exif.cpp
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/*M///////////////////////////////////////////////////////////////////////////////////////
//
// IMPORTANT: READ BEFORE DOWNLOADING, COPYING, INSTALLING OR USING.
//
// By downloading, copying, installing or using the software you agree to this license.
// If you do not agree to this license, do not download, install,
// copy or use the software.
//
//
// License Agreement
// For Open Source Computer Vision Library
//
// Copyright (C) 2000-2008, Intel Corporation, all rights reserved.
// Copyright (C) 2009, Willow Garage Inc., all rights reserved.
// Third party copyrights are property of their respective owners.
//
// Redistribution and use in source and binary forms, with or without modification,
// are permitted provided that the following conditions are met:
//
// * Redistribution's of source code must retain the above copyright notice,
// this list of conditions and the following disclaimer.
//
// * Redistribution's in binary form must reproduce the above copyright notice,
// this list of conditions and the following disclaimer in the documentation
// and/or other materials provided with the distribution.
//
// * The name of the copyright holders may not be used to endorse or promote products
// derived from this software without specific prior written permission.
//
// This software is provided by the copyright holders and contributors "as is" and
// any express or implied warranties, including, but not limited to, the implied
// warranties of merchantability and fitness for a particular purpose are disclaimed.
// In no event shall the Intel Corporation or contributors be liable for any direct,
// indirect, incidental, special, exemplary, or consequential damages
// (including, but not limited to, procurement of substitute goods or services;
// loss of use, data, or profits; or business interruption) however caused
// and on any theory of liability, whether in contract, strict liability,
// or tort (including negligence or otherwise) arising in any way out of
// the use of this software, even if advised of the possibility of such damage.
//
//M*/
#include "precomp.hpp"
#include "exif.hpp"
namespace {
class ExifParsingError {
};
}
namespace cv
{
ExifEntry_t::ExifEntry_t() :
field_float(0), field_double(0), field_u32(0), field_s32(0),
tag(INVALID_TAG), field_u16(0), field_s16(0), field_u8(0), field_s8(0)
{
}
/**
* @brief ExifReader constructor
*/
ExifReader::ExifReader() : m_format(NONE)
{
}
/**
* @brief ExifReader destructor
*/
ExifReader::~ExifReader()
{
}
/**
* @brief Get tag value by tag number
*
* @param [in] tag The tag number
*
* @return ExifEntru_t structure. Caller has to know what tag it calls in order to extract proper field from the structure ExifEntry_t
*
*/
ExifEntry_t ExifReader::getTag(const ExifTagName tag) const
{
ExifEntry_t entry;
std::map<int, ExifEntry_t>::const_iterator it = m_exif.find(tag);
if( it != m_exif.end() )
{
entry = it->second;
}
return entry;
}
/**
* @brief Parsing the exif data buffer and prepare (internal) exif directory
*
* @param [in] data The data buffer to read EXIF data starting with endianness
* @param [in] size The size of the data buffer
*
* @return true if parsing was successful
* false in case of unsuccessful parsing
*/
bool ExifReader::parseExif(unsigned char* data, const size_t size)
{
// Populate m_data, then call parseExif() (private)
if( data && size > 0 )
{
m_data.assign(data, data + size);
}
else
{
return false;
}
try {
parseExif();
if( !m_exif.empty() )
{
return true;
}
return false;
}
catch( ExifParsingError& ) {
return false;
}
}
/**
* @brief Filling m_exif member with exif directory elements
* This is internal function and is not exposed to client
*
* @return The function doesn't return any value. In case of unsuccessful parsing
* the m_exif member is not filled up
*/
void ExifReader::parseExif()
{
m_format = getFormat();
if( !checkTagMark() )
{
return;
}
uint32_t offset = getStartOffset();
size_t numEntry = getNumDirEntry( offset );
offset += 2; //go to start of tag fields
for( size_t entry = 0; entry < numEntry; entry++ )
{
ExifEntry_t exifEntry = parseExifEntry( offset );
m_exif.insert( std::make_pair( exifEntry.tag, exifEntry ) );
offset += tiffFieldSize;
}
}
/**
* @brief Get endianness of exif information
* This is internal function and is not exposed to client
*
* @return INTEL, MOTO or NONE
*/
Endianess_t ExifReader::getFormat() const
{
if (m_data.size() < 1)
return NONE;
if( m_data.size() > 1 && m_data[0] != m_data[1] )
{
return NONE;
}
if( m_data[0] == 'I' )
{
return INTEL;
}
if( m_data[0] == 'M' )
{
return MOTO;
}
return NONE;
}
/**
* @brief Checking whether Tag Mark (0x002A) correspond to one contained in the Jpeg file
* This is internal function and is not exposed to client
*
* @return true if tag mark equals 0x002A, false otherwise
*/
bool ExifReader::checkTagMark() const
{
uint16_t tagMark = getU16( 2 );
