WarpedPsf.cc

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// -*- lsst-c++ -*-

/* 
 * 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
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 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
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#include "lsst/pex/exceptions.h"
#include "lsst/meas/algorithms/WarpedPsf.h"
#include "lsst/afw/math/warpExposure.h"
#include "lsst/afw/image/Image.h"

namespace lsst { namespace meas { namespace algorithms {

namespace {

inline double min4(double a, double b, double c, double d) {
    return std::min(std::min(a,b), std::min(c,d));
}

inline double max4(double a, double b, double c, double d) {
    return std::max(std::max(a,b), std::max(c,d));
}

// TODO: make this routine externally callable and more generic using templates
//  (also useful in e.g. math/offsetImage.cc)
PTR(afw::detection::Psf::Image) zeroPadImage(afw::detection::Psf::Image const &im, int xPad, int yPad) {
    int nx = im.getWidth();
    int ny = im.getHeight();

    PTR(afw::detection::Psf::Image) out = std::make_shared<afw::detection::Psf::Image>(nx+2*xPad, ny+2*yPad);
    out->setXY0(im.getX0()-xPad, im.getY0()-yPad);

    afw::geom::Box2I box(afw::geom::Point2I(xPad,yPad), afw::geom::Extent2I(nx,ny));
    out->assign(im, box, afw::image::LOCAL);

    return out;
}

PTR(afw::detection::Psf::Image) warpAffine(
    afw::detection::Psf::Image const &im, afw::geom::AffineTransform const &t,
    afw::math::WarpingControl const &wc
) {
    static const int dst_padding = 0;

    afw::geom::AffineXYTransform xyTransform(t);

    afw::math::SeparableKernel const& kernel = *wc.getWarpingKernel();
    afw::geom::Point2I const& center = kernel.getCtr();
    int const xPad = std::max(center.getX(), kernel.getWidth() - center.getX());
    int const yPad = std::min(center.getY(), kernel.getHeight() - center.getY());

    // This is the maximum scaling I can imagine we'd want - it's approximately what you'd
    // get from trying to coadd 2"-pixel data (e.g. 2MASS) onto a 0.01"-pixel grid (e.g.
    // from JWST).  Anything beyond that is probably a bug elsewhere in the code, and
    // catching that can save us from segfaults and catastrophic memory consumption.
    static const double maxTransformCoeff = 200.0;

    if (t.getLinear().getMatrix().lpNorm<Eigen::Infinity>() > maxTransformCoeff) {
        throw LSST_EXCEPT(
            pex::exceptions::RangeError,
            "Unexpectedly large transform passed to WarpedPsf"
        );
    }

    // min/max coordinate values in input image
    int in_xlo = im.getX0();
    int in_xhi = im.getX0() + im.getWidth() - 1;
    int in_ylo = im.getY0();
    int in_yhi = im.getY0() + im.getHeight() - 1;

    // corners of output image
    afw::geom::Point2D c00 = t(afw::geom::Point2D(in_xlo,in_ylo));
    afw::geom::Point2D c01 = t(afw::geom::Point2D(in_xlo,in_yhi));
    afw::geom::Point2D c10 = t(afw::geom::Point2D(in_xhi,in_ylo));
    afw::geom::Point2D c11 = t(afw::geom::Point2D(in_xhi,in_yhi));

    //
    // bounding box for output image
    //
    int out_xlo = floor(min4(c00.getX(),c01.getX(),c10.getX(),c11.getX())) - dst_padding;
    int out_ylo = floor(min4(c00.getY(),c01.getY(),c10.getY(),c11.getY())) - dst_padding;
    int out_xhi = ceil(max4(c00.getX(),c01.getX(),c10.getX(),c11.getX())) + dst_padding;
    int out_yhi = ceil(max4(c00.getY(),c01.getY(),c10.getY(),c11.getY())) + dst_padding;

    // allocate output image
    PTR(afw::detection::Psf::Image) ret 
        = std::make_shared<afw::detection::Psf::Image>(out_xhi-out_xlo+1, out_yhi-out_ylo+1);
    ret->setXY0(afw::geom::Point2I(out_xlo,out_ylo));

    // zero-pad input image
    PTR(afw::detection::Psf::Image) im_padded = zeroPadImage(im, xPad, yPad);

    // warp it!
    afw::math::warpImage(*ret, *im_padded, xyTransform, wc, 0.0);
    return ret;
}

} // anonymous

WarpedPsf::WarpedPsf(
    PTR(afw::detection::Psf const) undistortedPsf,
    PTR(afw::geom::XYTransform const) distortion,
    CONST_PTR(afw::math::WarpingControl) control
    ) :
    ImagePsf(false),
    _undistortedPsf(undistortedPsf),
    _distortion(distortion),
    _warpingControl(control)
{
    _init();
}

WarpedPsf::WarpedPsf(
    PTR(afw::detection::Psf const) undistortedPsf,
    PTR(afw::geom::XYTransform const) distortion,
    std::string const& kernelName,
    unsigned int cache
    ) :
    ImagePsf(false),
    _undistortedPsf(undistortedPsf),
    _distortion(distortion),
    _warpingControl(new afw::math::WarpingControl(kernelName, "", cache))
{
    _init();
}

void WarpedPsf::_init()
{
    if (!_undistortedPsf) {
        throw LSST_EXCEPT(
            pex::exceptions::LogicError,
            "Undistorted Psf passed to WarpedPsf must not be None/NULL"
        );
    }
    if (!_distortion) {
        throw LSST_EXCEPT(
            pex::exceptions::LogicError,
            "XYTransform passed to WarpedPsf must not be None/NULL"
        );
    }
    if (!_warpingControl) {
        throw LSST_EXCEPT(
            pex::exceptions::LogicError,
            "WarpingControl passed to WarpedPsf must not be None/NULL"
        );
    }
}

afw::geom::Point2D WarpedPsf::getAveragePosition() const {
    return _distortion->forwardTransform(_undistortedPsf->getAveragePosition());
}

PTR(afw::detection::Psf) WarpedPsf::clone() const {
    return std::make_shared<WarpedPsf>(_undistortedPsf->clone(), _distortion->clone(), _warpingControl);
}

PTR(afw::detection::Psf::Image) WarpedPsf::doComputeKernelImage(
    afw::geom::Point2D const & position, afw::image::Color const & color
) const {
    afw::geom::AffineTransform t = _distortion->linearizeReverseTransform(position);
    afw::geom::Point2D tp = t(position);

    PTR(Image) im = _undistortedPsf->computeKernelImage(tp, color);

    // Go to the warped coordinate system with 'p' at the origin
    PTR(afw::detection::Psf::Psf::Image) ret
        = warpAffine(*im, afw::geom::AffineTransform(t.invert().getLinear()), *_warpingControl);

    double normFactor = 1.0;
    // 
    // Normalize the output image to sum 1
    // FIXME defining a member function Image::getSum() would be convenient here and in other places
    //
    normFactor = 0.0;
    for (int y = 0; y != ret->getHeight(); ++y) {
        afw::detection::Psf::Image::x_iterator imEnd = ret->row_end(y);
        for (afw::detection::Psf::Image::x_iterator imPtr = ret->row_begin(y); imPtr != imEnd; imPtr++) {
            normFactor += *imPtr;
        }
    }
    if (normFactor == 0.0) {
        throw LSST_EXCEPT(pex::exceptions::InvalidParameterError, "psf image has sum 0");
    }
    *ret /= normFactor;
    return ret;
}

}}} // namepace lsst::meas::algorithms