fastpack 0.21.0

FastPack — modern texture atlas packer
fastpack-0.21.0 is not a library.

FastPack

crates.io CI rustc 1.85+

Texture atlas packer written in Rust. Native GUI as the primary interface, plus a full CLI and TUI. Designed as an open-source replacement for TexturePacker.

Features

Packing

  • MaxRects (5 heuristics), Grid, and Basic strip algorithms
  • Trim modes: None, Trim, Crop, CropKeepPos, Polygon (convex hull)
  • Extrusion, rotation, nine-patch metadata, pivot points
  • Alias detection — deduplicates pixel-identical sprites
  • Multipack — overflow sprites across multiple sheets
  • Multi-resolution scale variants with per-variant suffix

Export

  • JSON Hash, JSON Array, Phaser 3, PixiJS
  • PNG (oxipng lossless), JPEG (mozjpeg), WebP, lossy PNG (imagequant)

GUI

  • Real-time atlas preview
  • Collapsible sprite tree with thumbnail previews
  • Watch mode — repacks on file change
  • .fpsheet project files (TOML)
  • Multi-language UI

Install

Download the installer for your platform from the releases page:

  • Windows — fastpack-windows-x86_64.msi
  • macOS (Apple Silicon) — fastpack-macos-aarch64.dmg
  • macOS (Intel) — fastpack-macos-x86_64.dmg
  • Linux — fastpack-linux-x86_64.tar.gz

macOS note: The app is not code-signed, so macOS will show "FastPack is damaged and can't be opened." after mounting the DMG. Run this once after copying the app to /Applications:

xattr -cr /Applications/FastPack.app

Or install from crates.io:

cargo install fastpack

Usage

# Open the GUI (default when no subcommand is given)
fastpack

# Pack a directory of sprites
fastpack pack sprites/ --output output/

# Pack with options
fastpack pack sprites/ --output output/ \
  --max-width 2048 --max-height 2048 \
  --trim-mode trim \
  --data-format phaser3 \
  --allow-rotation

# Load settings from a project file
fastpack pack --project atlas.fpsheet

# Watch for changes and repack automatically
fastpack watch sprites/ --output output/

# Split an atlas back into individual sprites
fastpack split atlas.png atlas.json --output-dir sprites/

# Generate a default project file
fastpack init --output atlas.fpsheet

Project File

Settings live in a .fpsheet TOML file:

[meta]
version = "1"

[output]
name = "atlas"
directory = "output/"
texture_format = "png"
pixel_format = "rgba8888"
data_format = "json_hash"
quality = 95

[layout]
max_width = 4096
max_height = 4096
size_constraint = "pot"
force_square = false
allow_rotation = true
pack_mode = "good"
border_padding = 2
shape_padding = 2

[sprites]
trim_mode = "trim"
trim_threshold = 1
extrude = 0
detect_aliases = true

[algorithm]
type = "max_rects"
heuristic = "best_short_side_fit"

[[variants]]
scale = 1.0
suffix = "@1x"
mode = "smooth"

[[sources]]
path = "sprites/"
filter = "**/*.png"

Export Formats

data_format in the project file or --data-format on the CLI accepts:

  • json_hash — TexturePacker-compatible JSON with frames as an object keyed by sprite ID. Default.
  • json_array — Same structure but frames as an array, each entry with a filename field.
  • phaser3 — Single JSON file with a textures array. Compatible with scene.load.multiatlas().
  • pixijs — JSON Hash format compatible with PixiJS sprite sheet loaders.

Building from Source

Requires Rust 1.85+.

git clone https://github.com/Hexeption/FastPack
cd FastPack
cargo build --release -p fastpack

The binary is at target/release/fastpack.

License

Licensed under MIT.