Amiga IFF Preview

A Visual Studio Code extension for previewing Amiga .iff, .ilbm, and .lbm images, including uppercase file extensions.

Created by Menno Homan (Windigo).

Installation

Once published, find Amiga IFF Preview by Menno Homan (Windigo) in the Extensions view, or search for @id:MennoHomanWindigo.amiga-iff-preview. To install a VSIX manually:

1. Open the Command Palette in VS Code (Cmd+Shift+P on macOS, Ctrl+Shift+P on Windows/Linux).
2. Choose Extensions: Install from VSIX… and select amiga-iff-preview-0.1.5.vsix.
3. Open an .iff file. The preview opens automatically.

The extension requires a trusted workspace to run. If the workspace is in Restricted Mode, review its trust settings before testing the preview.

If VS Code opens another editor, choose Reopen Editor With… → Amiga IFF Preview in the Command Palette. After updating the extension, run Developer: Reload Window if needed.

Features

• ILBM with 1–8 bitplanes, HAM6/HAM8, Extra Half-Brite, and 24-bit RGB.
• Packed bitmap (PBM), without a separate mask.
• Uncompressed and ByteRun1 image data.
• Transparent color and ILBM mask plane; checkerboard behind transparent pixels.
• Fit to window and 100%, 200%, 400%, 800% zoom with crisp pixels.
• Optional pixel aspect ratio from the BMHD header.
• Automatic refresh when the file changes on disk.
• Local, read-only preview with no runtime dependencies or network traffic.

Limitations

IFF is a container: audio (8SVX), ANIM, and other FORM types are not supported. Color cycling is displayed as a still image. PCHG, SHAM, CTBL, DEST, DCOL, and lasso masks are rejected. Missing or incomplete palettes use grayscale fallback colors with a warning. Files are limited to 64 MiB and images to 16 megapixels. Large images may briefly occupy the extension host while decoding.

Development

Open this folder in VS Code and press F5. Open an IFF file in the new Extension Development Host window. No build step is required.

npm test
npm run package

Packaging uses @vscode/vsce through npm. The extension itself has no external dependencies.

Format reference: AmigaOS ILBM specification. Editor integration: VS Code Custom Editor API.

Author and license

Copyright © 2026 Menno Homan (Windigo). Released under the MIT License.