Optimizing Images for the Web > Previewing and controlling dithering > Previewing and controlling application dither
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Previewing and controlling application dither


You can preview application dither in GIF and PNG-8 images. The Dither Algorithm pop-up menu lets you choose a dithering method for the image. Images with primarily solid colors may work well with Dither set to none. Images with continuous-tone color (especially color gradients) may require dithering to prevent color banding.

To control application dither:

1 Choose an option from the Dither Algorithm pop-up menu:

  • No Dither to apply no application dither to the image.
  • Pattern to apply a halftone-like square pattern to simulate any colors not in the color table.
  • Diffusion to apply a random pattern that is usually less noticeable than Pattern dither. The dither effects are diffused across adjacent pixels.
  • Noise to apply a random pattern similar to the Diffusion dither method, but without diffusing the pattern across adjacent pixels. No seams appear with the Noise dither method.

    • 2 If you chose Diffusion as the dithering algorithm, drag the Dither slider or enter a value to select a dithering percentage.

    The Dither percentage controls the amount of dithering that is applied to the image. A higher dithering percentage creates the appearance of more colors and more detail in an image, but can also increase the file size. For optimal compression, use the lowest percentage of application dither that provides the color detail you require.

    Optimizing Images for the Web > Previewing and controlling dithering > Previewing and controlling application dither