3 Image Enhancement 3.Intensity transformations spatial filtering Background Some basic intensity transformation Histogram-based image processing Fundamentals of spatial filtering Smoothing spatial filters Sharpen spatial filters 第3章第1页
3 Image Enhancement 第3章 第1页 3. Intensity transformations & spatial filtering Background Some basic intensity transformation Histogram-based image processing Fundamentals of spatial filtering Smoothing spatial filters Sharpen spatial filters
3 Image Enhancement 3.3 Histogram processing Motivation Intensity transform can enhance image because it properly changes the image histogram.So we can directly design an intensity transform function based on histogram 第3章第2页
3 Image Enhancement 第3章 第2页 3.3 Histogram processing Motivation Intensity transform can enhance image because it properly changes the image histogram. So we can directly design an intensity transform function based on histogram
3 Image Enhancement 3.3 Histogram processing > Definition of histogram (hist=bar,gram=) If the intensity levels is in the range [0,L-1],the histogram is a discrete function h(rg)=ng,(K=0,1,.,L-1). where rg is the kth intensity value,and ny is the number of pixels in the image with intensity rk. 6 Na.of pixels 2 3 2 5 4 3 4 3 2 histogram 3 5 3 2 4 2 2 1 4x4 image Gray scale [0,9] 0 1 2 3 4 5 6 7 8 9 Gray level 第3章第3页
3 Image Enhancement 第3章 第3页 3.3 Histogram processing Definition of histogram (hist=bar,gram=图) If the intensity levels is in the range [0,L-1], the histogram is a discrete function h(rk )=nk , (k=0,1,...,L-1). where rk is the kth intensity value, and nk is the number of pixels in the image with intensity rk . 2 3 3 2 4 2 4 3 3 2 3 5 2 4 2 4 4x4 image Gray scale = [0,9] histogram 1 2 3 4 5 6 No. of pixels 0 1 2 3 4 5 6 7 8 9 Gray level
3 Image Enhancement 3.3 Histogram processing Motivation Dark image Low-oontrast image Bright image High-contrast image 第3章第4页
3 Image Enhancement 第3章 第4页 3.3 Histogram processing Motivation
3 Image Enhancement 3.3 Histogram processing histogram processing histogram equalization (HE) histogram specification (HS) Local HE 第3章第5页
3 Image Enhancement 第3章 第5页 3.3 Histogram processing histogram equalization (HE) histogram processing histogram specification (HS) Local HE