Multiresolution Analysis 2D Express VI

LabVIEW 2014 Advanced Signal Processing Toolkit Help

Edition Date: June 2014

Part Number: 372656C-01

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Owning Palette: Discrete Wavelet VIs

Requires: Advanced Signal Processing Toolkit

Decomposes a 2D image according to the level you specify and reconstructs the 2D image from the frequency bands you select.

Example

Dialog Box Options
Block Diagram Inputs
Block Diagram Outputs

Dialog Box Options

ParameterDescription
Signal Contains the following options:
  • Data Source—Specifies whether this Express VI reads a 2D image from a block diagram input terminal or from a file. Contains the following options:
    • From terminal—Specifies that this Express VI reads data from the Image block diagram input terminal.
    • From file—Specifies that this Express VI reads data from a file. This Express VI can read data from BMP, JPG, and PNG files.
    • File path—Specifies and displays the path to the file from which this Express VI reads data. This option is available only if you select From file in the Data Source section.
    • Prompt to choose a file each time this VI runs—Specifies whether this Express VI displays a dialog box that prompts you to select a file each time this Express VI runs. This option is available only when you select the From file option in the Data Source section.
  • Wavelet Levels and Type—Specifies the wavelet level and wavelet type this Express VI uses for discrete wavelet analysis. Contains the following options:
    • Levels—Specifies the number of levels in the discrete wavelet analysis. Levels must be a positive integer no greater than log2(Ls), where Ls is the minimum dimensional size of the image you want to reconstruct.
    • Wavelet—Specifies the wavelet type this Express VI uses for discrete wavelet analysis. The default is db02. You can choose from the following options:
      • Customized Wavelet—Use the Wavelet Design page to configure a customized wavelet.
      • Haar—Orthogonal
      • dbxx—Orthogonal, Daubechies
      • coifx—Orthogonal, Coiflets
      • symx—Orthogonal, Symmlets
      • biorx_x—Biorthogonal
      • bior4_4 (FBI)—Biorthogonal, FBI
      where x indicates the order of the wavelet. The higher the order, the smoother the wavelet.
      Note  The orthogonal wavelets are not redundant and therefore are suitable for signal or image denoising and compression. The biorthogonal wavelets usually have the linear phase property and therefore are suitable for signal or image feature extraction.
  • Original Image—Displays the original 2D image.
  • Reconstructed Image—Displays the 2D image this Express VI reconstructs according to the Frequency Band Selection you make. If you place a checkmark in the Undecimated checkbox, this Express VI displays an image reconstructed by the wavelet coefficients from the undecimated wavelet transform (UWT). If you remove the checkmark from the Undecimated checkbox, this Express VI displays an image reconstructed by the wavelet coefficients from the discrete wavelet transform (DWT).
  • Frequency Band Selection—Specifies the frequency band(s) this Express VI uses to reconstruct the image. The discrete wavelet transform (DWT) decomposes a signal into a series of dyadic frequency subbands in two directions. Each wavelet level produces the following four subbands:
    • LL approximation—low-low
    • LH detail in column direction—low-high
    • HL detail in row direction—high-low
    • HH detail in diagonal direction—high-high
  • Wavelet Coefficients—Displays the wavelet coefficients of the frequency subband you select. If you place a checkmark in the Undecimated checkbox, this Express VI displays the wavelet coefficients from the undecimated wavelet transform (UWT). If you remove the checkmark from this checkbox, this Express VI displays the wavelet coefficients from the discrete wavelet transform (DWT).
    Note  The Wavelet Coefficients indicator changes depending on the Frequency Band Selection and whether you place a checkmark in the Undecimated checkbox.
  • Undecimated—Specifies whether this Express VI uses the undecimated wavelet transform (UWT) or discrete wavelet transform (DWT) for multiresolution analysis. If you place a checkmark in this checkbox, this Express VI applies UWT to the Original Image and reconstructs an image with the wavelet coefficients of the frequency band(s) you select by using inverse UWT. If you remove the checkmark from this checkbox, this Express VI applies DWT to the Original Image and reconstructs an image with the wavelet coefficients of the frequency band(s) you select by using inverse DWT.
  • Zoom in—Zooms in the frequency bands at the origin of the Frequency Band Selection.
  • Zoom out—Zooms out the frequency bands at the origin of the Frequency Band Selection.
  • Zoom reset—Resets the zoom value of Frequency Band Selection to display all the frequency bands.
  • Select none—Selects none of the frequency bands. If you click this button, the 2D image does not appear.
  • Select all—Selects all the frequency bands. Click this button to reconstruct the image from the approximation coefficients and the detail coefficients of all the frequency bands.
Wavelet DesignDesigns customized analysis filters and synthesis filters for discrete wavelet analysis and reconstruction, respectively. Contains the following options:

