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So, I use the following code to carry out the discrete wavelet transform on an image of Lena. I am interested in then doing some changes to a single image out of the obtained 4. How do I extract any of the images? How do I then put it back into an object which I can then carry out the inverse wavelet transform on?

img = ExampleData[{"TestImage", "Lena"}];

dwd = DiscreteWaveletTransform[img, HaarWavelet[], 2];

WaveletImagePlot[dwd, Automatic,ImageAdjust[ImageAdjust[#], {0.01, 0.2, 1.9}]&]

enter image description here

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  • $\begingroup$ Did you look at the "Properties and Relations" section of the docs for WaveletImagePlot[]? It's explained there how to obtain separate images instead of a hierarchical grid. $\endgroup$
    – J. M.'s eventual burnout ♦
    Oct 23, 2017 at 15:41
  • $\begingroup$ I must have missed it. Thank you @J.M., I have looked into now and realized that I missed it. $\endgroup$
    – user3318424
    Nov 21, 2017 at 14:33

2 Answers 2

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As I noted in the comments, the docs mention how to obtain the component images used in WaveletImagePlot[]:

img = ExampleData[{"TestImage", "Lena"}];
dwd = DiscreteWaveletTransform[img, HaarWavelet[], 2];

dwd[Automatic, "Image"]

component images

I'm not sure how to apply ImageAdjust[] to these component images to be consistent with the result of WaveletImagePlot[], however.

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Why not use ImageTake?

img = ExampleData[{"TestImage", "Lena"}];
dwd = DiscreteWaveletTransform[img, HaarWavelet[], 2];
wip = WaveletImagePlot[dwd, Automatic,ImageAdjust[ImageAdjust[#], {0.01, 0.2, 1.9}] &]

ImageTake[wip, {20, 300}, {20, 300}]

which gives:

lena

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  • $\begingroup$ Thank you for helping me out here @JeRut. This allows me to extract the parts I am interested in carrying out any processing on. Still the question remains, after doing the processing, how do I put that processed part of the image back and get its inverse DWT? $\endgroup$
    – user3318424
    Nov 21, 2017 at 14:36

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