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