Digital Image Processing: Image Enhancement - Duong Anh Duc

Digital Image Processing Image Enhancement 21/11/15 Duong Anh Duc - Digital Image Processing 1 Image Enhancement To process an image so that output is “visually better” than the input, for a specific application. Enhancement is therefore, very much dependent on the particular problem/image at hand. Enhancement can be done in either: – Spatial domain: operate on the original image g(m,n) = T[f(m,n)] – Frequency domain: operate on the DFT of the original image G(u,v) = T[F(u,v)], where F(u,v) = F[f(m,n)], and G(u,v) = F [g(m,n)], 21/11/15 Duong Anh Duc - Digital Image Processing 2 Image Enhancement Techniques Point Operations Mask Operations Transform Operations Coloring Operations • Image Negative • Contrast Stretching • Compression of dynamic range • Graylevel slicing • Image Subtraction • Image Averaging • Histogram operations • Smoothing operations • Median Filtering • Sharpening operations • Derivative operations • Histogram operations • Low pass Filtering • Hi pass Filtering • Band pass Filtering • Homomorphic Filtering • Histogram operations • False Coloring • Full color Processing 21/11/15 Duong Anh Duc - Digital Image Processing 3 Point Operations Output pixel value g(m, n) at pixel (m, n) depends only on the input pixel value at f(m, n) at (m, n) (and not on the neighboring pixel values). We normally write s = T(r), where s is the output pixel value and r is the input pixel value. T is any increasing function that maps [0,1] into [0,1]. 21/11/15 Duong Anh Duc - Digital Image Processing 4 Image Negative T(r) = s = L-1-r, L: max grayvalue 21/11/15 Duong Anh Duc - Digital Image Processing 5 ... - tailieumienphi.vn