mapnik/include/mapnik/view_transform.hpp

/*****************************************************************************
 *
 * This file is part of Mapnik (c++ mapping toolkit)
 *
 * Copyright (C) 2021 Artem Pavlenko
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library 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
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 *****************************************************************************/

#ifndef MAPNIK_VIEW_TRANSFORM_HPP
#define MAPNIK_VIEW_TRANSFORM_HPP

// mapnik
#include <mapnik/coord.hpp>
#include <mapnik/geometry/box2d.hpp>
#include <mapnik/proj_transform.hpp>

namespace mapnik {

class view_transform
{
  private:
    const int width_;
    const int height_;
    const box2d<double> extent_;
    const double sx_;
    const double sy_;
    const double offset_x_;
    const double offset_y_;
    int offset_;

  public:

    view_transform(int _width,
                   int _height,
                   box2d<double> const& _extent,
                   double _offset_x = 0.0,
                   double _offset_y = 0.0)
        : width_(_width)
        , height_(_height)
        , extent_(_extent)
        , sx_(extent_.width() > 0 ? static_cast<double>(width_) / extent_.width() : 1.0)
        , sy_(extent_.height() > 0 ? static_cast<double>(height_) / extent_.height() : 1.0)
        , offset_x_(_offset_x)
        , offset_y_(_offset_y)
        , offset_(0)
    {}

    view_transform(view_transform const&) = default;

    inline int offset() const { return offset_; }

    inline void set_offset(int _offset) { offset_ = _offset; }

    inline double offset_x() const { return offset_x_; }

    inline double offset_y() const { return offset_y_; }

    inline int width() const { return width_; }

    inline int height() const { return height_; }

    inline double scale_x() const { return sx_; }

    inline double scale_y() const { return sy_; }

    inline void forward(double* x, double* y) const
    {
        *x = (*x - extent_.minx()) * sx_ - (offset_x_ - offset_);
        *y = (extent_.maxy() - *y) * sy_ - (offset_y_ - offset_);
    }

    inline void backward(double* x, double* y) const
    {
        *x = extent_.minx() + (*x + (offset_x_ - offset_)) / sx_;
        *y = extent_.maxy() - (*y + (offset_y_ - offset_)) / sy_;
    }

    inline coord2d& forward(coord2d& c) const
    {
        forward(&c.x, &c.y);
        return c;
    }

    inline coord2d& backward(coord2d& c) const
    {
        backward(&c.x, &c.y);
        return c;
    }

    inline box2d<double> forward(box2d<double> const& e, proj_transform const& prj_trans) const
    {
        double x0 = e.minx();
        double y0 = e.miny();
        double x1 = e.maxx();
        double y1 = e.maxy();
        double z = 0.0;
        prj_trans.backward(x0, y0, z);
        forward(&x0, &y0);
        prj_trans.backward(x1, y1, z);
        forward(&x1, &y1);
        return box2d<double>(x0, y0, x1, y1);
    }

    inline box2d<double> forward(box2d<double> const& e) const
    {
        double x0 = e.minx();
        double y0 = e.miny();
        double x1 = e.maxx();
        double y1 = e.maxy();
        forward(&x0, &y0);
        forward(&x1, &y1);
        return box2d<double>(x0, y0, x1, y1);
    }

    inline box2d<double> backward(box2d<double> const& e, proj_transform const& prj_trans) const
    {
        double x0 = e.minx();
        double y0 = e.miny();
        double x1 = e.maxx();
        double y1 = e.maxy();
        double z = 0.0;
        backward(&x0, &y0);
        prj_trans.forward(x0, y0, z);
        backward(&x1, &y1);
        prj_trans.forward(x1, y1, z);
        return box2d<double>(x0, y0, x1, y1);
    }

    inline box2d<double> backward(box2d<double> const& e) const
    {
        double x0 = e.minx();
        double y0 = e.miny();
        double x1 = e.maxx();
        double y1 = e.maxy();
        backward(&x0, &y0);
        backward(&x1, &y1);
        return box2d<double>(x0, y0, x1, y1);
    }

    inline box2d<double> const& extent() const { return extent_; }
};

} // namespace mapnik

#endif // MAPNIK_VIEW_TRANSFORM_HPP