log.h File Reference

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Enumerations
enum	log_errmsg_enum {   LOGERR_SUCCESS = 0, LOGERR_NULL_POINTER = 1, LOGERR_BAD_LOG_REF_VAL = 2, LOGERR_BAD_X = 3,   LOGERR_BAD_WORLD = 4 }

Functions
int	logx2s (double crval, int nx, int sx, int slogc, const double x[], double logc[], int stat[])
	Transform to logarithmic coordinates. More...
int	logs2x (double crval, int nlogc, int slogc, int sx, const double logc[], double x[], int stat[])
	Transform logarithmic coordinates. More...

Variables
const char *	log_errmsg []
	Status return messages. More...

Detailed Description

Routines in this suite implement the part of the FITS World Coordinate System (WCS) standard that deals with logarithmic coordinates, as described in

"Representations of world coordinates in FITS", Greisen, E.W., & Calabretta, M.R. 2002, A&A, 395, 1061 (WCS 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 (WCS Paper III)

These routines 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.

Enumeration Type Documentation

enum log_errmsg_enum

Enumerator
LOGERR_SUCCESS
LOGERR_NULL_POINTER
LOGERR_BAD_LOG_REF_VAL
LOGERR_BAD_X
LOGERR_BAD_WORLD

Function Documentation

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

logx2s() transforms intermediate world coordinates to logarithmic coordinates.

Parameters

[in,out]	crval	Log-coordinate reference value (CRVALia).
[in]	nx	Vector length.
[in]	sx	Vector stride.
[in]	slogc	Vector stride.
[in]	x	Intermediate world coordinates, in SI units.
[out]	logc	Logarithmic coordinates, in SI units.
[out]	stat	Status return value status for each vector element: 0: Success.

Returns

Status return value:

• 0: Success.
• 2: Invalid log-coordinate reference value.

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

logs2x() transforms logarithmic world coordinates to intermediate world coordinates.

Parameters

[in,out]	crval	Log-coordinate reference value (CRVALia).
[in]	nlogc	Vector length.
[in]	slogc	Vector stride.
[in]	sx	Vector stride.
[in]	logc	Logarithmic coordinates, in SI units.
[out]	x	Intermediate world coordinates, in SI units.
[out]	stat	Status return value status for each vector element: 0: Success. 1: Invalid value of logc.

Returns

Status return value:

• 0: Success.
• 2: Invalid log-coordinate reference value.
• 4: One or more of the world-coordinate values are incorrect, as indicated by the stat vector.

Variable Documentation

const char * log_errmsg[]

Error messages to match the status value returned from each function.