Digital Image Processing: Image Enhancement Spatial Filtering - Duong Anh Duc

Digital Image Processing: Image Enhancement Spatial Filtering - Duong Anh Duc includes Image Enhancement - Spatial Filtering; How to specify T; Smoothing Filters; Image smoothing by averaging (lowpass spatial filtering); Image Sharpening; High-boost filtering; Prewitt operators. | 5/14/2020 4:35:03 AM Duong Anh Duc - Digital Image Processing Digital Image Processing Image Enhancement Spatial Filtering 5/14/2020 4:35:03 AM Duong Anh Duc - Digital Image Processing Image Enhancement: Spatial Filtering Image enhancement in the spatial domain can be represented as: g(m,n) = T(f)(m,n) The transformation T maybe linear or nonlinear. We will mainly study linear operators T but will see one important nonlinear operation. Enhanced Image Transformation Given Image 5/14/2020 4:35:03 AM Duong Anh Duc - Digital Image Processing How to specify T If the operator T is linear and shift invariant (LSI), characterized by the point-spread sequence (PSS) h(m,n) , then (recall convolution) 5/14/2020 4:35:03 AM Duong Anh Duc - Digital Image Processing How to specify T In practice, to reduce computations, h(m,n) is of “finite extent: h(k,l) = 0 for (k,l) where D is a small set (called neighborhood). D is also called as the support of h. In the frequency domain, . | 5/14/2020 5:31:14 AM Duong Anh Duc - Digital Image Processing Digital Image Processing Image Enhancement Spatial Filtering 5/14/2020 5:31:14 AM Duong Anh Duc - Digital Image Processing Image Enhancement: Spatial Filtering Image enhancement in the spatial domain can be represented as: g(m,n) = T(f)(m,n) The transformation T maybe linear or nonlinear. We will mainly study linear operators T but will see one important nonlinear operation. Enhanced Image Transformation Given Image 5/14/2020 5:31:14 AM Duong Anh Duc - Digital Image Processing How to specify T If the operator T is linear and shift invariant (LSI), characterized by the point-spread sequence (PSS) h(m,n) , then (recall convolution) 5/14/2020 5:31:14 AM Duong Anh Duc - Digital Image Processing How to specify T In practice, to reduce computations, h(m,n) is of “finite extent: h(k,l) = 0 for (k,l) where D is a small set (called neighborhood). D is also called as the support of h. In the frequency domain, this can be represented as: G(u,v) = He(u,v) Fe(u,v) where He(u,v) and Fe(u,v) are obtained after appropriate zeropadding. 5/14/2020 5:31:14 AM Duong Anh Duc - Digital Image Processing How to specify T Many LSI operations can be interpreted in the frequency domain as a “filtering operation.” It has the effect of filtering frequency components (passing certain frequency components and stopping others). The term filtering is generally associated with such operations. 5/14/2020 5:31:14 AM Duong Anh Duc - Digital Image Processing How to specify T Examples of some common filters (1-D case): Lowpass filter Highpass filter 5/14/2020 5:31:14 AM Duong Anh Duc - Digital Image Processing If h(m, n) is a 3 by 3 mask given by then w1 w2 w3 h= w4 w5 w6 w7 w8 w9 5/14/2020 5:31:14 AM Duong Anh Duc - Digital Image Processing The output g(m, n) is computed by sliding the mask over each pixel of the image f(m, n). This filtering procedure is sometimes referred to as moving average filter. .