add back GUI 2D display with optional raw / pure color background

examples/viz/render_2d.py

@@ -12,12 +12,12 @@ import orisys
 if TYPE_CHECKING:
     from pipeline.frame import FingerFrameView
 
-ArrowBackground = Literal["unrolled", "white"]
+ArrowBackground = Literal["unrolled", "pure_color"]
 
 
 @dataclass(frozen=True)
 class ArrowCanvasColors:
-    """BGR fill colors for synthetic UV arrow background (``background='white'``)."""
+    """BGR fill colors for synthetic UV arrow background (``background='pure_color'``)."""
 
     outside_bgr: tuple[int, int, int] = (0, 0, 0)
     uv_bgr: tuple[int, int, int] = (255, 255, 255)
@@ -67,6 +67,8 @@ def _arrow_background(
     """Return the BGR canvas for UV arrow drawing."""
     if background == "unrolled":
         return frame.unrolled
+    if background != "pure_color":
+        raise ValueError(f"unknown arrow background: {background!r}")
     h, w = frame.unrolled.shape[:2]
     outside = np.array(_as_bgr(canvas_colors.outside_bgr), dtype=np.uint8)
     uv = np.array(_as_bgr(canvas_colors.uv_bgr), dtype=np.uint8)