Image::ExifTool::AFCP - Read/write AFCP trailer
This module is used by Image::ExifTool
This module contains definitions required by Image::ExifTool to extract information from the AFCP trailer. Although the AFCP specification is compatible with various file formats, ExifTool currently only processes AFCP in JPEG images.
AFCP is a specification which allows meta information (including IPTC) to be appended to the end of a file.
It is a poorly designed protocol because (like TIFF) it uses absolute offsets to specify data locations. This is a huge blunder because it makes the AFCP information dependent on the file length, so it is easily invalidated by image editing software which doesn't recognize the AFCP trailer to fix up these offsets when the file length changes. ExifTool will attempt to fix these invalid offsets if possible.
Scanning for AFCP information may be time consuming, especially when reading from a sequential device, since the information is at the end of the file. In these instances, the ExifTool FastScan option may be used to disable scanning for AFCP information.
Copyright 2003-2013, Phil Harvey (phil at owl.phy.queensu.ca)
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.