pdwt

Synopsis

Description

pdwt calculates the wavelet coefficients of the input image im_in1 according to the pyramidal algorithm. For example, with scale=1, there are 4 subimages:

    [1][2]
    [3][4]

where [1] is the approximation image with undersampling factor of 2. and [2], [3], [4] correspond to the signal detail along each privileged direction (resp. horizontal, vertical, diagonal) undersampled with a factor 2.

The filter coefficients are stored from the input collection col_in and can be generated from the operator pqmf.

Important: The operator works with any image size. However, the algorithm needs image with a size power of 2. Therefore, the input image is magnified so as the size is closest to power 2. So output image has necessarily a size power of 2.

Parameters

• scale specifies the number of levels to be used for the decomposition of the input image.

Inputs

• im_in: a 2D float image.
• col_in: a collection that contains the filter coefficients.

Outputs

• im_out: a 2D float image.

Result

Returns SUCCESS or FAILURE.

Examples

Builds a synthetic image (a square) to illustrate the Gibbs phenomenon in wavelets analysis.

   pshapedesign 256 256 0 2 150 150 a.pan
   pqmf daubechies 4 b.pan
   pdwt 1 a.pan b.pan c.pan
   psplitimage c.pan d1.pan d2.pan d3.pan d4.pan
   pthresholding 20 400 d2.pan e2.pan
   pthresholding 20 400 d3.pan e3.pan
   pthresholding 20 400 d4.pan e4.pan
   pmergeimages d1.pan e2.pan e3.pan e4.pan f.pan
   pidwt 1 f.pan b.pan out.pan

See also

C++ prototype

Version française

Calcul de la transformée en ondelettes dyadiques biorthogonales d'une image.