updated best icon selection logic

ARCHITECTURE.md

@@ -273,19 +273,22 @@ WHERE url_path = '/'
 
 **Selection priority (decision flow):**
 
-1. Standard square sizes (32x32, 64x64, 48x48, 16x16) — ideal for tab display. Prefer larger.
-2. Other square sizes ≤64px — close enough. Prefer larger.
-3. Non-square but both dimensions ≤64px — acceptable. Prefer larger.
-4. Everything else (180x180, 192x192, SVG with no dimensions, etc.) — last resort, will be downscaled in bundle generation.
+Target: 32x32 source icon. The frontend displays favicons at 16x16 CSS pixels, which is 32x32 physical pixels on 2x Retina screens. So 32x32 is the ideal source resolution — crisp on Retina without wasting bundle space.
 
-Within the same tier: prefer PNG/GIF/ICO over WebP over SVG, then smaller file size as tiebreaker.
+1. **Icons ≥32px** (preferred): smallest first, so closest to 32 wins. A 32x32 beats a 48x48 beats a 180x180.
+2. **Icons <32px** (fallback): largest first. A 16x16 beats an 8x8.
+3. **Unknown dimensions** (NULL width/height): last resort.
+
+Within the same size tier:
+- Prefer PNG > ICO > GIF/JPEG/BMP > WebP
+- Tiebreaker: smaller file size
+
+SVGs excluded (can't rasterize without external deps). Icons ≤2x2 excluded (tracking pixels).
 
 Does not distinguish between `favicon_ico` and `link_rel` sources — purely based on what was actually downloaded and its dimensions/format.
 
 Uses `DISTINCT ON (host_id)` for efficient single-pass selection. See `pipeline/04_best_icon/select.sql`.
 
-**Note on SVG/WebP:** Lower priority because rasterizing SVG adds complexity and WebP-to-PNG re-encoding may increase size. Only selected when no raster alternatives exist.
-
 **Stats emitted:** Hosts with icons selected, hosts without any icon.
 
 ### Stage 5: Bundle Generation

pipeline/04_best_icon/select.sql

@@ -1,13 +1,14 @@
 -- Best Icon Selection
 -- Picks the best completed icon for each host and stores its s3_key in hosts.best_icon_s3_key.
 --
+-- Target: 32x32 source icon (displayed at 16x16 CSS, crisp on 2x Retina).
+--
 -- Priority:
---   1. Standard square sizes (64 > 48 > 32 > 16) — ideal for tab display
---   2. Other square sizes ≤64
---   3. Non-square sizes ≤64 on both axes
---   4. Anything larger (downloaded because rel_sizes was undeclared)
---   5. Among equal priority: prefer PNG/GIF/ICO over WebP (SVGs excluded — not supported in bundle generation)
---   6. Tiebreaker: smaller file size (less bandwidth in bundles)
+--   1. Icons ≥32px: prefer smallest first (closest to 32 — a 32x32 beats a 48x48 beats a 180x180)
+--   2. Icons <32px: prefer largest first (16x16 beats 8x8)
+--   3. Within same size: prefer PNG > ICO > GIF/JPEG/BMP > WebP
+--   4. Tiebreaker: smaller file size
+--   SVGs excluded (not supported in bundle generation). Icons ≤2x2 excluded (tracking pixels).
 --
 -- Usage: psql $DATABASE_URL -f pipeline/04_best_icon/select.sql
 
@@ -17,22 +18,30 @@ FROM (
   FROM icons i
   WHERE i.scan_state = 'completed'
     AND i.s3_key IS NOT NULL
-    AND i.content_type NOT IN ('image/svg+xml')
+    AND i.content_type != 'image/svg+xml'
     AND (i.width IS NULL OR i.width > 2)
     AND (i.height IS NULL OR i.height > 2)
   ORDER BY i.host_id,
+    -- Tier: ≥32 preferred over <32. NULL dimensions go last.
     CASE
-      WHEN i.width = i.height AND i.width IN (64, 48, 32, 16) THEN 0
-      WHEN i.width = i.height AND i.width <= 64 THEN 1
-      WHEN i.width IS NOT NULL AND i.width <= 64 AND i.height IS NOT NULL AND i.height <= 64 THEN 2
-      ELSE 3
-    END,
-    COALESCE(i.width, 0) DESC,
-    CASE
-      WHEN i.content_type IN ('image/png', 'image/gif', 'image/x-icon', 'image/vnd.microsoft.icon') THEN 0
-      WHEN i.content_type = 'image/webp' THEN 1
+      WHEN LEAST(COALESCE(i.width, 0), COALESCE(i.height, 0)) >= 32 THEN 0
+      WHEN COALESCE(i.width, 0) > 0 THEN 1
       ELSE 2
     END,
+    -- Within ≥32: smallest first (closest to 32). Within <32: largest first.
+    CASE
+      WHEN LEAST(COALESCE(i.width, 0), COALESCE(i.height, 0)) >= 32
+        THEN GREATEST(COALESCE(i.width, 0), COALESCE(i.height, 0))
+      ELSE -GREATEST(COALESCE(i.width, 0), COALESCE(i.height, 0))
+    END,
+    -- Format preference
+    CASE
+      WHEN i.content_type = 'image/png' THEN 0
+      WHEN i.content_type IN ('image/x-icon', 'image/vnd.microsoft.icon') THEN 1
+      WHEN i.content_type IN ('image/gif', 'image/jpeg', 'image/bmp') THEN 2
+      WHEN i.content_type = 'image/webp' THEN 3
+      ELSE 4
+    END,
     i.file_size ASC
 ) sub
 WHERE h.id = sub.host_id;