lsst.afw.image.basicUtils Namespace Reference

Functions
def	makeImageFromArray
def	makeMaskFromArray
def	makeMaskedImageFromArrays
def	_compareWcsOverBBox
	Compare two WCS over a rectangular grid of pixel positions. More...
def	wcsNearlyEqualOverBBox
	Return True if two WCS are nearly equal over a grid of pixel positions, else False. More...
def	assertWcsNearlyEqualOverBBox
	Compare pixelToSky and skyToPixel for two WCS over a rectangular grid of pixel positions. More...

Variables
list	__all__
dictionary	suffixes = {str(numpy.uint16): "U", str(numpy.int32): "I", str(numpy.float32): "F", str(numpy.float64): "D"}

Function Documentation

def lsst.afw.image.basicUtils._compareWcsOverBBox (   wcs0,   wcs1,   bbox,   maxDiffSky = 0.01*afwGeom.arcseconds,   maxDiffPix = 0.01,   nx = 5,   ny = 5,   doShortCircuit = True  )

private

Compare two WCS over a rectangular grid of pixel positions.

Parameters

[in]	wcs0	WCS 0 (an lsst.afw.image.Wcs)
[in]	wcs1	WCS 1 (an lsst.afw.image.Wcs)
[in]	bbox	boundaries of pixel grid over which to compare the WCSs (an lsst.afw.geom.Box2I or Box2D)
[in]	maxDiffSky	maximum separation between sky positions computed using Wcs.pixelToSky (an lsst.afw.geom.Angle)
[in]	maxDiffPix	maximum separation between pixel positions computed using Wcs.skyToPixel
[in]	nx	number of points in x for the grid of pixel positions
[in]	ny	number of points in y for the grid of pixel positions
[in]	doShortCircuit	if True then stop at the first error, else test all values in the grid and return information about the worst violations found

Returns

return an empty string if the WCS are sufficiently close; else return a string describing the largest error measured in pixel coordinates (if sky to pixel error was excessive) and sky coordinates (if pixel to sky error was excessive). If doShortCircuit is true then the reported error is likely to be much less than the maximum error across the whole pixel grid.

Definition at line 63 of file basicUtils.py.

    maxDiffPix=0.01, nx=5, ny=5, doShortCircuit=True):
    """!Compare two WCS over a rectangular grid of pixel positions

    @param[in] wcs0  WCS 0 (an lsst.afw.image.Wcs)
    @param[in] wcs1  WCS 1 (an lsst.afw.image.Wcs)
    @param[in] bbox  boundaries of pixel grid over which to compare the WCSs (an lsst.afw.geom.Box2I or Box2D)
    @param[in] maxDiffSky  maximum separation between sky positions computed using Wcs.pixelToSky
        (an lsst.afw.geom.Angle)
    @param[in] maxDiffPix  maximum separation between pixel positions computed using Wcs.skyToPixel
    @param[in] nx  number of points in x for the grid of pixel positions
    @param[in] ny  number of points in y for the grid of pixel positions
    @param[in] doShortCircuit  if True then stop at the first error, else test all values in the grid
        and return information about the worst violations found

    @return return an empty string if the WCS are sufficiently close; else return a string describing
    the largest error measured in pixel coordinates (if sky to pixel error was excessive) and sky coordinates
    (if pixel to sky error was excessive). If doShortCircuit is true then the reported error is likely to be
    much less than the maximum error across the whole pixel grid.
    """
    if nx < 1 or ny < 1:
        raise RuntimeError("nx = %s and ny = %s must both be positive" % (nx, ny))
    if maxDiffSky <= 0*afwGeom.arcseconds:
        raise RuntimeError("maxDiffSky = %s must be positive" % (maxDiffSky,))
    if maxDiffPix <= 0:
        raise RuntimeError("maxDiffPix = %s must be positive" % (maxDiffPix,))

    bboxd = afwGeom.Box2D(bbox)
    xList = numpy.linspace(bboxd.getMinX(), bboxd.getMaxX(), nx)
    yList = numpy.linspace(bboxd.getMinY(), bboxd.getMaxY(), ny)
    # we don't care about measured error unless it is too large, so initialize to max allowed
    measDiffSky = (maxDiffSky, "?") # (sky diff, pix pos)
    measDiffPix = (maxDiffPix, "?") # (pix diff, sky pos)
    for x, y in itertools.product(xList, yList):
        fromPixPos = afwGeom.Point2D(x, y)
        sky0 = wcs0.pixelToSky(fromPixPos)
        sky1 = wcs1.pixelToSky(fromPixPos)
        diffSky = sky0.angularSeparation(sky1)
        if diffSky > measDiffSky[0]:
            measDiffSky = (diffSky, fromPixPos)
            if doShortCircuit:
                break

        toPixPos0 = wcs0.skyToPixel(sky0)
        toPixPos1 = wcs1.skyToPixel(sky0)
        diffPix = math.hypot(*(toPixPos0 - toPixPos1))
        if diffPix > measDiffPix[0]:
            measDiffPix = (diffPix, sky0)
            if doShortCircuit:
                break

    msgList = []
    if measDiffSky[0] > maxDiffSky:
        msgList.append("%s arcsec max measured sky error > %s arcsec max allowed sky error at pix pos=%s" %
            (measDiffSky[0].asArcseconds(), maxDiffSky.asArcseconds(), measDiffSky[1]))
    if measDiffPix[0] > maxDiffPix:
        msgList.append("%s max measured pix error > %s max allowed pix error at sky pos=%s" %
                (measDiffPix[0], maxDiffPix, measDiffPix[1]))

    return "; ".join(msgList)