Stand up Print Forge as a 3D-printed toy shop with color variants and printer photography.

Replaces the client_site template branding, adds shop/shipping, and points beta CI at master for easy deploy.

Closes #1

site/shop/imaging.py

@@ -0,0 +1,121 @@
+"""Turn a raw product photo into a centered cutout on a square canvas."""
+
+from __future__ import annotations
+
+import logging
+from io import BytesIO
+from pathlib import PurePosixPath
+
+from PIL import Image, ImageOps
+
+logger = logging.getLogger(__name__)
+
+CANVAS_SIZE = 1200
+CUTOUT_MAX_SIDE = 1600
+PADDING = 0.1
+ALPHA_THRESHOLD = 128
+
+_session = None
+
+
+def _rembg_session():
+    global _session
+    if _session is None:
+        from rembg import new_session
+
+        _session = new_session("u2net")
+    return _session
+
+
+def open_image(data: bytes) -> Image.Image:
+    image = Image.open(BytesIO(data))
+    image.load()
+    image = ImageOps.exif_transpose(image) or image
+    if getattr(image, "n_frames", 1) > 1:
+        image.seek(0)
+        image = image.copy()
+    return image
+
+
+def downscale(image: Image.Image, max_side: int) -> Image.Image:
+    width, height = image.size
+    longest = max(width, height)
+    if longest <= max_side:
+        return image
+    scale = max_side / longest
+    return image.resize(
+        (max(1, int(width * scale)), max(1, int(height * scale))),
+        Image.Resampling.LANCZOS,
+    )
+
+
+def harden_cutout(image: Image.Image, threshold: int = ALPHA_THRESHOLD) -> Image.Image:
+    """Drop faint shadow/halo pixels rembg leaves around the subject."""
+    rgba = image.convert("RGBA")
+    red, green, blue, alpha = rgba.split()
+    alpha = alpha.point(lambda value: value if value >= threshold else 0)
+    return Image.merge("RGBA", (red, green, blue, alpha))
+
+
+def cutout_subject(image: Image.Image) -> Image.Image:
+    """Knock out the background. Falls back to the original on failure."""
+    rgba = downscale(image.convert("RGBA"), CUTOUT_MAX_SIDE)
+    try:
+        from rembg import remove
+
+        buf = BytesIO()
+        rgba.save(buf, format="PNG")
+        result = remove(
+            buf.getvalue(),
+            session=_rembg_session(),
+            post_process_mask=True,
+        )
+        return harden_cutout(Image.open(BytesIO(result)).convert("RGBA"))
+    except Exception:
+        logger.exception("product photo cutout failed; using original")
+        return rgba
+
+
+def center_on_square(
+    image: Image.Image,
+    *,
+    size: int = CANVAS_SIZE,
+    padding: float = PADDING,
+) -> Image.Image:
+    rgba = image.convert("RGBA")
+    alpha = rgba.getchannel("A")
+    mask = alpha.point(lambda value: 255 if value > ALPHA_THRESHOLD else 0)
+    bbox = mask.getbbox()
+    canvas = Image.new("RGBA", (size, size), (0, 0, 0, 0))
+    if bbox is None:
+        return canvas
+    cropped = rgba.crop(bbox)
+    max_inner = max(1, int(size * (1 - 2 * padding)))
+    width, height = cropped.size
+    scale = min(max_inner / width, max_inner / height)
+    new_w = max(1, int(width * scale))
+    new_h = max(1, int(height * scale))
+    resized = cropped.resize((new_w, new_h), Image.Resampling.LANCZOS)
+    x = (size - new_w) // 2
+    y = (size - new_h) // 2
+    canvas.paste(resized, (x, y), resized)
+    return canvas
+
+
+def encode_png(image: Image.Image) -> bytes:
+    buf = BytesIO()
+    image.save(buf, format="PNG", optimize=True)
+    return buf.getvalue()
+
+
+def prepare_product_photo(data: bytes) -> tuple[bytes, str]:
+    """Return a PNG cutout on a square canvas, plus content type."""
+    image = open_image(data)
+    cut = cutout_subject(image)
+    framed = center_on_square(cut)
+    return encode_png(framed), "image/png"
+
+
+def product_image_filename(original: str) -> str:
+    stem = PurePosixPath(original or "product").stem.strip() or "product"
+    return f"{stem[:200]}.png"