libpicinfo: A library to read image information

0.0.2

libpicinfo is a C++ library for reading auxiliary information from images. it currently supports TIFF, JPEG and Canon RAW files (CR2). Current feautures includes:

• intuitive C++ usage
• supports EXIF 2.2 specification
• supports TIFF files
• supports JPEG files (with/without JFIF header)
• supports RAW formats of digital cameras (currently Canon CR2 only)
• no library dependency other than C++ standard library
• fast startup time
• fast lookup of tags

Future release will support:

• other RAW camera formats (e.g. Canon CRW, Nikon, etc)
• decoding manufacturer notes (Canon, Nikon, Olympics)
• modification of the images
• C wrapper interface

Reading data from image files is as easy as:

    #include <ExifFile.hpp>
    #include <ExifEntry.hpp>
    #include <ExifTags.hpp>

    using namespace picinfo ;
    CExifFile image( "hello.jpg" ) ;
    CExifFile::iterator i = image.find( exif::f_number ) ;
    
    // check if the tag is present
    if ( i != image.end( ) )
        std::cout << "Aperature is " << *i << std::endl ;

Or if you want to iterate all tags in the file:

    #include <ExifFile.hpp>
    #include <ExifEntry.hpp>
    #include <ExifTags.hpp>
    
    using namespace picinfo ;
    CExifFile image( "hello.jpg" ) ;
    for ( CExifFile::iterator i = image.begin( ) ; i != image.end( ) ; ++i )
        std::cout << "The " << i->LongName( ) << " is " << *i << std::endl ;

After retrieving an data entry in the file, you can convert it to any type it supports by calling the picinfo::CExifEntry::As() function:

    #include <ExifFile.hpp>
    #include <ExifEntry.hpp>
    #include <ExifTags.hpp>
    
    using namespace picinfo ;
    
    CExifFile image( "hello.jpg" ) ;
    CExifFile::iterator i = image.find( exif::exposure_time ) ;
    
    // check if the tag is present
    if ( i != image.end( ) )
    {
        double t = i->As<double>( ) ;
        std::cout << "Exposure time is " << t << std::endl ;
    }

The template magic behind As() allows you to interpret the values of the entry using a different type than its actual type. For example, the actual type of the exposure_time entry is rational number, but it is can converted to double like the above example does. In addition, all types can be converted to std::string. It will be formatted in a human readable way.

If the conversion is not supported, e.g. converting a string entry to an integer, an exception will be thrown or the code cannot be compiled.

See here for all tags supported by libpicinfo.

Platform Supported

This project is being develop under Linux 2.6, and tested on Linux 2.6 and Windows XP Professional. The code depends only on the standard C++ library, so it should be ported easily to other platforms. The only catch is it needs a recent C++ compiler to compile the templates properly. I use gcc 3.4.4 on Linux and MSVC 7.1 on Windows, and both worked fine.

Installation

Under *nix(-like) environments, the standard autotools method works:

    ./configure
    make
    make install

The name of library will be libpicinfo. It can be link with -lpicinfo in the gcc command line.

If you are a autotools wizard and thinks my usage of autotools sucks, you are more than welcomed to submit a patch.

Under win32 environment, there are project files under the win32 directory. You can use Visual C++ .NET 2003 (a.k.a. VC 7.1) to compile it. Visual C++ 6.0 is not supported.

Contribute

If you want to contribute to the project, please send email to me on the following areas:

• Bug reports. A sample image and test program that will crash the code in the library. Backtraces are very welcome. A patch to fix the problem is even more welcomed.
• Documentation patches. Everything (including this web page) is done using Doxygen.
• Sample images and specifications of the image format you would like to get it supported.
• Patches that ports to other platforms/compilers, especially patches to the autotools files.
• Test suites. A sample image and code to read and verify the data of that image.

I will try to setup a mailing list for discussions of the development.

License

The libpicinfo library is release under GNU Lesser General Public License (LGPL). That means it is Free Software, but can be used by (linked to) in proprietary software, though all modification of the library MUST be released under LGPL, and the library MUST be linked dynamically.

Author(s)

Nestal W.H. Wan

Links

• Download libpicinfo
• Sourceforge Project Page

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