WCSLIB: tabprm Struct Reference

WCSLIB 8.9

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Data Fields
tabprm Struct Reference

Tabular transformation parameters. More...

`#include <tab.h>`

## Data Fields
int | flag
int | M
int * | K
int * | map
double * | crval
double ** | index
double * | coord
int | nc
int | padding
int * | sense
int * | p0
double * | delta
double * | extrema
struct wcserr * | err
int | m_flag
int | m_M
int | m_N
int | set_M
int * | m_K
int * | m_map
double * | m_crval
double ** | m_index
double ** | m_indxs
double * | m_coord

## Detailed Description

Tabular transformation parameters.

The tabprm struct contains information required to transform tabular coordinates. It consists of certain members that must be set by the user (given) and others that are set by the WCSLIB routines (returned). Some of the latter are supplied for informational purposes while others are for internal use only.

## Field Documentation

## ◆ flag

int tabprm::flag

(Given and returned) This flag must be set to zero (or 1, see tabset()) whenever any of the following tabprm members are set or changed:

- tabprm::M (q.v., not normally set by the user),
- tabprm::K (q.v., not normally set by the user),
- tabprm::map,
- tabprm::crval,
- tabprm::index,
- tabprm::coord.

This signals the initialization routine, tabset(), to recompute the returned members of the tabprm struct. tabset() will reset flag to indicate that this has been done.

PLEASE NOTE: flag should be set to -1 when tabini() is called for the first time for a particular tabprm struct in order to initialize memory management. It must ONLY be used on the first initialization otherwise memory leaks may result.

## ◆ M

int tabprm::M

(Given or returned) Number of tabular coordinate axes.

If tabini() is used to initialize the tabprm struct (as would normally be the case) then it will set M from the value passed to it as a function argument. The user should not subsequently modify it.

## ◆ K

int* tabprm::K

(Given or returned) Pointer to the first element of a vector of length tabprm::M whose elements record the lengths of the axes of the coordinate array and of each indexing vector.

If tabini() is used to initialize the tabprm struct (as would normally be the case) then it will set K from the array passed to it as a function argument. The user should not subsequently modify it.

## ◆ map

int* tabprm::map

(Given) Pointer to the first element of a vector of length tabprm::M that defines the association between axis m in the M-dimensional coordinate array (1 m M) and the indices of the intermediate world coordinate and world coordinate arrays, x[] and world[], in the argument lists for tabx2s() and tabs2x().

When x[] and world[] contain the full complement of coordinate elements in image-order, as will usually be the case, then map[m-1] == i-1 for axis i in the N-dimensional image (1 i N). In terms of the FITS keywords

map[PVi_3a - 1] == i - 1.

However, a different association may result if x[], for example, only contains a (relevant) subset of intermediate world coordinate elements. For example, if M == 1 for an image with N > 1, it is possible to fill x[] with the relevant coordinate element with nelem set to 1. In this case map[0] = 0 regardless of the value of i.

## ◆ crval

double* tabprm::crval

(Given) Pointer to the first element of a vector of length tabprm::M whose elements contain the index value for the reference pixel for each of the tabular coordinate axes.

## ◆ index

double** tabprm::index

(Given) Pointer to the first element of a vector of length tabprm::M of pointers to vectors of lengths of 0-relative indexes (see tabprm::K).

The address of any or all of these index vectors may be set to zero, i.e.

index[m] == 0;
tabprm::index
double ** index
Definition tab.h:629

this is interpreted as default indexing, i.e.

index[m][k] = k;

## ◆ coord

double* tabprm::coord

(Given) Pointer to the first element of the tabular coordinate array, treated as though it were defined as

double coord[K_M]...[K_2][K_1][M];
tabprm::M
int M
Definition tab.h:618
tabprm::coord
double * coord
Definition tab.h:631

(see tabprm::K) i.e. with the M dimension varying fastest so that the M elements of a coordinate vector are stored contiguously in memory.

## ◆ nc

int tabprm::nc

(Returned) Total number of coordinate vectors in the coordinate array being the product (see tabprm::K).

## ◆ padding

int tabprm::padding

(An unused variable inserted for alignment purposes only.)

## ◆ sense

int* tabprm::sense

(Returned) Pointer to the first element of a vector of length tabprm::M whose elements indicate whether the corresponding indexing vector is monotonic increasing (+1), or decreasing (-1).

## ◆ p0

int* tabprm::p0

(Returned) Pointer to the first element of a vector of length tabprm::M of interpolated indices into the coordinate array such that , as defined in Paper III, is equal to (p0[m] + 1) + tabprm::delta[m].

## ◆ delta

double* tabprm::delta

(Returned) Pointer to the first element of a vector of length tabprm::M of interpolated indices into the coordinate array such that , as defined in Paper III, is equal to (tabprm::p0[m] + 1) + delta[m].

## ◆ extrema

double* tabprm::extrema

(Returned) Pointer to the first element of an array that records the minimum and maximum value of each element of the coordinate vector in each row of the coordinate array, treated as though it were defined as

double extrema[K_M]...[K_2][2][M]
tabprm::extrema
double * extrema
Definition tab.h:644

(see tabprm::K). The minimum is recorded in the first element of the compressed dimension, then the maximum. This array is used by the inverse table lookup function, tabs2x(), to speed up table searches.

## ◆ err

struct wcserr* tabprm::err

(Returned) If enabled, when an error status is returned, this struct contains detailed information about the error, see wcserr_enable().

## ◆ m_flag

int tabprm::m_flag

(For internal use only.)

## ◆ m_M

int tabprm::m_M

(For internal use only.)

## ◆ m_N

int tabprm::m_N

(For internal use only.)

## ◆ set_M

int tabprm::set_M

(For internal use only.)

## ◆ m_K

int* tabprm::m_K

(For internal use only.)

## ◆ m_map

int * tabprm::m_map

(For internal use only.)

## ◆ m_crval

double* tabprm::m_crval

(For internal use only.)

## ◆ m_index

double ** tabprm::m_index

(For internal use only.)

## ◆ m_indxs

double ** tabprm::m_indxs

(For internal use only.)

## ◆ m_coord

double * tabprm::m_coord

(For internal use only.)