Adobe PHOTOSHOP ELEMENTS 2 User Manual page 221

3 Choose a color reduction algorithm for gener-
ating the color lookup table:
• Perceptual to create a custom color table by
giving priority to colors for which the human
eye has greater sensitivity.
• Selective to create a color table similar to the
Perceptual color table, but favoring broad areas
of color and the preservation of Web colors.
This color table usually produces images with
the greatest color integrity. (Selective is the
default choice.)
Adaptive to create a custom color table by
•
sampling colors from the spectrum appearing
most commonly in the image. For example, an
image with only shades of green and blue
produces a color table made primarily of greens
and blues. Most images concentrate colors in
particular areas of the spectrum.
Web to use the standard, Web-safe 216-color
•
color table common to the 8-bit (256-color)
palettes of Windows and Mac OS. This option
ensures that no browser dither is applied to
colors when the image is displayed using 8-bit
color. If your image has fewer than 216 colors,
unused colors are removed from the table. (See
"Previewing and controlling dithering" on
page 216.)
Custom to preserve the current color table as a
•
fixed palette that does not update when you
change the image.
To specify the maximum number of colors in
4
the color palette, select a number from the Colors
pop-up menu, enter a value in the text box, or click
the arrows to change the number of colors. If the
ADOBE PHOTOSHOP ELEMENTS 2.0
image contains fewer colors than the palette, the
color table reflects the smaller number of colors
that are in the image.
If you chose either Web or Custom for the color
reduction algorithm, you can choose Auto in the
Colors menu. Choose Auto if you want Photoshop
Elements to determine the optimal number of
colors in the color table based on the frequency of
colors in the image.
Choose a dithering algorithm option from the
5
pop-up menu. If you choose Diffusion, specify a
percentage for Dither. (See "Previewing and
controlling dithering" on page 216.)
If the image contains transparency, select
6
Transparency to preserve transparent pixels;
deselect Transparency to fill fully and partially
transparent pixels with the matte color. (See
"Making transparent and matted images" on
page 214.)
7 To create an animated GIF, select Animate. See
"Setting up animated GIFs" on page 219.
8 To save your optimized image, click OK. In the
Save Optimized As dialog box, type a filename,
and click Save.
Setting optimization options for PNG-24
format
PNG-24 format is suitable for compressing
continuous-tone images. However, PNG-24 files
are often much larger than JPEG files of the same
image. PNG-24 format is recommended only
when working with a continuous-tone image that
includes multilevel transparency. (See "About
PNG-24 format" on page 210.)
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User Guide