Phase 11

src/camera.py

@@ -0,0 +1,78 @@
+"""OpenCV camera and video input abstraction."""
+
+from pathlib import Path
+
+import cv2
+import numpy as np
+
+from .config_loader import InputSettings
+from .exceptions import CameraOpenError, FrameReadError
+
+
+class Camera:
+    """Read frames from a camera device or video file."""
+
+    def __init__(self, config: InputSettings) -> None:
+        self.config = config
+        self._capture: cv2.VideoCapture | None = None
+        self._consecutive_failures = 0
+
+    def open(self) -> None:
+        backend_map = {"auto": cv2.CAP_ANY, "dshow": cv2.CAP_DSHOW, "msmf": cv2.CAP_MSMF, "v4l2": cv2.CAP_V4L2}
+        source: int | str
+        if self.config.type == "camera":
+            source = self.config.camera_id
+        else:
+            path = Path(self.config.video_path or "")
+            if not path.is_file():
+                raise CameraOpenError(f"Video file does not exist: {path}")
+            source = str(path)
+        self._capture = cv2.VideoCapture(source, backend_map[self.config.backend])
+        if not self._capture.isOpened():
+            self.release()
+            raise CameraOpenError(f"Could not open {self.config.type} input: {source}")
+        if self.config.type == "camera":
+            self._capture.set(cv2.CAP_PROP_FRAME_WIDTH, self.config.width)
+            self._capture.set(cv2.CAP_PROP_FRAME_HEIGHT, self.config.height)
+            self._capture.set(cv2.CAP_PROP_FPS, self.config.fps)
+
+    def read(self) -> np.ndarray | None:
+        if self._capture is None or not self._capture.isOpened():
+            raise CameraOpenError("Input is not open")
+        ok, frame = self._capture.read()
+        if ok and frame is not None:
+            self._consecutive_failures = 0
+            return frame
+        if self.config.type == "video":
+            return None
+        self._consecutive_failures += 1
+        if self._consecutive_failures >= self.config.max_consecutive_read_failures:
+            raise FrameReadError(f"Camera read failed {self._consecutive_failures} consecutive times")
+        return None
+
+    def is_opened(self) -> bool:
+        return self._capture is not None and self._capture.isOpened()
+
+    def _property(self, property_id: int) -> float:
+        return float(self._capture.get(property_id)) if self._capture is not None else 0.0
+
+    def get_actual_width(self) -> int:
+        return round(self._property(cv2.CAP_PROP_FRAME_WIDTH))
+
+    def get_actual_height(self) -> int:
+        return round(self._property(cv2.CAP_PROP_FRAME_HEIGHT))
+
+    def get_actual_fps(self) -> float:
+        return self._property(cv2.CAP_PROP_FPS)
+
+    def release(self) -> None:
+        if self._capture is not None:
+            self._capture.release()
+            self._capture = None
+
+    def __enter__(self) -> "Camera":
+        self.open()
+        return self
+
+    def __exit__(self, *_args: object) -> None:
+        self.release()