Display PostScript: Difference between revisions

Revision as of 13:42, 25 July 2013

Revision as of 16:24, 26 July 2013

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* ''Halftone phase'': In order to improve scrolling performance, DPS only drew the small portion of the window that became visible, shifting the rest of the image instead of re-drawing it. However this meant that the [[halftone]]s might not line up, producing visible lines and boxes in the display of graphics. DPS included additional code to properly handle these cases. Modern full-color displays with no halftones have made this idea mostly obsolete.

* ''Incremental updates'': In printing applications the PS code is interpreted until it gets a <code>showpage</code> at which point it is actually printed out. This is not suitable for a display situation where a large number of minor updates are needed all the time. DPS included modes to allow semi-realtime display as the instructions were received from the user programs.

* ''Bitmap font support'': DPS added the ability to map PS fonts onto hand-drawn [[bitmap font]]s and change from one to the other on the fly. WhileAdobe PS's ability to display fonts on "low resolution" devices was(significantly good, "low resolution"less meant something on the order ofthan 300&nbsp;[[Dots per inch|dpi]],) notwas thevery 96&nbsp;dpipoor. thatFor example, a NeXT screen used only 96&nbsp;dpi. This resolutionPS limitation was worked around by requiredusing hand-built bitmap fonts to provide reasonablepassable quality. Later implementations of PS (including compatible replacements like [[Ghostscript]]) provided [[anti-aliased]] fonts on grayscale or colour displays, which significantly improved quality. However, this development was too late to be of much use. Modern displays are still around 100&nbsp;dpi, but have very much superior font quality without using bitmap fonts.

* ''Programming language support'': DPS introduced the concept of a "<code>pswrap</code>", which allowed [[Software developer|developers]] to wrap PostScript code into a [[C (programming language)|C language]] function which could then be called from an application.