Selections can be modified in many different ways to focus the application of tools on the desired pixels.

Add

Adds the pixels in the current drawing to the existing selection.

Default shortcut: shift and +

Substract

Deselects the pixels in the current drawing from the existing selection.

Default shortcut: shift and -

Intersect

Only keeps pixels from the existing selection that are also in current drawing.

Default shortcut: none

All

Select all data.

Default shortcut: Ctrl-A

None

Clears the selection. The current drawing is also cleared.

Default shortcut: esc

Invert

Performs a pixel-wise inversion of the existing selection.

Default shortcut: none

Grow

Iteratively grows (8-way) the existing selection.

Default shortcut: none

Erode

Iteratively erodes (8-way) the existing selection.

Default shortcut: none

Clean Up

Clean up provides several methods to refine a selection for further processing. It can be used to remove small and large holes within a selection or small and large selections that are not required.

1. Remove small holes - adds regions below the defined area within a selection that are unselected to the selected area
2. Remove large holes - adds regions above the defined area within a selection that are unselected to the selected area
3. Remove small selections - removes selected regions below the defined area that are selected from the selection mask
4. Remove large selections - removes selected regions above the defined area that are selected from the selection mask

Default shortcut: none

Filter

Removes all pixels from the current selection with values that do not meet a user-defined criterion.

Default shortcut: none

Select Values

Allows the query of a raster layer to add individual values or ranges of values to a selection.
Select values can operate on DEMs, Masks, and single channel (gray scale) imagery.

Default shortcut: none

Select Classes

Allows the query of a CLASS layer to select one or more land use classes.

Default shortcut: none

Load from File

Selects pixels using vectors or a raster mask from file.

Default shortcut: none

Save to File

Saves the current selection as a mask to file.

Default shortcut: none

Synchronize

Transfers the selection from the active data layer to all other selectable data layers.
This may be needed for newly loaded data layers, or if differences in projection or gridding create discrepancies between selections in different layers.

Default shortcut: none