Add a photo permalink menu (#36)

Right click or long press on a gallery photo now opens a menu to copy its permalink or share it.
The permalink id is the SHA-256 of the original photo file so it survives reordering and rebuilds.
Each photo also gets a small noindex share page carrying its own link preview image.
Fixed the entrypoint script being checked out with CRLF on Windows by adding a gitattributes file.

Reviewed-on: #36

src/py/builder/html_generator.py

@@ -1,6 +1,8 @@
 import json
 import logging
+from html import escape
 from pathlib import Path
+from urllib.parse import quote
 
 
 def render_template(template_path, context):
@@ -19,8 +21,11 @@ def render_gallery_images(images):
     for img in images:
         tags = " ".join(img.get("tags", []))
         tag_html = "".join(f'<span class="tag">#{t}</span>' for t in img.get("tags", []))
+        # data-photo-id is what js/lumeex.js's photo menu builds the permalink from
+        photo_id = img.get("photo_id")
+        photo_id_attr = f' data-photo-id="{photo_id}"' if photo_id else ""
         html += f"""
-        <div class="section" data-tags="{tags}">
+        <div class="section" data-tags="{tags}"{photo_id_attr}>
             <div class="tags">{tag_html}</div>
             <img class="fade-in-img lazyload" data-src="/img/{img["src"]}" alt="{img.get("alt", "")}" loading="lazy">
         </div>
@@ -83,3 +88,46 @@ def generate_sitemap_xml(canonical_url, allowed_paths, output_dir):
     with open(output_path, "w", encoding="utf-8") as f:
         f.write(sitemap_content)
     logging.info(f"[✓] sitemap.xml generated at {output_path}")
+
+
+def render_photo_page(
+    photo_id, site_title, description, alt, page_url, image_url, image_size, signature
+):
+    """
+    photo/<id>/index.html: the page a copied/shared photo link points at.
+    Link-preview crawlers read its og:/twitter: tags (without running
+    scripts) and show this photo; visitors are sent on to the gallery with
+    ?photo=<id>. Kept out of search results with noindex rather than
+    robots.txt, since preview crawlers such as Twitterbot honour robots.txt
+    and would then never read the tags.
+    """
+    title = f"{alt} - {site_title}" if alt else site_title
+    gallery_href = f"/?photo={quote(photo_id)}"
+    width, height = image_size
+    t = escape(title)
+    return f"""<!DOCTYPE html>
+{signature}
+<html lang='en'>
+<head>
+    <meta charset="utf-8">
+    <title>{t}</title>
+    <meta name="robots" content="noindex, follow">
+    <meta name="viewport" content="width=device-width, initial-scale=1">
+    <link rel="icon" href="/favicon.ico" type="image/x-icon">
+    <meta name="description" content="{escape(description)}">
+    <meta name="twitter:card" content="summary_large_image">
+    <meta property="og:type" content="website" />
+    <meta property="og:site_name" content="{escape(site_title)}" />
+    <meta property="og:title" content="{t}" />
+    <meta property="og:description" content="{escape(description)}" />
+    <meta property="og:url" content="{escape(page_url)}" />
+    <meta property="og:image" content="{escape(image_url)}" />
+    <meta property="og:image:width" content="{width}" />
+    <meta property="og:image:height" content="{height}" />
+    <meta property="og:image:alt" content="{escape(alt)}" />
+    <script>location.replace({json.dumps(gallery_href)});</script>
+</head>
+<body>
+    <p><a href="{escape(gallery_href)}">{t}</a></p>
+</body>
+</html>"""

src/py/builder/image_processor.py

@@ -1,9 +1,13 @@
+import hashlib
+import io
 import logging
 from pathlib import Path
 from shutil import copyfile
 
 from PIL import Image, features
 
+SHARE_PREVIEW_MAX_WIDTH = 1200
+
 
 def convert_and_resize_image(input_path, output_path, resize=True, max_width=1140):
     """Convert an image to WebP (or JPEG fallback) and optionally resize it."""
@@ -56,6 +60,64 @@ def process_images(images, resize_images, img_dir, build_dir):
                 img["src"] = str(Path(img["src"]).with_suffix(".jpg"))
 
