Median filter Implementation using TMS320C6745

1. Median filter
Implementation using
TMS320C6745
https://www.pantechsolutions.net/products/dsp-
dsc-boards/tms320c6745-tyro

2. Technology beyond the Dreams™ Copyright © 2014 Pantech Prolabs India Pvt Ltd.
• Types of noise:
– Salt and pepper noise
– Impulse noise
– Gaussian noise
• Due to
– transmission errors
– dead CCD pixels
– specks on lens
– can be specific to a sensor
Types of Noise

3. Technology beyond the Dreams™ Copyright © 2014 Pantech Prolabs India Pvt Ltd.
Median Filter

4. Technology beyond the Dreams™ Copyright © 2014 Pantech Prolabs India Pvt Ltd.
Median Filter
• The median filter is a sliding-window spatial filter.
• It replaces the value of the center pixel with the median of the
intensity values in the neighborhood of that pixel.
• to reduce "salt and pepper" noise.
• For every pixel, a 3x3 neighborhood with the pixel as center is
considered. In median filtering, the value of the pixel is replaced
by the median of the pixel values in the 3x3 neighborhood.
•

5. Technology beyond the Dreams™ Copyright © 2014 Pantech Prolabs India Pvt Ltd.
There are many masks used in Noise Elimination
Median Mask is a typical one
23 65 64
120 187 90
47 209 72
J=1 2 3
I=1
2
3
Rank: 23, 47, 64, 65, 72, 90, 120, 187, 209
median
Masked Original Image
The principle of Median Mask is to mask some sub-image,
use the median of the values of the sub-image as its value in
new image

6. Technology beyond the Dreams™ Copyright © 2014 Pantech Prolabs India Pvt Ltd.
• How can we
remove noise?
• Replace each pixel with
the average of a
kxk window around it
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 100 130 110 120 110 0 0
0 0 0 110 90 100 90 100 0 0
0 0 0 130 100 90 130 110 0 0
0 0 0 120 100 130 110 120 0 0
0 0 0 90 110 80 120 100 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0
Neighborhood Processing
Practical Noise Reduction
104

7. Technology beyond the Dreams™ Copyright © 2014 Pantech Prolabs India Pvt Ltd.
Median Filter Matlab code
I = imread('eight.tif');
J = imnoise(I,'salt & pepper',0.02);
K = medfilt2(J);
figure, imshow(J), figure, imshow(K)

8. Technology beyond the Dreams™ Copyright © 2014 Pantech Prolabs India Pvt Ltd.
C source code for Median filter
#include<stdio.h>
#include<math.h>
#include "Image1.h"
#define ROW 128
#define COL 128
unsigned int im[ROW][COL];
unsigned int i,j;
unsigned int SR7,SR1,SR2,SR3,SR4,SR5,SR6,SR8,SR9,bbr;
float median(int SR1,int SR2,int SR3,int SR4,int SR5,int SR6,int SR7,int SR8,int SR9);
void main()
{
for(i=0;i<ROW;i++)
{
for(j=0;j<COL;j++)
{
im[i][j]=Inp[i][j];
}
}
for(i=1;i<ROW-1;i++)
{
for(j=1;j<COL-1;j++)
{
SR1 = Inp[i-1][j-1];
SR2 = Inp[i-1][j];
SR3 = Inp[i-1][j+1];
SR4 = Inp[i][j-1];
SR5 = Inp[i][j];
SR6 = Inp[i][j+1];
SR7 = Inp[i+1][j-1];
SR8 = Inp[i+1][j];
SR9 = Inp[i+1][j+1];
bbr=median(SR1,SR2,SR3,SR4,SR5,SR6,SR7,SR8,SR9);
im[i][j]=bbr;
}
}
}

9. Technology beyond the Dreams™ Copyright © 2014 Pantech Prolabs India Pvt Ltd.
Image settings-Noisy Image

10. Technology beyond the Dreams™ Copyright © 2014 Pantech Prolabs India Pvt Ltd.
Image settings-Filtered Image