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detcoef2

2-D detail coefficients

    Description

    y = detcoef2(o,c,s,n) extracts from the wavelet decomposition structure [c,s] the detail coefficients of orientation o at level n. For more information on c and s, see wavedec2.

    example

    [h,v,d] = detcoef2('all',c,s,n) returns the horizontal h, vertical v, and diagonal d detail coefficients at level n.

    detcoef2('a',c,s,n) is equivalent to detcoef2('all',c,s,n).

    y = detcoef2('compact',c,s,n) returns all the detail coefficients stored row-wise.

    detcoef2('c',c,s,n) is equivalent to detcoef2('compact',c,s,n).

    If [H,V,D] = detcoef2('all',c,s,N) and Y = detcoef2('compact',c,s,N), then Y = [H(:)' V(:)' D(:)'].

    Examples

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    This example shows how to extract detail coefficients from a discrete wavelet analysis of an image. This example uses zero-padding.

    Set the extension mode to zero-padding. Load and display an image.

    origmode = dwtmode('status','nodisplay');
    dwtmode('zpd','nodisplay');
    
    load woman
    imagesc(X)
    colormap(gray)

    Figure contains an axes. The axes contains an object of type image.

    Obtain the wavelet decomposition of the image down to level two using the Haar wavelet.

    [c,s] = wavedec2(X,2,'haar');
    size(X)
    ans = 1×2
    
       256   256
    
    
    size(c)
    ans = 1×2
    
               1       65536
    
    
    s
    s = 4×2
    
        64    64
        64    64
       128   128
       256   256
    
    

    Extract the detail coefficients at level 2 in each orientation from the wavelet decomposition structure [c,s]. Display the diagonal detail coefficients.

    [chd2,cvd2,cdd2] = detcoef2('all',c,s,2);
    size(cdd2)
    ans = 1×2
    
        64    64
    
    
    imagesc(cdd2)
    colormap(gray)

    Figure contains an axes. The axes contains an object of type image.

    Extract the detail coefficients at level 1 in each orientation. Display the vertical detail coefficients.

    [chd1,cvd1,cdd1] = detcoef2('all',c,s,1);
    size(cvd1)
    ans = 1×2
    
       128   128
    
    
    imagesc(cvd1)
    colormap(gray)

    Figure contains an axes. The axes contains an object of type image.

    Restore the original extension mode.

    dwtmode(origmode,'nodisplay')

    Input Arguments

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    Orientation of detail coefficients, specified as:

    • 'h' — Horizontal

    • 'v' — Vertical

    • 'd' — Diagonal

    Wavelet decomposition vector, specified as a real-valued vector. The vector c contains the approximation and detail coefficients organized by level. The bookkeeping matrix s is used to parse c. See wavedec2.

    Data Types: double

    Bookkeeping matrix, specified as an integer-valued matrix. The matrix s contains the dimensions of the wavelet coefficients by level and is used to parse the wavelet decomposition vector c. See wavedec2.

    Data Types: double

    Detail level to extract from the wavelet decomposition, specified as an integer. The integer n must be in the interval [1,size(s,1)-2].

    Output Arguments

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    Detail coefficients, returned as a vector or matrix.

    Data Types: double

    Horizontal detail coefficients, returned as a matrix.

    Data Types: double

    Vertical detail coefficients, returned as a matrix.

    Data Types: double

    Diagonal detail coefficients, returned as a matrix.

    Data Types: double

    Tips

    • If c and s are obtained from an indexed image analysis or a truecolor image analysis, y is an m-by-n matrix or an m-by-n-by-3 array, respectively.

      For more information on image formats, see the image and imfinfo reference pages.

    Extended Capabilities

    C/C++ Code Generation
    Generate C and C++ code using MATLAB® Coder™.

    Introduced before R2006a