Describe the high pass filter. DIP

High Pass Filter: Considering the grey-scale values of a part of an image as below,
Here, we have taken 9 grey scale values. It is seen that the 5th value is very different than the other 8 values, that is a big change is occurring at that point due to the big change of the grey-scale value at that point than the other points. 

In this filter we do the following steps,

  1. First of all have to take a mask such as of 3×3. 
  2. Then we will add all the 8 neighboring values of the center.
  3. Then we will multiply the center value with 8. 
  4. Then we will subtract the summation of the neighboring values from the 8×(Center Value).
  5. Then we will divide the result of the calculation of the (iv) point with 9.
  6. Then we will replace the center value by the result of the calculation of (v) point. 

Places To Use This Filter:
  1. This filter is used to sharpen an image.
  2. As it will sharpen an image, the edges of the objects will become sharper. 

  1. It may sometimes cause noise.

Brightness and Contrast in Digital Image Processing.


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