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sn-image-base/scripts/sn_image_base/vlm/utils.py

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+"""Image encoding / decoding utilities for VLM."""
+
+from __future__ import annotations
+
+import base64
+import io
+from pathlib import Path
+
+from PIL import Image
+
+
+def read_image_bytes(image: str | bytes) -> bytes:
+    """Read raw image bytes from a path or return bytes unchanged.
+
+    Args:
+        image: File path to an image, or raw image bytes.
+
+    Returns:
+        bytes: Raw image bytes.
+
+    Raises:
+        FileNotFoundError: If image is a path and the file does not exist.
+    """
+    if isinstance(image, bytes):
+        return image
+    path = Path(image)
+    if not path.is_file():
+        raise FileNotFoundError(f"Image file not found: {image}")
+    return path.read_bytes()
+
+
+def detect_mime(data: bytes) -> str:
+    """Infer MIME type from image magic bytes.
+
+    Args:
+        data: Raw image bytes (at least 8 bytes for PNG check).
+
+    Returns:
+        str: 'image/png', 'image/jpeg', or 'image/png' as fallback.
+    """
+    if data[:8] == b"\x89PNG\r\n\x1a\n":
+        return "image/png"
+    if data[:3] == b"\xff\xd8\xff":
+        return "image/jpeg"
+    return "image/png"
+
+
+def detect_suffix(data: bytes) -> str:
+    """Infer file suffix from image magic bytes.
+
+    Args:
+        data: Raw image bytes.
+
+    Returns:
+        str: '.png', '.jpg', or '.bin' as fallback.
+    """
+    if data[:8] == b"\x89PNG\r\n\x1a\n":
+        return ".png"
+    if data[:3] == b"\xff\xd8\xff":
+        return ".jpg"
+    return ".bin"
+
+
+def image_to_mime_and_bytes(image: str | bytes) -> tuple[str, bytes]:
+    """Get MIME type and raw bytes; convert to PNG if format is not PNG/JPEG.
+
+    Args:
+        image: File path or raw image bytes.
+
+    Returns:
+        tuple[str, bytes]: (mime_type, raw_bytes). Unknown formats become PNG.
+    """
+    raw = read_image_bytes(image)
+    mime = detect_mime(raw)
+    if mime in ("image/png", "image/jpeg"):
+        return mime, raw
+    img = Image.open(io.BytesIO(raw)).convert("RGBA")
+    buf = io.BytesIO()
+    img.save(buf, format="PNG")
+    return "image/png", buf.getvalue()
+
+
+def image_to_base64(image: str | bytes) -> tuple[str, str]:
+    """Encode image to MIME type and base64 string.
+
+    Args:
+        image: File path or raw image bytes.
+
+    Returns:
+        tuple[str, str]: (mime_type, base64_encoded_string).
+    """
+    mime, raw = image_to_mime_and_bytes(image)
+    return mime, base64.b64encode(raw).decode("utf-8")
+
+
+def image_to_data_url(image: str | bytes) -> str:
+    """Build a data URL (data:mime;base64,...) for the image.
+
+    Args:
+        image: File path or raw image bytes.
+
+    Returns:
+        str: Data URL string.
+    """
+    mime, b64 = image_to_base64(image)
+    return f"data:{mime};base64,{b64}"
+
+
+def mask_secret(secret: str) -> str:
+    """Mask a secret for logging (e.g. show first 6 and last 4 chars).
+
+    Args:
+        secret: Raw secret string.
+
+    Returns:
+        str: Masked string (e.g. 'abcdef...ghij' or all '*' if length <= 8).
+    """
+    if len(secret) <= 8:
+        return "*" * len(secret)
+    return f"{secret[:6]}...{secret[-4:]}"