Initial commit: video effects processing system

Add S-expression based video effects pipeline with modular effect
definitions, constructs, and recipe files.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

effects/zoom.py

@@ -0,0 +1,91 @@
+# /// script
+# requires-python = ">=3.10"
+# dependencies = ["numpy", "opencv-python"]
+# ///
+"""
+@effect zoom
+@version 1.0.0
+@author artdag
+
+@description
+Zooms into the center of the frame. Values > 1 zoom in (magnify),
+values < 1 zoom out (shrink with black borders).
+
+@param factor float
+  @range 0.1 5
+  @default 1.0
+  Zoom factor. 1 = unchanged, 2 = 2x magnification, 0.5 = half size.
+
+@param center_x float
+  @range 0 1
+  @default 0.5
+  Horizontal center of zoom (0 = left, 1 = right).
+
+@param center_y float
+  @range 0 1
+  @default 0.5
+  Vertical center of zoom (0 = top, 1 = bottom).
+
+@example
+  (effect zoom :factor 1.5)
+
+@example
+  ;; Pulse zoom on bass
+  (effect zoom :factor (bind bass :range [1.0 1.5] :transform sqrt))
+
+@example
+  ;; Zoom to corner
+  (effect zoom :factor 2 :center_x 0 :center_y 0)
+"""
+
+import numpy as np
+import cv2
+
+
+def process_frame(frame: np.ndarray, params: dict, state: dict) -> tuple:
+    """
+    Zoom a video frame.
+
+    Args:
+        frame: Input frame as numpy array (H, W, 3) RGB uint8
+        params: Effect parameters
+            - factor: zoom multiplier (default 1.0)
+            - center_x: horizontal center 0-1 (default 0.5)
+            - center_y: vertical center 0-1 (default 0.5)
+        state: Persistent state dict (unused)
+
+    Returns:
+        Tuple of (processed_frame, new_state)
+    """
+    factor = params.get("factor", 1.0)
+    center_x = params.get("center_x", 0.5)
+    center_y = params.get("center_y", 0.5)
+
+    if factor is None or factor <= 0.01:
+        factor = 1.0
+
+    if factor == 1.0:
+        return frame, state
+
+    h, w = frame.shape[:2]
+
+    # Calculate crop region for zoom in
+    new_w = int(w / factor)
+    new_h = int(h / factor)
+
+    if new_w <= 0 or new_h <= 0:
+        return frame, state
+
+    # Calculate crop offset based on center
+    x_start = int((w - new_w) * center_x)
+    y_start = int((h - new_h) * center_y)
+
+    # Clamp to valid range
+    x_start = max(0, min(x_start, w - new_w))
+    y_start = max(0, min(y_start, h - new_h))
+
+    # Crop and resize back to original dimensions
+    cropped = frame[y_start:y_start + new_h, x_start:x_start + new_w]
+    result = cv2.resize(cropped, (w, h), interpolation=cv2.INTER_LINEAR)
+
+    return result, state