電腦視覺期末報告 Gradients 指導教授：張顧耀學生姓名：廖寶呈 學號： E

outline Gradients ? GradientMagnitudeImageFilter GradientMagnitudeRecursiveGaussianImageFilter DerivativeImageFilter

Gradients 組成：大小 (magnitude) 、方向 (direction) 功用 : 描述一個二維函數在某點的最大變化率與 方向

Gradients 在影像處理的應用 大小 : 某個 pixel 與相鄰點在 gray level 上的 最大變化量 方向 :gray level 有最大變化量的兩相鄰點之 間的方向 (gray level 低的 pixel 指向 gray level 高的 pixel)

help in the determination of object contours separation of homogeneous regions. GradientMagnitudeImageFilter

#include "itkCastImageFilter.h“ typedeffloatInputPixelType; typedeffloatOutputPixelType GradientMagnitudeImageFilter

使用前使用後

computes the magnitude of the image gradient at each pixel location computes the magnitude of the image gradient at each pixel location The standard deviation of the Gaussian smoothing kernel is now set filter->SetSigma( sigma ) GradientMagnitudeRecursiveGaus sianImageFilter

σ=3 σ=3 σ=5 σ=5 GradientMagnitudeRecursiveGaussianImageFilter

computing the partial derivative of an image computing the partial derivative of an image #include "itkCastImageFilter.h“ typedeffloatInputPixelType; typedeffloatOutputPixelType DerivativeImageFilter

the derivative is selected with the SetOrder() method. The direction along which the derivative will be computed is selected with the SetDirection() method.

DerivativeImageFilter 使用前使用後