Optimizing Web Images - Adobe PHOTOSHOP ELEMENTS 2 User Manual

CHAPTER 12
210
Optimizing Images for the Web and E-mail
As with the GIF format, you can choose the
number of colors in an image and select options to
control how colors dither in a browser. The PNG-
8 format supports background transparency and
background matting, in which you blend the edges
of the image with a Web page background color.
(See "Previewing and controlling dithering" on
page 216.)
PNG-8 with 256 colors and no dither, and PNG-8 with
16 colors and dithering
About PNG-24 format
The PNG-24 format supports 24-bit color. Like
the JPEG format, PNG-24 preserves the broad
range of colors and subtle variations in brightness
and hue found in photographs. Like the GIF and
PNG-8 formats, PNG-24 preserves sharp details
like those in line art, logos, or type.
The PNG-24 format uses the same lossless
compression method as the PNG-8 format.
For that reason, PNG-24 files are usually larger
than JPEG files of the same image. PNG-24
browser support is similar to that for PNG-8, so
you may want to avoid this format when your
image must be accessible to a wide audience.
In addition to supporting background trans-
parency and background matting, the PNG-24
format supports multilevel transparency. Multi-
level transparency allows you to preserve up to
256 levels of transparency, so you can blend the
edges of an image smoothly with any background
color. However, multilevel transparency is not
supported by all browsers.

Optimizing Web images

Optimization settings appear on the right side of
the Save For Web dialog box. You can quickly
choose predefined settings, or select format-
specific options to fine-tune the results of optimi-
zation.
Using predefined optimization settings
You can quickly and easily optimize an image for
the Web by choosing a predefined optimization
setting. Predefined settings are tailored to meet the
optimization needs of different types of images.
(See "Choosing a file format for the Web" on
page 207.)
The name of each predefined setting 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.