src/viz/structure.py

"""Render a guest 2D structure from SMILES with RDKit (no external service)."""
from __future__ import annotations

from io import BytesIO


def render_smiles(smiles: str, size: int = 320):
    """Return a PIL.Image of the molecule, or None if SMILES is empty/invalid."""
    if not smiles:
        return None
    try:
        from rdkit import Chem
        from rdkit.Chem.Draw import rdMolDraw2D
    except ImportError:
        return None

    mol = Chem.MolFromSmiles(smiles)
    if mol is None:
        return None
    drawer = rdMolDraw2D.MolDraw2DCairo(size, size)
    drawer.DrawMolecule(mol)
    drawer.FinishDrawing()

    from PIL import Image

    return Image.open(BytesIO(drawer.GetDrawingText()))