Split ExifDirectory into sub directories to avoid tag collisions

[GoogleCodeExporter]

Currently Metadata Extractor merged IFD0, Exif SubIFD and IFD1 into 
ExifDirectory.

It turns out that IFD0 (main image) and IFD1 (thumbnail image) use some of the 
same tags, and so the thumbnail values are overwriting values from the main 
image.

Specifically:

0x0112 Orientation     : Horizontal (normal)
0x011a X Resolution    : 72
0x011b Y Resolution    : 72
0x0128 Resolution Unit : inches

People are noticing that after rotating, the orientation may be incorrect, and 
that the resolution is always reported as 72 (common for thumbnails).

The solution is to split ExifDirectory into ExifIFD0Directory, 
ExifSubIFDDirectory and ExifIFD1Directory.

This will make it easier to support writing metadata back to files in future 
too.

Original issue reported on code.google.com by drewnoakes on 2 May 2011 at 10:54

[GoogleCodeExporter]

Note that as of version 2.5.0-RC1, the split of ExifDirectory in two has 
existed. However, now these two directories have many of the same tags. So in 
fact some kind of composition is required in the code, and it will take finding 
the appropriate part of the spec in order to fix this properly.

See http://code.google.com/p/metadata-extractor/wiki/ChangeLog

Original comment by drewnoakes on 16 Oct 2012 at 4:13

• Changed title: Split ExifDirectory into sub directories to avoid tag collisions
• Added labels: Component-TagComprehension, Milestone-2.7.0, Motive-Correctness

[GoogleCodeExporter]

This issue has been migrated along with the project to GitHub:

https://github.com/drewnoakes/metadata-extractor/issues/3

Original comment by drewnoakes on 19 Nov 2014 at 11:23