From dc299c7b795bdccc3b6071b8f49f44e4e6d1bd4e Mon Sep 17 00:00:00 2001
From: Simone Bortolin <simonebortolin@users.noreply.github.com>
Date: Thu, 8 Oct 2026 23:36:21 +0200
Subject: [PATCH 1/2] Serve WebP copies of the images

After the VitePress build, scripts/optimize-images.mjs makes a WebP copy
of every JPEG/PNG, at most 1920 px on the longer side and with the EXIF
orientation applied (256.6 MB -> 26.9 MB). ImageFigure serves it through
<picture>, keeps the original as fallback and links to it for the full
resolution. The images in the repository are untouched.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 .vitepress/theme/components/ImageFigure.vue |  13 +-
 package-lock.json                           | 668 ++++++++++++++++++++
 package.json                                |   3 +-
 scripts/optimize-images.mjs                 |  41 ++
 4 files changed, 721 insertions(+), 4 deletions(-)
 create mode 100644 scripts/optimize-images.mjs

diff --git a/.vitepress/theme/components/ImageFigure.vue b/.vitepress/theme/components/ImageFigure.vue
index 56391286..016ace07 100644
--- a/.vitepress/theme/components/ImageFigure.vue
+++ b/.vitepress/theme/components/ImageFigure.vue
@@ -12,15 +12,22 @@ const props = defineProps<{
 }>()
 
 const src = computed(() => withBase(`/assets/img/${props.file.replace(/\\/g, '/')}`))
+// The WebP copies are made by scripts/optimize-images.mjs, so they only exist in the built site
+const webp = computed(() =>
+  import.meta.env.PROD && /\.(jpe?g|png)$/i.test(src.value) ? src.value.replace(/\.(jpe?g|png)$/i, '.webp') : undefined
+)
 const style = computed(() => (props.maxWidth ? { maxWidth: `${props.maxWidth}px` } : undefined))
 </script>
 
