What is the effect of varying number of samples in an image. . includes matlab code ..

1. EFFECT OF VARYING
NUMBER OF SAMPLES ON
IMAGE QUALITY
LAKSHMI.M
M.E, COMMUNICATION SYSTEMS

2. SAMPLING
Sampling is the first operation done in digitalization of
an analog signal followed by quantization
Sampling - principal factor determining the spatial
resolution of an image.
Spatial resolution is the smallest discernible detail in an
image.

3. SAMPLING
UPSAMPLING
- INCREASING THE NUMBER OF SAMPLES
DOWNSAMPLING
- DECREASING THE NUMBER OF SAMPLES

4. Upsampling and Downsampling of a
discrete signal

6. CODE FOR DOWNSAMPLING:
clc;
clear all;
close all;
f=imread('cameraman.tif');
y=imresize(f,[1024 1024]);
figure; imshow(y);
down=y(1:2:end,1:2:end);
figure; imshow(down);
down1=y(1:4:end,1:4:end);
figure; imshow(down1);
down2=y(1:8:end,1:8:end);
figure; imshow(down2);
down3=y(1:16:end,1:16:end);
figure; imshow(down3);
down4=y(1:16:end,1:16:end);
figure; imshow(down4);

7. Fig1.
1024*1024
Fig2.
512*512
Fig3.
256*256
Fig4.
128*128
Fig5.
64*64
Fig6.
32*32
DOWNSAMPLED IMAGES

8. EFFECT OF VARYING NUMBER OF SAMPLES
256*256 256*256
Downsampled by
a factor of 3
Upsampled by a
factor of 3

9. clc;
clear all;
close all;
f=imread('cameraman.tif');
y=imresize(f,[8 8]);
figure; imshow(y);
disp(y);
display('size of original image:');
l1=size(y);
disp(l1);
%downsampling
down=y(1:2:end,1:2:end);
disp(down);
display('size of downsampled image:');
l2=size(down);
disp(l2);
figure; imshow(down);
Upsampling the downsampled image
% upsampling the downsampled image
up=down(1:0.4:end,1:0.4:end);
disp(up);
display('size of upsampled image:');
l3=size(up);
disp(l3);
figure; imshow(up);

10. Pixel values of original image

11. EFFECT OF VARYING NUMBER OF SAMPLES
256*256 256*256
Upsampled by a
factor of 3
Downsampled by
a factor of 3

12. f=imread('cameraman.tif');
y=imresize(f,[4 4]);
display('pixel values of original image');
figure; imshow(y);
title('original image');
disp(y);
display('size of original image:');
l1=size(y);
disp(l1);
%upsampling
up=y(1:0.4:end,1:0.4:end);
display('pixel values of downsampled
image');
disp(up);
display('size of upsampled image:');
l2=size(up);
disp(l2);
figure; imshow(up);
title('upsampled image');
Downsampling the upsampled image
%downsampling the upsampled image
down=up(1:2:end,1:2:end);
display('pixel values of reconstructed
image');
disp(down);
display('size of reconstructed image:');
l2=size(down);
disp(l2);
figure; imshow(down);

14. Inference:
Downsampling provides reduced pixel value
image which when zoomed, results in poor
image quality
In upsampling, no pixel value is removed
and hence when downsampled to its original
image size, almost the original image quality
is obtained.

15. THANK YOU