PDF (adobe.com)

Dither to simulate web-safe colors and transparency



When using a color that is not websafe, apply a web dither fill. Doing so enables you to approximate a websafe color that doesn't shift or dither when exported with a websafe palette.

To create the appearance of transparency, apply the Transparent dithering fill option. In transparent objects, the web page background shows through every other pixel of the transparent web dither fill.

Note: Web dithering can increase the size of the file.
Two websafe colors create a web dither fill.

Apply a web dither fill

  1. Select an object containing a non-websafe color.

  2. Select Web Dither from the Fill Options pop-up menu in the Property inspector.

  3. In the Property inspector, click the Fill Color box to display the Fill Options pop-up window.

    The object's non-websafe color appears in the Source color box. The two websafe dither colors appear in the color boxes to the right. The web dither appears on the object and becomes the active fill color.

    Note: Setting the edge of a web dither fill to Anti-Alias or Feather results in colors that are not websafe.

  4. Click outside the pop-up window to close it.

Apply a transparent dither fill

  1. Select an object to which you want to apply a transparent fill.

  2. Select Web Dither from the Fill Options pop-up menu in the Property inspector.

  3. In the Property inspector, click the Fill Color box to display the Fill Options pop-up window.

  4. Select Transparent.

    The object on the canvas becomes semi-opaque or translucent.

  5. Click outside the pop-up window to close it.

  6. Export the object as a GIF or PNG file and select Index Transparency or Alpha Channel Transparency. For more information, see Make areas transparent.

    Note: Not all browsers support PNG files.