Comments on: Image Blur Detection via Hough Transform — IV http://www.kerrywong.com/2009/07/03/image-blur-detection-via-hough-transform-iv/ Fri, 12 Mar 2010 01:25:24 +0000 http://wordpress.org/?v=2.9.2 hourly 1 By: kwong http://www.kerrywong.com/2009/07/03/image-blur-detection-via-hough-transform-iv/comment-page-1/#comment-42626 kwong Tue, 15 Dec 2009 00:11:17 +0000 http://www.kerrywong.com/?p=1277#comment-42626 The gradient calculation involves fitting a line through the detected edge points. After the linear equation is obtained, calculating the perpendicular line is simple. Similarly, the gradient can be calculated by modeling the intensity as a linear function (the simplest method) and the gradient would be the tangent of the linear function. Hope this helps. The gradient calculation involves fitting a line through the detected edge points. After the linear equation is obtained, calculating the perpendicular line is simple. Similarly, the gradient can be calculated by modeling the intensity as a linear function (the simplest method) and the gradient would be the tangent of the linear function. Hope this helps.

]]> By: Antonin JACQ http://www.kerrywong.com/2009/07/03/image-blur-detection-via-hough-transform-iv/comment-page-1/#comment-42625 Antonin JACQ Tue, 15 Dec 2009 00:06:08 +0000 http://www.kerrywong.com/?p=1277#comment-42625 Hi. I am currently a student at the university of La Rochelle, France, in an image processing & mathematics master. Our teachers asked us to build several image default detector: noise(salt&pepper, ccd), block artifact, color dominance, motion-blur and out-of-focus blur. I am working since yesterday on your articles for blur detection via Hough Transform. Working on Matlab, i succesfully reproduce almost everything, except for the final part of the algorythm: the calcul of the gradient on the line. I didn't understand what you are doing: - in which image is this line? In the Hough transform? In the orignal image? - Similarly, what is the use of the perpendicular line whom you speak of for the gradient calculation? My principal problem lies with the definition of the gradient D of an image : In classics way, D=[Ix,Iy] with Ix and Iy being a vector field (Ix(x,y)=I(x,y)-I(x-1,y), the same for Iy). Here i do not know what is it. If you're willing to enlight me, i would be thankful. Antonin. Hi.

I am currently a student at the university of La Rochelle, France, in an image processing & mathematics master.
Our teachers asked us to build several image default detector: noise(salt&pepper, ccd), block artifact, color dominance, motion-blur and out-of-focus blur.

I am working since yesterday on your articles for blur detection via Hough Transform.

Working on Matlab, i succesfully reproduce almost everything, except for the final part of the algorythm: the calcul of the gradient on the line.
I didn’t understand what you are doing:
- in which image is this line? In the Hough transform? In the orignal image?
- Similarly, what is the use of the perpendicular line whom you speak of for the gradient calculation?

My principal problem lies with the definition of the gradient D of an image :
In classics way, D=[Ix,Iy] with Ix and Iy being a vector field (Ix(x,y)=I(x,y)-I(x-1,y), the same for Iy). Here i do not know what is it.

If you’re willing to enlight me, i would be thankful.

Antonin.

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