Comments on: Antialiased polygon scan conversion: Are you interested? http://blogs.mathworks.com/steve/2007/02/06/antialiased-polygon-scan-conversion/ Steve Eddins manages the Image & Geospatial development team at The MathWorks and coauthored Digital Image Processing Using MATLAB. He writes here about image processing concepts, algorithm implementations, and MATLAB. Fri, 10 Feb 2012 18:55:59 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Steve http://blogs.mathworks.com/steve/2007/02/06/antialiased-polygon-scan-conversion/#comment-24388 Steve Mon, 08 Aug 2011 19:35:52 +0000 http://blogs.mathworks.com/steve/?p=114#comment-24388 Rishabh—I haven't written it. Rishabh—I haven’t written it.

]]> By: Rishabh Jain http://blogs.mathworks.com/steve/2007/02/06/antialiased-polygon-scan-conversion/#comment-24379 Rishabh Jain Mon, 01 Aug 2011 21:02:30 +0000 http://blogs.mathworks.com/steve/?p=114#comment-24379 Hi Steve, I really enjoyed your last several posts. I would really really find this code useful, esp. in generating stimuli at non grid locations for my simulations. Can you please share the code for the mentioned anti-aliased polyscan algorithm ? Thanks a lot in advance Rishabh Hi Steve,

I really enjoyed your last several posts. I would really really find this code useful, esp. in generating stimuli at non grid locations for my simulations. Can you please share the code for the mentioned anti-aliased polyscan algorithm ?

Thanks a lot in advance
Rishabh

]]> By: Rishabh Jain http://blogs.mathworks.com/steve/2007/02/06/antialiased-polygon-scan-conversion/#comment-24378 Rishabh Jain Mon, 01 Aug 2011 18:27:40 +0000 http://blogs.mathworks.com/steve/?p=114#comment-24378 Hi Steve, I really enjoyed your last several posts. I would really really find this code useful, esp. in generating stimuli at non grid locations for my simulations. Can you please share this anti-aliased polyscan algorithm ? Thanks a lot in advance Rishabh Hi Steve,

I really enjoyed your last several posts. I would really really find this code useful, esp. in generating stimuli at non grid locations for my simulations. Can you please share this anti-aliased polyscan algorithm ?

Thanks a lot in advance
Rishabh

]]> By: Steve http://blogs.mathworks.com/steve/2007/02/06/antialiased-polygon-scan-conversion/#comment-23425 Steve Fri, 03 Sep 2010 20:04:23 +0000 http://blogs.mathworks.com/steve/?p=114#comment-23425 Thomas—If you have enough memory to upsample your image by a factor of 3 in both directions, then you could do bwboundaries on the result. Then if you can scale the boundary locations back down you can get boundaries along the pixel edges instead of through the pixel centers. I'll think about doing a blog post on this idea. Thomas—If you have enough memory to upsample your image by a factor of 3 in both directions, then you could do bwboundaries on the result. Then if you can scale the boundary locations back down you can get boundaries along the pixel edges instead of through the pixel centers.

I’ll think about doing a blog post on this idea.

]]> By: Thomas http://blogs.mathworks.com/steve/2007/02/06/antialiased-polygon-scan-conversion/#comment-23367 Thomas Tue, 17 Aug 2010 09:01:58 +0000 http://blogs.mathworks.com/steve/?p=114#comment-23367 I'm using the following combination to obtain the boundary-pixels of the convex hull of some marks in an image: thresholding bwboundaries (to get more information for (un)selecting marks) convhull (gives me a poygon, but I need all the pixels, therefore ...) poly2mask bwtraceboundary If I use this procedure objects are always shrinking (although valid convex marks should be an invariant of that procedure). Since I'm using convhull, where I lose information about the boundary, I can not ensure that the marks don't get deformed slightly, but for keeping up the area it could be useful to have the fractional coverage for selection as parameter (better performance) or at least get it as result. This would be useful, when having a fast precompiled poly2mask-version - an interpreted one is as good as writing it on my own. (By the way: Another improvement for my algorithm would be, if bwtraceboundary would give me the outer coords, but not the center-coords of the pixels. Is there some way?) Regards, Thomas I’m using the following combination to obtain the boundary-pixels of the convex hull of some marks in an image:

thresholding
bwboundaries (to get more information for (un)selecting marks)
convhull (gives me a poygon, but I need all the pixels, therefore …)
poly2mask
bwtraceboundary

