Image compression in matlab with explaination




Image compression
Wcompress command:
The wcompress command performs either compression or uncompression of grayscale or truecolor images.
Spiht parameter of wcompress:
spiht'
Set Partitioning In Hierarchical Trees
Xc = wcompress('u','wpeppers.wtc');
uncompresses the file SAV_FILENAME, which contains the compressed image, and returns the image XC. Depending on the initial compressed image, XC can be a 2-D array containing either an indexed image or a 3-D array of uint8 containing a truecolor image.
[CR,BPP] = wcompress('c',X,'wpeppers.wtc','spiht','maxloop',12);
[COMPRAT,BPP] = wcompress('c',...) returns the compression ratio COMPRAT and the bit_per_pixel ratio BPP.`
Comprat states the compression ratio

‘BPP' = 'bpp' or 'BPP' sets the bit-per-pixel ratio.
'c' : color transformation type (RGB uint8).
axis square;
axis square makes the current axes region square (or cubed when three-dimensional). This option adjusts the x-axis, y-axis, and z-axis so that they have equal lengths and adjusts the increments between data units accordingly.
xlabel({['Compression Ratio: ' num2str(CR,'%1.2f %%')], ...
        ['BPP: ' num2str(BPP,'%3.2f')]})
xlabel(txt) labels the x-axis of the current axes or chart returned by the gca command.
 num2str   Convert numbers to character array.

output


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