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From "Martin Desruisseaux (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SIS-176) Provide an optimized MathTransform implementation for diagonal matrices
Date Fri, 14 Dec 2018 12:08:00 GMT

    [ https://issues.apache.org/jira/browse/SIS-176?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16721331#comment-16721331
] 

Martin Desruisseaux commented on SIS-176:
-----------------------------------------

Changed my mind about not providing a {{TranslationTransform}}. At least ±0.5 pixel translations
happen quite often with grid coverages. Will add in SIS 1.0.

> Provide an optimized MathTransform implementation for diagonal matrices
> -----------------------------------------------------------------------
>
>                 Key: SIS-176
>                 URL: https://issues.apache.org/jira/browse/SIS-176
>             Project: Spatial Information Systems
>          Issue Type: Improvement
>          Components: Referencing
>    Affects Versions: 0.6
>            Reporter: Martin Desruisseaux
>            Assignee: Martin Desruisseaux
>            Priority: Minor
>             Fix For: 0.7
>
>
> {{ProjectiveTransform}} handles arbitrary matrices in a generic way. However in practice,
many matrices are diagonal + a translation transform. We may get some performance improvement
if we write a specialized transform class for such matrices, because it would replace a O(_n_²)
operation by a O(_n_) one (_n_ is the matrix size).



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