//
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// Copyright 2007-2012 Christian Henning, Andreas Pokorny, Lubomir Bourdev
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//
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// Distributed under the Boost Software License, Version 1.0
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// See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt
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//
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#ifndef BOOST_GIL_EXTENSION_IO_PNG_DETAIL_SCANLINE_READ_HPP
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#define BOOST_GIL_EXTENSION_IO_PNG_DETAIL_SCANLINE_READ_HPP
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#include <boost/gil/extension/io/png/detail/is_allowed.hpp>
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#include <boost/gil/extension/io/png/detail/reader_backend.hpp>
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#include <boost/gil.hpp> // FIXME: Include what you use!
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#include <boost/gil/io/base.hpp>
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#include <boost/gil/io/conversion_policies.hpp>
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#include <boost/gil/io/device.hpp>
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#include <boost/gil/io/reader_base.hpp>
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#include <boost/gil/io/row_buffer_helper.hpp>
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#include <boost/gil/io/scanline_read_iterator.hpp>
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#include <boost/gil/io/typedefs.hpp>
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namespace boost { namespace gil {
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///
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/// PNG Reader
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///
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template< typename Device >
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class scanline_reader< Device
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, png_tag
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>
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: public reader_backend< Device
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, png_tag
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>
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{
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public:
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using tag_t = png_tag;
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using backend_t = reader_backend<Device, tag_t>;
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using this_t = scanline_reader<Device, tag_t>;
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using iterator_t = scanline_read_iterator<this_t>;
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//
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// Constructor
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//
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scanline_reader( const Device& io_dev
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, const image_read_settings< png_tag >& settings
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)
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: reader_backend< Device
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, png_tag
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>( io_dev
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, settings
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)
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{
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initialize();
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}
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void read( byte_t* dst
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, int
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)
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{
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read_scanline( dst );
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}
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/// Skip over a scanline.
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void skip( byte_t* dst, int )
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{
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read_scanline( dst );
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}
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iterator_t begin() { return iterator_t( *this ); }
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iterator_t end() { return iterator_t( *this, this->_info._height ); }
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private:
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void initialize()
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{
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// Now it's time for some transformations.
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if( little_endian() )
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{
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if( this->_info._bit_depth == 16 )
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{
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// Swap bytes of 16 bit files to least significant byte first.
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png_set_swap( this->get()->_struct );
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}
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if( this->_info._bit_depth < 8 )
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{
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// swap bits of 1, 2, 4 bit packed pixel formats
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png_set_packswap( this->get()->_struct );
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}
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}
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if( this->_info._color_type == PNG_COLOR_TYPE_PALETTE )
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{
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png_set_palette_to_rgb( this->get()->_struct );
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}
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if( this->_info._num_trans > 0 )
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{
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png_set_tRNS_to_alpha( this->get()->_struct );
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}
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// Tell libpng to handle the gamma conversion for you. The final call
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// is a good guess for PC generated images, but it should be configurable
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// by the user at run time by the user. It is strongly suggested that
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// your application support gamma correction.
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if( this->_settings._apply_screen_gamma )
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{
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// png_set_gamma will change the image data!
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#ifdef BOOST_GIL_IO_PNG_FLOATING_POINT_SUPPORTED
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png_set_gamma( this->get()->_struct
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, this->_settings._screen_gamma
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, this->_info._file_gamma
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);
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#else
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png_set_gamma( this->get()->_struct
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, this->_settings._screen_gamma
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, this->_info._file_gamma
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);
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#endif // BOOST_GIL_IO_PNG_FLOATING_POINT_SUPPORTED
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}
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// Interlaced images are not supported.
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this->_number_passes = png_set_interlace_handling( this->get()->_struct );
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io_error_if( this->_number_passes != 1
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, "scanline_read_iterator cannot read interlaced png images."
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);
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// The above transformation might have changed the bit_depth and color type.
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png_read_update_info( this->get()->_struct
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, this->get()->_info
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);
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this->_info._bit_depth = png_get_bit_depth( this->get()->_struct
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, this->get()->_info
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);
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this->_info._num_channels = png_get_channels( this->get()->_struct
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, this->get()->_info
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);
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this->_info._color_type = png_get_color_type( this->get()->_struct
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, this->get()->_info
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);
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this->_scanline_length = png_get_rowbytes( this->get()->_struct
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, this->get()->_info
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);
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}
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void read_scanline( byte_t* dst )
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{
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png_read_row( this->get()->_struct
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, dst
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, NULL
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);
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}
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};
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} // namespace gil
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} // namespace boost
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#endif
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