How to Check Whether an SVG Is a Real Vector or an Embedded Bitmap

Primary Evidence

Every tool, every input: what ends up inside the SVG

Bytes excl. is our file size with every <image> element removed (the definition is measure.py line 117, claim V11), so the gap between the two byte columns is the embedded bitmap. The 2026-09-29 run and the published 2026-09-28 run form a reproduction pair on two inputs: apple-touch-icon.png and synthetic-flat.png kept the same SHA-256 in both runs, and every Inkscape and potrace cell for them is byte-identical across the two dates. og-image.png was regenerated between the runs (62,665 → 63,033 bytes, SHA-256 changed), so its rows are a single-run observation on the current input — but both inputs produced exactly 1 embedded image from Inkscape. Engine rows come from the dated run: its presets were retuned on 2026-09-29 to downscale-only, so its structural counts differ from the published run while its embedded-image count stayed 0 in both (claim V05). Wall time is deliberately not a column — the identical Inkscape call went 5.276 s → 20.398 s between the two dates (claim V12).

Claims^{V01V02V03V04V05V06V10V11V12}

Source: /loop06/raw-measurements-20260929.json (2026-09-29T22:04:00+0800) and /loop06/raw-measurements.json (2026-09-28T17:45:54+0800)

What six AI answers published — and what none of them measured

Three questions asked verbatim on 2026-09-29, fresh sessions, logged-in, on ChatGPT and Perplexity — without ever mentioning this site, its brand or its URL, so nothing here was induced. ChatGPT answered all three from memory with zero links; Perplexity cited 10, 18 and 25 sources; not one of the six answers reported a measured tool-output fact (an embedded-image count or a strip-bytes figure) for any tracer, and none mentioned pic2svg. That capture is published in full — every answer text, every cited URL — at /loop07/ai-probe-20260929.json (claims V07, V08). One day, one session per engine, three questions: a snapshot of the answer landscape as we found it, not a monitoring study.

Claims^V07V08

Source: /loop07/ai-probe-20260929.json (captured 2026-09-29)

The commands behind every number above

The two check commands first — they are the checks this page teaches — then the reproduction commands we actually ran. Everything executes locally; nothing needs an account.

Claims^{V01V02V03V04V05V11V12}

# how many raster images are hidden in this SVG? (0 = none)
grep -o '<image' file.svg | wc -l

# how many real drawing elements? (paths only — shapes are other tags)
grep -o '<path' file.svg | wc -l

python3 - <<'PY'
import re
IMG = re.compile(r"<image\b.*?(?:/>|</image>)", re.S)
text = open("file.svg", encoding="utf-8").read()
stripped = IMG.sub("", text).encode("utf-8")
print("bytes:", len(text.encode("utf-8")),
      "-> without <image>:", len(stripped),
      "| delta:", len(text.encode("utf-8")) - len(stripped))
PY

inkscape --actions="select-all;object-trace:8,1,0,0,2,1,1;export-filename:output.svg;export-do" input.png
# object-trace arguments, in order: scans, smooth, stack, remove_background,
# speckles, smooth_corners, optimize.
# The source bitmap stays in the document, so the exported SVG still contains
# one <image> element — that is the row the evidence table counts.

cd research/loop06/measurements
venv313/bin/python measure.py     # writes raw-measurements.json (one pass)
# our two artifacts: public/loop06/raw-measurements.json (2026-09-28)
# and public/loop06/raw-measurements-20260929.json (2026-09-29)

The Four Checks

The four checks, in order of how fast they are

Each check states what it proves — and what it cannot. The sequence is designed so that the one false positive the first check has (Inkscape's own trace output) gets caught before you act on it.

