Note: You can see the progress of lengthy operations such
as image analysis on the progress bar at the bottom of the Fluid Mask
window. If required, you can cancel an operation using the 
button)
When you open an image, Fluid Mask automatically analyzes it to identify the distinct areas of color and texture within the image.
Note: You can see the progress of lengthy operations such
as image analysis on the progress bar at the bottom of the Fluid Mask
window. If required, you can cancel an operation using the button)
When Fluid Mask image analysis is finished, the edges of the "objects" found will be overlaid as blue outlines on the image – don’t worry nothing has been altered yet and your image is still untouched. You can now use these objects as a guide to flood-fill the areas you want to keep and those you want to delete.
Note: You can check or uncheck Show Object Edges at the bottom of the Fluid Mask window to hide or reveal the edges of the objects).
To create a mask, select a brush from the Tool Palette and start painting (i.e. filling "objects"). Use the green, keep tools to paint the parts of the image you want to keep. Use the red, delete tools to paint the parts of the image you want to remove. (The blue tools create a special mask for blending the border of the cutout.)
There are three brushes for each type of mask:
Exact brushes
mask only those pixels touched directly by your stroke (like a traditional
paint brush).
Local brushes work like a combination
of a traditional paint brush and a paint bucket tool. Every image object
that includes any pixels under your brush stroke will be flood-filled.
If you turn the brush strength above the minimum, neighboring objects
that are similar in color and texture will also be filled.
When using the local brush, paint a stroke through the segments you want masked. Any segments touched will be flood-filled.
Global brushes work much like the local
brushes, except they will fill similar objects anywhere in your image
(when the strength is above the minimum).
When using either local or global brushes, you can control the extent of the flood-fill of neighboring objects using the Strength setting at the top of the window). At minimum strength, only those objects touched by the brush will be filled. At maximum strength, large areas of the image can be masked in a single stroke. Use the Undo function (Ctrl-Z) while experimenting with the brush strength.
For more information on brushes and the other tools, see About Fluid Mask Tools.
To save your current masks, select Save Project from the File menu (Ctrl-Shift-S). You can load the saved project to restore your masks as long as you haven't changed the underlying image between Fluid Mask sessions.
Note: If you mask an image with only one type of mask (either keep or delete), Fluid Mask will mask the rest of the image for you when you click the Create Cut-out button (Ctrl-U) or select Auto-fill from the Image menu (Ctrl-F).