feat: add utilities for flipping images

Author: robgee86

src/arduino/app_utils/image/adjustments.py

@@ -65,7 +65,7 @@ def letterbox(
     if frame.ndim == 2:
         # Greyscale
         if hasattr(color, "__len__"):
-            color = color[0]
+            raise ValueError("For greyscale images, color must be a scalar (int), not a tuple or list.")
         canvas = np.full((target_h, target_w), color, dtype=original_dtype)
     else:
         # Colored (BGR/BGRA)
@@ -108,6 +108,32 @@ def resize(frame: np.ndarray, target_size: Tuple[int, int], maintain_ratio: bool
         return cv2.resize(frame, (target_size[0], target_size[1]), interpolation=interpolation)
 
 
+def flip_h(frame: np.ndarray) -> np.ndarray:
+    """
+    Flip frame horizontally.
+
+    Args:
+        frame (np.ndarray): Input frame
+
+    Returns:
+        np.ndarray: Horizontally flipped frame
+    """
+    return frame[:, ::-1, ...]
+
+
+def flip_v(frame: np.ndarray) -> np.ndarray:
+    """
+    Flip frame vertically.
+
+    Args:
+        frame (np.ndarray): Input frame
+
+    Returns:
+        np.ndarray: Vertically flipped frame
+    """
+    return frame[::-1, :, ...]
+
+
 def adjust(frame: np.ndarray, brightness: float = 0.0, contrast: float = 1.0, saturation: float = 1.0, gamma: float = 1.0) -> np.ndarray:
     """
     Apply image adjustments to a BGR or BGRA frame, preserving channel count
@@ -370,6 +396,26 @@ def resized(target_size: Tuple[int, int], maintain_ratio: bool = False, interpol
     return PipeableFunction(resize, target_size=target_size, maintain_ratio=maintain_ratio, interpolation=interpolation)
 
 
+def flipped_h():
+    """
+    Pipeable horizontal flip function - flip frame horizontally with pipe operator support.
+
+    Returns:
+        Function that takes a frame and returns horizontally flipped frame
+    """
+    return PipeableFunction(flip_h)
+
+
+def flipped_v():
+    """
+    Pipeable vertical flip function - flip frame vertically with pipe operator support.
+
+    Returns:
+        Function that takes a frame and returns vertically flipped frame
+    """
+    return PipeableFunction(flip_v)
+
+
 def adjusted(brightness: float = 0.0, contrast: float = 1.0, saturation: float = 1.0, gamma: float = 1.0):
     """
     Pipeable adjust function - apply image adjustments with pipe operator support.

tests/arduino/app_utils/image/test_adjustments.py

@@ -4,7 +4,7 @@
 
 import numpy as np
 import pytest
-from arduino.app_utils.image.adjustments import letterbox, resize, adjust, split_channels, greyscale
+from arduino.app_utils.image.adjustments import letterbox, resize, adjust, split_channels, greyscale, flip_h, flip_v
 
 
 # FIXTURES
@@ -440,3 +440,55 @@ def test_letterbox_color_tuple_error(frame_bgr_uint8):
         # BGRA (4-ch) frame with 3-ch padding
         frame_bgra = create_bgra_frame(np.uint8)
         letterbox(frame_bgra, (200, 200), color=(0, 0, 0))
+
+
+def test_flip_h_bgr(frame_bgr_uint8):
+    """Test horizontal flip for BGR image."""
+    flipped = flip_h(frame_bgr_uint8)
+    # Flipping twice should return the original
+    assert np.array_equal(flip_h(flipped), frame_bgr_uint8)
+    # Check that first column becomes last
+    assert np.array_equal(flipped[:, 0, :], frame_bgr_uint8[:, -1, :])
+    assert np.array_equal(flipped[:, -1, :], frame_bgr_uint8[:, 0, :])
+
+
+def test_flip_v_bgr(frame_bgr_uint8):
+    """Test vertical flip for BGR image."""
+    flipped = flip_v(frame_bgr_uint8)
+    # Flipping twice should return the original
+    assert np.array_equal(flip_v(flipped), frame_bgr_uint8)
+    # Check that first row becomes last
+    assert np.array_equal(flipped[0, :, :], frame_bgr_uint8[-1, :, :])
+    assert np.array_equal(flipped[-1, :, :], frame_bgr_uint8[0, :, :])
+
+
+def test_flip_h_greyscale(frame_grey_uint8):
+    """Test horizontal flip for greyscale image."""
+    flipped = flip_h(frame_grey_uint8)
+    assert np.array_equal(flip_h(flipped), frame_grey_uint8)
+    assert np.array_equal(flipped[:, 0], frame_grey_uint8[:, -1])
+    assert np.array_equal(flipped[:, -1], frame_grey_uint8[:, 0])
+
+
+def test_flip_v_greyscale(frame_grey_uint8):
+    """Test vertical flip for greyscale image."""
+    flipped = flip_v(frame_grey_uint8)
+    assert np.array_equal(flip_v(flipped), frame_grey_uint8)
+    assert np.array_equal(flipped[0, :], frame_grey_uint8[-1, :])
+    assert np.array_equal(flipped[-1, :], frame_grey_uint8[0, :])
+
+
+def test_flip_h_bgra(frame_bgra_uint8):
+    """Test horizontal flip for BGRA image."""
+    flipped = flip_h(frame_bgra_uint8)
+    assert np.array_equal(flip_h(flipped), frame_bgra_uint8)
+    assert np.array_equal(flipped[:, 0, :], frame_bgra_uint8[:, -1, :])
+    assert np.array_equal(flipped[:, -1, :], frame_bgra_uint8[:, 0, :])
+
+
+def test_flip_v_bgra(frame_bgra_uint8):
+    """Test vertical flip for BGRA image."""
+    flipped = flip_v(frame_bgra_uint8)
+    assert np.array_equal(flip_v(flipped), frame_bgra_uint8)
+    assert np.array_equal(flipped[0, :, :], frame_bgra_uint8[-1, :, :])
+    assert np.array_equal(flipped[-1, :, :], frame_bgra_uint8[0, :, :])