###

#

filter.hpp
//
// Copyright 2019 Miral Shah <miralshah2211@gmail.com>
//
// Use, modification and distribution are subject to the Boost Software License,
// Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at
// http://www.boost.org/LICENSE_1_0.txt)
//
#ifndef BOOST_GIL_IMAGE_PROCESSING_FILTER_HPP
#define BOOST_GIL_IMAGE_PROCESSING_FILTER_HPP
#include <boost/gil/extension/numeric/algorithm.hpp>
#include <boost/gil/extension/numeric/kernel.hpp>
#include <boost/gil/extension/numeric/convolve.hpp>
#include <boost/gil/image.hpp>
#include <boost/gil/image_view.hpp>
#include <cstddef>
#include <vector>
namespace boost { namespace gil {
template <typename SrcView, typename DstView>
void box_filter(
SrcView const& src_view,
DstView const& dst_view,
std::size_t kernel_size,
long int anchor = -1,
bool normalize=true,
boundary_option option = boundary_option::extend_zero
)
{
gil_function_requires<ImageViewConcept<SrcView>>();
gil_function_requires<MutableImageViewConcept<DstView>>();
static_assert(color_spaces_are_compatible
<
typename color_space_type<SrcView>::type,
typename color_space_type<DstView>::type
>::value, "Source and destination views must have pixels with the same color space");
std::vector<float> kernel_values;
if (normalize) { kernel_values.resize(kernel_size, 1.0f / float(kernel_size)); }
else { kernel_values.resize(kernel_size, 1.0f); }
if (anchor == -1) anchor = static_cast<int>(kernel_size / 2);
kernel_1d<float> kernel(kernel_values.begin(), kernel_size, anchor);
detail::convolve_1d
<
pixel<float, typename SrcView::value_type::layout_t>
>(src_view, kernel, dst_view, option);
}
template <typename SrcView, typename DstView>
void blur(
SrcView const& src_view,
DstView const& dst_view,
std::size_t kernel_size,
long int anchor = -1,
boundary_option option = boundary_option::extend_zero
)
{
box_filter(src_view, dst_view, kernel_size, anchor, true, option);
}
namespace detail
{
template <typename SrcView, typename DstView>
void filter_median_impl(SrcView const& src_view, DstView const& dst_view, std::size_t kernel_size)
{
std::size_t half_kernel_size = kernel_size / 2;
// deciding output channel type and creating functor
using src_channel_t = typename channel_type<SrcView>::type;
std::vector<src_channel_t> values;
values.reserve(kernel_size * kernel_size);
for (std::ptrdiff_t y = 0; y < src_view.height(); y++)
{
typename DstView::x_iterator dst_it = dst_view.row_begin(y);
for (std::ptrdiff_t x = 0; x < src_view.width(); x++)
{
auto sub_view = subimage_view(
src_view,
x - half_kernel_size, y - half_kernel_size,
kernel_size,
kernel_size
);
values.assign(sub_view.begin(), sub_view.end());
std::nth_element(values.begin(), values.begin() + (values.size() / 2), values.end());
dst_it[x] = values[values.size() / 2];
}
}
}
} // namespace detail
template <typename SrcView, typename DstView>
void median_filter(SrcView const& src_view, DstView const& dst_view, std::size_t kernel_size)
{
static_assert(color_spaces_are_compatible
<
typename color_space_type<SrcView>::type,
typename color_space_type<DstView>::type
>::value, "Source and destination views must have pixels with the same color space");
std::size_t half_kernel_size = kernel_size / 2;
auto extended_img = extend_boundary(
src_view,
half_kernel_size,
boundary_option::extend_constant
);
auto extended_view = subimage_view(
view(extended_img),
half_kernel_size,
half_kernel_size,
src_view.width(),
src_view.height()
);
for (std::size_t channel = 0; channel < extended_view.num_channels(); channel++)
{
detail::filter_median_impl(
nth_channel_view(extended_view, channel),
nth_channel_view(dst_view, channel),
kernel_size
);
}
}
}} //namespace boost::gil
#endif // !BOOST_GIL_IMAGE_PROCESSING_FILTER_HPP
boost::gil::view
const image< Pixel, IsPlanar, Alloc >::view_t & view(image< Pixel, IsPlanar, Alloc > &img)
Returns the non-constant-pixel view of an image.
Definition: image.hpp:538