Point og:image rasterizing at the shared og-svg renderer

[alcor]

Points og:image rasterizing at the shared og-svg renderer, and removes the local rasterizer that could never be reached.

The bug

metadata.js built the rasterizer URL as a path:

if (!info.i.startsWith("http")) info.i = "/.netlify/functions/rasterize/" + info.i

But functions/rasterize.js read event.rawQuery — the query string, never the path. Probed against production to confirm:

URL form	Result
/.netlify/functions/rasterize/svg:<b64> — as this code built it	502
/.netlify/functions/rasterize?<b64> — as the function read it	200 image/jpeg, 8707 bytes

The rasterizer worked fine. Nothing ever called it correctly, so i:-with-SVG links have been silently producing no preview image.

There was a second failure layered on top. By this point decodeURL has already run, and this repo's version does atob() with no try/catch. A payload that is not valid base64 throws, which the outer try swallows — killing all metadata for that page, not just the image.

The fix

renderUrl() builds an og-svg URL from the SVG markup decodeURL has already produced.

The payload is encoded as base64url, which stays URL-safe with no percent-encoding. That matters because Cloudflare caps URLs at 16KB, and percent-encoding raw markup is substantially more expensive — for the same test SVG, base64url produced a 346-character URL where percent-encoding produced 557.

Verified

Rendered against the live renderer:

200 PNG 600x315  len=346  markup -> base64url
200 PNG 400x200  len=301  unicode markup (via utoa)

The unicode case matters because btoa alone throws on non-Latin-1 input; this reuses the existing utoa helper.

Removed

functions/rasterize.js, the sharp dependency it needed, and the [functions] block that existed only to mark sharp as an external module. sharp appeared nowhere else in the repo.

Note on output format

og-svg returns PNG; the old rasterizer produced JPEG. Since no caller ever reached it successfully, there is no existing behaviour to stay compatible with, and every crawler accepts PNG.

Note on the base

This branch is rebased onto current main (25aa3cd). The working copy it was authored in predated that commit, which had removed the devDependencies block from package.json — rebasing rather than merging avoids silently re-adding netlify-cli. The resulting diff to package.json is only the removal of sharp.

🤖 Generated with Claude Code