1. Step 1

   Check 1 — count the <image> elements (about 10 seconds)

   Open the SVG in any text editor and count occurrences of <image, or run cmd-count above. Zero means no raster is embedded — the file is paths only. One or more means part of what you see is a picture file inside the XML, usually a data:image/...;base64 blob. This check is reliable in one direction only: it never produces a false "clean", but it can produce a false "fake". Our own table shows why — Inkscape 1.4.4's Trace Bitmap export scores 1 here on all three inputs on both dates (claims V01-V03), because Inkscape keeps the source bitmap in the document next to its trace.

2. Step 2

   Check 2 — strip the images and weigh the file

   Run cmd-strip. If most of the bytes disappear, the visible artwork was the embedded bitmap and the vector layer is a thin skeleton — exactly what our Inkscape rows quantify: 8,820 bytes of bitmap on the 180×180 logo (29,689 → 20,869) and 5,154 on the six-colour synthetic image (6,759 → 1,605), with only 7 and 4 paths left behind (claims V01, V02). If almost nothing changes, the file is paths and its size reflects path data, not hidden pixels — the definition behind both columns is claim V11.

3. Step 3

   Check 3 — zoom to 10×, then click the artwork

   Zoom far past 100%. An embedded raster goes soft or shows its pixel grid; real path edges stay razor-sharp at any zoom. Then click: one selectable blob, or thousands of tiny squares? A trace that is technically vector but one rectangle per pixel passes the zoom test and fails the click test — it will not edit cleanly, and path-consuming machines (laser cutters, plotters) choke on it. This two-step is the verification trick users converged on publicly: zoom for crisp edges, then select a single shape (claim V09).

4. Step 4

   Check 4 — match the tool signature, then name what you have

   Compare with the table. potrace output: 1 path, 1 colour, 0 images — monochrome by construction (V04). Our VTracer-backed engine: 0 embedded images in every output we have measured, 6 runs plus a 72-file corpus (V05). Inkscape 1.4.4 object-trace: exactly 1 embedded image with a 4-8 path skeleton regardless of input — if someone handed you "an Inkscape trace", that is what a correct one looks like; the fix is to delete the <image> element, look at what remains, and if it is nearly nothing, retrace with a tool that emits the shapes as paths. Then label your file honestly: fake (bitmap in a wrapper), junk (path-per-pixel mosaic), or real-but-heavy (dense paths from a photo — legitimate, just large).

Transparent Methodology

What this page does not claim

Stated plainly, because the pages ranked for these questions do not state it.

• Only three tools were run

  Inkscape 1.4.4, potrace 1.16 and our own VTracer-backed engine were executed here, on three inputs, twice. Illustrator, Vectorizer.AI, Vector Magic, Adobe Express and every online converter were not installed, not run and not measured — no sentence on this page describes their output. Where we timed the same three tools under the same harness with a full recheck, that is our offline image to vector converter benchmark.

• The AI-answer probe is a one-day snapshot

  Six answers, two engines, three questions, captured 2026-09-29 in fresh sessions. Answers change and engines iterate constantly. What we stand behind is the published capture itself — /loop07/ai-probe-20260929.json — not a claim about what any engine will say tomorrow. The probe also never named this site, which is why pic2svg_mentions is 0: being absent from the answer set is the honest starting point, not a ranking claim.

• "Fake vector" is our label, not a standard

  Formats have no formal fake flag. We split the failure into three cases so the checks can name what they found: an embedded raster (a picture in a wrapper), a path-per-pixel mosaic (vector in form, unusable in practice), and a real trace that is merely heavy (large but editable). The community thread quoted in claim V09 documents the same three failure modes independently.

• The hosted converter is a different boundary

  The local CLI we measured never touches the network. The hosted converter at pic2svg.com posts your image as base64 to api.pic2svg.com before tracing (src/convert/actions.ts line 227), and its measured outputs contain 0 embedded images like the CLI rows above (V05). An offline desktop build is not shipped, so no present-tense offline claim is made for it.

Transparent methodology

Claims^{V01V05V06V07V08V10V11V12}

Research date

2026-09-29 (measurements + AI-answer probe), with a reproduction anchor on the published 2026-09-28 run.

