Add reference-anchored concept generation

TODO.md

@@ -404,19 +404,23 @@ facade evidence is still the 2009 CC BY frame. The 8 downloaded candidates are i
 
 **Tool plan for reference-anchored generation (plan first, implement after this section's review):**
 
-- [ ] Add `scene_concepts.py generate --reference <photo.png>`: attach a licence-cleared real photo
-      as a source image to the OpenRouter image request (image-edit/image-to-image endpoint), with
-      a prompt suffix that preserves the photographed facade geometry ("keep the building's column
-      count, spacing, band heights and sign placement exactly"). Record the reference file, its
-      licence and the model/prompt/spend in the sidecar.
-- [ ] Extend `generate_textures.generate_image()` with an optional `reference_url` (base64 data URL
-      of the photo) and a `strength` argument; keep every existing call signature unchanged and
-      gate the new path behind the reference being licence-cleared in the sidecar.
+- [x] Add `scene_concepts.py generate --reference <photo.png>`: attach a licence-cleared real photo
+      as a source image to the OpenRouter image request (multimodal chat endpoint with a base64
+      data URL), with a prompt suffix that preserves the photographed facade geometry. Record the
+      reference file, its licence and page in the `.refgen.json` provenance sidecar next to the
+      generated frame.
+- [x] Extend `generate_textures.generate_image()` with an optional `reference_path` argument
+      (base64 data URL of the photo); existing call signatures unchanged, and the path is gated by
+      `scene_concepts._reference_source` requiring a refs-board `SIDECAR.md` row (or an explicit
+      `--reference-unchecked`). Verified live on the El Capitan day concept anchored on the CC BY
+      2.0 2009 facade photo; tests in `ReferenceGateTests`.
 - [ ] Add a sidecar-driven variant pass: for each real photo, generate day, night and weathered
       variants of the same framing so the concept board stays comparable with the photo board.
-- [ ] Generate facade, street and signage concept frames for the target block
+- [-] Generate facade, street and signage concept frames for the target block
       (`scene_concepts.py generate --reference ...`), commit only the selected frames, and record
-      model, prompt, spend **and source photo** in the block sidecar.
+      model, prompt, spend **and source photo** in the block sidecar. (First frame done:
+      `hollywood_boulevard_entrance_day-v2`, anchored on the facade photo; remaining framings
+      pending.)
 - [ ] Derive palette, lighting and material targets from the real-photo board and the generated
       concepts, and record the deltas the facade kit has to close.
 - [ ] Generate signage, awning and poster texture candidates with `asset_pipeline.py`; run the

docs/asset-tooling.md

@@ -192,6 +192,21 @@ Caveats:
   Blender still prints its own version banner before the script runs, so intake scripts should use
   `--json --out <file>` rather than parsing stdout.
 
+### Reference-anchored concept generation
+
+`tools/scene_concepts.py generate --reference <photo>` anchors a concept frame on a real
+photograph: the photo is sent to the OpenRouter multimodal chat endpoint as a base64 data URL
+(`generate_textures.generate_image(reference_path=...)`) with a prompt suffix that pins the
+photographed geometry (column rhythm, band heights, signage placement, camera angle) while the
+prompt restages lighting, weather and people.
+
+Licence gate: the reference must be listed in its `docs/screens/refs/<venue>/SIDECAR.md` row
+(which also supplies the licence and Commons page for provenance). A photo from anywhere else
+requires `--reference-unchecked`, which records `unchecked` in the provenance. Each anchored
+generation writes a `.refgen.json` sidecar next to the frame (`model`, reference file/licence/page,
+geometry suffix) so a concept frame can always be traced back to its evidence photo. Where a
+generated frame and its reference photo disagree, the photo wins for shape.
+
 ### Reference-board research (`refboard`)
 
 `tools/refboard.py` searches, fetches and documents Wikimedia Commons photos of a real location for

docs/screens/concepts/hollywood_boulevard/README.md

@@ -10,6 +10,18 @@ game textures. The geometry mapping and source links are in
 
 ![El Capitan Entertainment Centre entrance in daylight](hollywood_boulevard_entrance_day.png)
 
