pixel_scale.hpp

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#ifndef _BOOST_GIL_COLOR_SCALE_HPP_
#define _BOOST_GIL_COLOR_SCALE_HPP_

#include <terry/numeric/minmax.hpp>

namespace boost { namespace gil {

/**
 * @brief Scale pixel values.
 * Usefull to normalize an image.
 */
template<typename Pixel, typename CPixel = Pixel>
struct pixel_scale_t
{
        typedef typename boost::gil::channel_type<Pixel>::type Channel;
        typedef typename terry::channel_base_type<Channel>::type ChannelBaseType;

        const CPixel _ratio;
        CPixel _shift;

        pixel_scale_t( const CPixel& ratio, const CPixel& sCenter, const CPixel& dCenter )
        : _ratio(ratio)
        {
                BOOST_STATIC_ASSERT( boost::is_floating_point<ChannelBaseType>::value );
                // res = ( ( src - sCenter ) * _ratio ) + dCenter;
                // res = (src * _ratio) + (dCenter - (sCenter*ratio))
                // shift = (dCenter - (sCenter*ratio))
                pixel_assigns_t<CPixel,CPixel>()(
                        pixel_minus_t<CPixel,CPixel,CPixel>()(
                                dCenter,
                                pixel_multiplies_t<CPixel,CPixel,CPixel>()(
                                        sCenter,
                                        ratio
                                        )
                                ),
                        _shift );
        }

        pixel_scale_t( const CPixel& ratio, const CPixel& shift )
        : _ratio(ratio)
        , _shift(shift)
        {
                BOOST_STATIC_ASSERT( boost::is_floating_point<ChannelBaseType>::value );
        }

        Pixel operator()( const Pixel& src ) const
        {
                Pixel res;
                // res = (src * _ratio) + _shift
                pixel_assigns_t<CPixel,Pixel>()(
                        pixel_plus_t<CPixel,CPixel,CPixel>()(
                                pixel_multiplies_t<Pixel,CPixel,CPixel>()(
                                        src,
                                        _ratio
                                        ),
                                _shift ),
                        res );

                return res;
        }
};

}
}

#endif