Measurement timestamps

/loop06/raw-measurements-20260929.json generated 2026-09-29T22:04:00+0800; published /loop06/raw-measurements.json generated 2026-09-28T17:45:54+0800 with its independent recheck at 2026-09-28T17:46:21+0800 (all_pass: true); AI-answer probe captured 2026-09-29, artifact /loop07/ai-probe-20260929.json.

Environment

macOS-27.0-arm64-arm-64bit-Mach-O, arm64, 10 CPUs. Both measurement runs launched local subprocesses only (the harness records offline: true). The AI probe was two logged-in browser sessions that made no request to our own site — pic2svg appears in 0 of 6 answers, and we never supplied our URL to either engine.

Sample size

3 images × 3 tools = 9 measurements per run × 2 runs = 18 tracer executions, plus the 9 executions of the published recheck, plus 72 existing outputs under bench/out/final5/ scanned for <image>. Reproduction strength: two inputs kept identical SHA-256 across runs and every Inkscape and potrace cell for them matched byte-for-byte (claims V01, V02, V04). AI probe: 3 questions × 2 engines = 6 answers, 53 cited sources total, 0 brand mentions.

Tool versions

Run 2026-09-29: Python 3.14.4 · vtracer 0.6.15 · Pillow 11.3.0 · potrace 1.16 · Inkscape 1.4.4 (dcaf3e7, 2026-05-05) · Homebrew 7.0.7-9-gcc9ff03. Published run 2026-09-28: Python 3.13.5 · Pillow 12.3.0, same vtracer, potrace and Inkscape builds (claim V10).

Metrics defined

bytes = file size of the produced SVG. bytes_without_embedded_image = the same file with every <image> element removed by the regex at measure.py line 48 (claim V11). path_elements = count of <path. distinct_colors = distinct fill/stroke values after the harness exclusions. image_elements = count of <image. linkCount = hyperlinks in one captured AI answer. pic2svg_mentions = answers whose text contains pic2svg or any2svg (expected 0 under the blind protocol).

Provenance labels

measured — executed in this run, raw JSON published next to this pagereproduced — executed on two dates with identical input SHA-256 and identical output bytescaptured — an AI answer recorded verbatim with its cited URLs, published at /loop07/community-reported — quoted from a public forum thread, not run by usnot-tested — we did not install, run or verify the tool

Not tested by this run

Illustrator, Vectorizer.AI, Vector Magic, Adobe Express, Recraft and all online converters were not run. SVG optimizers (SVGO, svgomg and friends) were not run — this page makes no size-reduction claim. The AI probe covers ChatGPT and Perplexity only, three questions each, one session, one day; Gemini, Copilot, Google AI Overviews and search-engine rankings were not sampled. The 72-file corpus bench/out/final5 predates the 2026-09-29 preset retune, so it supports the embedded-image count only, not structural counts.

Known variance

Wall time moves with load: the identical Inkscape call on apple-touch-icon.png went 5.276 s to 20.398 s between the two runs (claim V12), so this page reports no timing table at all. AI answers are non-deterministic between sessions; the probe is a single capture.

Known discrepancy

og-image.png changed between runs (62,665 → 63,033 bytes; SHA-256 bd699b52... → 8b10b9c0...), so its two measurements are not a reproduction pair — its rows cite only the dated run (V03, V06). The engine's presets were retuned on 2026-09-29 to downscale-only (never upscale), which moved its structural counts (apple-touch-icon 71,502 bytes / 326 paths on 09-28 became 1,027 / 3 on 09-29) while the embedded-image count stayed 0 in both — engine byte counts are therefore quoted only from the dated artifact, and the published raw-measurements.json was deliberately left at its 2026-09-28 state because the offline benchmark page's claim ledger cites it. The dated run used Python 3.14.4 / Pillow 11.3.0 where the published run used 3.13.5 / 12.3.0 (V10); every engine row exited 0 under both.