Saturday, November 29, 2014


Image denoising is the process of removing noise from the image so that in  any case,no information is lost from it.A filter is a device that removes unwanted and irrelevant data from the actual information.Filtering is an important concept of image processing.It is also done to:
1.remove noise
2.sharpen contrast
3.highlight contours
4.detect edges.

Also,the process of denoising should be such as to preserve the edges.Non-linear  models can preserve the edges in a better way than the linear models.One of the non-linear models is Median Filter.

Median Filter smoothes the image and is thus helpful in removing noise. It is particularly effective at removing ‘salt and pepper’ type noise.The median filter works by moving through the image pixel by pixel, replacing each value with the median value of neighbouring pixels.
The median is calculated by first sorting all the pixel values from the window into numerical order, and then replacing the pixel being considered with the middle (median) pixel value.

   An Image with ‘salt and pepper  noise’

                 Image after filtering

This creats a new matrix that indicates the pixel intensities such that the image regenerated from it is free from noise.
Flow Chart illustrating the process of median filtering: