sampler.hpp

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/* Copyright © 2017 Apple Inc. All rights reserved.
 *
 * Use of this source code is governed by a BSD-3-clause license that can
 * be found in the LICENSE.txt file or at https://opensource.org/licenses/BSD-3-Clause
 */
/*
  Copyright 2005-2007 Adobe Systems Incorporated
  Distributed under the MIT License (see accompanying file LICENSE_1_0_0.txt
  or a copy at http://opensource.adobe.com/licenses.html)
*/

/*************************************************************************************************/

#ifndef GIL_SAMPLER_HPP
#define GIL_SAMPLER_HPP

#include <boost/gil/extension/dynamic_image/dynamic_image_all.hpp>
#include "pixel_numeric_operations.hpp"

////////////////////////////////////////////////////////////////////////////////////////
/// \file
/// \brief Nearest-neighbor and bilinear image samplers.
///        NOTE: The code is for example use only. It is not optimized for performance
/// \author Lubomir Bourdev and Hailin Jin \n
///         Adobe Systems Incorporated
/// \date   2005-2007 \n October 30, 2006
///
////////////////////////////////////////////////////////////////////////////////////////

namespace boost { namespace gil {

///////////////////////////////////////////////////////////////////////////
////
////     resample_pixels: set each pixel in the destination view as the result of a sampling function over the transformed coordinates of the source view
////
///////////////////////////////////////////////////////////////////////////
/*
template <typename Sampler>
concept SamplerConcept {
    template <typename DstP,      // Models PixelConcept
              typename SrcView,    // Models RandomAccessNDImageViewConcept
              typename S_COORDS>  // Models PointNDConcept, where S_COORDS::num_dimensions == SrcView::num_dimensions
    bool sample(const Sampler& s, const SrcView& src, const S_COORDS& p, DstP result);
};
*/

/// \brief A sampler that sets the destination pixel to the closest one in the source. If outside the bounds, it doesn't change the destination
/// \ingroup ImageAlgorithms
struct nearest_neighbor_sampler {};

template <typename DstP, typename SrcView, typename F>
bool sample(nearest_neighbor_sampler, const SrcView& src, const point2<F>& p, DstP& result) {
    point2<int> center(static_cast<int>(iround(p).x), static_cast<int>(iround(p).y));
    if (center.x>=0 && center.y>=0 && center.x<src.width() && center.y<src.height()) {
        result=src(center.x,center.y);
        return true;
    }
    return false;
}

struct cast_channel_fn {
    template <typename SrcChannel, typename DstChannel>
    void operator()(const SrcChannel& src, DstChannel& dst) {
        typedef typename channel_traits<DstChannel>::value_type dst_value_t;
        dst = dst_value_t(src);
    }
};

template <typename SrcPixel, typename DstPixel>
void cast_pixel(const SrcPixel& src, DstPixel& dst) {
    static_for_each(src,dst,cast_channel_fn());
}

namespace detail {

template <typename Weight>
struct add_dst_mul_src_channel {
    Weight _w;
    add_dst_mul_src_channel(Weight w) : _w(w) {}

    template <typename SrcChannel, typename DstChannel>
    void operator()(const SrcChannel& src, DstChannel& dst) const {
        dst += DstChannel(src*_w);
    }
};

// dst += DST_TYPE(src * w)
template <typename SrcP,typename Weight,typename DstP>
struct add_dst_mul_src {
    void operator()(const SrcP& src, Weight weight, DstP& dst) const {
        static_for_each(src,dst, add_dst_mul_src_channel<Weight>(weight));
//        pixel_assigns_t<DstP,DstP&>()(
//            pixel_plus_t<DstP,DstP,DstP>()(
//                pixel_multiplies_scalar_t<SrcP,Weight,DstP>()(src,weight),
//                dst),
//            dst);
    }
};
} // namespace detail

/// \brief A sampler that sets the destination pixel as the bilinear interpolation of the four closest pixels from the source.
/// If outside the bounds, it doesn't change the destination
/// \ingroup ImageAlgorithms
struct bilinear_sampler {};

template <typename DstP, typename SrcView, typename F>
bool sample(bilinear_sampler, const SrcView& src, const point2<F>& p, DstP& result) {
    typedef typename SrcView::value_type SrcP;
    point2<std::ptrdiff_t> p0(ifloor(p)); // the closest integer coordinate top left from p
    point2<F> frac(p.x-p0.x, p.y-p0.y);
    if (p0.x < 0 || p0.y < 0 || p0.x>=src.width() || p0.y>=src.height()) return false;

    pixel<F,devicen_layout_t<num_channels<SrcView>::value> > mp(0);                     // suboptimal
    typename SrcView::xy_locator loc=src.xy_at(p0.x,p0.y);

    if (p0.x+1<src.width()) {
        if (p0.y+1<src.height()) {
            // most common case - inside the image, not on the last row or column
            detail::add_dst_mul_src<SrcP,F,pixel<F,devicen_layout_t<num_channels<SrcView>::value> > >()(*loc,      (1-frac.x)*(1-frac.y),mp);
            detail::add_dst_mul_src<SrcP,F,pixel<F,devicen_layout_t<num_channels<SrcView>::value> > >()(loc.x()[1],   frac.x *(1-frac.y),mp);
            ++loc.y();
            detail::add_dst_mul_src<SrcP,F,pixel<F,devicen_layout_t<num_channels<SrcView>::value> > >()(*loc,      (1-frac.x)*   frac.y ,mp);
            detail::add_dst_mul_src<SrcP,F,pixel<F,devicen_layout_t<num_channels<SrcView>::value> > >()(loc.x()[1],   frac.x *   frac.y ,mp);
        } else {
            // on the last row, but not the bottom-right corner pixel
            detail::add_dst_mul_src<SrcP,F,pixel<F,devicen_layout_t<num_channels<SrcView>::value> > >()(*loc,      (1-frac.x),mp);
            detail::add_dst_mul_src<SrcP,F,pixel<F,devicen_layout_t<num_channels<SrcView>::value> > >()(loc.x()[1],   frac.x ,mp);
        }
    } else {
        if (p0.y+1<src.height()) {
            // on the last column, but not the bottom-right corner pixel
            detail::add_dst_mul_src<SrcP,F,pixel<F,devicen_layout_t<num_channels<SrcView>::value> > >()(*loc,      (1-frac.y),mp);
            ++loc.y();
            detail::add_dst_mul_src<SrcP,F,pixel<F,devicen_layout_t<num_channels<SrcView>::value> > >()(*loc,         frac.y ,mp);
        } else {
            // the bottom-right corner pixel
            detail::add_dst_mul_src<SrcP,F,pixel<F,devicen_layout_t<num_channels<SrcView>::value> > >()(*loc,1,mp);
        }
    }

    // Convert from floating point average value to the source type
    SrcP src_result;
    cast_pixel(mp,src_result);

    color_convert(src_result, result);
    return true;
}

} }  // namespace boost::gil

#endif