🚀 go-pugleaf

In article <1992Aug26.152939.4449@uxa.ecn.bgu.edu> mucds@uxa.ecn.bgu.edu  
(Corey D. Stinson) writes:
> 	Could someone help me with a problem.  I have a small sprite
> (bitmapped) and when animating, instead of re-drawing the picture over
> and over to repesent the rotation stages I would like to develop some
> algorithm to rotate the image.

There's a neat algorithm in Introduction to Computer Graphics by Foley,
van Dam et alia for rotating bit maps, or doing any linear operation.
If you're happy with matrices then write your rotation matrix as a product
of two shears, one preserving x-coordinates and one preserving
y-coordinates. Each one is then really easy to implement as it acts
only on a row or column at a time and so you only have to do a couple of
multiplications for the whole bitmap making it incredibly fast.
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 \_._/ Dan Piponi  dpiponi @ maths1.mth.kcl.ac.uk