FLI/FLC Format Guide

Available Conversions

About FLI/FLC Format

FLI and FLC are animation file formats collectively known as FLIC, created by Autodesk for their Animator and Animator Pro products. FLI (1985, Autodesk Animator) stores animations at a fixed resolution of 320x200 pixels with 256 colors from an indexed palette, while FLC (1992, Animator Pro) removes the resolution restriction and supports arbitrary frame sizes. Both formats store sequences of frames using delta compression, where only the differences between consecutive frames are recorded, resulting in efficient storage for animation sequences with relatively static backgrounds. FLIC files use palette mode ("P") with a maximum of 256 colors, and each frame represents a complete image that can be extracted independently. Pillow reads both FLI and FLC files natively through its FliImagePlugin, extracting the first frame as a palette-based image. The formats were ubiquitous in the DOS era for game cinematics, presentation graphics, scientific visualizations, and multimedia applications.

History of FLIC

The FLIC animation format originated with Autodesk Animator, released in 1985 for DOS-based PCs. Animator was one of the first affordable 2D animation programs for personal computers, enabling artists and designers to create frame-by-frame animations on standard IBM PC hardware. The original FLI format was designed for the 320x200 resolution of VGA Mode 13h, the standard 256-color video mode used by most DOS applications and games. When Autodesk released Animator Pro in 1992, the format was extended to FLC, removing the fixed resolution limitation and adding support for higher resolutions and improved delta compression. FLIC files became the de facto standard for animation on DOS systems throughout the late 1980s and 1990s. They were widely used in video game cutscenes (including titles like Wing Commander and Crusader: No Remorse), educational software, scientific visualizations, architectural walkthroughs, and multimedia CD-ROM presentations. The format's efficient delta compression made it particularly well-suited for the limited storage and processing power of the era. While FLIC has been superseded by modern video codecs for animation playback, the format remains historically significant as one of the earliest widely-adopted digital animation standards for personal computers.

Technical Details

FLIC files use a chunk-based binary structure with a file header followed by frame chunks. The header contains metadata including frame count, width, height, color depth (always 8 bits), frame delay in milliseconds, and format identifier (0xAF11 for FLI, 0xAF12 for FLC). Each frame chunk can contain multiple sub-chunks that describe palette changes and pixel updates. The key compression techniques include: COLOR_256 chunks for palette updates, BYTE_RUN (RLE) for the first frame, and DELTA_FLC (line-skip, packet-based delta) for subsequent frames. FLI uses a simpler DELTA_FLI compression with word-oriented packets. The delta compression is particularly effective for typical animations where large portions of each frame remain unchanged from the previous one. Frame delays in FLI are measured in 1/70th of a second intervals (matching the VGA vertical retrace rate), while FLC uses millisecond timing for more precise playback control. The format does not support audio, so FLIC animations were typically synchronized with separate sound files in multimedia applications.

Common Applications

FLIC animations were extensively used across the DOS computing era and continue to appear in retro computing and digital preservation contexts. In video games, FLI/FLC files served as cutscene cinematics, animated introductions, and in-game sequences for hundreds of DOS-era titles. Scientific and engineering applications used FLIC to animate simulation results, medical imaging sequences, and CAD model rotations. Multimedia authoring tools like Macromedia Director and Asymetrix ToolBook could import FLIC animations for interactive presentations and CD-ROM titles. Architectural visualization firms used Animator Pro with FLC output to create walkthrough animations of building designs. Educational software publishers relied on FLIC for animated lessons and interactive diagrams. Today, FLIC files are primarily encountered when preserving and archiving DOS-era software, extracting game assets for modding communities, converting legacy animation libraries to modern formats, and studying the history of computer animation. Converting FLI/FLC frames to PNG, JPG, or WebP is common when extracting individual frames for web display, documentation, or further editing in modern image editing applications.

Advantages and Disadvantages