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ADOBE PHOTOSHOP CS2
User Guide
To set ImageReady optimization preferences (ImageReady)
You can set preferences in ImageReady to determine the default optimization settings and the default configuration
of panels in 2-Up and 4-Up views.
1
Do one of the following:
•
In Windows, choose Edit > Preferences > Optimization.
•
In Mac OS, choose ImageReady > Preferences > Optimization.
2
Choose an option in the Default Optimization section:
Previous Settings
Applies the last-used optimization settings.
Auto Selected GIF or JPEG
Automatically optimizes the image in either GIF format or JPEG format. ImageReady
selects GIF or JPEG based on an analysis of the image.
Named Setting
Uses one of the preset optimization settings.
3
Under 2-Up Settings or 4-Up Settings, specify settings for the first, second, third, and fourth panes (third and
fourth panes apply to 4-Up view only):
Original
Displays the original image in the specified pane. (This option is available for the first pane only.)
Current
Displays the image with current Optimize palette settings in the specified pane. (This option is available for
all panes.)
Auto
Displays a smaller optimized version of the image generated automatically by ImageReady, based on the
current Optimize palette settings. (This option is available for the second, third, and fourth panes.)
Named presets
Select one of the named settings to display the optimized image with those settings. (This option is
available for the second, third, and fourth panes.)
4
Click OK.
Web graphics formats and options
Comparing web graphics formats
The file format that you choose depends largely on the characteristics of the image.
JPEG
JPEG is the standard format for compressing continuous-tone images such as photographs. Optimizing an image as
a JPEG format relies on
lossy
compression, which selectively discards data.
GIF and PNG-8
GIF is the standard format for compressing images with flat color and crisp detail, such as line art, logos, or illustra
tions with type. Like the GIF format, the PNG-8 format efficiently compresses solid areas of color while preserving
sharp detail. (See “Optimization options for GIF and PNG-8 formats” on page 635.)
PNG-8 and GIF files support 8-bit color, so they can display up to 256 colors. The process of determining which
colors to use is called
indexing
, so images in GIF and PNG-8 formats are sometimes called
indexed color
images. To
convert an image to indexed color, Photoshop builds a color lookup table, which stores and indexes the colors in the
image. 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.
