makeSipIwcToPixel¶

lsst.afw.geom.testUtils.
makeSipIwcToPixel
(metadata)¶ Make an IWC to pixel 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 inverse SIP coefficients
Returns:  lsst.afw.geom.TransformPoint2ToPoint2
Transform from IWC position to pixel position (zerobased) in the forward direction. The inverse direction is not defined.
Notes
The inverse SIP terms APn_m, BPn_m are polynomial coefficients x^n y^m for computing transformed x, y respectively. If we call the resulting polynomial inverseSipPolynomial, the returned transformation is:
pixelPosition = pixel origin + uv + inverseSipPolynomial(uv) where uv = inverseCdMatrix * iwcPosition