Aseprite Script: Amiga ACE Palette Exporter

This Aseprite extension provides tools for working with Amiga palettes: adjusting colors to the 12-bit OCS format and exporting to the ACE .plt format used by the ACE game engine.

https://sphair.itch.io/aseprite-script-plt-export

Changelog

v1.1.0

• Added Adjust to Amiga Palette (12-bit) command - converts palette colors to Amiga-compatible 12-bit precision

v1.0.0

• Added Export ACE Palette (.plt) command - exports palette to ACE .plt format for Amiga development

Installation

As Extension

1. Download pltexport.aseprite-extension
2. In Aseprite, go to Edit > Preferences > Extensions
3. Click Add Extension and select pltexport.aseprite-extension
4. Restart Aseprite
5. The commands will appear in the Palette menu (palette panel dropdown)

As Standalone Script

You can also run Amiga ACE Palette Export.lua directly from File > Scripts > Run Script without installation. Note, with this approach you only get access to the PLT exporter, not the palette tools.

Usage

Adjust to Amiga Palette (12-bit)

Converts all colors in the current palette to Amiga-compatible 12-bit colors (4096 color palette):

1. Open a sprite with an indexed palette in Aseprite
2. Click the menu button in the Palette panel and select Adjust to Amiga Palette (12-bit)
3. All palette colors will be adjusted to 4-bit precision per channel
4. A summary shows which colors were changed

This works on any number of colors and modifies the palette in place (can be undone with Ctrl+Z).

Export ACE Palette (.plt)

Exports the palette to ACE .plt format (limited to 32 colors):

1. Open a sprite with a palette in Aseprite
2. Click the menu button in the Palette panel and select Export ACE Palette (.plt)
3. Choose a filename and location
4. Click Export

PLT Format Specification

The ACE .plt format is a simple binary format:

Offset | Size | Description
-------|------|-----------
0x00   | 1    | Color count (1-32) 
0x01   | 2*N  | Color data (2 bytes per color) 

Color Encoding

Each color is stored in 2 bytes representing Amiga OCS 12-bit color:

• Byte 1: 0000RRRR - Lower 4 bits contain Red channel (0-15)
• Byte 2: GGGGBBBB - Upper 4 bits contain Green, lower 4 bits contain Blue

This matches the Amiga OCS color format where each RGB channel has 4-bit precision (16 levels per channel).

Color Conversion

8-bit RGB colors (0-255) are converted to 4-bit (0-15) using the same method as the Amiga OCS Palette Mixer:

8-bit to 4-bit (export):

value_4bit = floor(value_8bit / 255 * 15) 

Example

A palette with 3 colors:

• Color 0: RGB(255, 0, 0) → Red = 15, Green = 0, Blue = 0 → Bytes: 0x0F, 0x00
• Color 1: RGB(0, 255, 0) → Red = 0, Green = 15, Blue = 0 → Bytes: 0x00, 0xF0
• Color 2: RGB(0, 0, 255) → Red = 0, Green = 0, Blue = 15 → Bytes: 0x00, 0x0F

File contents (hex): 03 0F 00 00 F0 00 0F

Loading in ACE

Use the ACE palette functions to load the .plt file:

#include <ace/utils/palette.h>  
UWORD palette[32]; 
paletteLoadFromPath("data/mypalette.plt", palette, 32); 

License

This is free and unencumbered software released into the public domain. See UNLICENSE for details.