+## Entrance — day, photo-anchored
+
+![El Capitan Entertainment Centre entrance in daylight, anchored on the 2009 facade photo](hollywood_boulevard_entrance_day-v2.png)
+
+Generated with `generate --reference`, anchored on the licence-cleared
+[`el-capitan-facade-day-wikimedia-2009-10-27.jpg`](../../refs/hollywood/el-capitan-facade-day-wikimedia-2009-10-27.jpg)
+board photo (CC BY 2.0); provenance in
+[`hollywood_boulevard_entrance_day-v2.refgen.json`](hollywood_boulevard_entrance_day-v2.refgen.json).
+The facade geometry (motto band, column rhythm, lattice windows, banner slots,
+blade sign) follows the photograph; the street is restaged clean for art
+direction.
+
 ## Entrance — night
 
 ![El Capitan Entertainment Centre entrance at night](hollywood_boulevard_entrance_night.png)

docs/screens/concepts/hollywood_boulevard/hollywood_boulevard_entrance_day-v2.refgen.json

@@ -0,0 +1,12 @@
+{
+  "concept": "hollywood_boulevard_entrance_day",
+  "generated": "hollywood_boulevard_entrance_day-v2.png",
+  "model": "google/gemini-2.5-flash-image",
+  "reference": {
+    "file": "docs/screens/refs/hollywood/el-capitan-facade-day-wikimedia-2009-10-27.jpg",
+    "licence": "CC BY 2.0",
+    "page": "https://commons.wikimedia.org/wiki/File:El_Capitan_Theater_frontal_fachade-The_Masonic_Temple.jpg",
+    "licence_checked": true
+  },
+  "suffix": "Use the attached reference photograph as the fixed source of geometry and composition: keep the building's proportions, column rhythm, band heights, signage placement and camera angle exactly as photographed. Only restage lighting, weather, people and surface condition where the prompt asks for it. Do not invent extra storeys, wings or ornaments that the photo does not show."
+}

tools/generate_textures.py

@@ -21,8 +21,10 @@ import os
 import random
 import stat
 import sys
+import re
 import urllib.error
 import urllib.request
+from pathlib import Path
 from PIL import Image, ImageDraw, ImageFilter, ImageFont
 
 ROOT = os.path.join(os.path.dirname(os.path.abspath(__file__)), "..")
@@ -373,19 +375,122 @@ def _api_key() -> str:
     return key
 
 
+CHAT_COMPLETIONS_URL = "https://openrouter.ai/api/v1/chat/completions"
+_MIME_BY_SUFFIX = {".jpg": "image/jpeg", ".jpeg": "image/jpeg",
+                   ".png": "image/png", ".webp": "image/webp"}
+
+
+def _openrouter_headers() -> dict:
+    return {
+        "Authorization": f"Bearer {_api_key()}",
+        "Content-Type": "application/json",
+        "HTTP-Referer": "https://git.allucanget.biz/zwitschi/security-game",
+        "X-Title": "Gig Line",
+    }
+
+
+def _openrouter_post(req: urllib.request.Request) -> dict:
+    try:
+        with urllib.request.urlopen(req, timeout=300) as resp:
+            return json.loads(resp.read().decode("utf-8"))
+    except urllib.error.HTTPError as exc:
+        detail = exc.read().decode("utf-8", "replace")
+        sys.exit(f"error: OpenRouter returned HTTP {exc.code}: {detail}")
+    except urllib.error.URLError as exc:
+        sys.exit(f"error: could not reach OpenRouter: {exc.reason}")
+
+
+def _data_url(path) -> str:
+    """Encode a local image file as a base64 `data:` URL for multimodal input."""
+    path = Path(path)
+    if not path.is_file():
+        sys.exit(f"error: reference image not found: {path}")
+    mime = _MIME_BY_SUFFIX.get(path.suffix.lower())
+    if not mime:
+        sys.exit(f"error: unsupported reference image type: {path.suffix}")
+    encoded = base64.b64encode(path.read_bytes()).decode("ascii")
+    return f"data:{mime};base64,{encoded}"
+
+
+def _decode_chat_image(payload: dict) -> Image.Image:
+    """Pull the returned image out of a chat-completions response.
+
+    Models return either `message.images[].image_url.url` (a `data:` URL or an
+    https URL) or a `data:` URL embedded in the message content.
+    """
+    message = (payload.get("choices") or [{}])[0].get("message", {})
+    urls = []
+    for item in message.get("images") or []:
+        if isinstance(item, dict):
+            urls.append(item.get("image_url", {}).get("url", ""))
+    if not urls:
+        content = message.get("content") or ""
+        match = re.search(r"data:image/[a-z]+;base64,[A-Za-z0-9+/=]+", str(content))
+        if match:
+            urls.append(match.group(0))
+    if not urls:
+        sys.exit(f"error: OpenRouter returned no image data: {payload}")
+    url = urls[0]
+    if url.startswith("data:"):
+        raw = base64.b64decode(url.split(",", 1)[1])
+    else:
+        try:
+            with urllib.request.urlopen(urllib.request.Request(url), timeout=120) as resp:
+                raw = resp.read()
+        except urllib.error.URLError as exc:
+            sys.exit(f"error: could not download returned image: {exc.reason}")
+    try:
+        img = Image.open(io.BytesIO(raw))
+        img.load()
+    except Exception as exc:  # noqa: BLE001 - surface any decode failure clearly
+        sys.exit(f"error: could not decode returned image: {exc}")
+    return img
+
+
+def _generate_image_with_reference(prompt: str, model: str, reference_path) -> Image.Image:
+    """Image-to-image request: the reference photo anchors the composition."""
+    body = {
+        "model": model,
+        "messages": [{
+            "role": "user",
+            "content": [
+                {"type": "text", "text": prompt},
+                {"type": "image_url", "image_url": {"url": _data_url(reference_path)}},
+            ],
+        }],
+    }
+    req = urllib.request.Request(
+        CHAT_COMPLETIONS_URL,
+        data=json.dumps(body).encode("utf-8"),
+        headers=_openrouter_headers(),
+        method="POST",
+    )
+    return _decode_chat_image(_openrouter_post(req))
+
+
 def generate_image(prompt: str, model: str, size: int,
                    transparent: bool = False,
-                   aspect_ratio: str = "1:1") -> Image.Image:
+                   aspect_ratio: str = "1:1",
+                   reference_path=None) -> Image.Image:
     """Call the OpenRouter image API and return the decoded PIL image.
 
