makeSipPixelToIwc¶

lsst.afw.geom.testUtils.
makeSipPixelToIwc
(metadata)¶ Make a pixel to IWC transform with SIP distortion from FITSWCS metadata
This function is primarily intended for unit tests. IWC is intermediate world coordinates, as described in the FITS papers.
Parameters:  metadata : lsst.daf.base.PropertySet
FITS metadata describing a WCS with forward SIP coefficients
Returns:  lsst.afw.geom.TransformPoint2ToPoint2
Transform from pixel position (zerobased) to IWC position in the forward direction. The inverse direction is not defined.
Notes
The forward SIP terms An_m, Bn_m are polynomial coefficients x^n y^m for computing transformed x, y respectively. If we call the resulting polynomial sipPolynomial, the returned transformation is:
iwcPosition = cdMatrix * (dxy + sipPolynomial(dxy)) where dxy = pixelPosition  pixelOrigin