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C++

//
// Copyright 2012 Christian Henning
//
// 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_PNM_DETAIL_READER_BACKEND_HPP
#define BOOST_GIL_EXTENSION_IO_PNM_DETAIL_READER_BACKEND_HPP
#include <boost/gil/extension/io/pnm/tags.hpp>
namespace boost { namespace gil {
#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
#pragma warning(push)
#pragma warning(disable:4512) //assignment operator could not be generated
#endif
///
/// PNM Backend
///
template< typename Device >
struct reader_backend< Device
, pnm_tag
>
{
public:
using format_tag_t = pnm_tag;
public:
reader_backend( const Device& io_dev
, const image_read_settings< pnm_tag >& settings
)
: _io_dev ( io_dev )
, _settings( settings )
, _info()
, _scanline_length( 0 )
{
read_header();
if( _settings._dim.x == 0 )
{
_settings._dim.x = _info._width;
}
if( _settings._dim.y == 0 )
{
_settings._dim.y = _info._height;
}
}
void read_header()
{
// read signature
io_error_if( read_char() != 'P', "Invalid PNM signature" );
_info._type = read_char() - '0';
io_error_if( _info._type < pnm_image_type::mono_asc_t::value || _info._type > pnm_image_type::color_bin_t::value
, "Invalid PNM file (supports P1 to P6)"
);
_info._width = read_int();
_info._height = read_int();
if( _info._type == pnm_image_type::mono_asc_t::value || _info._type == pnm_image_type::mono_bin_t::value )
{
_info._max_value = 1;
}
else
{
_info._max_value = read_int();
io_error_if( _info._max_value > 255
, "Unsupported PNM format (supports maximum value 255)"
);
}
}
/// Check if image is large enough.
void check_image_size( const point_t& img_dim )
{
if( _settings._dim.x > 0 )
{
if( img_dim.x < _settings._dim.x ) { io_error( "Supplied image is too small" ); }
}
else
{
if( img_dim.x < _info._width ) { io_error( "Supplied image is too small" ); }
}
if( _settings._dim.y > 0 )
{
if( img_dim.y < _settings._dim.y ) { io_error( "Supplied image is too small" ); }
}
else
{
if( img_dim.y < _info._height ) { io_error( "Supplied image is too small" ); }
}
}
private:
// Read a character and skip a comment if necessary.
char read_char()
{
char ch;
if(( ch = _io_dev.getc() ) == '#' )
{
// skip comment to EOL
do
{
ch = _io_dev.getc();
}
while (ch != '\n' && ch != '\r');
}
return ch;
}
unsigned int read_int()
{
char ch;
// skip whitespaces, tabs, and new lines
do
{
ch = read_char();
}
while (ch == ' ' || ch == '\t' || ch == '\n' || ch == '\r');
if( ch < '0' || ch > '9' )
{
io_error( "Unexpected characters reading decimal digits" );
}
unsigned val = 0;
do
{
unsigned dig = ch - '0';
if( val > INT_MAX / 10 - dig )
{
io_error( "Integer too large" );
}
val = val * 10 + dig;
ch = read_char();
}
while( '0' <= ch && ch <= '9' );
return val;
}
public:
Device _io_dev;
image_read_settings< pnm_tag > _settings;
image_read_info< pnm_tag > _info;
std::size_t _scanline_length;
};
#if BOOST_WORKAROUND(BOOST_MSVC, >= 1400)
#pragma warning(pop)
#endif
} // namespace gil
} // namespace boost
#endif