Image resizing and Denoising

Question 1

Define interpolation:

Answer 1

Given a set of discrete data points (position and value), interpolation is used to find values at positions in between the points

Question 2

What is nearest neighbour interpolation?

Answer 2

For any sample position in between the existing ones, we find the closest sample points and use its value as our interpolated value.

Question 3

What is the equation for linear interpolation?

Answer 3

y = ya + (yb - ya) ( (x - xa) / (xb- xa) )

Question 4

What is the equation for the original x (ox) value in image resizing?

Answer 4

ox = new x position * (original width / new width)

Question 5

What is bi-linear interpolation?

Answer 5

Interpolation done in the x and y dimension, one after the other.

Question 6

What is the linear interpolation equation to find a value (e.g. colour) on a given position (y-axis)?

Answer 6

v = v1 + (v2 - v1) ( (y-y1) / (y2-y1) )
Same equation for x-axis

Question 7

What is the process of removing noise using non linear filtering?

Answer 7

• Using a small image, take the median filter size (e.g. 3x3)
• Create a list of all the pixels in the filter and sort it
• Find the median pixel, and use it as the new value