lsst.afw.cameraGeom._makePixelToTanPixel Namespace Reference

Functions
	makePixelToTanPixel (bbox, orientation, focalPlaneToField, pixelSizeMm)

Function Documentation

makePixelToTanPixel()

lsst.afw.cameraGeom._makePixelToTanPixel.makePixelToTanPixel	(		bbox,
			orientation,
			focalPlaneToField,
			pixelSizeMm )

Make a Transform whose forward direction converts PIXELS to TAN_PIXELS
for one detector.

Parameters
----------
bbox : `lsst.geom.Box2I`
    Detector bounding box.
orientation : `lsst.afw.cameraGeom.Orientation`
    Orientation of detector in focal plane.
focalPlaneToField : `lsst.afw.geom.TransformPoint2ToPoint2`
    A transform that converts from focal plane (mm) to field angle
    coordinates (radians) in the forward direction.
pixelSizeMm : `lsst.geom.Extent2D`
    Size of the pixel in mm in X and Y.

Returns
-------
transform : `lsst.afw.geom.TransformPoint2ToPoint2`
    A transform whose forward direction converts PIXELS to TAN_PIXELS.

Notes
-----
PIXELS and TAN_PIXELS are described in the CameraGeom documentation under
:ref:`camera coordinate systems<section_Camera_Coordinate_Systems>`.

Definition at line 28 of file _makePixelToTanPixel.py.

def makePixelToTanPixel(bbox, orientation, focalPlaneToField, pixelSizeMm):
    """Make a Transform whose forward direction converts PIXELS to TAN_PIXELS
    for one detector.
 
    Parameters
    ----------
    bbox : `lsst.geom.Box2I`
        Detector bounding box.
    orientation : `lsst.afw.cameraGeom.Orientation`
        Orientation of detector in focal plane.
    focalPlaneToField : `lsst.afw.geom.TransformPoint2ToPoint2`
        A transform that converts from focal plane (mm) to field angle
        coordinates (radians) in the forward direction.
    pixelSizeMm : `lsst.geom.Extent2D`
        Size of the pixel in mm in X and Y.
 
    Returns
    -------
    transform : `lsst.afw.geom.TransformPoint2ToPoint2`
        A transform whose forward direction converts PIXELS to TAN_PIXELS.
 
    Notes
    -----
    PIXELS and TAN_PIXELS are described in the CameraGeom documentation under
    :ref:`camera coordinate systems<section_Camera_Coordinate_Systems>`.
    """
    pixelToFocalPlane = orientation.makePixelFpTransform(pixelSizeMm)
    pixelToField = pixelToFocalPlane.then(focalPlaneToField)
    # fieldToTanPix is affine and matches fieldToPix at field center
    # Note: focal plane to field angle is typically a radial transform,
    # and linearizing the inverse transform of that may fail,
    # so linearize the forward direction instead. (pixelToField is pixelToFocalPlane,
    # an affine transform, followed by focalPlaneToField,
    # so the same consideration applies to pixelToField)
    pixAtFieldCtr = pixelToField.applyInverse(lsst.geom.Point2D(0, 0))
    tanPixToFieldAffine = lsst.afw.geom.linearizeTransform(pixelToField, pixAtFieldCtr)
    fieldToTanPix = lsst.afw.geom.makeTransform(tanPixToFieldAffine.inverted())
 
    return pixelToField.then(fieldToTanPix)