astTran2

Transform 2-dimensional coordinates

Description:

This function applies a Mapping to transform the coordinates of a set of points in two dimensions.

Synopsis

void astTran2( AstMapping $\ast$this, int npoint, const double xin[], const double yin[], int forward, double xout[], double yout[] )

Parameters:

this
Pointer to the Mapping to be applied.
npoint
The number of points to be transformed.
xin
An array of " npoint" X-coordinate values for the input (untransformed) points.
yin
An array of " npoint" Y-coordinate values for the input (untransformed) points.
forward
A non-zero value indicates that the Mapping’ s forward coordinate transformation is to be applied, while a zero value indicates that the inverse transformation should be used.
xout
An array (with " npoint" elements) into which the X-coordinates of the output (transformed) points will be written.
yout
An array (with " npoint" elements) into which the Y-coordinates of the output (transformed) points will be written.

Notes:

• The Mapping supplied must have the value 2 for both its Nin and Nout attributes.

Handling of Huge Pixel Arrays

If the number of points to be transformed exceeds the largest value that can be represented by a 4-byte integer, then the alternative " 8-byte" interface for this function should be used. This alternative interface uses 8 byte integer arguments (instead of 4-byte). Specifically, the argument " npoint" , is changed from type " int" to type " int64_t" (defined in header file stdint.h). The function name is changed by appending the digit " 8" to the name. Thus, astTran2 becomes astTran28