log.h

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/*============================================================================

  WCSLIB 4.4 - an implementation of the FITS WCS standard.
  Copyright (C) 1995-2009, Mark Calabretta

  This file is part of WCSLIB.

  WCSLIB is free software: you can redistribute it and/or modify it under the
  terms of the GNU Lesser General Public License as published by the Free
  Software Foundation, either version 3 of the License, or (at your option)
  any later version.

  WCSLIB is distributed in the hope that it will be useful, but WITHOUT ANY
  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
  FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for
  more details.

  You should have received a copy of the GNU Lesser General Public License
  along with WCSLIB.  If not, see <http://www.gnu.org/licenses/>.

  Correspondence concerning WCSLIB may be directed to:
    Internet email: mcalabre@atnf.csiro.au
    Postal address: Dr. Mark Calabretta
                    Australia Telescope National Facility, CSIRO
                    PO Box 76
                    Epping NSW 1710
                    AUSTRALIA

  Author: Mark Calabretta, Australia Telescope National Facility
  http://www.atnf.csiro.au/~mcalabre/index.html
  $Id: log_8h-source.html,v 1.1 2009/09/14 20:25:23 irby Exp $
*=============================================================================
*
* WCSLIB 4.4 - C routines that implement logarithmic coordinate systems as
* defined by the FITS World Coordinate System (WCS) standard.  Refer to
*
*   "Representations of world coordinates in FITS",
*   Greisen, E.W., & Calabretta, M.R. 2002, A&A, 395, 1061 (Paper I)
*
*   "Representations of spectral coordinates in FITS",
*   Greisen, E.W., Calabretta, M.R., Valdes, F.G., & Allen, S.L.
*   2006, A&A, 446, 747 (Paper III)
*
* Refer to the README file provided with WCSLIB for an overview of the
* library.
*
*
* Summary of the log routines
* ---------------------------
* These routines implement the part of the FITS WCS standard that deals with
* logarithmic coordinates.  They define methods to be used for computing
* logarithmic world coordinates from intermediate world coordinates (a linear
* transformation of image pixel coordinates), and vice versa.
*
* logx2s() and logs2x() implement the WCS logarithmic coordinate
* transformations.
*
* Argument checking:
* ------------------
* The input log-coordinate values are only checked for values that would
* result in floating point exceptions and the same is true for the
* log-coordinate reference value.
*
* Accuracy:
* ---------
* No warranty is given for the accuracy of these routines (refer to the
* copyright notice); intending users must satisfy for themselves their
* adequacy for the intended purpose.  However, closure effectively to within
* double precision rounding error was demonstrated by test routine tlog.c
* which accompanies this software.
*
*
* logx2s() - Transform to logarithmic coordinates
* -----------------------------------------------
* logx2s() transforms intermediate world coordinates to logarithmic
* coordinates.
*
* Given and returned:
*   crval     double    Log-coordinate reference value (CRVALia).
*
* Given:
*   nx        int       Vector length.
*   sx        int       Vector stride.
*   slogc     int       Vector stride.
*   x         const double[]
*                       Intermediate world coordinates, in SI units.
*
* Returned:
*   logc      double[]  Logarithmic coordinates, in SI units.
*   stat      int[]     Status return value status for each vector element:
*                         0: Success.
*                         1: Invalid value of x.
*
* Function return value:
*             int       Status return value:
*                         0: Success.
*                         2: Invalid log-coordinate reference value.
*                         3: One or more of the x coordinates were invalid,
*                            as indicated by the stat vector.
*
*
* logs2x() - Transform logarithmic coordinates
* --------------------------------------------
* logs2x() transforms logarithmic world coordinates to intermediate world
* coordinates.
*
* Given and returned:
*   crval     double    Log-coordinate reference value (CRVALia).
*
* Given:
*   nlogc     int       Vector length.
*   slogc     int       Vector stride.
*   sx        int       Vector stride.
*   logc      const double[]
*                       Logarithmic coordinates, in SI units.
*
* Returned:
*   x         double[]  Intermediate world coordinates, in SI units.
*   stat      int[]     Status return value status for each vector element:
*                         0: Success.
*                         1: Invalid value of logc.
*
* Function return value:
*             int       Status return value:
*                         0: Success.
*                         2: Invalid log-coordinate reference value.
*
*
* Global variable: const char *log_errmsg[] - Status return messages
* ------------------------------------------------------------------
* Error messages to match the status value returned from each function.
*
*===========================================================================*/

#ifndef WCSLIB_LOG
#define WCSLIB_LOG

#ifdef __cplusplus
extern "C" {
#endif


extern const char *log_errmsg[];


int logx2s(double crval, int nx, int sx, int slogc, const double x[],
           double logc[], int stat[]);

int logs2x(double crval, int nlogc, int slogc, int sx, const double logc[],
           double x[], int stat[]);


#ifdef __cplusplus
}
#endif

#endif /* WCSLIB_LOG */

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