Comments on: Active Contours http://www.shawnlankton.com/2007/05/active-contours/ computer vision, science, business, and life Sun, 14 Mar 2010 10:53:07 -0400 http://wordpress.org/?v=2.8 hourly 1 By: Shawn Lankton http://www.shawnlankton.com/2007/05/active-contours/comment-page-1/#comment-1124 Shawn Lankton Tue, 20 Oct 2009 14:03:58 +0000 http://www.shawnlankton.com/2007/05/active-contours/#comment-1124 @Flo Great questions, and some are bugs! Please check the newest (fastest, most correct) implementation found here: <a href="http://www.shawnlankton.com/2009/04/sfm-and-active-contours/" rel="nofollow">http://www.shawnlankton.com/2009/04/sfm-and-active-contours/</a> @Flo Great questions, and some are bugs!
Please check the newest (fastest, most correct) implementation found here:
http://www.shawnlankton.com/2009/04/sfm-and-active-contours/

]]> By: Flo http://www.shawnlankton.com/2007/05/active-contours/comment-page-1/#comment-1119 Flo Fri, 16 Oct 2009 13:54:50 +0000 http://www.shawnlankton.com/2007/05/active-contours/#comment-1119 Dear Shawn, thanks a lot for this toolbox. I have a few questions about the finite differences used to compute the curvature, function curvature = get_curvature(phi,idx) (these questions are certainly very basic !): 1. for the first order central differences, phi_x and phi_y, why don't you divide by 2 ? 2. Where does the phi_xy expression come from ? I suppose you derive phi_x against y, using again the central difference ? If so, are you sure about the sign of phi_xy (I would take the opposite) and is the coefficient 0.25 consistent with the absence of the coefficient 0.5 in the expressions of phi_x and phi_y ? If not, could you explain me how you get this expression? 3. I am not convinced either about the multiplying term "(phi_x2 + phi_y2).^(1/2)" in the calculus of the curvature (div(grad(phi)/|phi|)). Could you give us any reference ? Many thanks for your help, FT Dear Shawn,

thanks a lot for this toolbox. I have a few questions about the finite differences used to compute the curvature, function curvature = get_curvature(phi,idx) (these questions are certainly very basic !):
1. for the first order central differences, phi_x and phi_y, why don’t you divide by 2 ?
2. Where does the phi_xy expression come from ? I suppose you derive phi_x against y, using again the central difference ? If so, are you sure about the sign of phi_xy (I would take the opposite) and is the coefficient 0.25 consistent with the absence of the coefficient 0.5 in the expressions of phi_x and phi_y ? If not, could you explain me how you get this expression?
3. I am not convinced either about the multiplying term “(phi_x2 + phi_y2).^(1/2)” in the calculus of the curvature (div(grad(phi)/|phi|)). Could you give us any reference ?

Many thanks for your help,

FT

]]> By: shanka http://www.shawnlankton.com/2007/05/active-contours/comment-page-1/#comment-1096 shanka Mon, 07 Sep 2009 15:12:23 +0000 http://www.shawnlankton.com/2007/05/active-contours/#comment-1096 to add to the above, i feel very difficult to get into theory, pls help me. shanka to add to the above, i feel very difficult to get into theory, pls help me.

shanka

]]> By: shanka http://www.shawnlankton.com/2007/05/active-contours/comment-page-1/#comment-1095 shanka Mon, 07 Sep 2009 15:07:20 +0000 http://www.shawnlankton.com/2007/05/active-contours/#comment-1095 i like to work on active contours for biomedical images. will you suggest where to and with what to start. i mean fundamentals. with regards, shanka i like to work on active contours for biomedical images. will you suggest where to and with what to start. i mean fundamentals.

with regards,

shanka

]]> By: Shawn Lankton http://www.shawnlankton.com/2007/05/active-contours/comment-page-1/#comment-548 Shawn Lankton Mon, 29 Jun 2009 12:18:26 +0000 http://www.shawnlankton.com/2007/05/active-contours/#comment-548 All of the codes will be made available after my defense (September '09). In the meanwhile, please see this post <a href="http://www.shawnlankton.com/2009/04/sfm-and-active-contours/" rel="nofollow">on sparse field active contours</a> for a much faster active contour implementation. All of the codes will be made available after my defense (September ‘09). In the meanwhile, please see this post on sparse field active contours for a much faster active contour implementation.

