ogcard: ensure we use jpeg images for satori compat

bskyogcard/src/components/Img.tsx

@@ -1,5 +1,6 @@
 import React from 'react'
 
+// @NOTE satori does not currently support webp, see vercel/satori#273
 function detectMime(buf: Buffer): string {
   if (buf[0] === 0xff && buf[1] === 0xd8) return 'image/jpeg'
   if (buf[0] === 0x89 && buf[1] === 0x50) return 'image/png'

bskyogcard/src/routes/starter-pack.tsx

@@ -1,17 +1,17 @@
 import assert from 'node:assert'
 
 import React from 'react'
-import {AppBskyGraphDefs, AtUri} from '@atproto/api'
+import {type AppBskyGraphDefs, AtUri} from '@atproto/api'
 import resvg from '@resvg/resvg-js'
-import {Express} from 'express'
+import {type Express} from 'express'
 import satori from 'satori'
 
 import {
   StarterPack,
   STARTERPACK_HEIGHT,
   STARTERPACK_WIDTH,
 } from '../components/StarterPack.js'
-import {AppContext} from '../context.js'
+import {type AppContext} from '../context.js'
 import {httpLogger} from '../logger.js'
 import {loadEmojiAsSvg} from '../util.js'
 import {handler, originVerifyMiddleware} from './util.js'
@@ -83,12 +83,18 @@ export default function (ctx: AppContext, app: Express) {
 }
 
 async function getImage(url: string) {
-  const response = await fetch(url)
+  const response = await fetch(ensureJpeg(url))
   const arrayBuf = await response.arrayBuffer() // must drain body even if it will be discarded
   if (response.status !== 200) return null
   return Buffer.from(arrayBuf)
 }
 
+// CDN URLs end with @jpeg, @webp, or no extension (which may default to webp).
+// We want to ensure the image URLs we use are for jpegs, required for compat with satori.
+function ensureJpeg(url: string) {
+  return url.replace(/(@[a-z]{3,5})?$/, '@jpeg')
+}
+
 const hideAvatarLabels = new Set([
   '!hide',
   '!warn',