Adobe Photoshop CS4 - Manual (Page 475)

468 USING PHOTOSHOP CS4
Saving and exporting images
Last updated 1/10/2010
Photoshop recognizes two types of PDF files: Photoshop PDF files and generic PDF files. You can open both types of
PDF files. When you save PDF files, Photoshop saves them as Photoshop PDF files by default. Deselect Preserve
Photoshop Editing Capabilities in the General section of the Save PDF dialog box to save a generic PDF file.
Photoshop PDF files Created using the Photoshop Save As command with Preserve Photoshop Editing Capabilities
selected in the General section of the Save PDF dialog box. Photoshop PDF files can contain only a single image.
Photoshop PDF format supports all of the color modes (except Multichannel mode) and features that are supported
in standard Photoshop format. Photoshop PDF also supports JPEG and ZIP compression, except for Bitmap-mode
images, which use CCITT Group 4 compression.
Generic PDF files Created using the Photoshop Save As command, with Preserve Photoshop Editing Capabilities
deselected in the General section of the Save PDF dialog box, by creating a PDF presentation in Photoshop, or by using
applications other than Photoshop, such as Adobe Acrobat and Adobe Illustrator. They can contain multiple pages
and images. When you open a generic PDF file, Photoshop rasterizes the image.
PICT File
PICT format is used in Mac OS graphics and page-layout applications as an intermediary file format for transferring
images between applications. PICT format supports RGB images with a single alpha channel and Indexed Color,
Grayscale, and Bitmap mode images without alpha channels. PICT format is especially effective for compressing
images with large areas of solid color. This compression can be substantial for alpha channels with their large areas of
white and black.
When saving an RGB image in PICT format, you can choose either a 16-bit or 32-bit pixel resolution. For bitmap and
grayscale images, you can choose from 2, 4, or 8 bits per pixel. In Mac
OS with QuickTime™ installed, four JPEG
compression options are available.
PICT Resource
(Mac OS) A PICT resource is a PICT file but takes a name and resource ID number. The PICT Resource format
supports RGB images with a single alpha channel, and Indexed Color, Grayscale, and Bitmap mode images without
alpha channels.
You can use the Import command or the Open command to open a PICT resource. When saving a file as a PICT
resource, you can specify the resource ID and resource name. As with other PICT files, you also specify bit depth and
compression options.
Pixar format
The Pixar format is designed specifically for high-end graphics applications, such as those used for rendering three-
dimensional images and animation. Pixar format supports RGB and grayscale images with a single alpha channel.
PNG format
Developed as a patent-free alternative to GIF, Portable Network Graphics (PNG) format is used for lossless
compression and for display of images on the web. Unlike GIF, PNG supports 24-bit images and produces background
transparency without jagged edges; however, some web browsers do not support PNG images. PNG format supports
RGB, Indexed Color, Grayscale, and Bitmap mode images without alpha channels. PNG preserves transparency in
grayscale and RGB images.