KPG1_ASAPA

Determines which pixel axis is most closely aligned with a WCS axis

Description:

This routine aligns a supplied WCS axis to the best-matching pixel axis of an NDF. It also returns pixel co-ordinates corresponding to supplied WCS-axis limits, and where possible a mapping with one input and one output that transforms current Frame co-ordinates into pixel co-ordinates.

It first attempts to split the mapping to derive a one-to-one mapping. Failing that it

Invocation

CALL KPG1_ASAPA( INDF, FRM, MAP, IAXIS, AXLOW, AXHIGH, PAXIS, PXLOW, PXHIGH, MAP1D, STATUS )

Arguments

INDF = INTEGER (Given)
The identifier of the NDF containing a WCS component.
FRM = INTEGER (Given)
An AST pointer to the current Frame in the NDF.
MAP = INTEGER (Given)
The mapping from the PIXEL Frame to the current WCS Frame. This can also be a mapping from GRID to the current Frame. In which case the returned co-ordinates and mapping apply to GRID co-ordinates instead of PIXEL.
IAXIS = INTEGER (Given)
The index of the WCS axis in the current Frame to be aligned.
AXLOW = DOUBLE PRECISION (Given)
Lower bound of the WCS axis. If either AXLOW or AXHIGH is set to AST__BAD, then the whole axis range is used.
AXHIGH = DOUBLE PRECISION (Given)
Upper bound of the WCS axis. If either AXLOW or AXHIGH is set to AST__BAD, then the whole axis range is used.
PAXIS = INTEGER (Returned)
The index of the pixel most closely aligned with the supplied WCS axis.
PXLOW = DOUBLE PRECISION (Given)
Lower bound of the PIXEL axis corresponding to the AXLOW in the WCS axis.
PXHIGH = DOUBLE PRECISION (Given)
Upper bound of the PIXEL axis corresponding to the AXHIGH in the WCS axis.
MAP1D = INTEGER (Returned)
The mapping from the current WCS Frame to PIXEL whose input is purely along the chosen axis (IAXIS). It is set to AST__NULL if the supplied mapping (MAP) could not be split.
STATUS = INTEGER (Given and Returned)
The global status.