Proxy Buffer

A tiny, dependency-free web tool that adds a 1/8" black buffer border to MTG card images so they survive cutting when you print proxies. Drag images in, download them as PNGs (individually or as a zip). Everything runs in the browser, with no upload, no server, no tracking.

Live once you enable GitHub Pages (see below).

What it does

• Drag & drop / browse / paste any number of MTG card images at once.
• Adds a solid 1/8" (0.125") buffer border on all four sides, the standard proxy bleed. Sized as a true 1/8" relative to each image, so it stays 1/8" whether the source is 750px or 1500px wide (about 38px per side at 300 DPI).
• Fill in rounded corners (on by default): cards with transparent rounded corners get them filled with the border color so the card prints as a solid rectangle. Cards with transparent corners are detected and flagged. Turn it off to keep the original see-through corners.
• Border color (black by default; white or custom).
• The card art is never touched; the tool only adds the border and, optionally, fills the transparent corners behind the art.
• Checks each image against the standard 2.5 × 3.5" MTG card and flags:
  • Resolution: effective DPI. Under ~200 DPI = blurry (red), 200 to 299 = soft (amber), 300+ = good, 600+ = excellent.
  • Card shape: warns if the aspect ratio isn't ~2.5:3.5 (5:7), or if the image looks sideways.
• Download each card as a PNG, or Download all as .zip (zip is built in-browser with a hand-rolled store-only writer, no libraries).

The numbers it uses

Thing	Value
Card trim size	2.5 × 3.5 in (63 × 88 mm), aspect 5:7
Min crisp print	750 × 1050 px (300 DPI)
Excellent	1500 × 2100 px (600 DPI)
1/8" border	0.125" per side ≈ 37.5 px at 300 DPI
Card + 1/8" border	2.75 × 3.75 in = 825 × 1125 px at 300 DPI

Why the border? Cutters are never perfectly aligned. A solid border means a slightly-off cut trims into the border instead of leaving a white sliver or slicing the art. Real Magic cards are black-bordered, so a miscut into black is invisible. This is the same idea as "bleed" in print shops and MakePlayingCards uploads.

Host it on GitHub Pages

1. Create a new GitHub repo (e.g. proxy-buffer) and put index.html at its root.

   git init
   git add index.html README.md
   git commit -m "Proxy Buffer"
   git branch -M main
   git remote add origin https://github.com/<you>/proxy-buffer.git
   git push -u origin main

2. On GitHub: Settings → Pages → Build and deployment.
3. Set Source: Deploy from a branch, Branch: main, folder / (root), Save.
4. Wait ~1 minute. Your site is at https://<you>.github.io/proxy-buffer/.

That's it. A single static file, nothing else to configure.