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.

docs/index.md

@@ -8,5 +8,5 @@ AnyImage 是一款 Blender 扩展，可以粘贴和编辑图片、创建普通 P
 - 用 **Plane** 创建可调厚度和细分的图片网格
 - 用 **Depth Plane** 把静态图片转换为可调节的立体面片
 - 用 **Cutout** 从套索选区生成 Surface、Balloon 与两种 Depth Shape
-- 用 **Crop Box / Lasso / Polyline / Perspective** 清理或矫正 Image Empty
+- 用 **Frame** 从当前视角重新取景并合并 Image Empty，用 **Mask** 的 Lasso、Brush 或 Polyline 编辑 Alpha；Brush 拖动时以红色或灰色填充预览准确范围，释放后提交；用 **Rectify** 校正透视
 - 用 **Remove Background / Upscale** 处理单图、视频和序列帧