Sharpening Filters

Highpass Sharpening Filter

The highpass filter is simply implemented using a square mask of various sizes. The significant reduction of global
contrast is clearly visible. Also the result is charecterized by enhanced edges. When the mask is at pixels near the
boundary of the image then the porions of the mask outside the mask were neglected and the averaging factor adjusted
accordingly.
 
 

Original Image	Image sharpened by 3x3 mask	Image sharpened by 5x5 mask	Image sharpened by 7x7 mask

Image smoothened by 15x15 mask

The filter also works exactly similarly on color images.Here the edge enhancing property of the filter can be better appreciated.
 

Original Image	Image sharpened by 7x7 mask

High Boost Sharpening Filter

The high boost filter tendsto nullify the darkening effect of the high pass filter by adding a part of the original image's
intensity to the high pass result. This part depends on the value of 'A', if A = 1 the result is the same as the high pass,
for A > 1 the reult is more like the original image with edge enhancement.
 
 

Original Image	Image sharpened by 3x3 mask with A = 1	Image sharpened by 3x3 mask with A = 1.5	Image sharpened by 3x3 mask with A = 2

Image sharpened by a 7x7 mask with A = 3

This filter also works exactly simlarly on color images.Here the edge enhancing property of the filter can be better appreciated.
 

Original Image	Image sharpened by 7x7 mask with A = 1.5	Image sharpened by 7x7 mask with A = 2

Page last updated on 28 January, 2004.	AT cse.iitd.ac.in	© Parag Chaudhuri , 2009