Adobe PHOTOSHOP 5.0, User Manual, Page: 333 / 400

325 ADOBE PHOTOSHOP 5.0
User Guide
PIXAR
The PIXAR format is designed specifically for
exchanging files with PIXAR image computers.
PIXAR workstations are designed for high-end
graphics applications, such as those used for three-
dimensional images and animation. The PIXAR
format supports RGB and grayscale files with a
single alpha channel.
PNG
Developed as a patent-free alternative to GIF, the
Portable Network Graphics (PNG) format is used
for losslessly compressing and displaying images
on the World Wide Web. Unlike GIF, PNG
supports 24-bit images and produces background
transparency without jagged edges; however, some
older versions of Web browsers may not support
PNG images. The PNG format supports grayscale
and RGB color modes with a single alpha channel,
and Bitmap and indexed-color modes without
alpha channels. PNG uses the saved alpha channel
to define transparency in the file; be sure to delete
all but the desired alpha channel from your image
before saving as PNG.
When saving in PNG format, you can select
Adam7 to display the image in increasing detail as
it is downloaded. You can also run the image
through a filtering algorithm that prepares the
image data for optimal compression:
•
None compresses the image without a filter, and
is recommended for indexed-color and Bitmap-
mode images.
•
Sub optimizes the compression of images with
even horizontal patterns or blends.
•
Up optimizes the compression of images with
even vertical patterns.
•
Average optimizes the compression of low-level
noise by averaging the color values of adjacent
pixels.
•
Paeth optimizes the compression of low-level
noise by reassigning adjacent color values.
•
Adaptive applies the filter—Sub, Up, Average, or
Paeth—best-suited for the image. Select Adaptive
if you are unsure of which filter to use.
Raw
The Raw format is a flexible file format for
transferring files between applications and
computer platforms. This format supports
CMYK, RGB, and grayscale files with alpha
channels, and multichannel, Lab, indexed-color,
and duotone files without alpha channels.
For more information on the Raw format,
see online help.
Scitex CT
The Scitex Continuous Tone (CT) format is used
for high-end image processing on Scitex
computers. Contact Scitex to obtain utilities for
transferring files saved in the Scitex CT format to
a Scitex system. The Scitex CT format supports
CMYK, RGB, and grayscale files, and does not
support alpha channels.