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- From glynn.clements@virgin.net Wed Dec 12 19:13:35 2001
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- Wed, 12 Dec 2001 18:10:12 GMT
- From: Glynn Clements <glynn.clements@virgin.net>
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- Date: Wed, 12 Dec 2001 18:10:12 +0000
- To: Markus Neteler <neteler@itc.it>
- Subject: Re: affine transform
- In-Reply-To: <20011212165039.B4313@itc.it>
- References: <20011212165039.B4313@itc.it>
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- Markus Neteler wrote:
- > by chance I have found another implementation for affine
- > transform (or whatever there is implemented):
- > src/libes/vect32/libes/transform/
- > It is used in v.digit and maybe other programs.
- >
- > Is this a candidate for the GMATH library?
- > I think yes.
- The code there seems fairly specialised.
- The transformations are affine, but the means of generating the
- coefficients seems rather odd; in particular, the requirement that at
- least four reference points are provided. Three points will define an
- affine transformation; any more are either redundant or contradictory.
- If it were to go into the gmath library, it might be better for
- compute_transformation_coef() to return the resulting transformation
- in a gmath "mat_struct". transform_a_into_b() and transform_b_into_a()
- are largely redundant; they're either just a matrix multiplication (if
- using homogeneous coordinates) or multiply-and-add (otherwise).
- --
- Glynn Clements <glynn.clements@virgin.net>
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