In order to sharpen an image using Laplacian kernel, it should be convolved with the original image.
It is evident that the result might have negative values. I am not sure what to do with these values:
- Subtract the minimum from laplacian then map to [0, 255]
- Clip negative values to zero and map to [0, 255]
- Just clip negative values to zero
I know the next step is to add/subtract the laplacian to/from the original image and map to [0, 255] but I have doubts about the laplacian.
Indeed, I tested all three methods and 2, 3 got me to the right results but according to my Image Processing textbook, Laplacian should be scaled but it is not mentioned clearly that which version of laplacian is used to derive the sharpened image.