if( tagMark != tagMarkRequired )
{
return false;
}
return true;
}
/**
* @brief The utility function for extracting actual offset exif IFD0 info is started from
* This is internal function and is not exposed to client
*
* @return offset of IFD0 field
*/
uint32_t ExifReader::getStartOffset() const
{
return getU32( 4 );
}
/**
* @brief Get the number of Directory Entries in Jpeg file
*
* @return The number of directory entries
*/
size_t ExifReader::getNumDirEntry(const size_t offsetNumDir) const
{
return getU16( offsetNumDir );
}
/**
* @brief Parsing particular entry in exif directory
* This is internal function and is not exposed to client
*
* Entries are divided into 12-bytes blocks each
* Each block corresponds the following structure:
*
* +------+-------------+-------------------+------------------------+
* | Type | Data format | Num of components | Data or offset to data |
* +======+=============+===================+========================+
* | TTTT | ffff | NNNNNNNN | DDDDDDDD |
* +------+-------------+-------------------+------------------------+
*
* Details can be found here: http://www.media.mit.edu/pia/Research/deepview/exif.html
*
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return ExifEntry_t structure which corresponds to particular entry
*
*/
ExifEntry_t ExifReader::parseExifEntry(const size_t offset)
{
ExifEntry_t entry;
uint16_t tagNum = getExifTag( offset );
entry.tag = tagNum;
switch( tagNum )
{
case IMAGE_DESCRIPTION:
entry.field_str = getString( offset );
break;
case MAKE:
entry.field_str = getString( offset );
break;
case MODEL:
entry.field_str = getString( offset );
break;
case ORIENTATION:
entry.field_u16 = getOrientation( offset );
break;
case XRESOLUTION:
entry.field_u_rational = getResolution( offset );
break;
case YRESOLUTION:
entry.field_u_rational = getResolution( offset );
break;
case RESOLUTION_UNIT:
entry.field_u16 = getResolutionUnit( offset );
break;
case SOFTWARE:
entry.field_str = getString( offset );
break;
case DATE_TIME:
entry.field_str = getString( offset );
break;
case WHITE_POINT:
entry.field_u_rational = getWhitePoint( offset );
break;
case PRIMARY_CHROMATICIES:
entry.field_u_rational = getPrimaryChromaticies( offset );
break;
case Y_CB_CR_COEFFICIENTS:
entry.field_u_rational = getYCbCrCoeffs( offset );
break;
case Y_CB_CR_POSITIONING:
entry.field_u16 = getYCbCrPos( offset );
break;
case REFERENCE_BLACK_WHITE:
entry.field_u_rational = getRefBW( offset );
break;
case COPYRIGHT:
entry.field_str = getString( offset );
break;
case EXIF_OFFSET:
break;
default:
entry.tag = INVALID_TAG;
break;
}
return entry;
}
/**
* @brief Get tag number from raw exif data
* This is internal function and is not exposed to client
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return tag number
*/
uint16_t ExifReader::getExifTag(const size_t offset) const
{
return getU16( offset );
}
/**
* @brief Get string information from raw exif data
* This is internal function and is not exposed to client
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return string value
*/
std::string ExifReader::getString(const size_t offset) const
{
size_t size = getU32( offset + 4 );
size_t dataOffset = 8; // position of data in the field
if( size > maxDataSize )
{
dataOffset = getU32( offset + 8 );
}
if (dataOffset > m_data.size() || dataOffset + size > m_data.size()) {
throw ExifParsingError();
}
std::vector<uint8_t>::const_iterator it = m_data.begin() + dataOffset;
std::string result( it, it + size ); //copy vector content into result
return result;
}
/**
* @brief Get unsigned short data from raw exif data
* This is internal function and is not exposed to client
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return Unsigned short data
*/
uint16_t ExifReader::getU16(const size_t offset) const
{
if (offset + 1 >= m_data.size())
throw ExifParsingError();
if( m_format == INTEL )
{
return m_data[offset] + ( m_data[offset + 1] << 8 );
}
return ( m_data[offset] << 8 ) + m_data[offset + 1];
}
/**
* @brief Get unsigned 32-bit data from raw exif data
* This is internal function and is not exposed to client
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return Unsigned 32-bit data
*/
uint32_t ExifReader::getU32(const size_t offset) const
{
if (offset + 3 >= m_data.size())
throw ExifParsingError();
if( m_format == INTEL )
{
return m_data[offset] +
( m_data[offset + 1] << 8 ) +
( m_data[offset + 2] << 16 ) +
( m_data[offset + 3] << 24 );
}
return ( m_data[offset] << 24 ) +
( m_data[offset + 1] << 16 ) +
( m_data[offset + 2] << 8 ) +
m_data[offset + 3];
}
/**
* @brief Get unsigned rational data from raw exif data
* This is internal function and is not exposed to client
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return Unsigned rational data
*
* "rational" means a fractional value, it contains 2 signed/unsigned long integer value,
* and the first represents the numerator, the second, the denominator.
