To get more in-depth information on the what PostScript Level 2
provides over PostScript Level 1, Apple would suggest referring to the
"PostScript Language Reference Manual, Second Edition" by Adobe
Systems Incorporated (Addison Wesley). We have taken excerpts and/or
paraphrased an overview of PostScript Level 2 features outlined in the
reference manual, chapter 1, pages 7-9.
Here is a list of the new language features of PostScript Level 2,
which include previous language extension features:
* Dictionaries
Many Level 2 operators expect a dictionary operand. This allows for
optional parameters and future extensibility.
* Memory Management
In general, memory is more efficiently shared among different uses
and arbitrary memory restrictions have been eliminated.
* Resources
The language includes convenient facilities for locating and
managing resources.
* Filters
The language supports filters for ASCII encoding of binary data,
compression and decompression, and embedded subfiles.
* Binary Encoding
In addition to the standard ASCII encoding, the language syntax
includes two binary-encoded representations.
* User Paths
User path operators perform path construction and painting as a
single operation for convenience and efficiency. There is also a
user path cache and some convenience operators for painting
rectangles.
* Forms
There is a form cache to optimize repeated uses of the same form.
* Color Spaces
Colors can be specified according to a variety of color systems
(that is, gray scale, RGB, CMYK, and CIE based). The color space is
now an explicit parameter of the graphics state.
* CIE-based color spaces
The language supports several device-independent color spaces based
on the CIE 1931 (XYZ)-space.
* Patterns
It is possible to paint with patterns as well as with solid colors.
There is a pattern cache to optimize repeated uses of the same
pattern.
* Images
There are several enhancements to the facilities for painting
sampled images: use of any color space, 12-bit component values,
direct use of files as data sources, and additional decoding
and rendering options.
* Other text and graphic operators
There are several other new operators optimized for performance:
graphic state objects, automatic stroke adjustment, new variants of
"show", and a new "selectfont" operator.
* Device Setup
The setpagedevice operator provides a device-independent framework
for specifying the requirements of a page description and for
controlling both standard and optional features of a device.
* Interpreter Parameters
Administrative operations such as system configuration and changing
input-output device parameters are now organized in a more
systematic way.