Adobe ILLUSTRATOR 10 Using Manual page 324

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2 Set the desired options in each panel of the dialog box:
Average Downsampling Determines if the artwork is downsampled. Downsampling
reduces the resolution of the image to the specified pixels per inch. If you plan to print the
PDF file at high resolution, do not use downsampling. If you plan to use the PDF file on the
Web, using downsampling allows for higher compression.
Compression and Quality Determine the type and amount of compression that is used.
The Automatic option automatically sets the best possible compression and quality for
the artwork contained in the file. For most files, this option produces satisfactory results.
ZIP compression works well on images with large areas of single colors or repeating
patterns and for black-and-white images that contain repeating patterns. Illustrator
provides 4-bit and 8-bit ZIP compression options. If you use 4-bit ZIP compression with
4-bit images, or 8-bit ZIP compression with 4-bit or 8-bit images, the ZIP method is
lossless; that is, data is not removed to reduce file size and so image quality is not affected.
Using 4-bit ZIP compression with 8-bit data can affect the quality, however, because data
is lost.
JPEG compression is suitable for grayscale or color images. JPEG compression is lossy,
which means that it removes image data and may reduce image quality; however, it
attempts to reduce file size with a minimum loss of information. Because JPEG
compression eliminates data, it can achieve much smaller files sizes than ZIP compression.
CCITT and Run Length compression are only available for monochrome bitmap images.
CCITT (Consultative Committee on International Telegraphy and Telephony) compression
is appropriate for black-and-white images and any images scanned with an image depth
of 1 bit. Group 4 is a general-purpose method that produces good compression for most
monochromatic images. Group 3, used by most fax machines, compresses monochro-
matic bitmaps one row at a time. Run Length compression produces the best results for
images that contain large areas of solid black or white.
Compress Text and Line Art Applies ZIP compression to all text and line art in the file.
Saving artwork in an SVG format
SVG is a vector format that produces high-quality, interactive Web graphics. (See
Web graphics with SVG" on page
Compressed SVG (SVGZ). SVGZ can reduce file sizes by 50% to 80%; however, you cannot
edit SVGZ files using a text editor.
When you export artwork in an SVG format, mesh objects are rasterized. In addition,
images in the artwork that have no alpha channel are converted to the JPEG format.
Images with an alpha channel are converted to the PNG format.
To save artwork in an SVG format:
1 If the artwork contains any SVG filter effects, select each item to which an SVG filter
effects has been applied, and move the filter effect to the bottom of the Appearance
palette (just above the Transparency entry). (See
page 301.)
2 Save the artwork as described in
Choose SVG (SVG) or SVG Compressed (SVGZ) as the file format.
Using Help | Contents
| Index
300.) There are two versions of the SVG formats: SVG and
"About saving and exporting artwork" on page
| Index
Saving and Exporting
"Adding SVG filter effects to artwork" on
Back 324
"Creating
320.
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