Optimization options for GIF and PNG-8 formats

GIF is the standard format for compressing images with flat color and crisp detail, such as line art, logos, or illustrations with type. You can lower the size of GIF images by reducing the number of colors in the file. Like the GIF format, the PNG-8 format efficiently compresses solid areas of color while preserving sharp detail; however, not all Web browsers can display PNG-8 files. PNG-8 settings are very similar to the GIF settings. (See About GIF format.)

Lossy (GIF only)

Specify a value to allow for lossy compression. Lossy compression reduces file size by selectively discarding data--a higher Lossy setting results in more discarded data. You can often apply a Lossy value of 5-10, and sometimes up to 50, without degrading the image. File size can often be reduced 5%-40% using the Lossy option.

Note: You cannot use the Lossy option with the Interlaced option, or with Noise or Pattern Dither algorithms.

Colors

Choose a method for generating a color table from the Color Table pop-up menu. (See Using the Color Table palette.) Then specify the maximum number of colors in the Colors text box. If you choose Web from the Color Table pop-up menu, the Auto option becomes active in the Colors pop-up menu. Use the Auto option if you want GoLive to determine the number of colors in the color table based on the frequency of colors in the image.

Note: If the image contains fewer colors than the number specified, the color table contains only the number of colors in the image.

Dither

Choose a dithering method from the Dithering menu, and specify the amount of application dithering. Dithering refers to the method of simulating colors not available in the color display system of your computer. 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 dither that provides the color detail you require. Images with primarily solid colors or with fine lines may display better with no dither. Images with continuous-tone color (especially color gradients) may require dithering to prevent color banding. Choose No dither or select from the following options in the Dithering algorithm pop-up menu:

• Diffusion applies a random pattern that is usually less noticeable than Pattern dither. The dither effects are diffused across adjacent pixels.
• Pattern applies a halftone-like square pattern to simulate any colors not in the color table.
• Noise applies 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.

Transparency and Matte

Select a combination of Transparency and Matte options to specify how transparent pixels in the image are optimized:

• To make fully transparent pixels transparent and blend partially transparent pixels with a color, select Transparency and select a matte color.
• To make all pixels with greater than 50% transparency fully transparent and all pixels with 50% or less transparency fully opaque, select Transparency and choose None from the Matte pop-up menu.
• To fill fully transparent pixels with a color and blend partially transparent pixels with the same color, select a matte color and deselect Transparency.

To select a matte color, click the Matte color swatch and select a color in the color picker. Alternatively, choose an option from the Matte pop-up menu: Eyedropper (to use the color in the eyedropper sample box), White, Black, or Other (to use the color picker).

Interlaced

Select Interlaced to create an image that displays in low resolution in the browser while the full image file is downloading. Interlacing can make downloading time seem shorter and assures viewers that downloading is in progress. However, interlacing also increases file size.

Web Snap

Specify a tolerance level for shifting colors to the closest Web palette equivalents (and prevent the colors from dithering in a browser). A higher value shifts more colors.