XCF

XCF is the native file format for GIMP (GNU Image Manipulation Program). It supports all the possible information about an image, including layers and transparency, except for undo information.

An XCF file may be compressed using gzip or bzip2 format. Such files usually use extension .xcf.gz, .xcfgz, .xcf.bz2, or .xcfbz2.

See GIMP for additional GIMP formats and information.

Identification
The first 9 bytes of an XCF file are the ASCII string " ".

Specifications
The Wikipedia article says that the reference documentation is the source code for GIMP itself.
 * Specification of the XCF file format (draft)

Software

 * GIMP
 * ImageMagick
 * Konvertor
 * XnView
 * abydos

Sample files

 * https://telparia.com/fileFormatSamples/image/xcf/

Links

 * Wikipedia article