Common Mask Tool Controls
The Rectangle Mask, Ellipse Mask, Polygon Mask and Lasso Mask tools have a common set of control options. Those controls are covered in this topic.
![](https://media.screensteps.com/image_assets/assets/002/782/685/original/media_1316543743454.png)
- This drop down allow you to chose from 3 ways to combine new mask areas with the mask that is already present. These are Replace, Add and Subtract.
- The Invert option, when enabled, will invert the drawn mask before it is merged with the current mask.
- The Level slider controls the strength of the mask from 0 (no mask) to 100 (full mask).
Replace Mode
![Replace Mode](https://media.screensteps.com/image_assets/assets/002/782/687/original/media_1316545126168.png)
- Replace mode selected.
- A rectangle mask at 100% strength.
- A rectangle mask at 50% strength.
- Notice that the mask at 50% strength replaced the mask at 100% strength where it overlapped it.
Add Mode
![Add Mode](https://media.screensteps.com/image_assets/assets/002/782/683/original/media_1316546089208.png)
- The Add mode is selected.
- A rectangle mask at 100% strength
- 2 rectangle masks at 50% strength
- Notice that in Add mode the 50% strength mask added to the 100% strength mask remains at 100%
- Notice that in Add mode the 2 50% strength masks rectangles where they overlap combine to make a 100% strength mask area.
Subtract Mode
![Subtract Mode](https://media.screensteps.com/image_assets/assets/002/782/691/original/media_1316546414526.png)
In this example we have started with a full mask covering the entire image.
- Subtract mode selected.
- A rectangle mask at 100% strength completely removes the mask.
- 2 rectangle masks at 50% strength subtract from the existing mask.
- Subtracting from a full non-masked areas resulted in no change.
- The area where the 2 50% strength masks overlapped results in the mask being completely removed.
Invert Option
![Invert Option](https://media.screensteps.com/image_assets/assets/002/782/689/original/media_1316547012669.png)
The Invert option can require some abstract thinking to use. It is never required to use it but the feature exists for those building complex masks.
- The Invert option is selected.
- The Add mode is selected. Invert can be used with any mode, Replace, Add or Subtract.
- 2 rectangle masks at 50% strength are drawn. Since the Invert option is active the rectangle area drawn is the area that is not affected but everywhere else is. Where the mask strength is 50% is the area where only one of the masks inverted rectangles were drawn.
- This area while is seems like an intersecting area is actually the area that had not mask applied from either inverted rectangle.
- The large area at 100% strength is were both rectangle masks occurred.