     Requests a square image at `size` px or a role-shaped image at the matching
     resolution tier and decodes `data[].b64_json`. Seedream's square requests
     retain the existing GEN_SIZE floor. When `transparent` is true, the API is
     asked for a transparent PNG background.
+
+    When `reference_path` points at an image file, the request switches to the
+    multimodal chat endpoint and sends the file as a base64 data URL next to the
+    prompt (image-to-image guidance). Size/aspect parameters do not apply on
+    that endpoint; the caller crops or rescales the returned frame as usual.
+    Only licence-cleared reference photos may be passed (see
+    `scene_concepts._reference_source`).
     """
     size = max(1, int(size))
-    if model == DEFAULT_IMAGE_MODEL:
+    if model == DEFAULT_IMAGE_MODEL and reference_path is None:
         size = max(GEN_SIZE, size)
+    if reference_path is not None:
+        return _generate_image_with_reference(prompt, model, reference_path)
     body = {
         "model": model,
         "prompt": prompt,
@@ -405,22 +510,10 @@ def generate_image(prompt: str, model: str, size: int,
     req = urllib.request.Request(
         OPENROUTER_IMAGES_URL,
         data=json.dumps(body).encode("utf-8"),
-        headers={
-            "Authorization": f"Bearer {_api_key()}",
-            "Content-Type": "application/json",
-            "HTTP-Referer": "https://git.allucanget.biz/zwitschi/security-game",
-            "X-Title": "Gig Line",
-        },
+        headers=_openrouter_headers(),
         method="POST",
     )
-    try:
-        with urllib.request.urlopen(req, timeout=300) as resp:
-            payload = json.loads(resp.read().decode("utf-8"))
-    except urllib.error.HTTPError as exc:
-        detail = exc.read().decode("utf-8", "replace")
-        sys.exit(f"error: OpenRouter returned HTTP {exc.code}: {detail}")
-    except urllib.error.URLError as exc:
-        sys.exit(f"error: could not reach OpenRouter: {exc.reason}")
+    payload = _openrouter_post(req)
 
     data = payload.get("data") or []
     if not data or not data[0].get("b64_json"):

tools/scene_concepts.py

@@ -323,30 +323,104 @@ def compose_prompt(name: str) -> str:
     return f"{prompt}. {style}."
 
