Operation Manual
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Web graphics
Last updated 9/13/2015
Images in GIF and PNG-8 formats, sometimes called indexed-color images, can display up to 256 colors. To convert an
image to indexed-color format, Photoshop Elements builds a color lookup table. If a color in the original image does
not appear in the color lookup table, the application either chooses the closest color in the table or simulates the color
using a combination of available colors.
JPEG and PNG-24 files support 24-bit color, so they can display up to 16 million colors. Depending on the format, you
can specify image quality, background transparency or matting, color display, and the method a browser should use to
display the image while downloading.
The appearance of an image on the web also depends on the colors displayed by the computer platform, operating
system, monitor, and browser. You may want to preview images in different browsers and on different platforms to see
how they will appear on the web.
Apply a preset optimization setting
You can quickly and easily optimize an image for the web by choosing a predefined optimization setting, called a preset,
from the Preset menu near the upper-right corner of the Save For Web dialog box. Presets are tailored to meet the
optimization needs of different types of images.
The name of each preset reflects its file format and quality level. For example, choose JPEG High to optimize an image
in JPEG format with high image quality and low compression. Choose GIF 32 Dithered to optimize an image in GIF
format, reduce the number of colors to 32, and apply dithering.
1 In the Save For Web dialog box, choose a setting name from the Preset menu, and then click OK.
2 In the Save Optimized As dialog box, type a filename and click Save.
Note: If you change the options in a preset, the Preset menu displays the word “[Unnamed]”. You cannot save a custom
setting; however, the current settings appear in the Save For Web dialog box the next time you display it.
More Help topics
Preview an optimized image in a web browser
Preview variations in color display
View estimated download time
Dithering in web images
About dithering
Most web images are created by designers using 24-bit color displays (which display over 16 million colors), although
some users view web pages on computers with 8-bit color displays (which display only 256 colors). As a result, web
images often contain colors not available on some computers. Computers use a technique called dithering to simulate
colors they can’t display. Dithering uses adjacent pixels of different colors to give the appearance of a third color. For
example, a red color and a yellow color may dither in a mosaic pattern to produce the illusion of an orange color that
the 8-bit color panel doesn’t contain.