dimensioned export (gwy, HDF5)

backend/exporters/image.py

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+"""
+Exporter for IMAGE values (numpy arrays, ImageData annotation sources).
+
+Images are raw pixel arrays — no physical calibration by design — so none of
+the formats here round-trip dimensions. PNG/TIFF convert to uint8 via the
+same image_to_uint8 helper the preview pipeline uses; NPZ preserves the raw
+array.
+"""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import numpy as np
+
+from backend.data_types import image_to_uint8
+from backend.exporters._base import FormatSpec
+
+accepted_types: tuple[str, ...] = ("IMAGE", "ANNOTATION_SOURCE")
+
+FORMATS: dict[str, FormatSpec] = {
+    "PNG":  FormatSpec(ext=".png",  round_trip=False, label="PNG"),
+    "TIFF": FormatSpec(ext=".tiff", round_trip=False, label="TIFF"),
+    "NPZ":  FormatSpec(ext=".npz",  round_trip=False, label="NumPy (.npz)"),
+}
+
+
+def save(path: Path, value: np.ndarray, format_name: str, **_opts) -> None:
+    arr = np.asarray(value)
+    if format_name == "PNG":
+        from PIL import Image
+        Image.fromarray(image_to_uint8(arr)).save(str(path))
+        return
+    if format_name == "TIFF":
+        import tifffile
+        tifffile.imwrite(str(path), image_to_uint8(arr))
+        return
+    if format_name == "NPZ":
+        np.savez(str(path), image=arr)
+        return
+    raise ValueError(f"Format {format_name!r} is not supported for IMAGE.")