 
-def generate_one(name: str, model: str, request_size: int) -> Path:
+REFERENCE_PROMPT_SUFFIX = (
+    "Use the attached reference photograph as the fixed source of geometry and "
+    "composition: keep the building's proportions, column rhythm, band heights, "
+    "signage placement and camera angle exactly as photographed. Only restage "
+    "lighting, weather, people and surface condition where the prompt asks for it. "
+    "Do not invent extra storeys, wings or ornaments that the photo does not show."
+)
+
+REFS_DIR = ROOT / "docs" / "screens" / "refs"
+
+
+def _reference_source(path_str: str, allow_unchecked: bool = False) -> dict:
+    """Resolve and licence-check a reference photo for anchored generation.
+
+    A file under `docs/screens/refs/` must already be listed in that venue's
+    `SIDECAR.md` (the licence gate); its licence and Commons page are returned
+    for provenance. Anything else requires the explicit `--reference-unchecked`
+    override, which keeps unreviewed material out of the committed pipeline by
+    default.
+    """
+    path = Path(path_str).expanduser().resolve()
+    if not path.is_file():
+        sys.exit(f"error: reference photo not found: {path}")
+    if REFS_DIR in path.parents:
+        sidecar = path.parent / "SIDECAR.md"
+        text = sidecar.read_text(encoding="utf-8") if sidecar.is_file() else ""
+        row = next((line for line in text.splitlines()
+                    if f"`{path.name}`" in line), None)
+        if not row:
+            sys.exit(f"error: {path.name} is not listed in {sidecar}; add the "
+                     "sidecar row (licence gate) before anchoring generation on it")
+        cells = [c.strip() for c in row.split("|")]
+        licence = next((c for c in cells if c and c.lower().startswith(("cc", "public"))), "?")
+        page = next((c.strip("<> ") for c in cells if c.startswith("<http")), "")
+        return {"path": path, "licence": licence, "page": page, "checked": True}
+    if not allow_unchecked:
+        sys.exit(f"error: {path} is outside docs/screens/refs/ and not licence-checked; "
+                 "move it into a refs board with a SIDECAR row, or pass "
+                 "--reference-unchecked to accept the licence responsibility")
+    return {"path": path, "licence": "unchecked", "page": "", "checked": False}
+
+
+def _write_reference_provenance(out_path: Path, reference: dict, name: str,
+                                model: str) -> Path:
+    """Record which photo anchored a generated frame (`.refgen.json` sidecar)."""
+    sidecar = out_path.with_suffix(".refgen.json")
+    sidecar.write_text(json.dumps({
+        "concept": name,
+        "generated": out_path.name,
+        "model": model,
+        "reference": {"file": str(reference["path"].relative_to(ROOT))
+                      if reference["path"].is_relative_to(ROOT) else str(reference["path"]),
+                      "licence": reference["licence"],
+                      "page": reference["page"],
+                      "licence_checked": reference["checked"]},
+        "suffix": REFERENCE_PROMPT_SUFFIX,
+    }, indent=2) + "\n", encoding="utf-8")
+    return sidecar
+
+
+def generate_one(name: str, model: str, request_size: int,
+                 reference: dict | None = None) -> Path:
     group = CATALOGUE[name][0]
     prompt = compose_prompt(name)
+    if reference:
+        prompt = f"{prompt}\n\n{REFERENCE_PROMPT_SUFFIX}"
     if group == "scene":
         image = generate_textures.generate_image(prompt, model, request_size,
-                                                 transparent=False, aspect_ratio="3:2")
+                                                 transparent=False, aspect_ratio="3:2",
+                                                 reference_path=reference["path"]
+                                                 if reference else None)
         image = ImageOps.fit(image.convert("RGB"), (SCENE_W, SCENE_H),
                              method=Image.Resampling.LANCZOS)
     elif group == "backdrop":
         image = generate_textures.generate_image(prompt, model, request_size,
-                                                 transparent=True, aspect_ratio="3:2")
+                                                 transparent=True, aspect_ratio="3:2",
+                                                 reference_path=reference["path"]
+                                                 if reference else None)
     else:
         image = generate_textures.generate_image(prompt, model, request_size,
-                                                 transparent=False, aspect_ratio="1:1")
+                                                 transparent=False, aspect_ratio="1:1",
+                                                 reference_path=reference["path"]
+                                                 if reference else None)
         image = image.convert("RGB")
     out = next_free_path(raw_path(name))
     out.parent.mkdir(parents=True, exist_ok=True)
     image.save(out)
+    if reference:
+        provenance = _write_reference_provenance(out, reference, name, model)
+        print(f"provenance {_rel(provenance)} <- {reference['licence']}")
     print(f"wrote {_rel(out)} {image.size}")
     return out
 
