MATLAB: Using wcompress in Matlab

Question

I am trying to demonstrate image compression via the haar wavelet transform in Matlab with the following code:

Xc = wcompress('c', J, 'apples.wtc', 'haar')

And I am getting the message:

Undefined function or variable 'Encoded_wtbx_DEC'.

Error in wcompress (line 491)

fileSize = wtcmngr('save',typeSAVE,Sav_filename,method_COMP,Encoded_wtbx_DEC);

Does anyone know why this could be?

Answer 1

'haar' is not one of the valid compression methods for wcompress()

https://www.mathworks.com/help/wavelet/ref/wcompress.html#f11-1023199

The valid compression methods are divided in three categories.

• Progressive Coefficients Significance Methods (PCSM): MATLAB NameCompression Method Name
• 'ezw'Embedded Zerotree Wavelet'
• 'spiht'Set Partitioning In Hierarchical Trees
• 'stw'Spatial-orientation Tree Wavelet
• 'wdr'Wavelet Difference Reduction
• 'aswdr'Adaptively Scanned Wavelet Difference Reduction
• 'spiht_3d'Set Partitioning In Hierarchical Trees 3D for truecolor images

For more details on these methods, see the references and especially Walker and also Said and Pearlman.

• Coefficients Thresholding Methods (CTM-1): MATLAB NameCompression Method Name
• 'lvl_mmc'Subband thresholding of coefficients and Huffman encoding

For more details on this method, see the Strang and Nguyen reference.

• Coefficients Thresholding Methods (CTM-2): MATLAB NameCompression Method Name
• 'gbl_mmc_f'Global thresholding of coefficients and fixed encoding
• 'gbl_mmc_h'Global thresholding of coefficients and Huffman encoding

Notice the lack of a 'haar' option.