Masking refers to a process
used in image editing where certain
areas of the image are covered or
'masked' with a translucent color.
The goal of masking is to accurately
'select' specific portions of an
image for digital manipulation,
copying or removal. There are
several levels of masking including
quick masks, layer masks and alpha
(color) channel masks. The type of
masking utilized depends upon the
required task and its complexity.
Alpha channel masking is often
chosen for the most complicated of
images, where there are no defined
(hard) edges, and there are small
fine portions of the image (such as
wisps of hair) which the editor
wishes to include with the final
selection.
Alpha
or Color channel masking is possible
because of the method in which
digital color images are captured
and saved. Color
images prepared for viewing on
monitors or other projection devices
are typically saved in a color
separated layer format called Red,
Green, Blue (RGB). (As opposed to
images prepared for printing which
are typically saved as Cyan,
Magenta, Yellow, Black (CMYK)).
When a digital color image is
captured (camera or scan) each layer
records only pixels that represent
the various shades of the designated
color. When viewing each layer
individually, this variation in
color along with changes in
brightness often create enough
contrast between the area you wish
to select and the remaining image to
create a quality mask.
Anyone who can move a mouse can
select an area to cut and paste.
However, trying to create a
realistic, professional quality
image without visible signs of
digital manipulation can be
extremely tedious and time
consuming. Learning to create a
color channel mask will often be the
solution to a very imposing task.
