to the paletted color mode
The paletted color
mode, also called indexed color mode, is sometimes used for images on the World
Wide Web. When you convert an image to the paletted color mode, a fixed color
value is assigned to each pixel. These values are stored in a compact color
table, or palette containing up to 256 colors. As a result, the paletted color
mode image contains less data than a 24 bit color mode image, and it has a
smaller file size. Conversion to paletted color mode works best on images that
have a limited range of colors.
and saving a color palette
When you change an
image to the paletted color mode, you can use a predefined palette, or you can
customize a color palette by replacing individual colors.
After you choose a
color palette and set the dithering and range sensitivity for changing an image
to the paletted color mode, you can save the settings as a conversion preset
that you can use with other images. You can add as many conversion presets as
The color palette you
use is called the processed color palette. It can be saved for use with other
For more information
about the predefined color palettes available for the paletted color mode, see
"Palette types." For more information about creating and opening custom color
palettes, see "Creating custom color palettes."
Changing images to
the paletted color mode lets you use dithering to enhance color information.
Dithering places pixels with specific colors or values relative to other pixels
of a specific color. The relationship of one colored pixel to another creates
the appearance of additional colors that do not exist in the color palette.
You can use two types
of dithering: ordered dithering and error diffusion. Ordered dithering
approximates color blends using fixed dot patterns; as a result, solid colors
are emphasized and edges appear harder. Error diffusion scatters pixels
irregularly, making edges and colors softer. Jarvis, Stucki, and Floyd-Steinberg
are conversion options that provide error diffusion.
The Ordered dithering
option applies more quickly than the error diffusion options (Jarvis, Stucki,
and Floyd-Steinberg) but is less accurate.
You can change an
image to the paletted color mode and specify a focus color and a range
sensitivity for the focus color, so that the focus color and colors that fall
within the range settings are included in the processed color palette. You can
also specify how much emphasis to place on the range sensitivity. Because the
palette has a maximum of 256 colors, emphasizing a focus color reduces the
number of colors that fall outside the range sensitivity.