CHAPTER 13
232
Saving Images
Image Compression Specifies a method for
compressing the composite image data. (See
“About file compression” on page 232.) ZIP and
JPEG compression are only available when Enable
Advanced TIFF Save Options is selected in the
Saving Files preferences. (See “Setting preferences
for saving files” on page 233.)
Byte Order Photoshop and most recent applica-
tions can read files using either byte order.
However, if you don’t know what kind of program
the file may be opened in, select the platform on
which the file will be read.
Save Image Pyramid Preserves multiresolution
information. Photoshop Elements does not
provide options for opening multiresolution files;
the image opens at the highest resolution within
the file. However, Adobe InDesign
®
and some
image servers provide support for opening multi-
resolution formats.
Save Transparency Preserves transparency as an
additional alpha channel when the file is opened in
another application. (Transparency is always
preserved when the file is reopened in Photoshop
Elements or ImageReady.)
Layer Compression Specifies a method for
compressing data for pixels in layers (as opposed
to composite data). Layer compression options are
only available when Enable Advanced TIFF Save
Options is selected in the Saving Files preferences.
(See “Setting preferences for saving files” on
page 233.)
Many applications cannot read layer data and will
skip over it when opening a TIFF file. Photoshop,
however, can read layer data in TIFF files.
Although files that include layer data are larger
than those that don’t, saving layer data alleviates
the need to save and manage a separate PSD file to
hold the layer data. For more information on RLE
and ZIP compression, (see “About file
compression” on page 232). Choose Discard
Layers and Save a Copy to flatten the image.
About file compression
Many image file formats use compression
techniques that reduce the size of files.
Compression techniques differ in the way detail
and color are removed from the images.
Lossless techniques compress image data without
removing detail; lossy techniques compress images
by removing detail.
The following are commonly used compression
techniques:
RLE (Run Length Encoding) is a lossless
compression technique that will compress the
transparent portions of each layer in images with
multiple layers containing transparency.
LZW (Lemple-Zif-Welch) is a lossless compression
technique that provides the best results in
compressing images that contain large areas of
single color, such as screenshots or simple
paint images.
JPEG (Joint Photographic Experts Group) is a
lossy compression technique that provides the best
results with continuous-tone images, such as
photographs.
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