Comments on: Spatial transformations: Forward mapping http://blogs.mathworks.com/steve/2006/04/28/spatial-transforms-forward-mapping/ Steve Eddins manages the Image & Geospatial development team at <a href="http://www.mathworks.com/">The MathWorks</a> and coauthored <a href="http://www.mathworks.com/support/books/book5291.html?category=-1&language=-1">Digital Image Processing Using MATLAB</a>. He writes here about image processing concepts, algorithm implementations, and MATLAB.<br><br><img> Mon, 23 Nov 2009 01:35:21 +0000 http://wordpress.org/?v=2.3.1 By: Steve http://blogs.mathworks.com/steve/2006/04/28/spatial-transforms-forward-mapping/#comment-22148 Steve Tue, 22 Sep 2009 12:30:10 +0000 http://blogs.mathworks.com/steve/2006/04/28/spatial-transforms-forward-mapping/#comment-22148 Douglas—Use <tt>cp2tform</tt> to infer a spatial transformation from your point set. One of the spatially varying ones might be best. Then use <tt>imtransform</tt> to warp your image. Douglas—Use cp2tform to infer a spatial transformation from your point set. One of the spatially varying ones might be best. Then use imtransform to warp your image.

]]> By: douglas http://blogs.mathworks.com/steve/2006/04/28/spatial-transforms-forward-mapping/#comment-22147 douglas Tue, 22 Sep 2009 06:10:27 +0000 http://blogs.mathworks.com/steve/2006/04/28/spatial-transforms-forward-mapping/#comment-22147 Could you tell how to apply the grid points (data points from the transformation grid) in the transformation ? <em>[Points edited out for space.]</em> Could you tell how to apply the grid points (data points from the transformation grid) in the transformation ?

[Points edited out for space.]

]]> By: Rudolph http://blogs.mathworks.com/steve/2006/04/28/spatial-transforms-forward-mapping/#comment-22076 Rudolph Fri, 28 Aug 2009 08:05:13 +0000 http://blogs.mathworks.com/steve/2006/04/28/spatial-transforms-forward-mapping/#comment-22076 I managed to overcome the idea of linear indexing which imtransform use to determine the custom spatial transform. Thanks I managed to overcome the idea of linear indexing which imtransform use to determine the custom spatial transform. Thanks

]]> By: Rudolph http://blogs.mathworks.com/steve/2006/04/28/spatial-transforms-forward-mapping/#comment-22072 Rudolph Fri, 21 Aug 2009 09:23:06 +0000 http://blogs.mathworks.com/steve/2006/04/28/spatial-transforms-forward-mapping/#comment-22072 Hi Steve, I need to perform lense calibration on an image taken with specific camera. The lense coefficients are available. The distortions on the lense are radial distortion, decentering of the principal point and some affinity. According to me I'll have to calculate the (subpixel units) distance which I have to move each pixel in the x and y direction. So each pixel will have it's own resulting transformation. I went through most of your blogs and I want to create a custom tform struct which I can implement on bulk images. Now I can't see how I will be able to do this with inverse mapping, true? Will imtransform deal with the overlapping and gaps for me automatically with chosen interpolation? How do I deal with a pixel that moves 0.166 pixels up for instance? How will matlab save the info on output space? Any guidence would be appreciated. Hi Steve,

I need to perform lense calibration on an image taken with specific camera. The lense coefficients are available.

The distortions on the lense are radial distortion, decentering of the principal point and some affinity. According to me I’ll have to calculate the (subpixel units) distance which I have to move each pixel in the x and y direction. So each pixel will have it’s own resulting transformation. I went through most of your blogs and I want to create a custom tform struct which I can implement on bulk images.

Now I can’t see how I will be able to do this with inverse mapping, true? Will imtransform deal with the overlapping and gaps for me automatically with chosen interpolation? How do I deal with a pixel that moves 0.166 pixels up for instance? How will matlab save the info on output space?

Any guidence would be appreciated.

]]> By: Steve http://blogs.mathworks.com/steve/2006/04/28/spatial-transforms-forward-mapping/#comment-20560 Steve Sat, 05 Apr 2008 02:49:02 +0000 http://blogs.mathworks.com/steve/2006/04/28/spatial-transforms-forward-mapping/#comment-20560 Leonardo—Sounds like you could use <tt>cp2tform</tt> to estimate a spatial transform fitting your points. Leonardo—Sounds like you could use cp2tform to estimate a spatial transform fitting your points.

]]> By: Leonardo http://blogs.mathworks.com/steve/2006/04/28/spatial-transforms-forward-mapping/#comment-20559 Leonardo Fri, 04 Apr 2008 22:37:55 +0000 http://blogs.mathworks.com/steve/2006/04/28/spatial-transforms-forward-mapping/#comment-20559 Dear Steve, I have an input image from which I digitized grid points. I know the real distance between the grid points, so I can create an output array. I would like to specify a transformation using these points, so I can assign the real location to each point from the input. Is it possible? Best Leonardo Dear Steve,
I have an input image from which I digitized grid points.
I know the real distance between the grid points, so I can create an output array. I would like to specify a transformation using these points, so I can assign the real location to each point from the input.
Is it possible?
Best
Leonardo

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