Note  Except for the Wavelet and Filter Banks section, the following options are valid only if you select the Customized Wavelet option from the Wavelet pull-down menu.
  • Wavelet Type—Specifies the type of wavelet this Express VI uses to design a customized wavelet for discrete wavelet analysis and reconstruction. You can select the Orthogonal or Biorthogonal option.
  • Product of Lowpass (P0=G0*H0)—Specifies P0, which is the product of the lowpass analysis filter G0 and the lowpass synthesis filter H0. Contains the following options:
    • P0 type—Specifies the type of P0. The default is Maxflat. You can choose from the following options:
      • Maxflat
      • Positive Equiripple
      • General Equiripple
      Note  The General Equiripple option is available only if you select the Biorthogonal option in the Wavelet Type section.
    • Zero pairs at pi (P0)—Specifies the value of p in the Maxflat filter P0(z), where P0(z) = (1+1/z)^(2p)*Q(z). This option is available only if you select the Maxflat option in the P0 type section.
    • # of taps—Specifies the number of coefficients of P0(z). The length of P0(z) must be 4p–1, where p = 2, 3, …. This option is available only if you select the Positive Equiripple or General Equiripple option in the P0 type section.
    • Passband—Specifies the normalized cutoff frequency of P0(z). The value of Passband must be less than 0.5. Passband is available only if you select the Positive Equiripple or General Equiripple option in the P0 type section.
  • Factorization (Type of G0)—Contains the following options:
    • Filter type—Specifies how this Express VI factors P0 to G0 and H0. Contains the following options:
      • Arbitrary—Specifies that no restriction exists on the placement of zeros.
      • Minimum Phase—Specifies that the zeros of G0 are located inside the unit circle, except for the zeros at pi.
      • Linear Phase—Specifies that if one zero belongs to G0(H0), the reciprocal of that zero must belong to G0(H0).
      • B-Spline—Specifies that except for some zeros at pi, all the zeros of P0 belong to H0.
    • Zeros at pi (G0)—Controls how many zeros at z=–1 belong to G0(z). This option is available only if you select the Maxflat option in the P0 type section. The maximum value of this option is 2p, where p = the value of the Zero pairs at pi (P0) option.
  • Zeros of G0 and H0—Shows the distribution of the zeros of P0(z), G0(z) and H0(z). This Express VI uses this distribution to factor the zeros of P0(z) into the zeros of G0(z) and H0(z). Because the filter coefficients of P0(z) are real, all the zeros of P0(z) are symmetrical with respect to the x-axis. Consequently, this Express VI displays only the upper half of the plane. The zeros on the x-axis represent real-valued roots. The zeros outside of the x-axis represent complex-valued roots.

    The blue crosses represent the zeros of G0(z), and the red circles represent the zeros of H0(z).

    Click on the zero you want to select to switch the zero from that of G0(z) to that of H0(z) and vice versa. All the zeros belong to G0(z) or H0(z).

    Selecting different values for Filter type puts different constraints on the selections of zeros. For example, if you select Linear Phase for Filter type and select a zero for one filter, the filter automatically contains the reciprocal of the zero.
  • Wavelet and Filter Banks—Displays the following graphs:
    • Analysis scaling—Displays the scaling function of the analysis filter bank.
    • Analysis wavelet—Displays the mother wavelet of the analysis filter bank.
    • Analysis lowpass (G0)—Displays the coefficients of the lowpass analysis filter G0(z).
    • Analysis highpass (G1)—Displays the coefficients of the highpass analysis filter G1(z).
    • Synthesis scaling—Displays the scaling function of the synthesis filter bank.
    • Synthesis wavelet—Displays the mother wavelet of the synthesis filter bank.
    • Synthesis lowpass (H0)—Displays the coefficients of the lowpass synthesis filter H0(z).
    • Synthesis highpass (H1)—Displays the coefficients of the highpass synthesis filter H1(z).
  • Wavelet—Specifies the wavelet type this Express VI uses for discrete wavelet analysis. The default is db02. You can choose from the following options:
    • Customized Wavelet—Use the Wavelet Design page to configure a customized wavelet.
    • Haar—Orthogonal
    • dbxx—Orthogonal, Daubechies
    • coifx—Orthogonal, Coiflets
    • symx—Orthogonal, Symmlets
    • biorx_x—Biorthogonal
    • bior4_4 (FBI)—Biorthogonal, FBI
    where x indicates the order of the wavelet. The higher the order, the smoother the wavelet.
    Note  The orthogonal wavelets are not redundant and therefore are suitable for signal or image denoising and compression. The biorthogonal wavelets usually have the linear phase property and therefore are suitable for signal or image feature extraction.

Block Diagram Inputs

ParameterDescription
File pathSpecifies the file path of the 2D image you want to load. This input is available only if you select the From file option in the Data Source section.
ImageSpecifies the block diagram terminal of the 2D image you want to load. This input is available only if you select the From terminal option in the Data Source section.
error in (no error)Describes error conditions that occur before this node runs.

Block Diagram Outputs

ParameterDescription
Reconstructed ImageReturns the reconstructed image.
Selected CoefficientsReturns the wavelet coefficients of the frequency band(s) you select to reconstruct the 2D image.
error outContains error information. This output provides standard error out functionality.

This Express VI operates similarly to the following VIs and functions:

WA Discrete Wavelet Transform
WA Inverse Discrete Wavelet Transform

Example

Refer to the Multiresolution Analysis - Image VI in the labview\examples\Wavelet Analysis\WAGettingStarted directory for an example of using the Multiresolution Analysis 2D Express VI.

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