FastPack

Texture atlas packer written in Rust 2024. Replaces TexturePacker with a native GUI as the primary interface, plus a full-featured CLI and TUI.

Features

• Packing algorithms — MaxRects (5 heuristics), Grid, Basic strip
• Trim modes — None, Trim, Crop, CropKeepPos, Polygon (convex hull)
• Export formats — JSON Hash, JSON Array, Phaser 3, PixiJS
• Compression — PNG via oxipng (lossless), JPEG via mozjpeg, WebP, lossy PNG via imagequant
• Alias detection — content-hash dedup with pixel verification
• Sprite features — extrusion, rotation, nine-patch metadata, pivot points
• Multi-resolution — scale variants with per-variant suffix and resampling filter
• Watch mode — repack on file change
• Project files — .fpsheet TOML format
• Multipack — overflow sprites across multiple atlas sheets

Install

Download a prebuilt binary from the releases page.

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

# Open the TUI
fastpack tui 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; identical output to json_hash, distinguished by format ID.

License

Licensed under MIT.