OCA, The Open Cel Animation format

OCA is an open format to ease the exchange of traditionnal/frame-by-frame/cel animation between different applications.

Principles

• OCA has to be open and simple: it must be easy to implement an exporter or importer in any application providing a scripting API.

• As it relies on existing and standard file formats (images and json/text files) stored in a simple folder, the OCA format can be imported in any application manually, even if the application does not directly support it.

• Full freely available documentation.

• Extensible, but private undocumented extensions should be excluded, any extension should be added to the spec and documentation of the file format.

• OCA stores the most common features used by drawing/animation software: layers, groups, blending modes, animation exposure (x-sheet), etc.

• Applications are not expected to support all features of the file format, but when manipulating the file they should not lose any information they cannot handle

Implementation

We’re providing some implementations of OCA as add-ons for a few applications, and third-party developers have added support for it in their applications too. If the application you need is not listed, you can politely ask for it in a feature request and we’ll consider it.

App	Add-on	Exports	Imports	Comments	Maintainer
After Effects	DuIO	-	◉		RxLaboratory / Duduf
Animation Paper	Native	◉	?		Niels Krogh Mortensen
Blender	Bluik	○	◉	Exporter for Grease Pencil planned.	RxLaboratory / Duduf
Callipeg	Native	◉	-		Enoben
Fusion	Reactor (using Vonk Ultra)	-	◉		We Suck Less
Krita	OCA for Krita	◉	○		RxLaboratory / Duduf
OpenToonz	Native	◉	-	Some limitations, see https://github.com/opentoonz/opentoonz/pull/4483	Dwango
Photoshop	OCA	○	-		RxLaboratory / Duduf
TVPaint	OCA	○	-		RxLaboratory / Duduf
XDTS	OCA to XDTS converter	◉	◉	XDTS is a format supported by OpenToonz, Tahoma, Clip Studio Paint EX and Toei Animation Digital Exposure Sheet.	Wolf In A Bow

Legend:
◉ | Available
◔ | In development
○ | Planned
- | Not supported

Icon

You may use these icons when talking about or implementing OCA.

SVG:

PNG:

(Right-click on the images to save them)

Features

OCA supports the most common features of all drawing/animation software:

• Layers
• Layer Groups (and pass through mode if any)
• Layer Labels
• Layer Visibility
• Layer Blending Modes
• Layer Alpha options (inherit alpha)
• Keyframes and their duration (animation exposure)
• Opacity Keyframes
• Layer Sizes and Coordinates
• Document background color
• Document color depth
• Duration
• Framerate

All these properties are stored in a simple JSON file, and the images are stored in standard image file formats: PNG, EXR, SVG…

Everything is assembled in a folder which name ends with .oca. The JSON file is at the root, while the images are stored in subfolders corresponding to layers and groups.

More features may be added later, have a look at the Roadmap!

Specifications

• Examples
• Folder Structure
• File Specifications

JSON Objects

• Metadata Object Specs
• Root Object Specs
• Layer Object Specs
• Frame Object Specs

Values

• Durations
• Coordinates and transform
• Opacity, Colors and Color Depth
• Layer Types
• Blending Modes
• Layer Labels

License

Software

Copyright (C) 2020-2022 Nicolas Dufresne and Contributors.
This program is free software; you can redistribute them and/or modify them under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with DuBuilder. If not, see http://www.gnu.org/licenses/.

This Documentation

Copyright (C) 2020-2022 Nicolas Dufresne and Contributors.
Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation;
with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled “Documentation License”.