User Guide

Optimizing in the workspace 339
To select a color depth beyond 256 colors:
■ Select a 24- or 32-bit file format from the Export File Format pop-up menu in the
Optimize panel.
Removing unused colors
Removing unused colors from an image before exporting or saving makes its file size smaller.
To remove unused colors:
■ Select Remove Unused Colors from the Optimize panel Options menu.
To include all colors in the palette, including colors that are not present in the
exported or saved image:
■ Deselect Remove Unused Colors.
Dithering to approximate lost colors
Dithering approximates colors not in the current palette by alternating similarly colored
pixels. From a distance, the colors blend to create the appearance of the missing color.
Dithering is especially helpful when exporting images with complex blends or gradients or
when exporting photographic images to an 8-bit graphic file format such as GIF.
Dithering can greatly increase file size.
To dither a graphic:
■ Enter a percentage value in the Dither text box of the Optimize panel.
NOTE
Higher color depths create larger files and are typically not ideal for web graphics.
Use only 24- or 32-bit color depths when exporting or saving photographic images
with continuous tones or complex gradient blends of colors. For high-color-depth
graphics on the web, use JPEG files. For more information, see “Optimizing JPEGs”
on page 346.
NOTE
This option is available only for GIFs and other 8-bit graphic file formats.
NOTE
The dithering option is available only for GIFs, other 8-bit graphic file formats, and
WBMPs.