Adobe Photoshop CS2 On Demand [Electronic resources]

Andy Anderson; Steve Johnson

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Optimizing a PNG-8 Document

The PNG-8 file format is used primarily for images that contain solid colors with sharp edgesclipart, text, line art, and logosand was designed as an alternative to the GIF file format. Since the PNG-8 format generates an image with a maximum of 256 colors, it significantly reduces an images file size. While similar to the GIF file format, the PNG-8 format is not completely supported by older browsers. However, it is considered a native format to the creation of Flash animation movies.

Optimize a PNG-8 Document

Open a document in ImageReady by first opening the image in Photoshop and then click the

Jump To ImageReady button.

Click the

Original, Optimized, 2-Up , or

4-Up palettes to view the document using different layouts.

Click one of the sample images to change its default format.

Select the

Optimize palette.

Click the

Format list arrow, and then click

PNG

-8 .

Click the

Color Table arrow, and then select from the following options:

  • Reduction. Click to select a visual reduction method for the image colors.

  • Colors. Enter or select a value from 2 to 256 maximum colors.

  • Web Snap. Enter or select a value from 0 to 100 to instruct the PNG-8 compression utility how many of the image colors should be Web safe.

Click the

Dither arrow, and then select from the following options:

  • Method. Click the list arrow, and then select from the available dithering schemes. Dithering is how the PNG-8 format mixes the available image colors.

  • Amount. Enter or select a value from 0 to 100 to instruct the PNG-8 compression utility how many of the image colors should be dithered.

Click the

Transparency arrow, and then select from the following options:

  • Transparency. Check to make the transparent areas of a PNG-8 image transparent.

  • Matte. Click to fill the trans-parent areas of a PNG-8 image.

  • Dither. Click to select a dithering scheme, and enter an amount for the mixing of the matte color.

Click the

Options arrow, and then select from the following options:

  • Interlaced. Check to have the PNG image load in three scans.

  • Use Unified Color Table. Check to have the PNG-8 format apply a universal color table to all images used in a rollover image.

  • Add Metadata. Check to embed recoverable data about the files colors, creation, and even author information.

Click the

File menu, and then click

Save Optimized .

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