Adobe Photoshop CS4 - Manual (Page 534)

527 USING PHOTOSHOP CS4
Web graphics
Last updated 1/10/2010
PNG-24 optimization options
PNG-24 is suitable for compressing continuous-tone images; however, it produces much larger files than JPEG format.
The advantage of using PNG-24 is that it can preserve up to 256 levels of transparency in an image.
Transparency and Matte Determine how transparent pixels in the image are optimized. See “ Optimize transparency
in GIF and PNG images ” on page 523.
Interlace Displays a low-resolution version of the image in a browser while the full image file is downloading.
Interlacing can make downloading time seem shorter and can assure viewers that downloading is in progress.
However, interlacing also increases file size.
More Help topics
“ Optimize an image for the web ” on page 514
WBMP optimization options
WBMP format is the standard format for optimizing images for mobile devices, such as cell phones. WBMP supports
1-bit color, which means that WBMP images contain only black and white pixels.
The Dithering algorithm and percentage determine the method and amount of application dithering. For optimal
appearance, use the lowest percentage of dither that provides the detail you require.
You can select one of the following dithering methods:
No Dither Applies no dithering at all, rendering the image in purely black and purely white pixels.
Diffusion Applies a random pattern that is usually less noticeable than Pattern dither. The dither effects are diffused
across adjacent pixels. If you select this algorithm, specify a Dither percentage to control the amount of dithering
applied to the image.
Note: Diffusion dither may cause detectable seams to appear across slice boundaries. Linking slices diffuses the dither
pattern across all linked slices, and eliminates the seams.
Pattern Applies a halftone-like square pattern to determine the value of pixels.
Noise Applies a random pattern similar to the Diffusion dithering, but without diffusing the pattern across adjacent
pixels. No seams appear with the Noise algorithm.
More Help topics
“ Optimize an image for the web ” on page 514
SWF optimization options (Illustrator)
The Adobe Flash (SWF) file format is a vector-based graphics file format for the creation of scalable, compact graphics
for the web. Because the file format is vector-based, the artwork maintains its image quality at any resolution. The SWF
format is ideal for the creation of animation frames, but you can also save raster images in SWF format or mix raster
and vector graphics.