Online Help for Chasys Draw IES: File Formats - Chasys Draw Image (CD5), version 4

File Formats - Chasys Draw Image (CD5), version 4

What is CD5?

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 4.04, 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:

Feature Comments
Lossless compression since ver. 1
Transparency via independent alpha channel since ver. 1
Large image support (up to 65,535 by 65,535) since ver. 2
Adaptive multi-pass lossless compression (JpCHA² ACSC) since ver. 2
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

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.



Copyright © John Paul Chacha, 2001-2024