XCF (file format)

XCF, short for eXperimental Computing Facility,^[1] is the native image format of the GIMP image-editing program. It supports saving each layer, the current selection, channels, transparency, paths and guides.

The image data saved are compressed only by a simple RLE algorithm, but GIMP supports compressed files, using either gzip or bzip2. The compressed files can be opened as normal image files.

The XCF file format is mostly backward compatible. For example, GIMP 2.0 can save text in text layers while GIMP 1.2 can not. Text layers saved in GIMP 2.0 will open as ordinary image layers in GIMP 1.2.

The use of XCF as a data interchange format is not recommended by the GIMP developers,^[2] since the format reflects the GIMP's internal data structures, and there may be minor format changes in future versions. The source code of GIMP itself (which is freely available) is the reference documentation of the format. Henning Makholm (see XCFTools below) has written a specification which has been adopted by the GIMP developers. In addition, a collaborative effort between the GIMP developers and Krita developers is underway to design a raster file format called OpenRaster, modelled on the OpenDocument format, for use in both applications in a future version.

Software support

XCF is used as a file format in other programs besides the GIMP:

• Seashore is a lightweight native Mac OS X image editing program based on the GIMP.
• CinePaint is a fork of the GIMP with support for 16 bit and 32 bit floating point channels, and 16 bit integer channels. There are plans for CinePaint to move away from XCF as a file format. The XCF file format used in CinePaint has diverged from the GIMP's native format, so XCF files created in the GIMP cannot be opened in Cinepaint, and vice versa.

Some image viewers and conversion software can read the format with varying degrees of success:

• DBGallery displays multi-layer non-indexed images and allows indexing, searching and other photo database operations.
• ImageMagick has an XCF reader module that can read single-layer non-indexed images.
• Project Dogwaffle including PD Pro, PD Particles and PD Artist imports XCF files using the ImageMagick library.
• Krita imports XCF files using the GraphicsMagick library.
• ShowImg can display multi-layer non-indexed images.
• Gwenview can display multi-layer non-indexed images.
• GImageView [1] can display multi-layer non-indexed images.
• Digikam can display multi-layer non-indexed images.
• Imagine can display single-layer non-indexed images.
• XnView can display single-layer non-indexed images.
• Inkscape added support for XCF export in the 0.44 release.^[3]
• XCFTools [2] by Henning Makholm is a set of utilities which deformats and composes XCF images. It allows extraction of individual layers, or an entire composed image, as PNG or PNM.
• IrfanView can display multi-layer images (composite image and individual layers).

References