pngine

Pngine

PNG-8 encoder for Kotlin Multiplatform — Android, JVM/desktop, iOS and the web (JS and Wasm). Palette quantization with full alpha support, written in pure Kotlin: no NDK, no native binaries, no third-party dependencies, and no java.util.zip — the DEFLATE compressor is part of the library.

ARGB pixels in, PNG ByteArray out. On Android, android.graphics.Bitmap in as well.

val bytes = Pngine.encodePixels(argbPixels, width, height)

Why it exists

Bitmap.compress(PNG, …) always writes 24/32-bit PNG and ignores the quality argument, so it does not reduce colour depth at all. The usual answer is pngquant / libimagequant, which is excellent but needs JNI and is GPL-or-commercial.

Pngine fills the gap: Apache-2.0, pure Kotlin, runs on device — and, being pure Kotlin all the way down to DEFLATE, runs unchanged on iOS, desktop and in the browser.

It is not a reimplementation of anything novel — see Prior art. It is a permissively licensed, dependency-free implementation of well-established algorithms.

What it costs you

Measured on the sample app’s 320×320 test image (a two-axis gradient behind a soft-edged disc) at a 64-colour palette:

Target	Pngine PNG-8	Platform PNG	Encode time
Android emulator (Pixel 10 Pro XL)	12.9 KB	29.4 KB	369 ms
Web (Wasm, Chrome)	12.8 KB	—	73 ms

Encoding is CPU-bound. Run it off the main thread.

Where to go next

- :material-download: **[Installation](/pngine/installation.html)** — add the dependency - :material-code-braces: **[Usage](/pngine/usage.html)** — encode pixels, bitmaps, off-thread - :material-tune: **[Options](/pngine/options.html)** — every knob and what it does - :material-cog: **[How it works](/pngine/how-it-works.html)** — the pipeline, step by step

Licence

Apache-2.0. See LICENSE.

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