Photoshop

Customize indexed color tables

The Color Table command lets you make changes to the color table of an indexed-color image. These customization features are particularly useful with pseudocolor images—images displaying variations in gray levels with color rather than shades of gray, often used in scientific and medical applications. However, customizing the color table can also produce special effects with indexed-color images that have a limited number of colors.

Note: To shift colors simply in a pseudocolor image, choose Image > Adjustments, and use the color adjustment commands in the submenu.

Edit colors and assign transparency with a color table

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.

  1. Open the indexed-color image.
  2. Choose Image > Mode > Color Table.
  3. To change a single color, click the color and choose a new color in the color picker.
  4. To change a range of colors, drag in the table to choose the range of colors you want to change. In the color picker, choose the first color you want in the range and click OK. When the color picker redisplays, choose the last color you want in the range and click OK.

    The colors you selected in the Color Picker are placed in the range you selected in the Color Table dialog box.

  5. To assign transparency to a color, select the Eyedropper tool in the Color Table dialog box, and click the color in the table or in the image. The sampled color is replaced with transparency in the image.
  6. Click OK in the Color Table dialog box to apply the new colors to the indexed-color image.

Choose a predefined color table

  1. Open the indexed-color image.
  2. Do one of the following:

    • Choose Image > Mode > Color Table.

    • Choose Image > Mode > Indexed Color. In the Indexed Color dialog box, choose Custom from the Palette menu. This opens the Color Table dialog box.

  3. In the Color Table dialog box, choose a predefined table from the Table menu.
    Custom
    Creates a palette you specify.

    Black Body
    Displays a palette based on the different colors a black body radiator emits as it is heated—from black to red, orange, yellow, and white.

    Grayscale
    Displays a palette based on 256 levels of gray—from black to white.

    Spectrum
    Displays a palette based on the colors produced as white light passes through a prism—from violet, blue, and green to yellow, orange, and red.

    System (Mac OS)
    Displays the standard Mac OS 256-color system palette.

    System (Windows)
    Displays the standard Windows 256-color system palette.

Save and load color tables

You use the Save and Load buttons in the Color Table dialog box to save your indexed color tables for use with other Adobe Photoshop images. After you load a color table into an image, the colors in the image change to reflect the color positions they reference in the new color table.

Note: You can also load saved color tables into the Swatches palette.