Extract Sprites (OCaml CLI)

A fast, dependency-light sprite extractor written in OCaml.
It loads an image, thresholds it, finds connected components, and crops each sprite into its own PNG file.

Example usage: For developing games, you need to extract a lot of sprites off a spritesheet and create an atlas with Texture Packer Pro.

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Features

• Pure OCaml implementation — no Python or C dependencies (No OpenCV)
• Uses ImageLib for image I/O (.png, .jpg, etc.)
• Finds connected regions of non transparent pixels
• Filters small fragments of pixels
• Exports cropped sprite frames as PNGs
• CLI built with Cmdliner for flexible options

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Installation

OCaml, dune, and ImageLib:

opam install dune cmdliner imagelib
dune build

Command-line Options

Flag	Default	Description
INPUT	(required)	Path to spritesheet (.png, .jpg, etc.)
-o, --output-dir DIR	frames	Directory to write extracted sprites
-p, --prefix PREFIX	frame_	Prefix for output filenames
-m, --min-area AREA	64	Minimum connected component area (in pixels)
-t, --alpha-threshold THRESH	1	Pixel threshold for foreground (0–255)

Examples

Extract sprites using all defaults

dune exec -- ./extract_sprites.exe link_sprites.png

Custom output directory and prefix

dune exec -- ./extract_sprites.exe link_sprites.png \
  -o extracted_frames -p car_ -m 200 -t 5

• Works best on images with clear transparency between sprites.

• If tiny particles (dust, exhaust, particals) are cut as separate frames, increase --min-area.