Adobe PHOTOSHOP ELEMENTS Manual page 81

Provides options to force the inclusion of
Forced
certain colors in the color table. Black and White
adds a pure black and a pure white to the color
table; Primaries adds red, green, blue, cyan,
magenta, yellow, black, and white; Web adds the
216 Web-safe colors; and Custom lets you define
custom colors to add.
Specifies whether to preserve trans-
Transparency
parent areas of the image during conversion.
Selecting this option adds a special index entry in
the color table for transparent colors. Deselecting
this option fills transparent areas with the matte
color, or with white if no matte color is chosen.
Specifies the background color used to fill
Matte
anti-aliased edges that lie adjacent to transparent
areas of the image. With Transparency selected, the
matte is applied to edge areas to help blend the
edges with a Web background of the same color.
With Transparency deselected, the matte is applied
to transparent areas. Choosing None for the matte
creates hard-edged transparency if Transparency is
selected; otherwise, all transparent areas are filled
with 100% white.
Dithering in indexed-color images
Unless you're using the Exact color table option,
the color table may not contain all the colors used
in the image. To simulate colors not in the color
table, you can dither the colors. Dithering mixes
the pixels of the available colors to simulate the
missing colors.
Choose a dither option from the menu, and enter
a value for the dither amount. A higher amount
dithers more colors, but may increase file size. You
can choose from the following dither options:
ADOBE PHOTOSHOP ELEMENTS
Does not dither colors but instead uses the
None
color closest to the missing color. This tends to
result in sharp transitions between shades of color
in the image, creating a posterized effect.
Uses an error-diffusion method that
Diffusion
produces a less structured dither than the Pattern
option. To protect colors in the image that contain
entries in the color table from being dithered,
select Preserve Exact Colors. This is useful for
preserving fine lines and text for Web images.
Uses a halftone-like square pattern to
Pattern
simulate any colors not in the color table.
Helps to reduce seam patterns along the
Noise
edges of image slices.
Customizing indexed color tables
The Color Table command lets you make changes
to the color table of an indexed-color image. You
can edit colors in the color table to produce special
effects, or assign transparency in the image to a
single color in the table.
To edit colors in the color table:
Open the indexed-color image.
1
Choose Image > Mode > Color Table.
2
3 Click or drag in the table to choose the color or
range of colors you want to change.
4 Choose a color, as explained in "Using the
Adobe Color Picker" on page 77, and click OK.
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User Guide