An adaptive image enhancement algorithm Objective: smooth the uniform areas and sharpen the borders Method (1) determine each pixel in homogenous region or not (Haralick method). (2) according to the position property, assign to each pixel a new digital number.
Haralick method (cont) F has an F distribution with 2,6 degrees of freedom (considering 3* 3 window,n=9) We are interested in a1=0,a2=0 (homogenous region) 1% significance test if F<10.9, homogenous region,otherwise not 5% significance test if F<5.14, homogenous region,otherwise not
Results of F-test Use F-test to determine whether the window in a particular position is homogenous or not, if yes, mark 1;if not, mark Results of F-test
Step 2: image enhancement procedure Based on the F-test matrix, the image enhancement procedure is accomplished by assigning new digital number to each pixel, through this, to sharpen the border and smooth the uniform area. Compute RV(reference value): If F_test(x,y)=1 RV is the average within the window. If F_test(x,y)=2 RV is taken as the highest or the lowest digital number within the window, the one closest to the digital number of the central pixel. Compute new digital number: DN(new)=WF*RV+(1-WF)*DN(old).