Rank level processing

Question 1

What is Rank based

Answer 1

It is a class of  none Linear filters, and it is based on computing the median of pixels neighbourhood, in reality, it is neither a low pass filter or a high pass filter, we usually notice that small objects are removed while bigger transitions and bigger objects are usually conserved
and it is a good candidate for omitting noise

Question 2

What is a local maximum and local minimum

Answer 2

both are special cases of gray level,
for the local maximum consist of replacing the pixel by the highest value of its neighbourhood.

while local minimum, consist of replacing the pixel by the lowest value of its neighbourhood.

Question 3

The local enhancement consist of what

Answer 3

local enhancement consist mainly of a way to stretch the grey level, useful when the intention is to obtain the details of on image, but the grey levels are lost,

Question 4

what is the local morphological enhancement

Answer 4

it consists of either replacing a specific grey level by a higher lowest value depending on how close it is, this is done by using the local histogram, usually, the obtained image is crispier and sharp

Question 5

What are the three categories of local contrast enhancement

Answer 5

Local contrast equalization,

Local Auto Level and Local morphological contrast enhancement

Question 6

what is local equalization

Answer 6

consist simply of applying equalization mechanism locally

Question 7

what is the Local Auto Level

Answer 7

consist of applying grey level stretching in order to stretch the Gray level we use a lookup table such that the Gray level is stretched to 0 as minimum and 255 as max

Question 8

What is the Local threshold

Answer 8

you know that the local threshold consists of replacing the value according to a certain threshold in this case it is applied locally

Question 9

what is Bi lateral filtering

Answer 9

We define the neighbourhood of a pixel as:

a local spatial neighbourhood and
a spectral (gray-level) neighbourhood

Question 10

what is the nago filter

Answer 10

nago filter usually changes according to the image texture for instance omitting the noise in an image having the zebra texture. The idea here consists of defining 9 neighbourhoods for each pixel, the filter value is obtained with the neighbourhood having the lowest variance of these 9, smoothing with edge-preserving.

Question 11

What is the diffusion filter

Answer 11

we make the hypothesis that the pixel value

propagation is similar to heat, this reflects the local derivative