readme.txt

此代码是C编的EWZ的测试程序,大家可以尝试对这个包里lena.pgm进行图像压缩处理.

I have rewritten the EZW coder sometime ago.

The older version was written when I first learned about wavelet based image coding, at the time many things weren't clear to me.

The newer version is in my opinion much simple to understand and follow. Moreover, the structure of the program is easily modified for other bitplane based coding.

In this version, I have also updated the arithmetic coding and discrete wavelet transform codes.

There Hilbert scan and morton scan options have been added and I mush thanl Dror for the demo code on Hilbert scan. They are quite easy to implement once you understand the recursive nature of the scan.

Download the new code here.

The older version and page can be found here.

As for usage, it is a little bit different. Please read the program regarding the usage. Here is a simple example of command line:

ezw e lena 0.5 -l 5 -o out

The image is lena.pgm, note that there is no need of file extension. The pgm image must be binary. The bitrate is 0.5bpp and the number of decomposition levels is 5. The encoded stream is to be stored as out.ezw, note that the ".ezw" extension is added by the program.

As for decoding of out.ezw at a sepecific bitrate, try

ezw d out -r 0.25

This will decode the image at 0.25bpp.

We also have an option to do encode followed by decode to facilitate rate-distortion comparision. Another option could generate the rate-distortion profile directly. Please check the code for more details.    
 


mow-song, ng
5 Nov 2004