From: Dr. Olaf Hoffmann <Dr.O.Hoffmann@gmx.de>

Date: Thu, 15 Nov 2007 14:52:42 +0100

To: www-svg@w3.org

Message-Id: <200711151452.42509.Dr.O.Hoffmann@gmx.de>

Date: Thu, 15 Nov 2007 14:52:42 +0100

To: www-svg@w3.org

Message-Id: <200711151452.42509.Dr.O.Hoffmann@gmx.de>

Well, lets see if this helps. zooming and panning is related somehow to the zoomAndPan attribute, this is explained in SVGT1.2 in chapter 13.10. Zooming is a scaling mechanism provided by the user agent/viewer. Panning is a shift/translation mechanism provided by the user agent/viewer. How this is done (menue item, formula, button, pointer interactions, keys), depends on the viewer and is not specified. Therefore this is mathematically similar to the related transform operation from the author of the document, but zooming and panning is done or specified by the user. Therefore they cannot replaced in general by transform attributes. However if you are both, author and user of the same document, it is possible to simulate a specific result of a user action with the transform attribute somehow (and maybe with interactive animation). Concerning constrained transformation this simulation requires a specific document structure, because implicite transformations related to the attribute viewBox and preserveAspectRatio (called VB) behave different with constrained transformations as user transformations (called U) and transformations inside the document (called CTM) . I already tried to understand this in detail to create some tests related to animation, if I understand it correct: To see, what happens, one has to analyse, how the the resulting transformations are derived from inverse matrices and how the different transformations have to be combined to get the final effect (one has to note too, that not all matrices have an inverse, but the effect of constrained transformations is still defined/possible). If you are not familiar with matrices: If A is a matrix and B its inverse and I the identity, then: AB = I = BA (and AI= A = IA for any A). In general it is not XY=YX for matrices X,Y, therefore care has to be taken, how they are multiplied.Received on Thursday, 15 November 2007 14:03:12 UTC

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