11.10. Some of the features of Level 2   

Filters

Filters transform data as they are sent to or written to a file. Extensions in this area have greatly improved performance. The encoding, decoding, compression and decompression of data have been improved so as to reduce the amount of storage space used.

Optimized graphics operators

Rectangle operator which is used for filling, clipping and stroking rectangle and is highly optimized. Filling a rectangle is now three times faster than an equivalent moveto, lineto, lineto, lineto, closepath, fill. A user path cache is used to optimize interpretation of user paths that are invoked repeatedly.

Optimized text operators

A selectfont operator is introduced to optimize the switching between fonts by using a caching mechanism. The operators that do the clipping, filling, stroking etc, were optimised. Half-tone specifiers were improved so as to get a more precise way of representing half- tone dots.

Images

Several enhancements to the facilities for painting sampled images. For example, use of any colour space, direct use of files as data sources.

Composite Fonts

These fonts provide a page description language for international business. Fonts were of a limited range when PostScript was first introduced. It had only enough room to encode 256 distinct characters. With the new improvements, font encoding of large character sets was made possible. Non-horizontal writing is now possible and the inclusion of metrics in the font allows the setting character spacing.

New Colour Spaces

There are three classes of color spaces in PostScript 2 which are device independent, special and device dependent. An example of device independent colour space is CIEBasedABC colour space which is defined in terms of a two-stage, non-linear transformation of the CIE 1931 (XYZ)-space. An example of special colour space is the pattern colour space which enables painting with a that are to be painted. An examplr of device dependent colour space is the DeviceRGB which is same as the existing RGB colour model. When PostScript was first introduced, the colour could only be specified with the red-green-blue (RGB) and hue-saturation- brightness (HSB) colour models. With the new improvements, the colour could be specified with cyan-magenta-yellow-black (CMYB) colour models. The improvements also include colour transformations for colour components, under-colour removal and a colour image operator that renders colour image samples.

The use of Forms.

The use of forms, such as letter heads etc, has made the language more convenient. Forms are self-contained descriptions of graphics that could be painted on several pages at different locations on a page.

Display PostScript extentions.

This allowed the PostScript imaging model to deal specifically with displays and windowing systems and optimised operators to increase efficiency and performance. (See later.)

There were quite a number of other improvements such as :

        Improvements for printer support.

        Improvements in image and pattern processing.

        Improvements on resources , dictionaries, etc.

        All these improvements were made to increase efficiency,

           performance, flexibility and convenience.