电子科发女学光电科学与工程学院 SCHOOL OF OPTOELECTRONIC SCIENCE AND ENGINEERING OF UESTC 4.Piecewise-Linear Transformation Functions Linear Transformation Functions gx,以 8K,以 d L-1 (r,s) : c f在，y以 a b 0 L-1 fx,y以 s=L-1-r
0 f(x,y) g(x,y) a b c d ◼ Linear Transformation Functions f(x,y) 0 g(x,y) L-1 s L-1 r (r,s) s = L-1-r 4. Piecewise-Linear Transformation Functions
电子科发女学光电科学与工程学院 SCHOOL OF OPTOELECTRONIC SCIENCE AND ENGINEERING OF UESTC 4.Piecewise-Linear Transformation Functions Piecewise-Linear Transformation Functions g(x.y) d M:-d [f(x,y)-b]+db≤f(x,y)≤M M,-b g(x,y)= 8-y-c a≤f(x,y)<b f(x,y) 0≤f(x,y)<a 0 a b Mfxy）
0 f(x,y) g(x,y) a b c d Mf Mg 4. Piecewise-Linear Transformation Functions − + − − − + − − = f x y f x y a a c f x y a c a f x y b b a d c f x y b d b f x y M M b M d g x y f f g ( , ) 0 ( , ) [ ( , ) ] ( , ) [ ( , ) ] ( , ) ( , ) ◼ Piecewise-Linear Transformation Functions
电子科发女学光电科学与工程学院 SCHOOL OF OPTOELECTRONIC SCIENCE AND ENGINEERING OF UESTC 4.Piecewise-Linear Transformation Functions ■ Contrast stretching L-1 3L/4 L/2 -T(r) L/4 0 0 L/4 L/23L/4L-1 Input intensity level,r ab cd FIGURE 3.10 Contrast stretching. (a)Form of transformation function.(b)A low-contrast image. (c)Result of contrast stretching. (d)Result of thresholding
4. Piecewise-Linear Transformation Functions ◼ Contrast stretching
电子科发女学光电科学与工程学院 SCHOOL OF OPTOELECTRONIC SCIENCE AND ENGINEERING OF UESTC 4.Piecewise-Linear Transformation Functions Intensity-level slicing ab L-1 L- FIGURE 3.11 (a)This transformation highlights intensity range [A,B]and reduces all other intensities to a lower -T) T(r) level.(b)This transformation highlights range [A,B]and preserves all other intensity levels. A B L- B
4. Piecewise-Linear Transformation Functions ◼ Intensity-level slicing
电子科线女学光电科学与工程学院 SCHOOL OF OPTOELECTRONIC SCIENCE AND ENGINEERING OF UESTC Example-Intensity-level slicing Intensity-level slicing a b c FIGURE 3.12 (a)Aortic angiogram.(b)Result of using a slicing transformation of the type illustrated in Fig. 3.11(a),with the range of intensities of interest selected in the upper end of the gray scale.(c)Result of using the transformation in Fig.3.11(b),with the selected area set to black,so that grays in the area of the blood vessels and kidneys were preserved.(Original image courtesy of Dr.Thomas R.Gest,University of Michigan Medical School.)
Example - Intensity-level slicing ◼ Intensity-level slicing