 <template>
   <figure class="image-figure">
-    <a v-if="url" :href="url" target="_blank" rel="noopener">
-      <img :src="src" :alt="alt" :style="style" loading="lazy" />
+    <!-- Without an explicit link, the image opens the original at full resolution -->
+    <a :href="url ?? src" target="_blank" rel="noopener">
+      <picture>
+        <source v-if="webp" :srcset="webp" type="image/webp" />
+        <img :src="src" :alt="alt" :style="style" loading="lazy" />
+      </picture>
     </a>
-    <img v-else :src="src" :alt="alt" :style="style" loading="lazy" />
     <figcaption v-if="caption" v-html="caption" />
   </figure>
 </template>
diff --git a/package-lock.json b/package-lock.json
index 304e9026..be1fdd3a 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -12,6 +12,7 @@
         "liquidjs": "^10.30.0",
         "markdown-it-footnote": "^4.0.0",
         "mermaid": "^12.1.0",
+        "sharp": "^0.35.5",
         "vitepress": "^1.6.4",
         "vue": "^3.5.25"
       }
@@ -438,6 +439,17 @@
         }
       }
     },
+    "node_modules/@emnapi/runtime": {
+      "version": "1.11.3",
+      "resolved": "https://registry.npmjs.org/@emnapi/runtime/-/runtime-1.11.3.tgz",
+      "integrity": "sha512-Xz4Tpyki7XyrpbUK1jR1AhdAdaXyhhY4lZ3neLodmhpuWfy2PAQN5B46sAiU4liOXGLkHypn/qU+jvfWSCYYLA==",
+      "dev": true,
+      "license": "MIT",
+      "optional": true,
+      "dependencies": {
+        "tslib": "^2.4.0"
+      }
+    },
     "node_modules/@esbuild/aix-ppc64": {
       "version": "0.21.5",
       "resolved": "https://registry.npmjs.org/@esbuild/aix-ppc64/-/aix-ppc64-0.21.5.tgz",
@@ -858,6 +870,581 @@
         "import-meta-resolve": "^4.2.0"
       }
     },
+    "node_modules/@img/colour": {
+      "version": "1.1.0",
+      "resolved": "https://registry.npmjs.org/@img/colour/-/colour-1.1.0.tgz",
+      "integrity": "sha512-Td76q7j57o/tLVdgS746cYARfSyxk8iEfRxewL9h4OMzYhbW4TAcppl0mT4eyqXddh6L/jwoM75mo7ixa/pCeQ==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=18"
+      }
+    },
+    "node_modules/@img/sharp-darwin-arm64": {
+      "version": "0.35.5",
+      "resolved": "https://registry.npmjs.org/@img/sharp-darwin-arm64/-/sharp-darwin-arm64-0.35.5.tgz",
+      "integrity": "sha512-QRUlFQ0WxvdWyqqG/WtI3iupfD5rBzmCHXSdPsY91sAtVtTo7Q4cb6zOccZ3gqEqkr0f1As1ehLqmEpDsRf+lg==",
+      "cpu": [
+        "arm64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "darwin"
+      ],
+      "engines": {
+        "node": ">=20.9.0"
+      },
+      "funding": {
+        "url": "https://opencollective.com/libvips"
+      },
+      "optionalDependencies": {
+        "@img/sharp-libvips-darwin-arm64": "1.3.4"
+      }
+    },
+    "node_modules/@img/sharp-darwin-x64": {
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+      "funding": {
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+      "cpu": [
+        "x64"
+      ],
+      "dev": true,
+      "libc": [
+        "musl"
+      ],
+      "license": "Apache-2.0",
+      "optional": true,
+      "os": [
+        "linux"
+      ],
+      "engines": {
+        "node": ">=20.9.0"
+      },
+      "funding": {