If I use this procedure objects are always shrinking (although valid convex marks should be an invariant of that procedure). Since I’m using convhull, where I lose information about the boundary, I can not ensure that the marks don’t get deformed slightly, but for keeping up the area it could be useful to have the fractional coverage for selection as parameter (better performance) or at least get it as result.
This would be useful, when having a fast precompiled poly2mask-version – an interpreted one is as good as writing it on my own.

(By the way: Another improvement for my algorithm would be, if bwtraceboundary would give me the outer coords, but not the center-coords of the pixels. Is there some way?)

Regards,
Thomas

]]> By: Steve http://blogs.mathworks.com/steve/2007/02/06/antialiased-polygon-scan-conversion/#comment-21239 Steve Tue, 11 Nov 2008 16:35:26 +0000 http://blogs.mathworks.com/steve/?p=114#comment-21239 Ruthy—Thanks for the suggested application. Ruthy—Thanks for the suggested application.

]]> By: Ruthy http://blogs.mathworks.com/steve/2007/02/06/antialiased-polygon-scan-conversion/#comment-21238 Ruthy Tue, 11 Nov 2008 13:17:28 +0000 http://blogs.mathworks.com/steve/?p=114#comment-21238 Hi Steve, I am doing a segmentation of an image and I use the boundary information to compare between two curves and decide weather they match. If I am using the output of the segmentation as a discrete numbers, I will have a very noise edge and the comparison will not be robust. I want to get the edge of the shape in a sub-pixel resolution to be able to better compare the edges. Ruthy Hi Steve,

I am doing a segmentation of an image and I use the boundary information to compare between two curves and decide weather they match.
If I am using the output of the segmentation as a discrete numbers, I will have a very noise edge and the comparison will not be robust.
I want to get the edge of the shape in a sub-pixel resolution to be able to better compare the edges.

Ruthy

]]> By: Steve http://blogs.mathworks.com/steve/2007/02/06/antialiased-polygon-scan-conversion/#comment-21101 Steve Thu, 25 Sep 2008 11:21:59 +0000 http://blogs.mathworks.com/steve/?p=114#comment-21101 Ruthy—I'm not sure what you mean by "a mask containing subpixel coordinates." Ruthy—I’m not sure what you mean by “a mask containing subpixel coordinates.”

]]> By: Ruthy http://blogs.mathworks.com/steve/2007/02/06/antialiased-polygon-scan-conversion/#comment-21099 Ruthy Thu, 25 Sep 2008 09:21:22 +0000 http://blogs.mathworks.com/steve/?p=114#comment-21099 Hi, I read your blog today and it is very close to what I am looking for. In your blog you describe a better poly2mask function. I am looking for a function that "smoothens" a mask using the original image information and returns a mask containing subpixel coordinates. I am using this information to compare between similar contours of objects, and the granolarity of full pixel location causes errors in the similarity measure. Thanks, Ruthy Hi,

I read your blog today and it is very close to what I am looking for.
In your blog you describe a better poly2mask function.
I am looking for a function that “smoothens” a mask using the original image information and returns a mask containing subpixel coordinates.
I am using this information to compare between similar contours of objects, and the granolarity of full pixel location causes errors in the similarity measure.

Thanks,
Ruthy

]]> By: Steve http://blogs.mathworks.com/steve/2007/02/06/antialiased-polygon-scan-conversion/#comment-6669 Steve Wed, 18 Apr 2007 22:06:52 +0000 http://blogs.mathworks.com/steve/?p=114#comment-6669 David - Thanks for your input. David – Thanks for your input.

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