Masks

A mask is a 256 color grey scale bitmap similar to a stencil.

It has "open" areas that allow changes to the image and "closed" areas, that do not. white is a completely "open" area, black is completely "closed" and shades of grey allow varying degrees of changes to be made to the image.

Masks can be created in one of three ways:

from scratch (empty mask)
from an image
from a selection (coming soon)

to see the effect

click view/through mask
click mask/invert to preview the effect with opposite areas masked

edit your mask

five tools work with masks

airbrush
clone brush
Fill Tool
Paint Brush
Retouch Tool

five color functions work with masks

Brightness/Contrast Adjustment
Colorization
Negative Image
Posterize
Solarize

Four Image Processing features work with masks

Buttonize
Deformations and Filters
Hot Wax Coating
User Defined Filters

finishing: For the finished effect to appear the same as the preview, you must click mask/invert before you adjust the brightness/contrast

Adjust brightness contrast - click on colors/adjust/brightness-contrast

Settings:

brightness -100 (minus 100)
contrast 0
click ok

Save

Creating an empty mask