lsst.skypix.quadsphere Namespace Reference

Classes
class	QuadSpherePixelization

Functions
def	_rotX (v, sin, cos)
def	_rotY (v, sin, cos)
def	_rotZ (v, sin, cos)
def	_rotNX (v, sin, cos)
def	_rotNY (v, sin, cos)
def	_rotNZ (v, sin, cos)
def	createQuadSpherePixelization (policy=None)
def	imageToPolygon (wcs, widthPix, heightPix, padRad=0.0)

Function Documentation

_rotNX()

def lsst.skypix.quadsphere._rotNX (   v,   sin,   cos  )

private

Definition at line 47 of file quadsphere.py.

def _rotNX(v, sin, cos):
    return _rotX(v, -sin, cos)

_rotNY()

def lsst.skypix.quadsphere._rotNY (   v,   sin,   cos  )

private

Definition at line 51 of file quadsphere.py.

def _rotNY(v, sin, cos):
    return _rotY(v, -sin, cos)

_rotNZ()

def lsst.skypix.quadsphere._rotNZ (   v,   sin,   cos  )

private

Definition at line 55 of file quadsphere.py.

def _rotNZ(v, sin, cos):
    return _rotZ(v, -sin, cos)

_rotX()

def lsst.skypix.quadsphere._rotX (   v,   sin,   cos  )

private

Definition at line 35 of file quadsphere.py.

def _rotX(v, sin, cos):
    return (v[0], v[1] * cos - v[2] * sin, v[1] * sin + v[2] * cos)

_rotY()

def lsst.skypix.quadsphere._rotY (   v,   sin,   cos  )

private

Definition at line 39 of file quadsphere.py.

def _rotY(v, sin, cos):
    return (v[0] * cos + v[2] * sin, v[1], -v[0] * sin + v[2] * cos)

_rotZ()

def lsst.skypix.quadsphere._rotZ (   v,   sin,   cos  )

private

Definition at line 43 of file quadsphere.py.

def _rotZ(v, sin, cos):
    return (v[0] * cos - v[1] * sin, v[0] * sin + v[1] * cos, v[2])

createQuadSpherePixelization()

def lsst.skypix.quadsphere.createQuadSpherePixelization

(

policy = None

)

Definition at line 773 of file quadsphere.py.

def createQuadSpherePixelization(policy=None):
    policyFile = pexPolicy.DefaultPolicyFile(
        "skypix", "QuadSpherePixelizationDictionary.paf", "policy")
    defaults = pexPolicy.Policy.createPolicy(
        policyFile, policyFile.getRepositoryPath())
    if policy is None:
        policy = pexPolicy.Policy()
    policy.mergeDefaults(defaults)
    # Obtain resolution and padding from policy
    resolution = policy.get('resolutionPix')
    padding = math.radians(policy.get('paddingArcsec') / 3600.0)
    return QuadSpherePixelization(resolution, padding)

imageToPolygon()

def lsst.skypix.quadsphere.imageToPolygon	(		wcs,
			widthPix,
			heightPix,
			padRad = 0.0
	)

Computes and returns a spherical convex polygon approximation to the
region of the unit sphere covered by an image specified with a WCS and
a width/height (pixels). The polygon is computed by connecting the
world coordinates of the 4 image corners with great circles, and can
optionally be padded by padRad radians.

Definition at line 787 of file quadsphere.py.

def imageToPolygon(wcs, widthPix, heightPix, padRad=0.0):
    """Computes and returns a spherical convex polygon approximation to the
    region of the unit sphere covered by an image specified with a WCS and
    a width/height (pixels). The polygon is computed by connecting the
    world coordinates of the 4 image corners with great circles, and can
    optionally be padded by padRad radians.
    """
    # Compute image corners
    cd = wcs.getCdMatrix()
    xpad = math.degrees(padRad) / math.sqrt(cd[0, 0]**2 + cd[0, 1]**2)
    ypad = math.degrees(padRad) / math.sqrt(cd[1, 0]**2 + cd[1, 1]**2)
    xmin, ymin = -0.5 - xpad, -0.5 - ypad
    xmax, ymax = widthPix + xpad - 0.5, heightPix + ypad - 0.5
    # Produce a lsst.afw.coord.coordLib.Coord object for each vertex
    coords = [wcs.pixelToSky(xmin, ymin), wcs.pixelToSky(xmax, ymin),
              wcs.pixelToSky(xmax, ymax), wcs.pixelToSky(xmin, ymax)]
    # Map these to python tuples containing cartesian unit vectors
    verts = []
    for c in coords:
        verts.append(tuple(c.getVector()))
    # and turn them into a spherical convex polygon
    convex, cc = geom.convex(verts)
    if not convex:
        raise RuntimeError('Image corners do not form a convex polygon: ' + cc)
    elif not cc:
        verts.reverse()
    return geom.SphericalConvexPolygon(verts)

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