To view a discontiguous group of colors, press Ctrl (Windows) or Command (Mac OS) and click each color that you want to select, and hold the mouse button down on any color in the group.

To deselect all colors:

Choose Deselect All Colors from the Color Table palette menu.

Shifting colors

You can change a selected color in the color table to any other RGB color value. When you regenerate the optimized image, the selected color changes to the new color wherever it appears in the image.

To shift a color:

1Double-click the color in the color table to display the default color picker.

2Select a color.

The original color appears at the upper left of the color swatch and the new color at the lower right. The small square at the lower right of the color swatch indicates that the color is locked. If you shift to a Web-safe color, a small white diamond appears at the center of the swatch.

To revert shifted colors to their original colors:

Do one of the following:

•Double-click the swatch for the shifted color. The original color is selected in the color picker. Click OK to restore the color.

•To revert all shifted colors in a color table (including Web-shifted colors), choose Unshift All Colors from the Color Table palette menu.

Shifting to Web-safe colors

To protect colors from dithering in a browser, you can shift the colors to their closest equivalents in the Web palette.This ensures that the colors won’t dither when displayed in browsers on either Windows or Macintosh operating systems capable of displaying only 256 colors.

To shift colors to the closest Web palette equivalent:

1Select one or more colors in the optimized image or color table. (See “Selecting colors” on page 434.)

2Do one of the following:

•Click the Web Shift button in the Color Table palette.

•Choose Shift Selected Colors to Web Palette from the Color Table palette menu.

The original color appears at the upper left of the color swatch and the new color at the lower right.The small white diamond in the center of the color swatch indicates that the color is Web-safe; the small square at the lower right of the color swatch indicates that the color is locked.

To revert Web-shifted colors to their original colors:

Do one of the following:

•Select a Web-shifted color in the color table and click the Web Shift button in the Color Table palette.

•To revert all Web-shifted colors in the color table, choose Unshift All Web Shifted Colors from the Color Table palette menu.

To specify tolerance for shifting colors automatically to the closest Web palette equivalents:

In the Optimize panel/palette, enter a value for Web Snap or drag the pop-up slider. A higher value shifts more colors.

(In ImageReady, click the Show Options control on the Optimize palette tab or choose Show Options from the Optimize palette menu to view the Web Snap option.)

Mapping colors to transparency

You can add transparency to an optimized image by mapping existing colors to transparency.

To map colors to transparency:

1Select one or more colors in the optimized image or color table. (See “Selecting colors” on page 434.)

2Do one of the following:

•Click the Map Transparency button in the Color Table palette.

•Choose Map Selected Colors to Transparent from the Color Table palette menu.

The transparency grid appears in half of each mapped color. The small square at the lower right of the color swatch indicates that the color is locked.

To revert transparency to its original colors:

Do one of the following:

•Select the colors you want to revert, click the Map Transparency button or choose Unmap Selected Colors from Transparent from the Color Table palette menu.

•To revert all transparency-mapped colors, choose Unmap All Transparent Colors.

Locking colors in the color table

You can lock selected colors in the color table to prevent them from being dropped when the number of colors is reduced and to prevent them from dithering in the application.

Note: Locking colors does not prevent them from dithering in a browser.

To lock a color:

1Select one or more colors in the color table. (See “Selecting colors” on page 434.)

2Lock the color:

•Click the Lock button .

•Choose Lock/Unlock Selected Colors from the Color Table palette menu.

A white square appears in the lower right corner of each locked color.

Note: If the selected colors include both locked and unlocked colors, all colors will be locked.

To unlock a color:

1Click the locked color to select it.

2Unlock the color:

•Click the Lock button .

•Choose Lock/Unlock Selected Colors from the Color Table palette menu. The white square disappears from the color swatch.

Deleting colors from the color table

You can delete selected colors from the color table to decrease the image file size. When you delete a color, areas of the optimized image that previously included that color are rerendered using the closest color remaining in the palette.

When you delete a color, the color table automatically changes to a Custom palette.This is because the Adaptive, Perceptual, and Selective palettes automatically add the deleted color back into the palette when you reoptimize the image—the Custom palette does not change when you reoptimize the image.

To delete selected colors:

1Select one or more colors in the color table. (See “Selecting colors” on page 434.)

2Delete the color:

•Click on the Trash button .

•Choose Delete Color from the Color Table palette menu.

Loading and saving color tables

You can save color tables from optimized images to use with other images and to load color tables created in other applications. Once you load a new color table into an image, the colors in the optimized image are changed to reflect the colors in the new color table.

To save a color table:

1Select Save Color Table from the Color Table palette menu.

2Name the color table and choose a location where it will be saved. By default, the color table file is given the extension .act (for Adobe Color Table).

If you want to access the color table when selecting Optimization options for a GIF or PNG image, save the color table in the Presets/Optimized Colors folder inside the Photoshop program folder.

3 Click Save.

Important: When you reload the table, all shifted colors will appear as full swatches and they will be unlocked.

To load a color table:

1Select Load Color Table from the Color Table palette menu.

2Navigate to a file containing the color table you want to load—either an Adobe Color Table (.act) file, an Adobe Color Swatch (.aco) file, or a GIF file (to load the file’s embedded color table).

3Click Open.

Using master palettes (ImageReady)

You can create a master palette to use with a group of GIF or PNG-8 images that will be placed on a CD-ROM or other multimedia storage medium. When you include the master palette with a batch of images, all images display using the same colors.

To build a master palette, you add colors from a set of images and then build and save the master palette. To create a master palette for a batch of images, you add colors to the palette from other optimized images.

To create and apply a master palette:

1With an image displayed, choose Image > Master Palette > Clear Master Palette (if available). Clearing the master palette ensures that colors from previous images are not included in the new palette.

2Open an image whose colors you want to include in a master palette.

3Choose Image > Master Palette > Add To Master Palette. All color information for the current image is added to the master palette.

4Repeat steps 2 and 3 for all images whose colors you want to include in the master palette.

5In the Optimize palette, select optimization settings for the master palette.

6Choose Image > Master Palette > Build Master Palette to create a new color table from the color information of images used in steps 2, 3, and 4.

7Choose Image > Master Palette > Save Master Palette.

8Name the master palette and choose a location where it will be saved. By default, the master palette file is given the extension .act (for Adobe Color Table).

If you want to access the color table when selecting Optimization options for a GIF or PNG image, save the master palette in the Optimized Colors folder, inside the Presets folder in the Adobe Photoshop folder.

9Click Save.

10To apply the master palette to the image or images for which it was created, open the image or images and select the master palette:

•If the master palette appears in the Color Reduction Algorithm menu in the Optimize palette, select the master palette from this menu. (The Color Reduction Algorithm menu includes all palettes saved in the Optimized Colors folder, inside the Presets folder in the Adobe Photoshop folder.)

•Load the master palette. (See “Loading and saving color tables” on page 437.)