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3D EDGE DETECTION BY SEPARABLE RECURSIVE
FILTERING AND EDGE CLOSING
2010/05/06
Author: Monga, O.; Deriche, R.; Malandain, G.; Cocquerez, J.P.Source: Pattern Recognition, 1990. Proceedings., 10th International Conference , Page(s): 652 - 654Student: Jia – Hong ChenAdvisor: Ku – Yaw Chang
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Outline
Introduction A 3D edge detection scheme Closing 3D edges Conclusion
2010/05/06
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Introduction
3D edge detectors are issued a generalization in 3D of 2D edge detectors
we propose an unified formalism for 3D edge detection recursive filters tracking/closing algorithm
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Outline
Introduction A 3D edge detection scheme Closing 3D edges Conclusion
2010/05/06
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A 3D edge detection scheme
Canny 演算法 Step1: smoothing, 降低雜訊 Step2: 找邊緣 , 求梯度的強度 Step3: hysteresis
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A 3D edge detection scheme
Step1: smoothing 使用 Gaussian filter, 在 Gaussian filter 函式中使
用到 variance 來調整 Gaussian filter 的值
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A 3D edge detection scheme
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A 3D edge detection scheme
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A 3D edge detection scheme
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A 3D edge detection scheme
Step2: 找邊緣 , 求梯度的強度 使用 Sobel method 找出邊緣 , 他會先計算出每一個
像素的值再利用 求出梯度
另外利用 求出梯度方向
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A 3D edge detection scheme
1st Derivative (Gradient)
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A 3D edge detection scheme
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A 3D edge detection scheme
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A 3D edge detection scheme
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A 3D edge detection scheme
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A 3D edge detection scheme
Step3: hysteresis 設定 2 個門檻值 T1 和 T2, 由 G 得到的結果 , 任何像
素如果大於 T1 則被認定為邊緣像素 , 而在這個邊緣像素鄰近的點如果有大於 T2 也會被認定為邊緣像素 .
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Outline
Introduction A 3D edge detection scheme Closing 3D edges Conclusion
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Closing 3D edges
It is often very difficult select adequate thresholds for the
thresholding stage High thresholds allows to remove noisy edge
points but also true edge points low thresholds allow to obtain all true edge
points but also noisy edge points
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Closing 3D edges
Generally it is easier extend uncompleted contours than validate
true contours in a noisy edge image choose high thresholds
remove false edge points use a tracking/closing algorithm
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Closing 3D edges
Deriche and Cocquerez 2D edge closing method proposed supposes that it is possible to recognize
endpoints of contours Examination of a neighbourhood 3 x 3 of an edge
point The implementation of this algorithm is
easy if an edge point is identified as an extremity
the algorithm is applied recursively to the involved extremity until a stop condition is verified
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Closing 3D edges
The 3D extension of this algorithm applying it on each plane XY, YZ, ZX adding the three edge images obtained
This can be justified by the assumption the intersection of a 3D surface by at least
one plane among XY,YZ and ZX
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Closing 3D edges
it remains some localized information lacks cause holes of width 1 along X,Y or Z
To solve this problem select the codes corresponding to holes of
width 1 2D implementation consists in scanning the
image fill up each identified hole
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Outline
Introduction A 3D edge detection scheme Closing 3D edges Conclusion
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Conclusion
We have proposed a 3D edge detection scheme
saving in computational effort is of great interest
Currently we investigate true 3D closing edge methods
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The End
2010/05/06
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