Photoshop Image Resources
Photoshop Image Resources consists of a sequence of blocks, each with a numeric Resource ID indicating the type of data stored in the block. Each block also contains a name, but the name is often left empty.
Each block begins with ASCII characters "8BIM", a signature which appears in several Photoshop formats.
Not all Resource IDs are publicly documented.
Apparently Photoshop data (at least in Mac formats) also makes use of the ANPA-1312 format, a news-media industry markup format, for metadata storage.
Custom application data ("plug-in resources") can be stored using resource IDs 4000–4999 (0x0FA0–0x1387). There might be more information about this somewhere in the Photoshop SDK.
[TODO: How are these resources identified? 1000 ID numbers seems insufficient for global uniqueness. Some or all plug-in resources appear to begin with a FourCC.]
[TODO: Is there any documentation available about specific plug-in resource formats?]
- In a TIFF file, tag 34377 contains Photoshop Image Resources.
- In a JPEG file, an APP13 marker with an identifier of "Photoshop 3.0" contains Photoshop Image Resources.
- Resource ID 0x0404 contains IPTC data.
- Resource ID 0x040c may contain a thumbnail in JPEG/JFIF format.
- Resource ID 0x040F contains an ICC profile.
- Resource ID 0x0422 contains Exif data.
- Resource ID 0x0424 contains XMP data.