feat: add OpenCV camera source wrapper

bookmark/camera.py

@@ -0,0 +1,34 @@
+from typing import Protocol
+
+import cv2
+import numpy as np
+
+
+class FrameSource(Protocol):
+    def read_frame(self) -> np.ndarray: ...
+
+
+class CameraSource:
+    """Thin wrapper around cv2.VideoCapture for a single physical camera."""
+
+    def __init__(self, device_index: int = 0) -> None:
+        self.device_index = device_index
+        self._capture: cv2.VideoCapture | None = None
+
+    def open(self) -> None:
+        self._capture = cv2.VideoCapture(self.device_index)
+        if not self._capture.isOpened():
+            raise RuntimeError(f"Could not open camera at index {self.device_index}")
+
+    def read_frame(self) -> np.ndarray:
+        if self._capture is None:
+            raise RuntimeError("Camera not opened - call open() first")
+        ok, frame = self._capture.read()
+        if not ok:
+            raise RuntimeError("Failed to read frame from camera")
+        return frame
+
+    def close(self) -> None:
+        if self._capture is not None:
+            self._capture.release()
+            self._capture = None

tests/test_camera.py

@@ -0,0 +1,51 @@
+from unittest.mock import MagicMock, patch
+
+import numpy as np
+import pytest
+
+from bookmark.camera import CameraSource
+
+
+def test_open_raises_when_capture_not_opened():
+    with patch("bookmark.camera.cv2.VideoCapture") as mock_video_capture:
+        mock_instance = MagicMock()
+        mock_instance.isOpened.return_value = False
+        mock_video_capture.return_value = mock_instance
+
+        source = CameraSource(device_index=0)
+        with pytest.raises(RuntimeError, match="Could not open camera"):
+            source.open()
+
+
+def test_read_frame_returns_frame_from_capture():
+    with patch("bookmark.camera.cv2.VideoCapture") as mock_video_capture:
+        mock_instance = MagicMock()
+        mock_instance.isOpened.return_value = True
+        fake_frame = np.zeros((10, 10, 3), dtype=np.uint8)
+        mock_instance.read.return_value = (True, fake_frame)
+        mock_video_capture.return_value = mock_instance
+
+        source = CameraSource(device_index=0)
+        source.open()
+        frame = source.read_frame()
+
+        assert frame.shape == (10, 10, 3)
+
+
+def test_read_frame_raises_when_capture_fails():
+    with patch("bookmark.camera.cv2.VideoCapture") as mock_video_capture:
+        mock_instance = MagicMock()
+        mock_instance.isOpened.return_value = True
+        mock_instance.read.return_value = (False, None)
+        mock_video_capture.return_value = mock_instance
+
+        source = CameraSource(device_index=0)
+        source.open()
+        with pytest.raises(RuntimeError, match="Failed to read frame"):
+            source.read_frame()
+
+
+def test_read_frame_raises_if_not_opened():
+    source = CameraSource(device_index=0)
+    with pytest.raises(RuntimeError, match="not opened"):
+        source.read_frame()