*/
u_rational_t ExifReader::getURational(const size_t offset) const
{
uint32_t numerator = getU32( offset );
uint32_t denominator = getU32( offset + 4 );
return std::make_pair( numerator, denominator );
}
/**
* @brief Get orientation information from raw exif data
* This is internal function and is not exposed to client
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return orientation number
*/
uint16_t ExifReader::getOrientation(const size_t offset) const
{
return getU16( offset + 8 );
}
/**
* @brief Get resolution information from raw exif data
* This is internal function and is not exposed to client
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return resolution value
*/
std::vector<u_rational_t> ExifReader::getResolution(const size_t offset) const
{
std::vector<u_rational_t> result;
uint32_t rationalOffset = getU32( offset + 8 );
result.push_back( getURational( rationalOffset ) );
return result;
}
/**
* @brief Get resolution unit from raw exif data
* This is internal function and is not exposed to client
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return resolution unit value
*/
uint16_t ExifReader::getResolutionUnit(const size_t offset) const
{
return getU16( offset + 8 );
}
/**
* @brief Get White Point information from raw exif data
* This is internal function and is not exposed to client
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return White Point value
*
* If the image uses CIE Standard Illumination D65(known as international
* standard of 'daylight'), the values are '3127/10000,3290/10000'.
*/
std::vector<u_rational_t> ExifReader::getWhitePoint(const size_t offset) const
{
std::vector<u_rational_t> result;
uint32_t rationalOffset = getU32( offset + 8 );
result.push_back( getURational( rationalOffset ) );
result.push_back( getURational( rationalOffset + 8 ) );
return result;
}
/**
* @brief Get Primary Chromaticies information from raw exif data
* This is internal function and is not exposed to client
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return vector with primary chromaticies values
*
*/
std::vector<u_rational_t> ExifReader::getPrimaryChromaticies(const size_t offset) const
{
std::vector<u_rational_t> result;
uint32_t rationalOffset = getU32( offset + 8 );
for( size_t i = 0; i < primaryChromaticiesComponents; i++ )
{
result.push_back( getURational( rationalOffset ) );
rationalOffset += 8;
}
return result;
}
/**
* @brief Get YCbCr Coefficients information from raw exif data
* This is internal function and is not exposed to client
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return vector with YCbCr coefficients values
*
*/
std::vector<u_rational_t> ExifReader::getYCbCrCoeffs(const size_t offset) const
{
std::vector<u_rational_t> result;
uint32_t rationalOffset = getU32( offset + 8 );
for( size_t i = 0; i < ycbcrCoeffs; i++ )
{
result.push_back( getURational( rationalOffset ) );
rationalOffset += 8;
}
return result;
}
/**
* @brief Get YCbCr Positioning information from raw exif data
* This is internal function and is not exposed to client
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return vector with YCbCr positioning value
*
*/
uint16_t ExifReader::getYCbCrPos(const size_t offset) const
{
return getU16( offset + 8 );
}
/**
* @brief Get Reference Black&White point information from raw exif data
* This is internal function and is not exposed to client
* @param [in] offset Offset to entry in bytes inside raw exif data
* @return vector with reference BW points
*
* In case of YCbCr format, first 2 show black/white of Y, next 2 are Cb,
* last 2 are Cr. In case of RGB format, first 2 show black/white of R,
* next 2 are G, last 2 are B.
*
*/
std::vector<u_rational_t> ExifReader::getRefBW(const size_t offset) const
{
const size_t rationalFieldSize = 8;
std::vector<u_rational_t> result;
uint32_t rationalOffset = getU32( offset + rationalFieldSize );
for( size_t i = 0; i < refBWComponents; i++ )
{
result.push_back( getURational( rationalOffset ) );
rationalOffset += rationalFieldSize;
}
return result;
}
} //namespace cv