+        "url": "https://opencollective.com/libvips"
+      },
+      "optionalDependencies": {
+        "@img/sharp-libvips-linuxmusl-x64": "1.3.4"
+      }
+    },
+    "node_modules/@img/sharp-wasm32": {
+      "version": "0.35.5",
+      "resolved": "https://registry.npmjs.org/@img/sharp-wasm32/-/sharp-wasm32-0.35.5.tgz",
+      "integrity": "sha512-Ptsga1su4tQx+LLF1ECS9U6nz5kmrXKo6XVbtR48Ke3ZRxxgaWBu7IDtEe1quo8hiupwm6WFqxVlXaSf7IINGQ==",
+      "dev": true,
+      "license": "Apache-2.0 AND LGPL-3.0-or-later AND MIT",
+      "optional": true,
+      "dependencies": {
+        "@emnapi/runtime": "^1.11.3"
+      },
+      "engines": {
+        "node": ">=20.9.0"
+      },
+      "funding": {
+        "url": "https://opencollective.com/libvips"
+      }
+    },
+    "node_modules/@img/sharp-webcontainers-wasm32": {
+      "version": "0.35.5",
+      "resolved": "https://registry.npmjs.org/@img/sharp-webcontainers-wasm32/-/sharp-webcontainers-wasm32-0.35.5.tgz",
+      "integrity": "sha512-hfhF/FmoQyTUkA0bIKFOtw536BQSeBMe6BF6QyWlrPxT754+TFLaZ7sKKTfvvM0yJgKgaYTwnFCIZ/GuDw5SUA==",
+      "cpu": [
+        "wasm32"
+      ],
+      "dev": true,
+      "license": "Apache-2.0",
+      "optional": true,
+      "dependencies": {
+        "@img/sharp-wasm32": "0.35.5"
+      },
+      "engines": {
+        "node": ">=20.9.0"
+      },
+      "funding": {
+        "url": "https://opencollective.com/libvips"
+      }
+    },
+    "node_modules/@img/sharp-win32-arm64": {
+      "version": "0.35.5",
+      "resolved": "https://registry.npmjs.org/@img/sharp-win32-arm64/-/sharp-win32-arm64-0.35.5.tgz",
+      "integrity": "sha512-X4t7g+7ZA5DKblCBEXGjUqqemj4vczING/5viFwAL8h4N3qYeyjwdCvRLHi4EdOUI+2Z7UFlp1VM+p/AuEtm6Q==",
+      "cpu": [
+        "arm64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0 AND LGPL-3.0-or-later",
+      "optional": true,
+      "os": [
+        "win32"
+      ],
+      "engines": {
+        "node": ">=20.9.0"
+      },
+      "funding": {
+        "url": "https://opencollective.com/libvips"
+      }
+    },
+    "node_modules/@img/sharp-win32-ia32": {
+      "version": "0.35.5",
+      "resolved": "https://registry.npmjs.org/@img/sharp-win32-ia32/-/sharp-win32-ia32-0.35.5.tgz",
+      "integrity": "sha512-5Zm82LoBc43nhwNybZlG7Y1KO//Zhsn306fQl29ZOuStHLGTo3BWL83q3cznX0poxSAMuYL1On/BHBxkBeKr6A==",
+      "cpu": [
+        "ia32"
+      ],
+      "dev": true,
+      "license": "Apache-2.0 AND LGPL-3.0-or-later",
+      "optional": true,
+      "os": [
+        "win32"
+      ],
+      "engines": {
+        "node": "^20.9.0"
+      },
+      "funding": {
+        "url": "https://opencollective.com/libvips"
+      }
+    },
+    "node_modules/@img/sharp-win32-x64": {
+      "version": "0.35.5",
+      "resolved": "https://registry.npmjs.org/@img/sharp-win32-x64/-/sharp-win32-x64-0.35.5.tgz",
+      "integrity": "sha512-x76eH0vEiHlcMQu8Y8IenntaACtddpT6W0wmXtWrnKcnKI7ME5DdgqhAD6SEWOEl1v2zDvkZDhFA9KnURwpfqg==",
+      "cpu": [
+        "x64"
+      ],
+      "dev": true,
+      "license": "Apache-2.0 AND LGPL-3.0-or-later",
+      "optional": true,
+      "os": [
+        "win32"
+      ],
