# PhotoshopElements

# 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 palette 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 palette contains all of the colors in the image, there is no dithering.

     System (Mac OS)
       Uses the Mac OS default 8‑bit palette, which is based on a uniform sampling of RGB colors.

     System (Windows)
       Uses the Windows system’s default 8‑bit palette, 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 palette 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 palette 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 palette by giving priority to colors to which the human eye has greater sensitivity. Local Perceptual applies the palette to individual images; Master Perceptual applies the selected palette 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 palette to individual images; Master Selective applies the selected palette to multiple images (for example, for multimedia production).

     Local or Master Adaptive
       Creates a palette 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 palette made primarily of greens and blues. Most images concentrate colors in particular areas of the spectrum. To control a palette 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 palette to individual images; Master Adaptive applies the selected palette to multiple images (for example, for multimedia production).

     Custom
       Creates a custom palette 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 palette, which is useful for previewing the colors most often used in the image.

     Previous
       Uses the custom palette from the previous conversion, making it easy to convert several images with the same custom palette.

   Colors
     Specifies the number of colors to include in the color table (up to 256) for Uniform, Perceptual, Selective, or Adaptive palettes.

   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 mixes the pixels of the available colors to simulate the missing colors.
     None
       Does not dither colors but, instead, uses the color closest to the missing color. This tends to result in sharp transitions between shades of color in the image, creating a posterized effect.

     Diffusion
       Uses an error-diffusion method that produces a less structured dither than the Pattern option. To protect colors in the image that contain entries in the color table from being dithered, select Preserve Exact Colors. This is useful for preserving fine lines and text for web images.

     Pattern
       Uses a halftone-like square pattern to simulate any colors not in the color table.

     Noise
       Helps to reduce seam patterns along the edges.

   Amount
     Specifies the percentage of image colors to dither. A higher amount dithers more colors, but may increase file size.

   Preserve Exact Colors
     Prevents colors in the image that are in the color table from being dithered.

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