Vecline

Measurable raster ⇄ SVG conversion — and a broad image + document toolkit. Ten raster formats, every one convertible to every other, with the accuracy of every conversion actually measured rather than asserted; plus PDF & Office (docx/xlsx/pptx) rendering and conversion, images → PDF, DXF at a real physical cut size alongside EPS and G-code for makers, centerline tracing and content-aware crop — most of it in a zero-dependency core that is CI-proven to bundle for a browser.

On flat artwork — logos, icons, UI, screenshots, pixel art — the output is bit-exact: SSIM 1.0000, PSNR ∞, zero differing pixels, and on a real logo smaller than imagetracerjs or vtracer manage while still only approximating — 24 KB against their 60 and 64. That comes from recognising the image is cheaper to encode exactly than to approximate, not from a better curve fit. Tracing now emits real curves by default — sub-pixel edge placement is on, which is the only thing that lets the curve fitter run at all; before this the default returned a staircase with zero curve commands on real artwork. It costs about 2.35x the gzipped bytes, because moving coordinates off the integer lattice costs compression, and --no-subpixel buys the old smaller output back. Pixel and exact modes are untouched and stay bit-exact. potrace is smaller than everyone and much less accurate, which is a real trade and not one this README will hide. On real photographs it leads all three on SSIM by 0.05–0.18 at their default settings; one documented vtracer flag closes part of that. It is not the fastest — imagetracerjs is quicker on every fixture measured. Every number in this README is reproducible: node scripts/fetch-corpus.mjs && npm run compare. (The corpus is fetched rather than committed — the photographs are not ours to redistribute.)

▶ Vecline Studio — vecline.xyz — the whole toolkit in your browser. Drop an image, a PDF, or a TGA/PNM/ICO no browser can read; tune it; watch live SSIM / PSNR / CIEDE2000; export SVG, DXF at a real cut size, EPS, PDF, G-code, React/Vue/Svelte/Solid components, colour separations, sprite sheets, favicons, BlurHash, or just re-encode between ten raster formats. Free, unlimited, no signup, works offline, and nothing is uploaded — every conversion runs in your tab, not on a server. (How it compares · dev playground)

vecline vectorize logo.png --verify

✓ logo.svg  400×300  pixel mode  4 shapes  2.1 KB → 7.5 KB  228 ms
  · Auto-selected pixel mode: 4 distinct colours, 1.0% run density. Output is bit-exact.

Accuracy  bit-exact (lossless)
  PSNR        ∞
  SSIM        1.000000 (luma 1.000000)
  RMSE        0.0000

The lossless guarantee

vecline vectorize anything.png --lossless

--lossless returns a bit-exact SVG or it fails. It never silently gives you a near-miss.

That is enforced by measurement, not by construction. Every candidate encoding is rendered back to pixels and compared against the source; anything that is not bit-identical is discarded, and if nothing survives, the command errors out. Candidates are tried in order of how useful the result is:

1. Exact geometry — real, editable, infinitely scalable paths. Rectangles or contours, whichever encodes smaller.
2. Embed, original bytes preserved — a byte-identical round trip of the source file, not just of its pixels.
3. Embed, re-encoded as PNG — always renders exactly, but no longer carries the original file.

Measured across every fixture in the test suite — flat artwork, pixel art, soft alpha, photographs, JPEG sources, a single pixel — all of them come back PSNR ∞, maxChannelDiff 0.

Byte-identical, and provable

When the original file is preserved, the SVG records its SHA-256. extract hands the file back and checks the digest:

vecline vectorize logo.png -o keep.svg --mode embed --embed-strategy preserve
vecline extract keep.svg -o recovered.png --against logo.png

✓ recovered.png  image/png  2.1 KB
  sha256   1c4f95f66b28a40a75672614796de762f6ef8a6afec3191b460dbbd556f10366
  digest   matches the value recorded when the SVG was written
  payload  the original file, preserved byte for byte
  vs source byte-identical to logo.png

extract exits non-zero on any mismatch, so it works as a CI gate. Note the honest caveat: an embedded JPEG survives byte for byte but does not render bit-identically, because resvg's decoder rounds its inverse DCT differently. Strict --lossless detects that, discards the candidate, and says so.

Which one you get

A photograph can be emitted as exact geometry, and --prefer geometry will do it — but it costs one rectangle per pixel, so that same photo becomes a 1.99 MB file of 42,933 shapes. It is vector in name only, so auto uses the bitmap and tells you the ratio it measured. Nothing is hidden.

The honest version of "100% accuracy"

Most vectorizers claim perfect accuracy. Here is what is actually true, because it determines which tool you should use:

Anyone promising exact photo-to-curves vectorization is either embedding a bitmap and calling it vector, or is wrong. Vecline does both exact conversions properly, does the approximate one well, and always tells you which one you got and how close it landed.

Three strategies, and when each is right

auto (the default) inspects the image and picks between pixel and trace. --lossless overrides everything with the guarantee described above.

pixel mode is the one people don't expect. It produces genuine, editable, infinitely-scalable vector paths that rasterise back to your input with zero differing pixels — not "visually identical", literally identical. For flat artwork it is usually what you actually wanted.

Install

npm install -g vecline        # the CLI
npm install vecline           # the library

Node.js 18.17+. The native dependencies (sharp, resvg) ship prebuilt binaries for Linux, macOS and Windows.

Any project architecture

Install only what you use. Every none subpath imports in isolation with the native codecs omitted (npm install vecline --omit=optional), and the package is "sideEffects": false, so a bundler drops everything you never import. vecline/core is the vectorisation and measurement engine with zero dependencies and no Node built-ins. It takes a plain { width, height, data } — byte-for-byte the layout of the browser's ImageData — so canvas pixels go straight in:

import { vectorizeExact } from 'vecline/core';

const { data, width, height } = ctx.getImageData(0, 0, canvas.width, canvas.height);
const { svg } = vectorizeExact({ width, height, data });   // bit-exact, no codec needed