+      "engines": {
+        "node": ">=20.9.0"
+      },
+      "funding": {
+        "url": "https://opencollective.com/libvips"
+      }
+    },
     "node_modules/@jridgewell/sourcemap-codec": {
       "version": "1.6.0",
       "resolved": "https://registry.npmjs.org/@jridgewell/sourcemap-codec/-/sourcemap-codec-1.6.0.tgz",
@@ -2718,6 +3305,16 @@
         "node": ">=6"
       }
     },
+    "node_modules/detect-libc": {
+      "version": "2.1.2",
+      "resolved": "https://registry.npmjs.org/detect-libc/-/detect-libc-2.1.2.tgz",
+      "integrity": "sha512-Btj2BOOO83o3WyH59e8MgXsxEQVcarkUOpEYrubB0urwnN10yQ364rsiByU11nZlqWYZm05i/of7io4mzihBtQ==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "engines": {
+        "node": ">=8"
+      }
+    },
     "node_modules/devlop": {
       "version": "1.1.0",
       "resolved": "https://registry.npmjs.org/devlop/-/devlop-1.1.0.tgz",
@@ -3478,6 +4075,69 @@
       "license": "MIT",
       "peer": true
     },
+    "node_modules/semver": {
+      "version": "7.8.5",
+      "resolved": "https://registry.npmjs.org/semver/-/semver-7.8.5.tgz",
+      "integrity": "sha512-Y7/KDsb8LjooZpwaqGyulO6DQlksgCncchHGk+sZIY4SBvUocMBEFH5Ur1fI4dV+Jvl0w6cjvucaIi40puRioA==",
+      "dev": true,
+      "license": "ISC",
+      "bin": {
+        "semver": "bin/semver.js"
+      },
+      "engines": {
+        "node": ">=10"
+      }
+    },
+    "node_modules/sharp": {
+      "version": "0.35.5",
+      "resolved": "https://registry.npmjs.org/sharp/-/sharp-0.35.5.tgz",
+      "integrity": "sha512-Ywn4OnzGukp7CDMrp08RQ50YKmuwG47brZgIVPTvBaaAfQlRlygrRqSrxdCiL9M+LlzLBiJ68IR1QqvzHyjC7g==",
+      "dev": true,
+      "license": "Apache-2.0",
+      "dependencies": {
+        "@img/colour": "^1.1.0",
+        "detect-libc": "^2.1.2",
+        "semver": "^7.8.5"
+      },
+      "engines": {
+        "node": ">=20.9.0"
+      },
+      "funding": {
+        "url": "https://opencollective.com/libvips"
+      },
+      "optionalDependencies": {
+        "@img/sharp-darwin-arm64": "0.35.5",
+        "@img/sharp-darwin-x64": "0.35.5",
+        "@img/sharp-freebsd-wasm32": "0.35.5",
+        "@img/sharp-libvips-darwin-arm64": "1.3.4",
+        "@img/sharp-libvips-darwin-x64": "1.3.4",
+        "@img/sharp-libvips-linux-arm": "1.3.4",
+        "@img/sharp-libvips-linux-arm64": "1.3.4",
+        "@img/sharp-libvips-linux-ppc64": "1.3.4",
+        "@img/sharp-libvips-linux-riscv64": "1.3.4",
+        "@img/sharp-libvips-linux-s390x": "1.3.4",
+        "@img/sharp-libvips-linux-x64": "1.3.4",
+        "@img/sharp-libvips-linuxmusl-arm64": "1.3.4",
+        "@img/sharp-libvips-linuxmusl-x64": "1.3.4",
+        "@img/sharp-linux-arm": "0.35.5",
+        "@img/sharp-linux-arm64": "0.35.5",
+        "@img/sharp-linux-ppc64": "0.35.5",
+        "@img/sharp-linux-riscv64": "0.35.5",
+        "@img/sharp-linux-s390x": "0.35.5",
+        "@img/sharp-linux-x64": "0.35.5",
+        "@img/sharp-linuxmusl-arm64": "0.35.5",
+        "@img/sharp-linuxmusl-x64": "0.35.5",
+        "@img/sharp-webcontainers-wasm32": "0.35.5",
+        "@img/sharp-win32-arm64": "0.35.5",
