Adobe 29180155 - Photoshop Elements 4.0 Tutorial page 157

Convert an image to indexed color
Converting to indexed color reduces the number of colors in the image to a maximum of 256—the standard number of colors supported by the GIF
and PNG-8 formats and many web browsers. This conversion reduces file size by deleting color information from the image.
Note: To convert to indexed color, you must start with either a grayscale or an RGB image.
1. Choose Image > Mode > Indexed Color.
2. Click OK to flatten layers.
Note: This will flatten all visible layers and discard hidden layers.
For grayscale images, the conversion happens automatically. For RGB images, the Indexed Color dialog box appears.
3. Select Preview in the Indexed Color dialog box to display a preview of the changes.
4. Specify any of the following conversion options and click OK.
Palette Specifies the color palette to apply to the indexed-color image. There are 10 color palettes available:
Exact Creates a panel using the exact colors that appear in the RGB image—an option available only if the image
uses 256 or fewer colors. Because the image's panel contains all of the colors in the image, there is no dithering.
System (Mac OS) Uses the Mac OS default 8-bit panel, which is based on a uniform sampling of RGB colors.
System (Windows) Uses the Windows system's default 8-bit panel, which is based on a uniform sampling of RGB
colors.
Web Uses the 216 colors that web browsers, regardless of platform, use to display images on a monitor limited to
256 colors. Use this option to avoid browser dither when images are viewed on a monitor display limited to 256
colors.
Uniform Creates a panel by uniformly sampling colors from the RGB color cube. For example, if Photoshop Elements
takes 6 evenly spaced color levels, each of red, green, and blue, the combination produces a uniform panel of 216
colors (6 cubed = 6 x 6 x 6 = 216). The total number of colors displayed in an image corresponds to the nearest
perfect cube (8, 27, 64, 125, or 216) that is less than the value in the Colors text box.
Local or Master Perceptual Creates a custom panel by giving priority to colors to which the human eye has greater
sensitivity. Local Perceptual applies the panel to individual images; Master Perceptual applies the selected panel to
multiple images (for example, for multimedia production).
Local or Master Selective Creates a color table similar to the Perceptual color table, but favoring broad areas of
color and the preservation of web colors. This option usually produces images with the greatest color integrity. Local
Selective applies the panel to individual images; Master Selective applies the selected panel to multiple images (for
example, for multimedia production).
Local or Master Adaptive Creates a panel by sampling the colors from the spectrum appearing most often in the
image. For example, an RGB image with only the colors green and blue produces a panel made primarily of greens
and blues. Most images concentrate colors in particular areas of the spectrum. To control a panel more precisely, first
select a part of the image that contains the colors you want to emphasize. Photoshop Elements weights the
conversion toward these colors. Local Adaptive applies the panel to individual images; Master Adaptive applies the
selected panel to multiple images (for example, for multimedia production).
Custom Creates a custom panel by using the Color Table dialog box. Either edit the color table and save it for later
use, or click Load to load a previously created color table. This option also displays the current Adaptive panel, which
is useful for previewing the colors most often used in the image.
Previous Uses the custom panel from the previous conversion, making it easy to convert several images with the
same custom panel.
Colors Specifies the number of colors to include in the color table (up to 256) for Uniform, Perceptual, Selective, or Adaptive
panels.
Forced Provides options to force the inclusion of certain colors in the color table. Black And White adds a pure black and a
pure white to the color table; Primaries adds red, green, blue, cyan, magenta, yellow, black, and white; Web adds the 216
web-safe colors; and Custom lets you define custom colors to add.
Transparency Specifies whether to preserve transparent areas of the image during conversion. Selecting this option adds a
special index entry in the color table for a transparent color. Deselecting this option fills transparent areas with the matte color,
or with white if no matte color is chosen.
Matte Specifies the background color used to fill anti-aliased edges that lie adjacent to transparent areas of the image. With
Transparency selected, the matte is applied to edge areas to help blend the edges into a web background of the same color.
With Transparency deselected, the matte is applied to transparent areas. Choosing None for the matte creates hard-edged
transparency, if Transparency is selected; otherwise, all transparent areas are filled with 100% white.
Dither Specifies whether to use a dither pattern or not. Unless you're using the Exact color table option, the color table may
not contain all the colors used in the image. To simulate colors not in the color table, you can dither the colors. Dithering
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