 
 def cmd_generate(args) -> int:
     _load_env_file()
+    reference = _reference_source(args.reference, args.reference_unchecked) \
+        if args.reference else None
     names = _select(args.group, args.only)
     if not names:
         print("nothing selected", file=sys.stderr)
@@ -356,7 +430,7 @@ def cmd_generate(args) -> int:
         for _ in range(max(1, args.variants)):
             print(f"generating {name} ...", flush=True)
             try:
-                generate_one(name, args.model, args.request_size)
+                generate_one(name, args.model, args.request_size, reference=reference)
             except SystemExit as exc:  # generate_textures exits on API errors
                 failed.append(name)
                 print(f"  FAILED {name}: {exc}", file=sys.stderr)
@@ -1032,6 +1106,12 @@ def build_parser():
     gen.add_argument("--variants", type=int, default=1)
     gen.add_argument("--model", default=DEFAULT_MODEL)
     gen.add_argument("--request-size", type=int, default=1536)
+    gen.add_argument("--reference", default="",
+                     help="anchor generation on a licence-cleared reference photo "
+                          "(must be listed in its refs-board SIDECAR.md)")
+    gen.add_argument("--reference-unchecked", action="store_true",
+                     help="allow a reference photo from outside docs/screens/refs/ "
+                          "(you take responsibility for its licence)")
     gen.set_defaults(handler=cmd_generate)
     proc = sub.add_parser("process")
     proc.add_argument("--group", choices=("backdrop", "texture"))

tools/test_scene_concepts.py

@@ -1,5 +1,7 @@
+import json
 import tempfile
 import unittest
+from unittest import mock
 from pathlib import Path
 
 from PIL import Image
@@ -31,6 +33,62 @@ class CatalogueTests(unittest.TestCase):
         self.assertTrue(sc.raw_path("asphalt").is_relative_to(sc.RAW_DIR))
 
 
+class ReferenceGateTests(unittest.TestCase):
+    ROOT = Path(sc.__file__).resolve().parent.parent
+
+    def test_refs_photo_listed_in_sidecar_passes_with_provenance(self):
+        result = sc._reference_source(
+            self.ROOT / "docs/screens/refs/hollywood/"
+            "el-capitan-facade-day-wikimedia-2009-10-27.jpg")
+        self.assertTrue(result["checked"])
+        self.assertEqual(result["licence"], "CC BY 2.0")
+        self.assertIn("commons.wikimedia.org", result["page"])
+
+    def test_refs_photo_missing_from_sidecar_is_refused(self):
+        with tempfile.TemporaryDirectory(dir=self.ROOT / "docs/screens/refs") as tmp:
+            path = Path(tmp) / "unlisted.jpg"
+            path.write_bytes(b"x")
+            with self.assertRaises(SystemExit):
+                sc._reference_source(path)
+
+    def test_outside_photo_requires_the_explicit_override(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            path = Path(tmp) / "photo.jpg"
+            path.write_bytes(b"x")
+            with self.assertRaises(SystemExit):
+                sc._reference_source(path)
+            result = sc._reference_source(path, allow_unchecked=True)
+            self.assertFalse(result["checked"])
+            self.assertEqual(result["licence"], "unchecked")
+
+    def test_missing_file_is_refused(self):
+        with self.assertRaises(SystemExit):
+            sc._reference_source(self.ROOT / "docs/screens/refs/nope.jpg")
+
+    def test_generate_one_writes_reference_provenance(self):
+        reference = {"path": self.ROOT / "docs/screens/refs/hollywood/"
+                     "el-capitan-facade-day-wikimedia-2009-10-27.jpg",
+                     "licence": "CC BY 2.0", "page": "https://commons/x",
+                     "checked": True}
+        class FakeImage:
+            def convert(self, mode):
+                return Image.new("RGB", (1600, 900))
+        with tempfile.TemporaryDirectory() as tmp:
+            out = Path(tmp) / "hollywood_boulevard_entrance_day.png"
+            with mock.patch.object(sc.generate_textures, "generate_image",
+                                   return_value=FakeImage()) as mocked, \
+                    mock.patch.object(sc, "next_free_path", return_value=out), \
+                    mock.patch.object(sc, "_rel", side_effect=str):
+                sc.generate_one("hollywood_boulevard_entrance_day", "m", 1536,
+                                reference=reference)
+            call = mocked.call_args
+            self.assertIn("keep the building", call.args[0].lower())
+            self.assertEqual(call.kwargs["reference_path"], reference["path"])
+            provenance = json.loads(out.with_suffix(".refgen.json").read_text())
+            self.assertEqual(provenance["reference"]["licence"], "CC BY 2.0")
+            self.assertTrue(provenance["reference"]["licence_checked"])
+
+
 class NoOverwriteTests(unittest.TestCase):
     def test_next_free_path_never_returns_an_existing_file(self):
         with tempfile.TemporaryDirectory() as tmp: