how to display multi-level wavedec2 in MATLAB

Question

After computing the 4-level discrete wavelet transform of an image, how do I display this multi-level transformation in matlab? And how do I plot the histogram of the corresponding DWT coefficients?

Here is what I did so far:

I = imread('image.png');
N = 4;
[C,S] = wavedec2(im2double(I),N,'haar');
A = appcoef2(C,S,'haar',1);
[H1,V1,D1] = detcoef2('all',C,S,1);
[H2,V2,D2] = detcoef2('all',C,S,2);
[H3,V3,D3] = detcoef2('all',C,S,3);
[H4,V4,D4] = detcoef2('all',C,S,4);

Answer 1

This is what I would do it:

N = 4;

img = imread('image.png');
img = im2double(img);

[C,S] = wavedec2(img,N,'haar');

for i = 1:N
    lvl = ['Level ' num2str(i)];

    A = appcoef2(C,S,'haar',i);
    [H,V,D] = detcoef2('all',C,S,i);

    figure('Name',['Images (' lvl ')']);
    % Eventually, you can define a colormap for your images...
    % colormap(pink(255));
    subplot(2,2,1); imagesc(A);
    title('Approximation')
    subplot(2,2,2); imagesc(H);
    title('Horizontal Detail');
    subplot(2,2,3); imagesc(V);
    title('Vertical Detail');
    subplot(2,2,4); imagesc(D);
    title('Diagonal Detail'); 
    suptitle(lvl);

    % tweak the histogram bins as you prefer
    figure('Name',['Histograms (' lvl ')']);
    subplot(2,2,1); hist(A(:),32);
    subplot(2,2,2); hist(H(:),32);
    subplot(2,2,3); hist(V(:),32);
    subplot(2,2,4); hist(D(:),32);
    suptitle(lvl);
end

Actually, since I'm not very esperienced in digital image processing, it's up to you to tweak my example and make it fits your needs.