Graphics Programs Reference
In-Depth Information
FIGURe 3.12
Red tinted mask shown when Alpha 1
channel is toggled on
selecting Image Modes
Photoshop's image modes correspond to different systems for handling color
and/or light intensity. The following are Photoshop's color modes:
bitmap
Bitmap mode stores black and white pixels only, without any interme-
diate shades of gray. Bitmap files are extremely small because binary information
(1 for black and 0 for white) is all that is required to describe them. Bitmap mode
may be entered only from grayscale mode.
Grayscale
Black, white, and intermediate shades of gray are represented in
grayscale mode. No hues are recorded, only light intensity values.
duotone
Duotone, tritone, and quadtone images using two to four inks can
be created in this mode that employs but a single channel. Duotone is a special-
ized printing technique in which shadows are typically printed with black ink
and the mid-tones and/or highlights are printed with one or more separate ink
colors, producing an old-fashioned cyanotype or sepiatone look. Duotone mode
may be entered only from grayscale mode.
Indexed color
A color index is a list of up to 256 colors that reference a single
channel. Indexed color mode produces small image files that are suitable for
deployment on the Web in file formats such as GIF or PNG. This mode does not
support layers or filters. In addition, many adjustments are unavailable in indexed
color mode, greatly limiting its image manipulation capabilities.
