Editing Shape table

{{Short description|Apple II graphics feature}}
{{multiple issues|
{{essay like|date=July 2018}}
{{refimprove|date=April 2015}}
}}

'''Shape tables''' are a feature of the [[Apple II]] ROMs which allows for manipulation of small images encoded as a series of vectors. An image (or ''shape'') can be drawn in the high-resolution graphics mode—with scaling and rotation—via software routines in the ROM. Shape tables are supported via [[Applesoft BASIC]] and from [[machine code]] in the "Programmer's Aid" package that was bundled with the original [[Integer BASIC]] ROMs for that computer.

Applesoft's high-resolution graphics routines were not optimized for speed,<ref name="simoni198308">{{cite news | url=https://archive.org/stream/byte-magazine-1983-08/1983_08_BYTE_08-08_The_C_Language#page/n291/mode/2up | title=A New Shape Subroutine for the Apple | work=BYTE | date=August 1983 | accessdate=9 February 2015 | author=Simoni, Richard T. Jr. | pages=292}}</ref> so shape tables were not typically used for performance-critical software such as games, which were typically written in [[assembly language]] and used pre-shifted bitmap shapes. Shape tables were used primarily for static shapes and sometimes for fancy text; Beagle Bros offered a number of fonts in ''Font Mechanic'' as Applesoft shape tables.

==Technical details==
The [[Tuple|vector]]s of a two-dimensional graphic, each encoding a direction from the previous pixel along with a flag indicating whether the new pixel should be illuminated or not, were encoded up to three in a byte. These were stored in a table via the Monitor or the <code>[[PEEK and POKE|POKE]]</code> command. From there, the graphic could be referenced by number (a table could contain up to 255 shapes), and built-in Applesoft routines permitted scaling, rotating, and drawing or erasing the shape. An [[Exclusive or|XOR]] mode was also available to allow the shape to be visible on any color background; this had the advantage, also, of allowing the shape to be easily erased by redrawing it.

Apple did not provide any utilities for creating shape tables; they had to be created by hand, usually by plotting on [[graph paper]], then calculating the hexadecimal values and entering them into the computer.  [[Beagle Bros]] created a shape table editing program, which eliminated the "number crunching", called ''[[Apple Mechanic]]'', and a related program, ''[[Font Mechanic]]''.

== See also ==
* [[Sprite (computer graphics)|Sprite]]

==References==
{{reflist}}

== External links ==
* [http://www.atariarchives.org/cgp/Ch03_Sec05.php Atariarchives.org example], detailed instructions on assembling shape tables by hand

[[Category:Computer graphics]]