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Re: [PATCH] Fixes to AffineTransform


From: Olga Rodimina
Subject: Re: [PATCH] Fixes to AffineTransform
Date: 04 Feb 2004 11:19:40 -0500

On Wed, 2004-02-04 at 00:33, graydon hoare wrote:
> Olga Rodimina wrote:
> 
> > Here is the patch that fixes few errors in the AffineTransform class. 
> > It corrects a small error in shear transformation and fixes
> > createInverse() to return correct inverse matrix.
> 
> hi olga,
> 
> this stuff looks good, thanks a lot! it's surprising this just sat there 
> broken for so long. I've checked it against a few algebra texts I have 
> kicking around and some geometry libraries (including cairo) and they 
> seem to mostly agree with your calculation; though just to be difficult 
> they all use different notation and half of them do it upside down :)
> 

Hi,

I fixed the suggested changes. Attached is the revised patch that I'll
be committing.


> 
> it might be nice to write up a mauve testsuite which generates a bunch 
> of pseudorandom vectors and runs them through a bunch of pseudorandom 
> scaled, sheared and translated transformations (and their inverses) and 
> checks that the vectors pop out the same as they went in, within some 
> epsilon to account for floating point error. anything to make this stuff 
> less fidgety and prone to eyes-glossing-over would probably be good. 
> it's too easy to make a minor arithmetic mistake which completely breaks it.
> 

Sure. I'll do that.

Olga.

Attachment: patch
Description: Text document


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