qr - generate a QR code (printed right in your terminal), or read one from an image

Usage:
  curl https://ttykit.com/qr/<text>
  curl --data "<text>" https://ttykit.com/qr

Query params:
  ec=L|M|Q|H    error correction level (default M; H survives the most damage)
  invert=1      for light-background terminals (default assumes a dark one)
  format=svg    return the QR code as an SVG image instead of terminal output
  format=text   plain terminal output, even from a browser

Examples:
  curl https://ttykit.com/qr/hello
  curl --data "https://example.com/some/long/url?a=1&b=2" https://ttykit.com/qr
  curl "https://ttykit.com/qr/WIFI:T:WPA;S:MyNet;P:secret;;?ec=Q"
  curl "https://ttykit.com/qr/hello?format=svg" > hello.svg

Styling (SVG output and the browser view; terminal output is always the plain blocks):
  fg=0b6b3a            foreground color (hex; with a # it must be %23-encoded)
  bg=f4f1de            background color, or bg=transparent
  fg2=4338ca           second color: diagonal gradient from fg to fg2
  shape=square|round|dot
  size=512             SVG width/height in pixels (64-4096; it stays scalable)
  download=1           send the SVG as a file download

  curl "https://ttykit.com/qr/hello?format=svg&fg=0b6b3a&bg=f4f1de&shape=dot" > hello.svg
  curl "https://ttykit.com/qr/hello?format=svg&shape=round&fg=0f766e&fg2=4338ca" > hello.svg

Colors must have at least 3:1 contrast against bg so the code still scans.
Light-on-dark codes work in many readers but not all.

Center logo (PNG or JPEG up to 256 KB; uses ec=H and a larger code to leave room):
  curl -F text="https://example.com" -F logo=@icon.png "https://ttykit.com/qr?format=svg" > qr.svg
  curl -F text="https://example.com" -F logo=@icon.png \
       "https://ttykit.com/qr?format=svg&shape=dot&fg=14532d&bg=f4f1de" > qr.svg
Styling options and logos only change SVG/browser output, so with plain curl you get
the terminal code plus a one-line reminder of that.

In the URL path, percent-encode anything that isn't plain text ("?", "#",
spaces); POSTing the text as the body avoids that. Max about 2,900 bytes.
(To encode the literal word "read", "check" or "scan", use: curl "https://ttykit.com/qr?text=read")

Got a QR code image to decode? See ttykit.com/qr/read
Already have the decoded text? See ttykit.com/qr/check
Scanning with a phone? Open ttykit.com/qr/scan