CD5 is Chasys Draw IES’s native image file format, which
supports all the features provided by the suite. It is a binary tag-based container
format for images and animations. Image data in CD5 files is losslessly compressed using a highly optimized adaptive proprietary multi-pass algorithm called ACSC. The current version is
4.08, and offers many enhancements over previous versions. Although CD5 is designed to be used as a working format (i.e. a format for storing work that is currently
being edited or that may need to be modified later), it may be used for distribution because the policy is to support all versions of it in future versions, a policy that has
been observed faithfully since 2001.
The name CD5 comes from the original specification of the format, named Chasys Draw Image Specification 5. There were earlier specifications, but those never made it to a mass-market release.
Chasys Draw IES supports exporting to other layered and/or native file formats, including Adobe Photoshop’s PSD, GIMP’s XCF and OpenRaster, which is a cross-platform layered file format.
What features does CD5 offer?
CD5 supports all image semantics available in the Chasys
Draw IES suite. A few of these are:
Encryption and password protection, with placeholder auto-generation
since ver. 2 rev. 40, supported but not used by newer versions
Tag-based container format
since ver. 3 rev. 00
Layers
since ver. 3 rev. 01
Layer naming and notes
since ver. 3 rev. 01
Multi-resolution / Mipmapping
since ver. 3 rev. 01
High Dynamic Range
since ver. 3 rev. 01, currently not used
16-bit-per-channel Sampling
since ver. 3 rev. 01, currently not used
Animation, frame-based
since ver. 3 rev. 02
Metadata, including paths, text, adjustment layers and other data
since ver. 3 rev. 05
Full UNICODE and UTF-8 support
since ver. 3 rev. 10
Layer groups
since ver. 3 rev. 24
Per-layer global transparency
since ver. 3 rev. 26
Inter-frame compression with variable reference
since ver. 3 rev. 30
Animation, object-based with descriptors
since ver. 3 rev. 31
Sprite-sheet definition and animation
since ver. 3 rev. 32
Simpler tag format with support for extra-large tags
since ver. 4 rev. 01
Extra-large image support (practically unlimited)
since ver. 4 rev. 01, currently not used
Adaptive variable bit-depth with zero-bit option
since ver. 4 rev. 04
GCCA colorspace for better compression of real-world photos
since ver. 4 rev. 06
Embedded Thumbnails
since ver. 4 rev. 08
CD5 is an extensible format that allows for new features to be supported without changing the file format. New features rarely ever require a change to the CD5 file format specification; all that is required is application-level support. Backwards compatibility, and in many cases forwards compatibility, is maintained as much as possible. Either way, new versions of the software fully support all previous versions of the format.
