Interface to access (Exif) metadata in binary form
The Exif data in a Jpeg image is in an "Exif APP1 segment". This is convenient because it contains all Exif data in a small block of memory (up to 64kB).
Various applications need an interface in Exiv2 to access such a binary Exif representation. Currently this interface is provided by ExifData::load / ExifData::copy (and similarly by IptcData::load / IptcData::copy for IPTC)
Issues with this current implementation:
1) It is specific to Jpeg.
2) It is in the wrong class (see bug #405), ExifData and IptcData shouldn't do parsing/writing of data from/to specific formats
3) There are a few slightly different valid requirements with regards to the beginning of this data block, e.g.:
a) start with the APP1 signature (see bug #465)
b) start with the Exif string (libjpeg)
c) start with the TIFF header (current implementation)
#2 Updated by Andreas Huggel almost 10 years ago
With the introduction of the new TIFF parser, the ExifData::load / ExifData::copy methods moved to ExifParser::decode and ExifParser::encode.
There is still a need to access the binary representation of the Exif data (starting with the TIFF header) of images in JPEG and other formats which have a similar Exif data block.
#4 Updated by Robin Mills almost 2 years ago
- Target version changed from 1.0 to 0.28
I'm moving this issue to v0.27. The
image->printStructure() interface provides this interface for ICC profiles and I'm confident we can add a
kpsPrintStructure enumerator to export binary information to a stream. In v0.26, the user can use
$ exiv2 -pX foo.xxx and
$ exiv2 -pC foo.xxx to extract XMP and ICC Profiles from an image. I believe it's straightforward to extend this to implement options such as -pE which would create a TIFF from the Exif metadata in an image.