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Re: Wavelet and histogram

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  • Subject: [mg115886] Re: Wavelet and histogram
  • From: "Vivek J. Joshi" <vivekj at>
  • Date: Mon, 24 Jan 2011 05:23:01 -0500 (EST)


Following is an example demonstrating how you can do this,

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

dwd == DiscreteWaveletTransform[img,DaubechiesWavelet[],3];

(* Extract wavelet Coefficients as Images and use ImageHistogram *)

Map[Part[#,1]->ImageHistogram[Part[#,2],Appearance-> "Stacked",ImageSize->2=

(* When using data form "Image" (as above) the Image coefficients have resc=
aled coefficient values (ImageAdjust[ImageApply[Abs,#]]&), Use ImageFunctio=
n->Identity to get "Actual  Coefficient Values" *)

Map[Part[#,1]->ImageHistogram[Part[#,2],128,{-1,3},Appearance-> "Stacked",I=

Taking a closer look at Min and Max values in each color channel,


You can also use Histogram in place of ImageHistogram,


Hope this helps.


Vivek J. Joshi
Kernel Developer
Wolfram Research, Inc.

On Jan 23, 2011, at 4:04 PM, Robert Pigeon wrote:

> Hello all,
>                Let say i have a image that I defined using img == pasted
> pictured. Then I do a wavelet transfom:
> dwd ==  DiscreteWaveletTransform[img,DaubechiesWavelet[],3]. Now I can us=
> WaveletImagePlot[dwd] to look at the wavelet levels. I would like to do a=
> histogram on all or some level of dwd. I can't find how to do it. I looke=
> at  WaveletMapIndexed, but I cant figure out how to do it....
> Any help will be appreciated.
> Thanks
> Robert

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