/**
* @brief Get exif directory structure contained in file (if any)
* This is internal function and is not exposed to client
*
* @return Map where key is tag number and value is ExifEntry_t structure
*/
std::map<int, ExifEntry_t > ExifReader::getExif()
{
const std::streamsize markerSize = 2;
const std::streamsize offsetToTiffHeader = 6; //bytes from Exif size field to the first TIFF header
unsigned char appMarker[markerSize];
m_exif.erase( m_exif.begin(), m_exif.end() );
std::streamsize count;
bool exifFound = false, stopSearch = false;
while( ( !m_stream.eof() ) && !exifFound && !stopSearch )
{
m_stream.read( reinterpret_cast<char*>(appMarker), markerSize );
count = m_stream.gcount();
if( count < markerSize )
{
break;
}
unsigned char marker = appMarker[1];
size_t bytesToSkip;
size_t exifSize;
switch( marker )
{
//For all the markers just skip bytes in file pointed by followed two bytes (field size)
case SOF0: case SOF2: case DHT: case DQT: case DRI: case SOS:
case RST0: case RST1: case RST2: case RST3: case RST4: case RST5: case RST6: case RST7:
case APP0: case APP2: case APP3: case APP4: case APP5: case APP6: case APP7: case APP8:
case APP9: case APP10: case APP11: case APP12: case APP13: case APP14: case APP15:
case COM:
bytesToSkip = getFieldSize();
if (bytesToSkip < markerSize) {
throw ExifParsingError();
}
m_stream.seekg( static_cast<long>( bytesToSkip - markerSize ), m_stream.cur );
if ( m_stream.fail() ) {
throw ExifParsingError();
}
break;
//SOI and EOI don't have the size field after the marker
case SOI: case EOI:
break;
case APP1: //actual Exif Marker
exifSize = getFieldSize();
if (exifSize <= offsetToTiffHeader) {
throw ExifParsingError();
}
m_data.resize( exifSize - offsetToTiffHeader );
m_stream.seekg( static_cast<long>( offsetToTiffHeader ), m_stream.cur );
if ( m_stream.fail() ) {
throw ExifParsingError();
}
m_stream.read( reinterpret_cast<char*>(&m_data[0]), exifSize - offsetToTiffHeader );
count = m_stream.gcount();
exifFound = true;
break;
default: //No other markers are expected according to standard. May be a signal of error
stopSearch = true;
break;
}
}
if( !exifFound )
{
return m_exif;
}
parseExif();
return m_exif;
}
/**
* @brief Get exif directory structure contained in jpeg file (if any)
* This is internal function and is not exposed to client
*
* @return Map where key is tag number and value is ExifEntry_t structure
*/
std::map<int, ExifEntry_t > ExifReader::getExif()
{
const size_t markerSize = 2;
const size_t offsetToTiffHeader = 6; //bytes from Exif size field to the first TIFF header
unsigned char appMarker[markerSize];
m_exif.erase( m_exif.begin(), m_exif.end() );
size_t count;
FILE* f = fopen( m_filename.c_str(), "rb" );
if( !f )
{
return m_exif; //Until this moment the map is empty
}
bool exifFound = false;
while( ( !feof( f ) ) && !exifFound )
{
count = fread( appMarker, sizeof(unsigned char), markerSize, f );
if( count < markerSize )
{
break;
}
unsigned char marker = appMarker[1];
size_t bytesToSkip;
size_t exifSize;
switch( marker )
{
//For all the markers just skip bytes in file pointed by followed two bytes (field size)
case SOF0: case SOF2: case DHT: case DQT: case DRI: case SOS:
case RST0: case RST1: case RST2: case RST3: case RST4: case RST5: case RST6: case RST7:
case APP0: case APP2: case APP3: case APP4: case APP5: case APP6: case APP7: case APP8:
case APP9: case APP10: case APP11: case APP12: case APP13: case APP14: case APP15:
case COM:
bytesToSkip = getFieldSize( f );
fseek( f, static_cast<long>( bytesToSkip - markerSize ), SEEK_CUR );
break;
//SOI and EOI don't have the size field after the marker
case SOI: case EOI:
break;
case APP1: //actual Exif Marker
exifSize = getFieldSize(f);
m_data.resize( exifSize - offsetToTiffHeader );
fseek(f, static_cast<long>( offsetToTiffHeader ), SEEK_CUR);
count = fread( &m_data[0], sizeof( unsigned char ), exifSize - offsetToTiffHeader, f );
exifFound = true;
break;
default: //No other markers are expected according to standard. May be a signal of error
break;
}
}
fclose(f);
if( !exifFound )
{
return m_exif;
}
parseExif();
return m_exif;
}
