[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Help-gsl] Daubechies and images

From: Humberto Luiz Razente
Subject: [Help-gsl] Daubechies and images
Date: Thu, 21 Dec 2006 14:01:39 -0200 (BRST)
User-agent: SquirrelMail/1.4.7


I applied Daubechies on a gray scale 256*256 pixels image.
Considering pixels[][] is a matrix where each value is the
color of a pixel, the source code is:

    gsl_wavelet *w = gsl_wavelet_alloc (gsl_wavelet_daubechies_centered, 4);
    gsl_wavelet_workspace *work = gsl_wavelet_workspace_alloc (width *
    double *data = malloc (width * height * sizeof (double));
    for (i = 0; i < width; i++)
        for (j = 0; j < height; j++)
            data[i * width + j] = pixels[i][j];
    gsl_wavelet2d_nstransform (w, data, width, width, height, +1, work);

After running gsl_wavelet2d_nstransform, the data vector contains
the transformed data, but the values varies from -1466.34 to 8443.58
I tried to normalize the data using:

    for (i = 0; i < width*height; i++)
        data[i] = ((data[i] - lowestvalue) / (greatestvalue -
lowestvalue)) * 255;

and the result and original images can be seen in:

Does anybody have an idea of what am I doing wrong?


Humberto Razente

Brian Gough wrote:
Date: Mon, 18 Dec 2006 17:50:27 +0000
From: Brian Gough <address@hidden>
Subject: Re: [Help-gsl] Daubechies and images and CBIR
To: Humberto Luiz Razente <address@hidden>
Cc: address@hidden
Message-ID: <address@hidden>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Humberto Luiz Razente wrote:
> I'd like to extract Daubechies features from
> medical images for content based image retrieval (CBIR).
> Does anybody have an example using gsl?
> I couldn't understand how to do this in the reference manual
> and I couldn't adapt the example for images.
> Should I have read other documentation?
> I already opened the images and I have a matrix containing
> colors of the pixels.

I didn't see any replies on the list, but if anyone does have an example
of that I'd be glad to add it to the manual.

Brian Gough
(GSL Maintainer)

reply via email to

[Prev in Thread] Current Thread [Next in Thread]