@catlabtech/webcvt-image-jsquash-oxipng

Lossless PNG optimisation / encoding backend for webcvt, wrapping @jsquash/oxipng (OxiPNG in WebAssembly).

OxiPNG losslessly re-compresses an existing PNG (often 10–40% smaller) or encodes raw pixels to a smaller PNG than the browser's canvas encoder.

Overlaps image-canvas

Both this backend and @catlabtech/webcvt-image-canvas produce image/png. Register only one per registry: this one for the smallest lossless output, image-canvas for the zero-dependency / hardware-accelerated path.

Installation

npm i @catlabtech/webcvt-image-jsquash-oxipng @jsquash/oxipng

Supported conversions

PNG is always the output:

Input	Output
PNG	PNG (lossless re-compression)
JPEG, WebP	PNG

Cross-format paths use a canvas pixel-bridge (OffscreenCanvas). PNG→PNG works anywhere.

Usage

import { registerOxipngBackend } from '@catlabtech/webcvt-image-jsquash-oxipng';

registerOxipngBackend(undefined, { optimise: { level: 4 } });

Free function optimisePng(bytesOrImageData, options) is also exported.

Options

{
  level?: number;          // 0 (fast) – 6 (smallest), default 2
  interlace?: boolean;     // default false
  optimiseAlpha?: boolean; // default false
}

OxiPNG is lossless — there is no quality knob; level trades encode time for size.

Notes

• The wasm codec needs script-src 'wasm-unsafe-eval'.
• Security caps: 256 MiB max input, 25 MP max image (typed errors on violation).

Source

packages/image-jsquash-oxipng/src