A "mask" allows the user to exclude certain pixels from plots and calculations. These might be known "bad" pixels, scattering near the beamstop, scattering near known spurious features, etc. By default, pixels outside the data collection area are excluded, but these boundaries can be moved in. The user has the option of adding additional masks to exclude data inside specified rows or columns, individual pixels, inside a user-defined box or circle, or outside a user-defined circle.
To edit a current mask, either type the new desired value(s) in the box, or drag the blue cursor dot corresponding to that mask. For example, the first mask always excludes points outside the left-hand side of the image, and the default setting is to exclude pixels with -1 >= x.
To create a new mask, select the desired mask type from the drop-down menu and then click Apply. Currently available options are: "Exclude Points In Row", "Exclude Points In Column", "Exclude Points In One Pixel", "Exclude Points Inside Box", "Exclude Points Inside Circle", "Exclude Points Outside Circle".
To use the new masks, click Done.
To revert to previously used masks, click Cancel.