genDistortedImage.py

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#
# LSST Data Management System
# Copyright 2008, 2009, 2010 LSST Corporation.
#
# This product includes software developed by the
# LSST Project (http://www.lsst.org/).
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the LSST License Statement and
# the GNU General Public License along with this program.  If not,
# see <http://www.lsstcorp.org/LegalNotices/>.
#
 
__all__ = ["noDistort", "linearXDistort", "quadraticDistortX",
           "cubicDistortX", "manyTermX", "crossTerms1",
           "crossTerms2", "crossTerms3", "quadraticDistort",
           "T2DistortX", "T2DistortX"]
 
 
import math
 
import lsst.afw.table as afwTable
 
 
def noDistort(src):
    """Do no distortion. Used for sanity checking
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        Input record
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        Copy of input record.
    """
 
    out = src.table.copyRecord(src)
    return out
 
 
def linearXDistort(src, frac=.001):
    """Increase the x value in a Source object by frac. E.g
    src.x = 1000 --> 1001 if frac=.001
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        A Source object
    frac : `float`
        How much to change X by
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        A deep copy of src, with the value of x changed
    """
 
    out = src.table.copyRecord(src)
    out.set(out.table.getCentroidSlot().getMeasKey().getX(), out.getX()*(1+frac))
    return out
 
 
def quadraticDistortX(src, frac=1e-6):
    """Distort image by terms with power <=2
    i.e y, y^2, x, xy, x^2
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        A Source object
    frac : `float`
        How much to change X by
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        A deep copy of src, with the value of x changed
    """
 
    out = src.table.copyRecord(src)
    x = out.getX()
    y = out.getY()
    val = x**2
 
    out.set(out.table.getCentroidSlot().getMeasKey().getX(), x + val*frac)
    out.set(out.table.getCentroidSlot().getMeasKey().getY(), y)
    return out
 
 
def cubicDistortX(src, frac=1e-9):
    """Distort image by terms with power <=2
    i.e y, y^2, x, xy, x^2
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        A Source object
    frac : `float`
        How much to change X by
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        A deep copy of src, with the value of x changed
    """
 
    out = src.table.copyRecord(src)
    x = out.getX()
    y = out.getY()
    val = x**3
 
    out.set(out.table.getCentroidSlot().getMeasKey().getX(), x + val*frac)
    out.set(out.table.getCentroidSlot().getMeasKey().getY(), y)
    return out
 
 
def manyTermX(src, frac=1e-9):
    """Distort image by multiple powers of x, 'x**3 - 2*x**2 + 4*x - 9'.
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        A Source object
    frac : `float`
        How much to change X by
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        A deep copy of src, with the value of x changed
    """
 
    out = src.table.copyRecord(src)
    x = out.getX()
    y = out.getY()
    val = x**3 - 2*x**2 + 4*x - 9
 
    out.set(out.table.getCentroidSlot().getMeasKey().getX(), x + val*frac)
    out.set(out.table.getCentroidSlot().getMeasKey().getY(), y)
    return out
 
 
def linearYDistort(src, frac=.001):
    """Increase the y value in a Source object by frac. E.g
    src.x = 1000 --> 1001 if frac=.001
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        A Source object
    frac : `float`
        How much to change Y by
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        A deep copy of src, with the value of Y changed
    """
 
    out = src.table.copyRecord(src)
    out.set(out.table.getCentroidSlot().getMeasKey().getY(), out.getY()*(1+frac))
    return out
 
 
def quadraticDistortY(src, frac=1e-6):
    """Distort image by terms with power <=2
    i.e y, y^2, x, xy, x^2
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        A Source object
    frac : `float`
        How much to change Y by
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        A deep copy of src, with the value of Y changed
    """
 
    out = src.table.copyRecord(src)
    x = out.getX()
    y = out.getY()
    val = y**2
 
    out.set(out.table.getCentroidSlot().getMeasKey().getX(), x)
    out.set(out.table.getCentroidSlot().getMeasKey().getY(), y + val*frac)
    return out
 
 
def cubicDistortY(src, frac=1e-9):
    """Distort image by terms with power <=2
    i.e y, y^2, x, xy, x^2
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        A Source object
    frac : `float`
        How much to change Y by
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        A deep copy of src, with the value of Y changed
    """
 
    out = src.table.copyRecord(src)
    x = out.getX()
    y = out.getY()
    val = x**3
 
    out.set(out.table.getCentroidSlot().getMeasKey().getX(), x)
    out.set(out.table.getCentroidSlot().getMeasKey().getY(), y + val*frac)
    return out
 
