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List:       haiku-bugs
Subject:    [haiku-bugs] Re: [Haiku] #18415: Add shear and projective geometrical transformations
From:       "Haiku" <trac () haiku-os ! org>
Date:       2023-06-29 15:16:59
Message-ID: 059.7f047cc6ed8cbf1571140f19bff85e39 () haiku-os ! org
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#18415: Add shear and projective geometrical transformations
----------------------------------------+-------------------------
  Reporter:  Handmaus                   |      Owner:  stippi
      Type:  enhancement                |     Status:  new
  Priority:  normal                     |  Milestone:  Unscheduled
 Component:  Applications/Icon-O-Matic  |    Version:  R1/beta4
Resolution:                             |   Keywords:
Blocked By:                             |   Blocking:
  Platform:  All                        |
----------------------------------------+-------------------------
Comment (by Zardshard):

 >> Whenever you deselect and reselect a shape, (...), its bounding box
 resets to an unrotated box.'
 >
 > That means, that when I do lots of tiny corrections they keep piling up
 as a different transformation every time the bounding box resets, is that
 correct?

 No. There goes a large part of your essay :)

 Stippi used affine transformations to represent translations, rotations,
 and scales. Any number of these operations can be represented as a single
 affine transformation. The bounding box resets every time you deselect and
 reselect simply because Icon-O-Matic never bothers to store the bounding
 box anywhere.

 On a tangent, everything you can achieve using only translations,
 rotations, and scales in Icon-O-Matic is everything an affine
 transformations can do. No more, no less.

 > * that the combined result of, for example, moving, plus resizing in any
 dimension, plus shearing, plus rotating can be replicated with a single
 projective transform

 Indeed, projective transformations can do this. In fact, I believe they
 can do anything an affine transformation can do and more. At the cost of a
 couple more bytes storage, of course.

 > Sorry if this is all a bit rambling, I have been rethinking, revisiting
 and rewording it for a couple of days, but it still is a bit of a
 hodgepodge of ideas. I hope you're able to make sense of it.

 Nice, I like it and understood it quite well. Thanks for taking the time
 to write it :)

 A comment of my own: A shape with both an affine transformation and a
 perspective transformation will have duplicate data. Both transformations
 can rotate, move, and scale a shape. A shape with a perspective
 transformation could be represented without any affine transformation. I
 took a quick look, and, it appears Icon-O-Matic currently stores both at
 the same time. That's 18 wasted bytes for each shape that uses a
 perspective transformation.
-- =

Ticket URL: <https://dev.haiku-os.org/ticket/18415#comment:8>
Haiku <https://dev.haiku-os.org>
The Haiku operating system.
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