Boost C++ Libraries

boost/gil/extension/io/jpeg/detail/scanline_read.hpp

//
// Copyright 2007-2012 Christian Henning, Andreas Pokorny, Lubomir Bourdev
//
// Distributed under 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_EXTENSION_IO_JPEG_DETAIL_SCANLINE_READ_HPP
#define BOOST_GIL_EXTENSION_IO_JPEG_DETAIL_SCANLINE_READ_HPP


#include <boost/gil/extension/io/jpeg/detail/base.hpp>
#include <boost/gil/extension/io/jpeg/detail/is_allowed.hpp>
#include <boost/gil/extension/io/jpeg/detail/reader_backend.hpp>

#include <boost/gil/io/base.hpp>
#include <boost/gil/io/conversion_policies.hpp>
#include <boost/gil/io/device.hpp>
#include <boost/gil/io/reader_base.hpp>
#include <boost/gil/io/scanline_read_iterator.hpp>
#include <boost/gil/io/typedefs.hpp>

#include <csetjmp>
#include <vector>

namespace boost { namespace gil {

#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
#pragma warning(push)
#pragma warning(disable:4611) //interaction between '_setjmp' and C++ object destruction is non-portable
#endif

///
/// JPEG Scanline Reader
///
template< typename Device >
class scanline_reader< Device
                     , jpeg_tag
                     >
    : public reader_backend< Device
                           , jpeg_tag
                           >
{
public:

    using tag_t = jpeg_tag;
    using backend_t = reader_backend<Device, tag_t>;
    using this_t = scanline_reader<Device, tag_t>;
    using iterator_t = scanline_read_iterator<this_t>;

public:
    scanline_reader( Device&                                device
                   , const image_read_settings< jpeg_tag >& settings
                   )
    : reader_backend< Device
                    , jpeg_tag
                     >( device
                      , settings
                      )
    {
        initialize();
    }

    void read( byte_t* dst
             , int
             )
    {
        // Fire exception in case of error.
        if( setjmp( this->_mark )) { this->raise_error(); }

        // read data
        read_scanline( dst );
    }

    /// Skip over a scanline.
    void skip( byte_t* dst, int )
    {
        // Fire exception in case of error.
        if( setjmp( this->_mark )) { this->raise_error(); }

        // read data
        read_scanline( dst );
    }

    iterator_t begin() { return iterator_t( *this ); }
    iterator_t end()   { return iterator_t( *this, this->_info._height ); }

private:

    void initialize()
    {
        this->get()->dct_method = this->_settings._dct_method;

        io_error_if( jpeg_start_decompress( this->get() ) == false
                    , "Cannot start decompression." );

        switch( this->_info._color_space )
        {
            case JCS_GRAYSCALE:
            {
                this->_scanline_length = this->_info._width;

                break;
            }

            case JCS_RGB:
            //!\todo add Y'CbCr? We loose image quality when reading JCS_YCbCr as JCS_RGB
            case JCS_YCbCr:
            {
                this->_scanline_length = this->_info._width * num_channels< rgb8_view_t >::value;

                break;
            }


            case JCS_CMYK:
            //!\todo add Y'CbCrK? We loose image quality when reading JCS_YCCK as JCS_CMYK
            case JCS_YCCK:
            {
                this->get()->out_color_space = JCS_CMYK;
                this->_scanline_length = this->_info._width * num_channels< cmyk8_view_t >::value;

                break;
            }

            default: { io_error( "Unsupported jpeg color space." ); }
        }
    }

    void read_scanline( byte_t* dst )
    {
        JSAMPLE *row_adr = reinterpret_cast< JSAMPLE* >( dst );

        // Read data.
        io_error_if( jpeg_read_scanlines( this->get()
                                        , &row_adr
                                        , 1
                                        ) != 1
                    , "jpeg_read_scanlines: fail to read JPEG file"
                    );

    }
};

#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
#pragma warning(pop)
#endif

} // namespace gil
} // namespace boost

#endif