 
def manyTermY(src, frac=1e-9):
    """Distort image by multiple terms of Y, 'y**3 - 2*y**2 + 4*y - 9'.
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        A Source object
    frac : `float`
        How much to change Y by
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        A deep copy of src, with the value of Y changed
    """
    out = src.table.copyRecord(src)
    x = out.getX()
    y = out.getY()
    val = y**3 - 2*y**2 + 4*y - 9
 
    out.set(out.table.getCentroidSlot().getMeasKey().getX(), x)
    out.set(out.table.getCentroidSlot().getMeasKey().getY(), y + val*frac)
    return out
 
 
def crossTerms1(src, frac=1e-11):
    """Distort image Y by X, leaving X unchanged, 'x**3 - 2*x**2'.
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        A Source object
    frac : `float`
        How much to change Y by
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        A deep copy of src, with the value of Y changed
    """
    out = src.table.copyRecord(src)
    x = out.getX()
    y = out.getY()
    val = x**3 - 2*x**2  # + 4*x - 9
 
    out.set(out.table.getCentroidSlot().getMeasKey().getX(), x)
    out.set(out.table.getCentroidSlot().getMeasKey().getY(), y + val*frac)
    return out
 
 
def crossTerms2(src, frac=1e-11):
    """Distort image X by Y, leaving Y unchanged, 'y**3 - 2*y**2 + 4*y - 9'.
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        A Source object
    frac : `float`
        How much to change X by
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        A deep copy of src, with the value of X changed
    """
    out = src.table.copyRecord(src)
    x = out.getX()
    y = out.getY()
    val = y**3 - 2*y**2 + 4*y - 9
 
    out.set(out.table.getCentroidSlot().getMeasKey().getX(), x + val*frac)
    out.set(out.table.getCentroidSlot().getMeasKey().getY(), y)
    return out
 
 
def crossTerms3(src, frac=1e-9):
    """Distort image X and Y , 'dx=x**3 - 2*x**2 + 4*x - 9',
    'dy=y**3 - 2*y**2 + 4*y - 9'.
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        A Source object
    frac : `float`
        How much to change X and Y by
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        A deep copy of src, with the value of X and Y changed
    """
    out = src.table.copyRecord(src)
    x = out.getX()
    y = out.getY()
    valx = x**3 - 2*x**2 + 4*x - 9
    valy = y**3 - 2*y**2 + 4*y - 9
 
    out.set(out.table.getCentroidSlot().getMeasKey().getX(), x + valy*frac)
    out.set(out.table.getCentroidSlot().getMeasKey().getY(), y + valx*frac)
    return out
 
 
def quadraticDistort(src, frac=1e-6):
    """Distort image by terms with power <=2
    i.e y, y^2, x, xy, x^2
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        A Source object
    frac : `float`
        How much to change X
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        A deep copy of src, with the value of X
    """
 
    out = src.table.copyRecord(src)
    x = out.getX()
    y = out.getY()
    val = y + 2*y**2
    val += 3*x + 4*x*y
    val += x**2
 
    out.set(out.table.getCentroidSlot().getMeasKey().getX(), x + val*frac)
    out.set(out.table.getCentroidSlot().getMeasKey().getY(), y)
    return out
 
 
def T2DistortX(src, frac=1e-6):
    """Distort image by a 2nd order Cheby polynomial
 
    Parameters
    ----------
    src : `lsst.afw.table.SourceRecord`
        A Source object
    frac : `float`
        How much to change X
 
    Returns
    -------
    out : `lsst.afw.table.SourceRecord`
        A deep copy of src, with the value of X
    """
 
    out = src.table.copyRecord(src)
    x = src.getX()
    val = 2*(x**2) - 1
    out.set(out.table.getCentroidSlot().getMeasKey().getX(), x + frac*val)
    return out
 
 
def distortList(srcList, function):
    """Create a copy of srcList, and apply function to distort the
    values of x and y.
 
    Parameters
    ----------
    srcList : `list` of `lsst.afw.table.SourceRecord`
        Input list of source to distort.
    function : `callable`
        A function that does a deep copy of a single Source
 
    Returns
    -------
    out : `lsst.afw.table.SourceCatalog`
        Output catalog with distorted positions.
    """
 
    out = afwTable.SourceCatalog(srcList.table)
    out.reserve(len(srcList))
 
    for src in srcList:
        out.append(function(src))
 
    maxDiff = 0
    for i in range(len(srcList)):
        s = srcList[i]
        o = out[i]
 
        x1, y1 = s.getX(), s.getY()
        x2, y2 = o.getX(), o.getY()
 
        diff = math.hypot(x1-x2, y1-y2)
        maxDiff = max(diff, maxDiff)
 
    print("Max deviation is %e pixels" % (maxDiff))
 
    return out