// This file is part of the AliceVision project.
// Copyright (c) 2016 AliceVision contributors.
// Copyright (c) 2012 openMVG contributors.
// This Source Code Form is subject to the terms of the Mozilla Public License,
// v. 2.0. If a copy of the MPL was not distributed with this file,
// You can obtain one at https://mozilla.org/MPL/2.0/.

#pragma once

#include <aliceVision/config.hpp>

namespace aliceVision {
namespace image {

/// Apply inplace homography transform for the given point (x,y).
/// Return true if H is orientation preserving around the point.
bool applyHomographyAndCheckOrientation(const Mat3& H, double& x, double& y)
{
    Vec3 X(x, y, 1.0);
    X = H * X;
    X /= X(2);
    x = X(0);
    y = X(1);
    return (X(2) * H(2, 2) > 0.0);
}

/// Warp an image im given a homography H with a backward approach
/// H must be already have been resized accordingly
template<class Image>
void warp(const Image& im, const Mat3& H, Image& out)
{
    const int wOut = static_cast<int>(out.width());
    const int hOut = static_cast<int>(out.height());

    const Sampler2d<SamplerLinear> sampler;
    for (int j = 0; j < hOut; ++j)
#pragma omp parallel for
        for (int i = 0; i < wOut; ++i)
        {
            double xT = i, yT = j;
            if (applyHomographyAndCheckOrientation(H, xT, yT) && im.contains(yT, xT))
                out(j, i) = sampler(im, (float)yT, (float)xT);
        }
}

};  // namespace image
};  // namespace aliceVision
