Add comprehensive tests for image processing and mask functionalities

- Introduced tests for color image handling, ensuring source preservation and premultiplied alpha usage.
- Implemented tests for brush stroke operations, validating segment boundaries and brush anti-aliasing.
- Added tests for frame anti-aliasing, confirming correct rendering behavior with various alpha values and depth settings.
- Created tests for frame projection, ensuring accurate overlap calculations and half-plane clipping.
- Developed tests for image premultiplied retention, verifying behavior during loading and packing processes.
- Added undo functionality tests for mask operations, ensuring single transaction behavior during edits.

tests/test_mask_undo.py

@@ -0,0 +1,68 @@
+import sys
+from pathlib import Path
+from unittest.mock import patch
+
+import bpy
+import numpy as np
+import pytest
+
+sys.path.insert(0, str(Path(__file__).parents[1] / "src"))
+
+from anyimage.common import image, viewport
+from anyimage.operators.image_edit_tool import mask
+
+
+@pytest.mark.parametrize("gesture", ["LASSO", "BRUSH", "POLYLINE"])
+def test_mask_commit_is_one_undo_transaction(gesture):
+    source = bpy.data.images.new("Undo source", width=8, height=8, alpha=True)
+    source.pixels.foreach_set(np.ones(8 * 8 * 4, dtype=np.float32))
+    source.pack()
+    owner = bpy.data.objects.new("Mask undo owner", None)
+    owner.empty_display_type = "IMAGE"
+    owner.data = source
+    bpy.context.scene.collection.objects.link(owner)
+    shared = bpy.data.objects.new("Mask undo shared", None)
+    shared.empty_display_type = "IMAGE"
+    shared.data = source
+    bpy.context.scene.collection.objects.link(shared)
+    owner_name, shared_name, source_name = owner.name, shared.name, source.name
+    before = image.image_pixels(source)
+    options = mask.EditImageAlpha.bl_options
+    assert options == {"UNDO"}
+
+    def execute(operator, context):
+        """Drive gesture completion without a window event in background bpy."""
+        operator.gesture, operator.mode, operator.radius = gesture, "SUBTRACT", 2
+        operator.source_object_name = owner_name
+        operator.source_matrix_data = viewport.serialize_matrix(owner.matrix_world)
+        operator._path = [(2, 2), (6, 2), (6, 6), (2, 6)]
+        operator._path_samples = list(operator._path)
+        return operator._complete(context)
+
+    bpy.context.preferences.edit.use_global_undo = True
+    with patch.object(mask.EditImageAlpha, "execute", execute, create=True), patch.object(
+        mask.EditImageAlpha, "poll", classmethod(lambda cls, context: True)
+    ), patch.object(viewport, "screen_path_to_image_pixels", side_effect=lambda path, *args, **kwargs: path), patch.object(
+        mask, "screen_path_to_image_pixels", side_effect=lambda path, *args, **kwargs: path
+    ), patch.object(mask, "create_image_edit_result", wraps=mask.create_image_edit_result) as create:
+        bpy.utils.register_class(mask.EditImageAlpha)
+        try:
+            bpy.ops.ed.undo_push(message="Before Mask")
+            assert bpy.ops.anyimage.edit_image_alpha("EXEC_DEFAULT", True) == {"FINISHED"}
+            create.assert_called_once()
+            result = bpy.data.objects[owner_name].data
+            assert result.packed_file is not None and result.alpha_mode == "PREMUL"
+            assert bpy.data.objects[shared_name].data.name == source_name
+            np.testing.assert_array_equal(image.image_pixels(bpy.data.images[source_name]), before)
+            assert bpy.ops.ed.undo() == {"FINISHED"}
+            assert bpy.data.objects[owner_name].data.name == source_name
+            np.testing.assert_array_equal(image.image_pixels(bpy.data.objects[owner_name].data), before)
+        finally:
+            bpy.utils.unregister_class(mask.EditImageAlpha)
+            for name in (owner_name, shared_name):
+                obj = bpy.data.objects.get(name)
+                if obj is not None:
+                    bpy.data.objects.remove(obj, do_unlink=True)
+            source = bpy.data.images.get(source_name)
+            if source is not None:
+                bpy.data.images.remove(source)