+        "@img/sharp-win32-ia32": "0.35.5",
+        "@img/sharp-win32-x64": "0.35.5"
+      },
+      "peerDependenciesMeta": {
+        "@types/node": {
+          "optional": true
+        }
+      }
+    },
     "node_modules/shiki": {
       "version": "2.5.0",
       "resolved": "https://registry.npmjs.org/shiki/-/shiki-2.5.0.tgz",
@@ -3599,6 +4259,14 @@
         "node": ">=6.10"
       }
     },
+    "node_modules/tslib": {
+      "version": "2.8.1",
+      "resolved": "https://registry.npmjs.org/tslib/-/tslib-2.8.1.tgz",
+      "integrity": "sha512-oJFu94HQb+KVduSUQL7wnpmqnfmLsOA/nAh6b6EH0wCEoK0/mPeXU6c3wKDV83MkOuHPRHtSXKKU99IBazS/2w==",
+      "dev": true,
+      "license": "0BSD",
+      "optional": true
+    },
     "node_modules/unist-util-is": {
       "version": "6.0.1",
       "resolved": "https://registry.npmjs.org/unist-util-is/-/unist-util-is-6.0.1.tgz",
diff --git a/package.json b/package.json
index 067d195c..bac22ae6 100644
--- a/package.json
+++ b/package.json
@@ -4,7 +4,7 @@
   "type": "module",
   "scripts": {
     "dev": "vitepress dev",
-    "build": "vitepress build",
+    "build": "vitepress build && node scripts/optimize-images.mjs",
     "preview": "vitepress preview",
     "convert": "node scripts/jekyll-to-vitepress.mjs"
   },
@@ -15,6 +15,7 @@
     "liquidjs": "^10.30.0",
     "markdown-it-footnote": "^4.0.0",
     "mermaid": "^12.1.0",
+    "sharp": "^0.35.5",
     "vitepress": "^1.6.4",
     "vue": "^3.5.25"
   }
diff --git a/scripts/optimize-images.mjs b/scripts/optimize-images.mjs
new file mode 100644
index 00000000..6114e645
--- /dev/null
+++ b/scripts/optimize-images.mjs
@@ -0,0 +1,41 @@
+// Create a WebP copy of every JPEG/PNG in the built site, at most MAX_SIZE
+// pixels on the longer side: <ImageFigure> serves it and links to the original.
+// Runs after `vitepress build`, so the images in the repository are untouched.
+import { readdir, stat } from 'node:fs/promises'
+import { availableParallelism } from 'node:os'
+import path from 'node:path'
+import sharp from 'sharp'
+
+const IMG_DIR = path.resolve('.vitepress/dist/assets/img')
+const MAX_SIZE = 1920
+const QUALITY = 80
+
+const files = (await readdir(IMG_DIR, { recursive: true }))
+  .filter((file) => /\.(jpe?g|png)$/i.test(file))
+  .map((file) => path.join(IMG_DIR, file))
+
+let before = 0
+let after = 0
+
+async function convert(file) {
+  const output = file.replace(/\.(jpe?g|png)$/i, '.webp')
+  // rotate() applies the EXIF orientation, which is lost in the WebP copy
+  await sharp(file)
+    .rotate()
+    .resize({ width: MAX_SIZE, height: MAX_SIZE, fit: 'inside', withoutEnlargement: true })
+    .webp({ quality: QUALITY })
+    .toFile(output)
+  const [original, converted] = await Promise.all([stat(file), stat(output)])
+  before += original.size
+  after += converted.size
+}
+
+const queue = [...files]
+await Promise.all(
+  Array.from({ length: availableParallelism() }, async () => {
+    while (queue.length) await convert(queue.shift())
+  })
+)
+
+const mb = (bytes) => (bytes / 1024 / 1024).toFixed(1)
+console.log(`Converted ${files.length} images to WebP: ${mb(before)} MB -> ${mb(after)} MB`)

