Re: Creating an CGAffineTransform From Sample Points
Re: Creating an CGAffineTransform From Sample Points
- Subject: Re: Creating an CGAffineTransform From Sample Points
- From: glenn andreas <email@hidden>
- Date: Mon, 18 Feb 2008 09:33:09 -0600
On Feb 18, 2008, at 12:54 AM, Quincey Morris wrote:
On Feb 17, 2008, at 20:47, Bridger Maxwell wrote:
Hello, I have a few questions on CGAffineTransform. I would like to
construct one to represent a calibration from x y values from a
camera to x
y values on a screen.
[explanation snipped]
All of this assumes that the transformation really is affine (no
warping, no variation of the transformation in different parts of
the image) and invertible.
This, of course, is the key point, and based on the description from
the OP, it probably isn't affine, since affine projections don't do
perspective. So if you take a camera looking at a piece of graph
paper that is slightly tilted, you're going to need something more
powerful than an affine projection.
Fortunately, you can use Core Image's CIPerspectiveTransform which
just requires the four control (corner) points, rather than having to
calculate the perspective matrix from those four control points.
Glenn Andreas email@hidden
<http://www.gandreas.com/> wicked fun!
quadrium | prime : build, mutate, evolve, animate : the next
generation of fractal art
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