PhotoDithering

src/routes/admin.js

@@ -392,12 +392,14 @@ router.patch('/sites/:id', (req, res) => {
   const badge = req.body?.badge || {};
   const branding = req.body?.branding || {};
   const printerCfg = req.body?.printer || {};
+  const photoCfg = req.body?.photo || {};
   db.prepare(
     `UPDATE sites SET name = ?, slug = ?, active = ?, badge_enabled = ?, badge_width_mm = ?,
       badge_height_mm = ?, badge_show_photo = ?, badge_accent = ?, badge_note = ?,
       colour_brand = ?, colour_signout = ?, colour_page = ?, colour_text = ?,
       banner_height = ?, banner_align = ?, printer_enabled = ?, printer_host = ?,
-      printer_port = ?, printer_model = ?, printer_rotate = ?, printer_label = ? WHERE id = ?`
+      printer_port = ?, printer_model = ?, printer_rotate = ?, printer_label = ?,
+      photo_mode = ?, photo_threshold = ?, photo_contrast = ? WHERE id = ?`
   ).run(
     clean(req.body?.name ?? site.name, 100) || site.name,
     req.body?.slug ? uniqueSlug(req.body.slug, site.id) : site.slug,
@@ -435,7 +437,16 @@ router.patch('/sites/:id', (req, res) => {
       : site.printer_rotate,
     printerCfg.label !== undefined
       ? (Object.hasOwn(printer.ROLL_TYPES, printerCfg.label) ? printerCfg.label : '62')
-      : site.printer_label
+      : site.printer_label,
+    photoCfg.mode !== undefined
+      ? (Object.hasOwn(printer.PHOTO_MODES, photoCfg.mode) ? photoCfg.mode : 'dither')
+      : site.photo_mode,
+    photoCfg.threshold !== undefined
+      ? Math.min(95, Math.max(5, Number(photoCfg.threshold) || 50))
+      : site.photo_threshold,
+    photoCfg.contrast !== undefined
+      ? Math.min(100, Math.max(-100, Number(photoCfg.contrast) || 0))
+      : site.photo_contrast
   , site.id);
 
   res.json(shapeSite(db.prepare('SELECT * FROM sites WHERE id = ?').get(site.id)));
@@ -561,6 +572,37 @@ router.post('/visits/:id/print', async (req, res) => {
   }
 });
 
+/** The same photo at several halftone settings, to choose between by eye. */
+router.get('/sites/:id/photo-preview', async (req, res) => {
+  const site = db.prepare('SELECT * FROM sites WHERE id = ?').get(req.params.id);
+  if (!site) return res.status(404).send('Not found.');
+
+  // Whatever real photo is closest to hand: the most recent visit at this site,
+  // then any stored recurring visitor photo.
+  const recent =
+    db
+      .prepare(
+        'SELECT photo_path FROM visits WHERE site_id = ? AND photo_path IS NOT NULL ORDER BY id DESC LIMIT 1'
+      )
+      .get(site.id) ||
+    db.prepare('SELECT photo_path FROM frequent_visitors WHERE photo_path IS NOT NULL LIMIT 1').get();
+
+  const overrides = {
+    photo_mode: req.query.mode || site.photo_mode,
+    photo_threshold: req.query.threshold || site.photo_threshold,
+    photo_contrast: req.query.contrast || site.photo_contrast,
+  };
+
+  try {
+    const png = await printer.photoPreviewPng(recent?.photo_path || null, overrides);
+    res.setHeader('Content-Type', 'image/png');
+    res.setHeader('Cache-Control', 'no-store');
+    res.send(png);
+  } catch (err) {
+    res.status(500).send(`Could not render the preview: ${err.message}`);
+  }
+});
+
 router.get('/sites/:id/badge-preview', (req, res) => {
   const site = db.prepare('SELECT * FROM sites WHERE id = ?').get(req.params.id);
   if (!site) return res.status(404).send('Not found.');