确定画布中的 UI 元素的缩放方式。
| ConstantPixelSize | 使用“Constant Pixel Size”模式时，可在屏幕上按像素指定 UI 元素的位置和大小。 |
| ScaleWithScreenSize | Using the Scale With Screen Size mode, positions and sizes can be specified according to the pixels of a specified reference resolution. If the current screen resolution is larger then the reference resolution, the Canvas will keep having only the resolution of the reference resolution, but will scale up in order to fit the screen. If the current screen resolution is smaller than the reference resolution, the Canvas will similarly be scaled down to fit. |
| ConstantPhysicalSize | 使用“Constant Physical Size”模式时，可按物理单位（如毫米、点或派卡）指定 UI 元素的位置和大小。 |