Adobe Photoshop File Formats
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Preface
Welcome to the Adobe Photoshop® File Format Specification!
This document is the detailed specification of the Adobe Photoshop file format and other pertinent file formats that Adobe Photoshop reads and writes.
Audience
This document is provided for 3rd parties to read and write the Photoshop native file format. This document does not explain how to interpret the data. This document describes the format of the data only.
What Is In This Document
This document has three chapters:
The Photoshop File Format describes the Photoshop PSD and PSB native file format in detail.
Other Document File Formats discusses Photoshop's handling of the EPS and TIFF file formats, which Photoshop can also create and read.
Additional File Formats describes the formats of other files used by Photoshop to store information about such items as colors, contours, curves, levels and so forth.
For more information about file formats, you may wish to consult the Encyclopedia of Graphics File Formats by James D. Murray & William vanRyper (1994, O'Reilly & Associates, Inc., Sebastopol, CA, ISBN 1-56592-058-9).
The Photoshop File Format
This chapter discusses the Photoshop native file format
OS
|
Filetype/extension
|
|---|---|
Mac OS
|
8BPS
|
Windows
|
.PSD
|
Large Document Format
The Large Document Format (8BPB/PSB) supports documents up to 300,000 pixels in any dimension. All Photoshop features, such as layers, effects, and filters, are supported by the PSB format. The PSB format is identical to the Photoshop native format in many ways. This document will cover the differences found in the PSB format by donating a **PSB** marker.
Windows
All data is stored in big endian byte order. On the Windows platform, you must byte swap short and long integers when reading or writing.
Mac OS
For cross-platform compatibility, all information needed by Photoshop is stored in the data fork. For interoperability with other Macintosh applications, however, some information is duplicated in resources stored in the resource fork of the file:
For compatibility with image cataloging applications, the 'pnot' resource id 0 contains references to thumbnail, keywords, and caption information stored in other resources.
The thumbnail picture is stored in a 'PICT' resource, the keywords are stored in 'STR#' resource 128 and the caption text is stored in 'TEXT' resource 128. For more information on the format of these resources see Inside Macintosh: QuickTime Components and the Extensis Fetch Awareness Developer's Toolkit .
Photoshop also creates 'icl8' -16455 and 'ICN#' -16455 resources containing thumbnail images which will be shown in the Mac OS Finder.
All of the data from Photoshop's File Info dialog is stored in 'ANPA' resource 10000. The data in this resource is stored as an IPTC-NAA record 2.For more information on the format of this resource, see the documents in the IPTC folder of the Documentation folder.