MATLAB: What wcompress error means

image compression wcompress

I want to compress an image using

wcompress( 'c','bmp1.bmp','compimg1.wtc','stw');

But I get an error Subscripted assignment dimension mismatch. What this error means?

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x,y dimensions of image should be power of 2

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MATLAB: Using wcompress in Matlab

'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.

MATLAB: Wcompress

You need to extend the one dimension of your image to the next power of 2 - 64x64x3, you can pad with zeros, see wextend() for help, then the above will work.

For example:

X = randi([0 255],64,64,3,'uint8');

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