Refactor imports in ProjectView for clarity and maintainability

croppa/capture.py

@@ -0,0 +1,87 @@
+import cv2
+
+
+class Cv2BufferedCap:
+    """Buffered wrapper around cv2.VideoCapture that handles frame loading, seeking, and caching correctly"""
+    
+    def __init__(self, video_path, backend=None):
+        self.video_path = video_path
+        self.cap = cv2.VideoCapture(str(video_path), backend)
+        if not self.cap.isOpened():
+            raise ValueError(f"Could not open video: {video_path}")
+        
+        # Video properties
+        self.total_frames = int(self.cap.get(cv2.CAP_PROP_FRAME_COUNT))
+        self.fps = self.cap.get(cv2.CAP_PROP_FPS)
+        self.frame_width = int(self.cap.get(cv2.CAP_PROP_FRAME_WIDTH))
+        self.frame_height = int(self.cap.get(cv2.CAP_PROP_FRAME_HEIGHT))
+        
+        # Frame cache
+        self.frame_cache = {}
+        self.cache_access_order = []
+        self.MAX_CACHE_FRAMES = 3000
+        
+        # Current position tracking
+        self.current_frame = 0
+        
+    def _manage_cache(self):
+        """Manage cache size using LRU eviction"""
+        while len(self.frame_cache) > self.MAX_CACHE_FRAMES:
+            oldest_frame = self.cache_access_order.pop(0)
+            if oldest_frame in self.frame_cache:
+                del self.frame_cache[oldest_frame]
+    
+    def _add_to_cache(self, frame_number, frame):
+        """Add frame to cache"""
+        self.frame_cache[frame_number] = frame.copy()
+        if frame_number in self.cache_access_order:
+            self.cache_access_order.remove(frame_number)
+        self.cache_access_order.append(frame_number)
+        self._manage_cache()
+    
+    def _get_from_cache(self, frame_number):
+        """Get frame from cache and update LRU"""
+        if frame_number in self.frame_cache:
+            if frame_number in self.cache_access_order:
+                self.cache_access_order.remove(frame_number)
+            self.cache_access_order.append(frame_number)
+            return self.frame_cache[frame_number].copy()
+        return None
+    
+    def get_frame(self, frame_number):
+        """Get frame at specific index - always accurate"""
+        # Clamp frame number to valid range
+        frame_number = max(0, min(frame_number, self.total_frames - 1))
+        
+        # Check cache first
+        cached_frame = self._get_from_cache(frame_number)
+        if cached_frame is not None:
+            self.current_frame = frame_number
+            return cached_frame
+        
+        # Not in cache, seek to frame and read
+        self.cap.set(cv2.CAP_PROP_POS_FRAMES, frame_number)
+        ret, frame = self.cap.read()
+        
+        if ret:
+            self._add_to_cache(frame_number, frame)
+            self.current_frame = frame_number
+            return frame
+        else:
+            raise ValueError(f"Failed to read frame {frame_number}")
+    
+    def advance_frame(self, frames=1):
+        """Advance by specified number of frames"""
+        new_frame = self.current_frame + frames
+        return self.get_frame(new_frame)
+    
+    def release(self):
+        """Release the video capture"""
+        if self.cap:
+            self.cap.release()
+    
+    def isOpened(self):
+        """Check if capture is opened"""
+        return self.cap and self.cap.isOpened()
+
+