Table of Contents NAME mgfelics - fast and efficient lossless image (de)compression ...

Table of Contents ## NAME

mgfelics - fast and efficient lossless image (de)compression ## SYNOPSIS

mgfelics -e [ -k *n* ] *infile* [ >*compressed*-*outfile* ] or

mgfelics -d*compressed*-*infile* [ >*outfile* ] ## DESCRIPTION

mgfelics is a lossless compression process which can (de)compress portable bitmap files in *pgm* format. mgfelics writes to *stdout*. ## OPTIONS

-k *n* An integer parameter (< 32) which controls the compression speed and ratio. The value of *n* is included in the output stream, and therefore is not needed in the decompression stage. The default value of *n* is equal to the number of bits required to represent each grey level. ## NOTE

mgfelics uses a combination of adjusted binary and Rice codes, the choice of which for any given pixel depends on the environment as determined by the intensity values of neighbouring pixels. The result is a very fast and lossless algorithm for compressing grayscale images. The optional parameter -k *n* corresponds to the maximum exponent of the same name in Rice encoding. Smaller values of -k *n* can result in significant improvement in compression times with a corresponding loss in compression ratio. However the reduction in compression ratio with a small -k *n* parameter may be insignificant for many images. ## REFERENCES

Algorithm by Paul G. Howard and Jeffrey Scott Vitter of Brown University, RI, and Duke University, NC, respectively. ## SEE ALSO

mg(1), mg_compression_dict(1), mg_fast_comp_dict(1), mg_get(1), mg_invf_dict(1), mg_invf_dump(1), mg_invf_rebuild(1), mg_passes(1), mg_perf_hash_build(1), mg_text_estimate(1), mg_weights_build(1), mgbilevel(1), mgbuild(1), mgdictlist(1), mgquery(1), mgstat(1), mgtic(1), mgticbuild(1), mgticdump(1), mgticprune(1), mgticstat(1).

mgfelics -d

- -e
- Encodes the file
*infile*, sending the output to*stdout*.

- -d
- Decodes the file from
*compressed*-*infile*, sending the output to*stdout*.