 
+def compute_photo_ids(images, img_dir):
+    """
+    Set each image's permalink id (img["photo_id"]): the SHA-256 of its
+    original file, so the same photo keeps the same link whatever its
+    position or filename, across rebuilds. lumeex-web computes the same
+    value. Duplicates of the same file get "-2", "-3"... in list order.
+    Must run before process_images, which rewrites img["src"].
+    """
+    seen = {}
+    for img in images:
+        src_path = img_dir / img["src"]
+        if not src_path.exists():
+            continue
+        digest = hashlib.sha256(src_path.read_bytes()).hexdigest()
+        seen[digest] = seen.get(digest, 0) + 1
+        img["photo_id"] = digest if seen[digest] == 1 else f"{digest}-{seen[digest]}"
+
+
+def _to_srgb(img, icc_profile):
+    """Convert to sRGB when Pillow was built with LittleCMS; unchanged otherwise."""
+    try:
+        from PIL import ImageCms
+    except ImportError:
+        return img
+    try:
+        src_profile = ImageCms.ImageCmsProfile(io.BytesIO(icc_profile))
+        return ImageCms.profileToProfile(img, src_profile, ImageCms.createProfile("sRGB"))
+    except ImageCms.PyCMSError as e:
+        logging.warning(f"[~] Could not convert embedded profile to sRGB: {e}")
+        return img
+
+
+def generate_share_preview(input_path, output_path, max_width=SHARE_PREVIEW_MAX_WIDTH):
+    """
+    Link-preview image for one gallery photo (photo/<id>/ pages): a plain
+    sRGB JPEG no wider than max_width, since WebP and wide-gamut profiles
+    aren't handled by every messaging app. Returns (width, height), or None
+    on failure.
+    """
+    try:
+        img = Image.open(input_path)
+        icc_profile = img.info.get("icc_profile")
+        img = img.convert("RGB")
+        if icc_profile:
+            img = _to_srgb(img, icc_profile)
+        width, height = img.size
+        if width > max_width:
+            height = int((max_width / width) * height)
+            width = max_width
+            img = img.resize((width, height), Image.LANCZOS)
+        output_path.parent.mkdir(parents=True, exist_ok=True)
+        img.save(output_path, "JPEG", quality=85)
+        return width, height
+    except Exception as e:
+        logging.error(f"[✗] Error generating share preview for {input_path}: {e}")
+        return None
+
+
 def copy_original_images(images, img_dir, build_dir):
     """Copy original image files without processing."""
     for img in images:

src/py/builder/site_builder.py

@@ -11,12 +11,15 @@ from .html_generator import (
     generate_robots_txt,
     generate_sitemap_xml,
     render_gallery_images,
+    render_photo_page,
     render_template,
 )
 from .image_processor import (
+    compute_photo_ids,
     copy_original_images,
     generate_favicon_ico,
     generate_favicons_from_logo,
+    generate_share_preview,
     process_images,
 )
 from .utils import copy_assets, ensure_dir, load_theme_config, load_yaml
@@ -91,6 +94,13 @@ def build():
     hero_images = gallery_vars.get("hero", {}).get("images", [])
     gallery_images = gallery_vars.get("gallery", {}).get("images", [])
 
+    # Permalink ids for gallery photos (not the hero carousel), hashed from
+    # the original files — before process_images rewrites their src
+    compute_photo_ids(gallery_images, IMG_DIR)
+    original_src_by_photo_id = {
+        img["photo_id"]: img["src"] for img in gallery_images if "photo_id" in img
+    }
+
     if convert_images:
         process_images(hero_images, resize_images, IMG_DIR, BUILD_DIR)
         process_images(gallery_images, resize_images, IMG_DIR, BUILD_DIR)
@@ -191,6 +201,34 @@ def build():
     else:
         logging.warning("[~] No legals section found in site.yaml")
 
+    # One link-preview page + preview image per gallery photo. og:image and
+    # og:url must be absolute for crawlers, hence the canonical URL.
+    site_info = site_vars.get("info", {})
+    share_pages = 0
+    for img in gallery_images:
+        photo_id = img.get("photo_id")
+        if not photo_id:
+            continue
+        preview_path = BUILD_DIR / "img" / "share" / f"{photo_id}.jpg"
+        size = generate_share_preview(IMG_DIR / original_src_by_photo_id[photo_id], preview_path)
+        if not size:
+            continue
+        page = render_photo_page(
+            photo_id,
+            site_title=site_info.get("title", ""),
+            description=site_info.get("description", ""),
+            alt=img.get("alt", ""),
+            page_url=f"{canonical_url}/photo/{photo_id}/",
+            image_url=f"{canonical_url}/img/share/{photo_id}.jpg",
+            image_size=size,
+            signature=signature,
+        )
+        page_path = BUILD_DIR / "photo" / photo_id / "index.html"
+        page_path.parent.mkdir(parents=True, exist_ok=True)
+        page_path.write_text(page, encoding="utf-8")
+        share_pages += 1
+    logging.info(f"[✓] Photo share pages generated: {share_pages}")
+
     # Hero carrousel generator
     if hero_images:
         generate_gallery_json_from_images(hero_images, BUILD_DIR)