i am working on DWT. Further i want to work on individual bands. I want to know how to pick a specific band.

e.g like i only want to pick up LL band of the image to further modify it. Then what will be the matlab expression.

Answer 1

[Christiaan]

Dear Miss Jain,

The dwt-command performs a single-level one-dimensional wavelet decomposition with respect to either a particular wavelet ('wname', see wfilters for more information) or particular wavelet decomposition filters (Lo_D and Hi_D) that you specify. This means that a filter is used to include certain frequencies in your wavelet data. For more information you can look at dwt example how to implement this in your code.

A second method would be to use a low or high pass filter with the filter-command:

clc;clear all;close all; 

load noisdopp;
s = noisdopp; 

subplot(3,1,1)
plot(s);grid on; title('original signal')

subplot(3,1,2)
b = [1 -1]; 
a = [1 -0.9]; 
c = filter(b,a,s);
plot(c);grid on; title('high pass filter')

subplot(3,1,3)
b = 1;
a = [0.5 -0.5];
c = filter(b,a,s)
plot(c);grid on;title('low pass filter')

Good Luck! Christiaan

[tina jain]

thank you Christiaan, but can you show me this on any image instead of noisdopp signals.

[tina jain]

this is not what i actually want. I want to pick up a particular band as Lo_D or Ho_D and have to further compress it individually. For this I am not getting how to pick up a particular band e.g and Ho_D or Lo_D.