lecture6

Image Zooming
After we have cropped a sub image from the original image we can
zoom in on it by enlarging it. The zoom process can be done in
numerous ways:
1. Zero-Order Hold.
2. First _Order Hold.
3. Convolution.
Zero-Order hold: is performed by repeating previous pixel values,
thus creating a blocky effect.
Example: if we have an image of size(n*n), we can zooming it using
zero order method with size (2n)*(2n)
First _Order Hold: is performed by finding linear interpolation
between a adjacent pixels, i.e., finding the average value between two
pixels and use that as the pixel value between those two, we can do
this for the rows first as follows:
8 2 8
4 8 4
8 4 8
? ? ?
?
?
? ? ?
?
?
? ? ?
?
?
? ? ?
?
?
8 5 2 5 8
4 6 8 6 4
8 6 4 6 8
The first two pixels in the first row are averaged (8+4)/2=6, and this
number is inserted between those two pixels. This is done for every
pixel pair in each row. Next, take result and expanded the columns in
the same way as follows:
? ? ? ? ? ?
?
?
? ? ? ? ? ?
?
?
8 5 2 5 8
6 5.5 5 5.5 6
4 6 8 6 4
6 6 6 6 6
8 6 4 6 8
This method allows us to enlarge an N×N sized image to a size of
(2N-1) ×(2N-1) and be repeated as desired.