add: script to generate thumbnails

scripts/generate-thumbnails.js

@@ -0,0 +1,93 @@
+const fs = require("fs");
+const path = require("path");
+const sharp = require("sharp");
+
+const { loadMeals, repoRoot } = require("./lib/meals");
+
+const fullsDir = path.join(repoRoot, "images", "fulls");
+const thumbsDir = path.join(repoRoot, "images", "thumbs");
+
+const THUMB_WIDTH = 240;
+const THUMB_HEIGHT = 320;
+const JPEG_QUALITY = 82;
+
+function clamp(value, min, max) {
+  return Math.min(Math.max(value, min), max);
+}
+
+function getThumbnailPaths(meal) {
+  return {
+    fullPath: path.join(fullsDir, `${meal.id}.jpg`),
+    thumbPath: path.join(thumbsDir, `${meal.id}.jpg`),
+  };
+}
+
+function getCropArea(width, height, focus) {
+  const targetRatio = THUMB_WIDTH / THUMB_HEIGHT;
+  const sourceRatio = width / height;
+
+  let cropWidth = width;
+  let cropHeight = height;
+
+  if (sourceRatio > targetRatio) {
+    cropWidth = Math.round(height * targetRatio);
+  } else if (sourceRatio < targetRatio) {
+    cropHeight = Math.round(width / targetRatio);
+  }
+
+  const centerX = (focus?.x ?? 0.5) * width;
+  const centerY = (focus?.y ?? 0.5) * height;
+  const left = Math.round(centerX - cropWidth / 2);
+  const top = Math.round(centerY - cropHeight / 2);
+
+  return {
+    left: clamp(left, 0, width - cropWidth),
+    top: clamp(top, 0, height - cropHeight),
+    width: cropWidth,
+    height: cropHeight,
+  };
+}
+
+async function generateThumbnail(meal) {
+  const { fullPath, thumbPath } = getThumbnailPaths(meal);
+
+  if (!fs.existsSync(fullPath)) {
+    throw new Error(`Missing full-size image for meal ${meal.id}: ${fullPath}`);
+  }
+
+  const image = sharp(fullPath);
+  const metadata = await image.metadata();
+
+  if (!metadata.width || !metadata.height) {
+    throw new Error(`Could not read image dimensions for ${fullPath}`);
+  }
+
+  const cropArea = getCropArea(
+    metadata.width,
+    metadata.height,
+    meal.thumbnail?.focus
+  );
+
+  await image
+    .extract(cropArea)
+    .resize(THUMB_WIDTH, THUMB_HEIGHT)
+    .jpeg({ quality: JPEG_QUALITY, mozjpeg: true })
+    .toFile(thumbPath);
+}
+
+async function main() {
+  const meals = loadMeals();
+
+  await fs.promises.mkdir(thumbsDir, { recursive: true });
+
+  for (const meal of meals) {
+    await generateThumbnail(meal);
+  }
+
+  console.log(`Generated ${meals.length} thumbnails in images/thumbs`);
+}
+
+main().catch((error) => {
+  console.error(error.message);
+  process.exitCode = 1;
+});