Point Processing 1.In a digital image point is called pixel (point ≡ ≡≡ ≡ pixel); 2.Point Processing transforms a pixel’s value to function of its value alone: T: f(x,y) → →→ → g(x,y) or G(x,y) = T(f(x,y)) where a=f(x,y), s=g(x,y) 3. Point Processing does not depend on the values of the neighbors. 1192013 2 Image Processing Point Processing 1. Brightness and contrast adjustment 2. Gamma correction 3. Histogram equalization 4. Histogram matching 5. Color correction 1192013 3 Image Processing Point Processing Origin image Histogram equalization brightness +brightness +contrast contrast γ γγ γ γγ γ =1.25 γ γγ γ γγ γ =0.9 negative bitplan 5 1192013 4 Image Processing Point Processing Negative image of image I Let I is an image with gray levels in the range L , L , i.e., L ≤ ≤≤ ≤ ≤≤ ≤ f(x,y) ≤ ≤≤ ≤ ≤≤ ≤ L , for all (x,y) in an image I. The negative transformation is given by: g(x,y) = L f(x,y), for all (x,y) ∈ ∈∈ ∈ ∈∈ ∈I 1192013 5 Image Processing Point Processing Ảnh I Ảnh âm bản của I 1192013 6 Image Processing Point Processing Negative image of image I For a color image I: g(x,y).R = LR f(x,y).R g(x,y).G = LG f(x,y).G g(x,y).B = LB f(x,y).B In general, can be choosen LR=LG=LB 1192013 7 Image Processing Point Processing The original color image and the negative image Negative image
Image Processing Point Processing 1.In a digital image point is called pixel (point ≡ pixel); 2.Point Processing transforms a pixel’s value to function of its value alone: T: f(x,y) → g(x,y) or G(x,y) = T(f(x,y)) where a=f(x,y), s=g(x,y) Point Processing does not depend on the values of the neighbors 1/19/2013 Image Processing Point Processing Brightness and contrast adjustment Gamma correction Histogram equalization Histogram matching Color correction 1/19/2013 Point Processing Image Processing Origin image -brightness 1/19/2013 +contrast +brightness -contrast γ=1.25 bit-plan bit- γ=0.9 negative Histogram equalization Image Processing Point Processing Negative image of image I Let I is an image with gray levels in the range [L*, L*], i.e., L* ≤ f(x,y) ≤ L*, for all (x,y) in an image I The negative transformation is given by: g(x,y) = L* - f(x,y), for all (x,y) ∈I 1/19/2013 Image Processing Point Processing nh I 1/19/2013 nh âm b n c a I Image Processing Point Processing Negative image of image I For a color image I: g(x,y).R = LR* - f(x,y).R g(x,y).G = LG* - f(x,y).G g(x,y).B = LB* - f(x,y).B In general, can be choosen LR*=LG*=LB* 1/19/2013 Image Processing Point Processing The original color image Negative image and the negative image 1/19/2013 Image Processing Point Processing Brightness g(x,y) = f(x,y)*α α for all (x,y) in image where: α >1 : + brightness α 1 0