This document summarizes a MATLAB project on digital image processing involving subsampling an image. It describes 4 parts: 1) Implementing subsampling on a "high quality" necktie image. 2) Creating 3 subsampled images at ratios of 1/2, 1/3, and 1/4 the original size. 3) Upsampling the subsampled images back to the original size using interpolation. 4) Analyzing the effects of subsampling like aliasing and noise, which increase with greater subsampling ratios.

1. Digital Image Processing
Project # 4
Dr.Nathir Rawashdeh
Name : Majd Ali Khaleel
ID # :2008102003
26.Dec.2010

2. Part 1: firstly I have written a MATLAB script to
implement subsampling .
In this part I have loadeda ''high quality'' image of
necktie and I have used it in my code.
Code:
*I have used a built in function ''resample'' which used to resample the
sequence in vector x at p/q times the original sampling rate.

3. Part 2: in this part I create three new subsampled image ''shrunken
image'' by ratio p/q = 1/2 , 1/3 & 1/4 .
Part 3:
Here I used resample function by ratio 2, 3 & 4 to back the shrunken
images size to the their original sizes ,and u can use imresizefunction
with bilinear , bicubic or nearest method .

4. *by imresizefunction :
Idown33=Idow33/(max(max(Idown33)));ex:
Y=imresize(Idown33,size(I),'bilinear');
Part 4:
In image # 2 we can notice thin lines occurred in the image beside the
edges.
In image # 3 there are thicker lines than the image # 2 ,the image has
aliasing more than the second image .
In image # 4 we can see the aliasing & noise clearly ,and it made the
image like cheesboard .there r many small squares in image therefore, it
make new frequency patterns.
*in image # 4 we can notice the artifacts are strongest,becausei have
taken a pixel fromevery 4 pixels therefore, I have lost information more
than other images .