Using Help
|
Contents
|
Index
Back
432
Adobe Photoshop Help
Preparing Graphics for the Web
Using Help
|
Contents
|
Index
Back
432
To select a color reduction algorithm:
Choose an option from the Color Reduction Algorithm pop-up menu (below the file
format menu in the Optimize panel/palette):
Perceptual
Creates a custom color table by giving priority to colors for which the human
eye has greater sensitivity.
Selective
Creates 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 option.
Adaptive
Creates a custom color table by sampling colors from the spectrum appearing
most commonly in the image. For example, an image with only the colors green and blue
produces a color table made primarily of greens and blues. Most images concentrate
colors in particular areas of the spectrum.
Web
Uses the standard 216-color color table common to the Windows and Mac OS 8-bit
(256-color) palettes. This option ensures that no browser dither is applied to colors when
the image is displayed using 8-bit color. (This palette is also called the Web-safe palette.)
If your image has fewer colors than the total number specified in the color palette, unused
colors are removed.
Using the Web palette can create larger files, and is recommended only when avoiding
browser dither is a high priority.
Custom
Preserves the current color table as a fixed palette that does not update with
changes to the image.
Mac OS
Uses the Mac OS system’s default 8-bit (256-color) color table, which is based on a
uniform sampling of RGB colors. If your image has fewer colors than the total number
specified in the color palette, unused colors are removed.
Windows
Uses the Windows system’s default 8-bit (256-color) color table, which is based
on a uniform sampling of RGB colors. If your image has fewer colors than the total number
specified in the color palette, unused colors are removed.
Other color tables appear in the menu if you have saved them previously. (See
“Loading
and saving color tables” on page 437
.)
You can use an alpha channel to influence the generation of color tables. (See
“Using
masks to modify color reduction” on page 430
.)
To regenerate a color table (ImageReady):
Choose Rebuild Color Table from the Color Table palette menu. Use this command to
generate a new color table when the Auto Regenerate option is off. (See
“Controlling
optimization (ImageReady)” on page 426
.)
Changing the display of the color table
You can sort colors in the color table by hue, luminance, or popularity, making it easier to
see an image’s color range and locate particular colors. In ImageReady, you can also
change the size of the color swatches in the color table.
To sort a color table:
Choose a sorting order from the Color Table palette menu:
•
Unsorted. Restores the original sorting order.