From 6c06310539a219c3593debfee08bf2f2fce07a0f Mon Sep 17 00:00:00 2001
From: Simone Bortolin <simonebortolin@users.noreply.github.com>
Date: Fri, 9 Oct 2026 18:54:22 +0200
Subject: [PATCH 2/2] Open the images in a lightbox instead of a new tab

Clicking an image shows the original in an overlay, with the WebP copy
while it loads; another click zooms to 100% around the clicked point,
and Esc, the close button or the backdrop close it. Images with an
explicit url still open that link.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 .vitepress/theme/components/ImageFigure.vue | 116 +++++++++++++++++++-
 1 file changed, 113 insertions(+), 3 deletions(-)

diff --git a/.vitepress/theme/components/ImageFigure.vue b/.vitepress/theme/components/ImageFigure.vue
index 016ace07..ffcad3fa 100644
--- a/.vitepress/theme/components/ImageFigure.vue
+++ b/.vitepress/theme/components/ImageFigure.vue
@@ -1,6 +1,6 @@
 <script setup lang="ts">
 import { withBase } from 'vitepress'
-import { computed } from 'vue'
+import { computed, nextTick, onBeforeUnmount, ref } from 'vue'
 
 /** Image stored in `public/assets/img/`, with an optional caption and link. */
 const props = defineProps<{
@@ -17,12 +17,64 @@ const webp = computed(() =>
   import.meta.env.PROD && /\.(jpe?g|png)$/i.test(src.value) ? src.value.replace(/\.(jpe?g|png)$/i, '.webp') : undefined
 )
 const style = computed(() => (props.maxWidth ? { maxWidth: `${props.maxWidth}px` } : undefined))
+
+// Lightbox with the original image: click to zoom to 100% and scroll around, Esc to close
+const open = ref(false)
+const zoomed = ref(false)
+// The WebP is shown while the original, which can weigh several MB, is loading
+const original = ref<string>()
+const scroller = ref<HTMLElement>()
+
+function show() {
+  open.value = true
+  zoomed.value = false
+  original.value = undefined
+  const img = new Image()
+  img.onload = () => {
+    if (open.value) original.value = img.src
+  }
+  img.src = src.value
+  document.documentElement.style.overflow = 'hidden'
+  window.addEventListener('keydown', onKeydown)
+}
+
+function close() {
+  open.value = false
+  document.documentElement.style.overflow = ''
+  window.removeEventListener('keydown', onKeydown)
+}
+
+function onKeydown(event: KeyboardEvent) {
+  if (event.key === 'Escape') close()
+}
+
+// Zooms in keeping the clicked point in the middle of the screen
+async function toggleZoom(event: MouseEvent) {
+  const rect = (event.target as HTMLElement).getBoundingClientRect()
+  const x = (event.clientX - rect.left) / rect.width
+  const y = (event.clientY - rect.top) / rect.height
+  zoomed.value = !zoomed.value
+  if (!zoomed.value || !scroller.value) return
+  await nextTick()
+  const el = scroller.value
+  el.scrollLeft = x * el.scrollWidth - el.clientWidth / 2
+  el.scrollTop = y * el.scrollHeight - el.clientHeight / 2
+}
+
+onBeforeUnmount(() => {
+  if (open.value) close()
+})
 </script>
 
 <template>
   <figure class="image-figure">
-    <!-- Without an explicit link, the image opens the original at full resolution -->
-    <a :href="url ?? src" target="_blank" rel="noopener">
+    <a v-if="url" :href="url" target="_blank" rel="noopener">
+      <picture>
+        <source v-if="webp" :srcset="webp" type="image/webp" />
+        <img :src="src" :alt="alt" :style="style" loading="lazy" />
+      </picture>
+    </a>
+    <a v-else :href="src" class="zoomable" @click.prevent="show">
       <picture>
         <source v-if="webp" :srcset="webp" type="image/webp" />
         <img :src="src" :alt="alt" :style="style" loading="lazy" />
@@ -30,6 +82,15 @@ const style = computed(() => (props.maxWidth ? { maxWidth: `${props.maxWidth}px`
     </a>
     <figcaption v-if="caption" v-html="caption" />
   </figure>
+
+  <Teleport to="body">
+    <div v-if="open" class="lightbox" role="dialog" aria-modal="true" :aria-label="alt" @click.self="close">
+      <div ref="scroller" class="lightbox-scroller" :class="{ zoomed }" @click.self="close">
+        <img :src="original ?? webp ?? src" :alt="alt" @click="toggleZoom" />
+      </div>
+      <button class="lightbox-close" type="button" aria-label="Close" @click="close">×</button>
+    </div>
+  </Teleport>
 </template>
 
 <style scoped>
@@ -46,9 +107,58 @@ const style = computed(() => (props.maxWidth ? { maxWidth: `${props.maxWidth}px`
   max-width: 100%;
 }
 
+.image-figure .zoomable {
+  cursor: zoom-in;
+}
+
 .image-figure figcaption {
   padding: 8px 12px;
   font-size: 14px;
   background-color: var(--vp-c-bg-soft);
 }
+
+.lightbox {
+  position: fixed;
+  inset: 0;
+  z-index: 200;
+  background-color: rgba(0, 0, 0, 0.9);
+}
+
+.lightbox-scroller {
+  width: 100%;
+  height: 100%;
+  display: flex;
+  overflow: auto;
+}
+
+.lightbox-scroller img {
+  margin: auto;
+  max-width: 100%;
+  max-height: 100%;
+  object-fit: contain;
+  cursor: zoom-in;
+}
+
+.lightbox-scroller.zoomed img {
+  max-width: none;
+  max-height: none;
+  cursor: zoom-out;
+}
+
+.lightbox-close {
+  position: absolute;
+  top: 12px;
+  right: 12px;
+  width: 40px;
+  height: 40px;
+  border-radius: 50%;
+  font-size: 28px;
+  line-height: 40px;
+  color: #fff;
+  background-color: rgba(0, 0, 0, 0.5);
+}
+
+.lightbox-close:hover {
+  background-color: rgba(255, 255, 255, 0.2);
+}
 </style>