Using image modes and color tables

Converts pixels with gray values above the middle gray level (128) to white, and those below to black. The result is a very high-contrast, black-and-white representation of the image.

Converts an image by organizing the gray levels into geometric configurations of black and white dots.

Converts an image by using an error-diffusion process, starting at the pixel in the upper-left corner of the image. If the pixel’s value is above middle gray (128), the pixel is changed to white—if it’s below middle gray, it’s changed to black. Because the original pixel is rarely pure white or pure black, error is inevitably introduced. This error is transferred to surrounding pixels and diffused throughout the image, resulting in a grainy, film-like texture. This option is useful for viewing images on a black-and-white screen.

The size ratio is the factor for scaling down the image. For example, to reduce a grayscale image by 50%, enter 2 for the size ratio. If you enter a number greater than 1, the program averages multiple pixels in the bitmap-mode image to produce a single pixel in the grayscale image. This process lets you generate multiple shades of gray from an image scanned on a 1‑bit scanner.

For grayscale images, the conversion happens automatically. For RGB images, the Indexed Color dialog box appears.

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.

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

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.

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.

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.

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.

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

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

If you are changing a range of colors, Photoshop Elements creates a gradient in the color table between the starting and ending colors. The first color you choose in the Color Picker is the beginning color in the range. When you click OK, the Color Picker reappears, so that you can choose the last color in the range.

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

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

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

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

Displays the standard 256-color system panel for Mac OS or Windows.