@create-design/png

Deterministic PNG projection for create-design documents. The package contains no DOM, Node built-in, native binary, timestamp, or random input, so the exact same API runs in a browser worker and in noninteractive Node.

const result = await exportPng(document, {
	scope: { kind: "active", artboardId: "artboard:page" },
	scale: 2,
	background: { kind: "transparent" },
})

Pixel contract

• Output dimensions are max(1, round(artboard dimension × scale)).
• Pixel centers are mapped evenly across the exact artboard rectangle; artwork is clipped at that rectangle.
• The reference backend uses a fixed ordered 4 × 4 subpixel grid. Set samples to 1 or 2 when explicitly trading edge quality for throughput.
• Paint follows the shared flattened layer/group order, with fill before stroke. Hidden layers are omitted, locked layers stay output-visible, and CMYK colors use the same deterministic sRGB alternate as SVG.
• Open contours use the shared derived fill region (a straight endpoint closure) but retain authored open topology for stroke caps, joins, and dashes.
• Valid live contour blends are lowered through the shared model projection; incompatible blends block output with the shared blend diagnostics.
• Color and alpha use half-up 8-bit rounding. Partially covered transparent pixels are accumulated premultiplied and stored as straight RGBA.
• Encoding is RGBA8, non-interlaced, filter 0, and deterministic stored-DEFLATE. Only IHDR, IDAT, and IEND are emitted; timestamps and ancillary metadata are intentionally absent.

The stable PngRasterBackend interface keeps orchestration independent of the reference renderer. A future accelerator must pass the byte, decoded-pixel, browser-worker, Node, lifecycle, and benchmark suites before becoming default.

Rasterizer appraisal

The initial implementation deliberately has no outside rasterizer. Native and WASM SVG engines offer higher throughput, but add platform binaries or WASM, browser/Node loading differences, a larger bundle, a second SVG interpretation layer, and additional license/provenance review. Canvas APIs are browser-only and vary by engine; native canvas and image libraries are not worker-portable. The pure TypeScript backend is MPL-compatible with this package, auditable from the repository, and produces identical bytes in every runtime. Its known cost is CPU time on large or high-scale artboards, so live proof is opt-in, debounced, cancellable, and yields between row batches.

Run pnpm --filter @create-design/png run profile for repeatable cold, warm, batch, and retained-heap measurements.