User Guide

CHAPTER 5
Icons
5-10 Extras Drawer Icons
When a user selects an icon, the Extras Drawer creates the selected form of
the icon by combining the unselected form of the icon with the icon’s mask.
The Extras Drawer uses the same method to animate one icon as it uses to
highlight another. The design of the mask determines how the selected form
of an icon looks—highlighted or animated. Figure 5-7 compares a mask used
for highlighting with a mask used for animation.
Figure 5-7 An icon’s mask either highlights or animates the icon
The selected form of an icon is black only in spots where either the mask is
black or the unselected form of the icon is black. The selected form is white
wherever both the unselected form and the mask are black as well as where
both are white.
You create a mask by comparing each pixel of the unselected form of an icon
to the corresponding pixel of the selected form. If both forms of the icon have
a black pixel in the same position or if both have a white pixel in the same
position, the mask has a white pixel there. The mask has a black pixel where
one form of the icon or the other has a black pixel, but not where both do. In
making this comparison of the pixels, you are following the exclusive-or rule
of logic. Figure 5-8 shows the masks of several animated icons.
A
nother mask
c
reates an
a
lternate form of
t
he icon
A
n all-black
s
hadow mask
h
ighlights an icon
Not selected Mask Selected
Note: bounding boxes are for illustration only. Actual icons do not
have bounding boxes.