Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!apple!well!levine
From: levine@well.UUCP (Ron Levine)
Newsgroups: comp.graphics
Subject: Re: Wanted: Bitmap rotation algorithm
Message-ID: <12310@well.UUCP>
Date: 22 Jun 89 04:59:29 GMT
References: <8.UUL1.2#261@persoft.UUCP>
Reply-To: levine@well.UUCP (Ron Levine)
Organization: Whole Earth 'Lectronic Link, Sausalito, CA
Lines: 33

In article <8.UUL1.2#261@persoft.UUCP> ericf@persoft.UUCP (Eric R. Feigenson) writes:
>
>I am look for any and all algorithms relating to rotating a bitmap an
>aribtrary amount.  Efficiency and accuracy (minimal distortion) are,
>of course, important considerations.  ....
>

I believe that the fastest methods of rotating raster images, and 
the easiest to which to add filtering to fix the aliasing (holes 
in the image), are the so-called two-pass methods, in which one 
pass preserves horizontal scan lines and the other preserves 
vertical scan lines.  These are especially effective when frame 
buffer memory has been designed for efficient access by 
horizontal and vertical scan lines.  This is the basis of the 
ADO, (Ampex Digital Optics), the machine which makes most of the 
real-time video effects that we see so much of on TV, involving 
rotations and other 2D linear transformations.

References: 

        Ed Catmull and Alvy Ray Smith, 3-D Transformations of 
        Images in Scan-Line Order, Computer Graphics, Vol. 14, 
        No. 3, pp.279-285, July, 1980 (Siggraph Proceedings)  

        Philip P. Bennet and Steven A. Gabriel, System for 
        Spatially Transforming Images, U.S. Patent #4,472,732, 
        September 18, 1984. 

        Alvy Ray Smith, Planar 2-Pass Texture Mapping and 
        Warping, Computer Graphics, Vol 21, No. 4, July 1987 
        (Siggraph Proceedings)

--Ron Levine