Grayscale function

src/imagenie/grayscale.py

@@ -1,3 +1,5 @@
+import numpy as np
+
 def grayscale(image):
     """
     Converts an image to grayscale.
@@ -14,12 +16,30 @@ def grayscale(image):
 
     Raises:
     ------
+    TypeError
+        If the input is not a NumPy array.
     ValueError
-        If the input is not a 2D or 3D NumPy array.
+        If the input is not a 2D or 3D NumPy array, or if the 3D array does not have 3 channels.
 
     Examples:
     ---------
     Convert an RGB image to grayscale:
     >>> gray_image = grayscale(image)
     """
-    pass
+    # Ensure the input is a valid NumPy array
+    if not isinstance(image, np.ndarray):
+        raise TypeError("The input image must be a NumPy array.")
+
+    # Handle already grayscale (2D) images
+    if image.ndim == 2:
+        return image
+
+    # Handle RGB images (3D)
+    elif image.ndim == 3:
+        if image.shape[-1] != 3:
+            raise ValueError("The input image must have 3 channels in the last dimension for RGB.")
+        # Use weighted average to convert to grayscale
+        return np.dot(image[..., :3], [0.2989, 0.5870, 0.1140])
+
+    else:
+        raise ValueError("The input image must be a 2D or 3D NumPy array.")

tests/test_grayscale.ipynb

@@ -0,0 +1,72 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": 10,
+   "id": "f6be37b7-8203-43ea-b4f6-8c9a7823e0f9",
+   "metadata": {},
+   "outputs": [
+    {
+     "ename": "ModuleNotFoundError",
+     "evalue": "No module named 'imagenie'",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mModuleNotFoundError\u001b[0m                       Traceback (most recent call last)",
+      "Cell \u001b[0;32mIn[10], line 3\u001b[0m\n\u001b[1;32m      1\u001b[0m \u001b[38;5;28;01mimport\u001b[39;00m \u001b[38;5;21;01munittest\u001b[39;00m\n\u001b[1;32m      2\u001b[0m \u001b[38;5;28;01mimport\u001b[39;00m \u001b[38;5;21;01mnumpy\u001b[39;00m \u001b[38;5;28;01mas\u001b[39;00m \u001b[38;5;21;01mnp\u001b[39;00m\n\u001b[0;32m----> 3\u001b[0m \u001b[38;5;28;01mfrom\u001b[39;00m \u001b[38;5;21;01mimagenie\u001b[39;00m \u001b[38;5;28;01mimport\u001b[39;00m grayscale  \n\u001b[1;32m      5\u001b[0m \u001b[38;5;28;01mdef\u001b[39;00m \u001b[38;5;21mtest_grayscale\u001b[39m():\n\u001b[1;32m      6\u001b[0m \u001b[38;5;250m    \u001b[39m\u001b[38;5;124;03m\"\"\"Test all cases for the grayscale function.\"\"\"\u001b[39;00m\n",
+      "\u001b[0;31mModuleNotFoundError\u001b[0m: No module named 'imagenie'"
+     ]
+    }
+   ],
+   "source": [
+    "import unittest\n",
+    "import numpy as np\n",
+    "from imagenie import grayscale  \n",
+    "\n",
+    "def test_grayscale():\n",
+    "    \"\"\"Test all cases for the grayscale function.\"\"\"\n",
+    "\n",
+    "    # Test that an already grayscale image (2D array) is returned unchanged\n",
+    "    gray_image = np.array([[10, 20, 30], [40, 50, 60]], dtype=np.uint8)\n",
+    "    result = grayscale(gray_image)\n",
+    "    np.testing.assert_array_equal(result, gray_image)\n",
+    "\n",
+    "    # Test that an empty array is handled correctly\n",
+    "    empty_image = np.array([], dtype=np.uint8).reshape(0, 0)\n",
+    "    result = grayscale(empty_image)\n",
+    "    np.testing.assert_array_equal(result, empty_image)\n",
+    "\n",
+    "    # Test that a TypeError is raised if the input is not a NumPy array\n",
+    "    try:\n",
+    "        grayscale([[255, 0, 0], [0, 255, 0]])  # Input is a Python list, not a NumPy array\n",
+    "    except TypeError as e:\n",
+    "        assert str(e) == \"The input image must be a NumPy array.\"\n",
+    "\n",
+    "if __name__ == \"__main__\":\n",
+    "    test_grayscale()\n",
+    "    print(\"All tests passed.\")"
+   ]
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3 (ipykernel)",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.12.7"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 5
+}