wcsbdx
int wcsbdx(int nwcs, struct wcsprm **wcs, int type, short alts[1000][28])
Index alternate coordinate representions.
wcshdr_errmsg_enum
wcshdr_errmsg_enum
Definition: wcshdr.h:1331