Switch to headless OpenCV

requirements.txt

@@ -1,3 +1,3 @@
 numpy==2.1.3
-opencv-python==4.10.0.84
+opencv-python-headless==4.10.0.84
 pillow==11.0.0

serPy/serPy.py

@@ -2,34 +2,31 @@
 import numpy as np
 from datetime import datetime, timedelta
 from PIL import Image
-import cv2
 import logging
 
 logger = logging.getLogger(__name__)
 
-# Mapping of color_id to OpenCV Bayer conversion codes
-BAYER_CONVERSION_CODES = {
-    8: cv2.COLOR_BAYER_RG2RGB,
-    9: cv2.COLOR_BAYER_GR2RGB,
-    10: cv2.COLOR_BAYER_GB2RGB,
-    11: cv2.COLOR_BAYER_BG2RGB,
-    # Other Bayer patterns (e.g., CYMG) are less commonly supported in OpenCV
-    # These require custom processing if needed
-}
 
 def save_frame_as_png(frame, output_path, color_id, align_rgb=True):
-    """
-    Saves a debayered and optionally RGB-aligned frame as a PNG file.
-
-    Parameters:
-        frame (np.ndarray): Frame array (2D Bayer-encoded or grayscale).
-        output_path (str): File path for the output PNG.
-        color_id (int): Color format ID, determines the Bayer pattern.
-        align_rgb (bool): Whether to perform RGB alignment.
-    """
-    if color_id in BAYER_CONVERSION_CODES:
+    """Saves a debayered and optionally RGB-aligned frame as a PNG file."""
+
+    # Import OpenCV lazily so the module can be imported without the library
+    # being available. This avoids requiring system packages like libGL when
+    # the functionality is not used (e.g. during tests).
+    import cv2
+
+    # Mapping of ``color_id`` to OpenCV Bayer conversion codes. Defined here so
+    # it is only created when ``cv2`` is available.
+    bayer_conversion_codes = {
+        8: cv2.COLOR_BAYER_RG2RGB,
+        9: cv2.COLOR_BAYER_GR2RGB,
+        10: cv2.COLOR_BAYER_GB2RGB,
+        11: cv2.COLOR_BAYER_BG2RGB,
+    }
+
+    if color_id in bayer_conversion_codes:
         # Perform debayering using OpenCV
-        debayered_frame = cv2.cvtColor(frame, BAYER_CONVERSION_CODES[color_id])
+        debayered_frame = cv2.cvtColor(frame, bayer_conversion_codes[color_id])
     elif color_id == 0:  # MONO
         # No debayering needed, use the frame directly
         debayered_frame = frame
@@ -47,7 +44,9 @@ def save_frame_as_png(frame, output_path, color_id, align_rgb=True):
         # Align Blue to Green
         warp_matrix = np.eye(2, 3, dtype=np.float32)
         try:
-            _, warp_matrix = cv2.findTransformECC(g, b, warp_matrix, warp_mode, criteria)
+            _, warp_matrix = cv2.findTransformECC(
+                g, b, warp_matrix, warp_mode, criteria
+            )
             b_aligned = cv2.warpAffine(
                 b,
                 warp_matrix,
@@ -61,7 +60,9 @@ def save_frame_as_png(frame, output_path, color_id, align_rgb=True):
         # Align Red to Green
         warp_matrix = np.eye(2, 3, dtype=np.float32)
         try:
-            _, warp_matrix = cv2.findTransformECC(g, r, warp_matrix, warp_mode, criteria)
+            _, warp_matrix = cv2.findTransformECC(
+                g, r, warp_matrix, warp_mode, criteria
+            )
             r_aligned = cv2.warpAffine(
                 r,
                 warp_matrix,
@@ -86,7 +87,8 @@ def save_frame_as_png(frame, output_path, color_id, align_rgb=True):
     # Save the image as PNG
     image.save(output_path)
     print(f"Frame saved as {output_path}")
-
+
+
 def ser_timestamp_to_datetime(timestamp):
     """
     Converts an SER timestamp (8-byte integer) to a readable date-time string.
@@ -109,6 +111,7 @@ def ser_timestamp_to_datetime(timestamp):
     # Return as a readable string
     return readable_datetime.isoformat()
 
+
 def write_ser(output_path, metadata, frames, timestamps=None):
     """
     Writes an SER file with the given metadata, frames, and optional timestamps.
@@ -168,7 +171,9 @@ def write_ser(output_path, metadata, frames, timestamps=None):
         # Write the frames
         for frame in frames:
             if frame.shape != (frame_height, frame_width):
-                raise ValueError(f"Frame dimensions {frame.shape} do not match metadata ({frame_height}, {frame_width}).")
+                raise ValueError(
+                    f"Frame dimensions {frame.shape} do not match metadata ({frame_height}, {frame_width})."
+                )
             ser_file.write(frame.astype(dtype).tobytes())
 
         # Write the timestamps (if provided)
@@ -180,6 +185,7 @@ def write_ser(output_path, metadata, frames, timestamps=None):
 
     print(f"SER file written successfully to {output_path}")
 
+
 def read_ser(input_path):
     """
     Reads an SER file with the updated header structure.
@@ -214,7 +220,7 @@ def read_ser(input_path):
             instrument,
             telescope,
             date_time,
-            date_time_utc
+            date_time_utc,
         ) = struct.unpack(header_format, header)
 
         # Validate the file