]]> By: Mewada Hiren K http://www.shawnlankton.com/2007/05/active-contours/comment-page-1/#comment-547 Mewada Hiren K Mon, 29 Jun 2009 10:14:21 +0000 http://www.shawnlankton.com/2007/05/active-contours/#comment-547 Dear Sir, I am persuing Ph D from India. I am doing the work in inthe same field.Will you please give me the matlab code for localizing region based active contour using local histogram separation energy measurement. Thanking You, Hiren Mewada Dear Sir,
I am persuing Ph D from India. I am doing the work in inthe same field.Will you please give me the matlab code for localizing region based active contour using local histogram separation energy measurement.

Thanking You,

Hiren Mewada

]]> By: Nyan Khin http://www.shawnlankton.com/2007/05/active-contours/comment-page-1/#comment-492 Nyan Khin Thu, 30 Apr 2009 19:47:37 +0000 http://www.shawnlankton.com/2007/05/active-contours/#comment-492 I am using your Active Contours Without Edges program. Just wanted to so it had helped alot with my thesis and is a brilliant piece of work! Many thanks for publishing it. I am using your Active Contours Without Edges program.

Just wanted to so it had helped alot with my thesis and is a brilliant piece of work!

Many thanks for publishing it.

]]> By: Jack cc http://www.shawnlankton.com/2007/05/active-contours/comment-page-1/#comment-453 Jack cc Tue, 24 Mar 2009 07:36:01 +0000 http://www.shawnlankton.com/2007/05/active-contours/#comment-453 I got it, sorry!! I got it, sorry!!

]]> By: Jack cc http://www.shawnlankton.com/2007/05/active-contours/comment-page-1/#comment-452 Jack cc Tue, 24 Mar 2009 07:23:29 +0000 http://www.shawnlankton.com/2007/05/active-contours/#comment-452 Hi,I've read your papers“Active Contours Without Edges,”and have some confused. In the paper of MS Energy part Eq(17) It looks as: [(I-u)^2 / Au] - [(I-v)^2 / Av] And in your matlab code it shows F = -((u-v).*((I(idx)-u)./Ain+(I(idx)-v)./Aout)) just like [(I-u)*(v-u) / Au] - [(I-v)*(u-v)] / Av] I really cannot understand if that's right or not. I look forward your relpy. Thanks in advance! Hi,I’ve read your papers“Active Contours Without Edges,”and have some confused.

In the paper of MS Energy part Eq(17)
It looks as:
[(I-u)^2 / Au] – [(I-v)^2 / Av]

And in your matlab code it shows
F = -((u-v).*((I(idx)-u)./Ain+(I(idx)-v)./Aout))
just like
[(I-u)*(v-u) / Au] – [(I-v)*(u-v)] / Av]

I really cannot understand if that’s right or not.
I look forward your relpy.
Thanks in advance!

]]> By: Mark http://www.shawnlankton.com/2007/05/active-contours/comment-page-1/#comment-436 Mark Tue, 03 Mar 2009 14:49:55 +0000 http://www.shawnlankton.com/2007/05/active-contours/#comment-436 Hi. Am trying to convert your code to java. Was wondering if you could explain what the bwdist function does. Does it compute the distance from each pixel to he next or does it find the nearest neighbouring pixel and then find the distance between them Hi. Am trying to convert your code to java. Was wondering if you could explain what the bwdist function does. Does it compute the distance from each pixel to he next or does it find the nearest neighbouring pixel and then find the distance between them

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