quadtree decomposition of wavelet coefficients

Question

After retrieving image coeffients (both approximate and detailed) in wavelet decomposition, i want quadtree structure for appoximate and detailed coefficients. but every time i am getting same error. Please help. I tried to make it power of 3 instead of 2 but it coudnt help. may be i am going wrong somehwhere.

code for image decomposition


X=imread('abc.tif');
close all
clf
image(X)
colormap('default')
axis ('image'); set(gca,'XTick',[],'YTick',[]); title('Original')
pause

dwtmode('sym')
wname = 'bior4.4'

t = wtree(X,2,'bior4.4');
plot(t)
pause
close(2)

[wc,s] = wavedec2(X,5,wname);

a1 = appcoef2(wc,s,wname,1);         
h1 = detcoef2('h',wc,s,1);           
v1 = detcoef2('v',wc,s,1);           
d1 = detcoef2('d',wc,s,1);           

a2 = appcoef2(wc,s,wname,2);
h2 = detcoef2('h',wc,s,2);
v2 = detcoef2('v',wc,s,2);
d2 = detcoef2('d',wc,s,2);

a3 = appcoef2(wc,s,wname,3);         
h3 = detcoef2('h',wc,s,3);           
v3 = detcoef2('v',wc,s,3);           
d3 = detcoef2('d',wc,s,3);           

a4 = appcoef2(wc,s,wname,4);         
h4 = detcoef2('h',wc,s,4);           
v4 = detcoef2('v',wc,s,4);           
d4 = detcoef2('d',wc,s,4);           

a5 = appcoef2(wc,s,wname,5);         
h5 = detcoef2('h',wc,s,5);           
v5 = detcoef2('v',wc,s,5);           
d5 = detcoef2('d',wc,s,5); 

For quadtree i am using:

S = qtdecomp(I,.27); %I is image in greyscale.
blocks = repmat(uint8(0),size(S));

for dim = [512 256 128 64 32 16 8 4 2 1];    
  numblocks = length(find(S==dim));    
  if (numblocks > 0)        
    values = repmat(uint8(1),[dim dim numblocks]);
    values(2:dim,2:dim,:) = 0;
    blocks = qtsetblk(blocks,S,dim,values);
  end
end

blocks(end,1:end) = 1;
blocks(1:end,end) = 1;

imshow(I), figure, imshow(blocks,[])

the error it is showing is:

??? Error using ==> qtdecomp>ParseInputs at 229
MAXDIM / MINDIM is not a power of 2

Error in ==> qtdecomp at 88
[A, func, params, minDim, maxDim] = ParseInputs(varargin{:});

or

??? Error using ==> qtdecomp>ParseInputs at 145
A must be two-dimensional

Error in ==> qtdecomp at 88
[A, func, params, minDim, maxDim] = ParseInputs(varargin{:});

Answer 1

The error is pretty clear. Your image must have dimensions that belong to a power of two. As such, you need to resize your image so that it follows this. qtdecomp computes the quadtree decomposition algorithm, and a pre-condition for this function is that it NEEDS to have an image that has each dimension as a power of two as input.

You asked something similar in another question that I provided an answer to. What is curious is that this other question you asked was 6 days ago before this one, and you accepted my answer for that other one. The issue that you were experiencing is more or less the same thing.

Quadtree decomposition