FlateDecode, ASCIIHexDecode, ASCII85Decode, and LZWDecode streams

FlateDecode, ASCIIHexDecode, ASCII85Decode, and LZWDecode streams

[Fren Zeee]

Dear All,

I have been playing for a while with files that have small bits of
FlateDecode, ASCIIHexDecode, ASCII85Decode, and LZWDecode streams. My
familiarity with these compression methods is limited to using the
unix uncompress, gunzip and other compiled commands. At one time I was
able to conveniently decode base64 fragments in emacs using the
following commands.

base64-decode-region
  Command: Base64-decode the region between BEG and END.

hexlify-buffer and dehexlify-buffer

Is there a solution within emacs or someone has a method to use
libraries or to translate code from python/ruby etc. I could not find
any (apropos decode) with reference to the above compression methods.

In ruby, FlateDecode and ASCII85Decode can be decompressed with
existing ruby module which are zlib and Ascii85.

Thank You.

P.S. I am including links that may help anyone interested.

http://www.frugalcorner.com/lzw/lzwfree.html
http://groups.google.com/group/comp.compression/browse_thread/thread/2d88635982a60b54/15fc41f6e3556d9?q=Decompressing+LZW+compression+from+PDF#015fc41f6e3556d9

Re: FlateDecode, ASCIIHexDecode, ASCII85Decode, and LZWDecode streams

[bugbear]

Fren Zeee wrote:
> Dear All,
> 
> I have been playing for a while with files that have small bits of
> FlateDecode, ASCIIHexDecode, ASCII85Decode, and LZWDecode streams. My
> familiarity with these compression methods is limited to using the
> unix uncompress, gunzip and other compiled commands. At one time I was
> able to conveniently decode base64 fragments in emacs using the
> following commands.
> 
> base64-decode-region
>   Command: Base64-decode the region between BEG and END.
> 
> hexlify-buffer and dehexlify-buffer
> 
> Is there a solution within emacs or someone has a method to use
> libraries or to translate code from python/ruby etc. I could not find
> any (apropos decode) with reference to the above compression methods.
> 
> In ruby, FlateDecode and ASCII85Decode can be decompressed with
> existing ruby module which are zlib and Ascii85.

The PostScript spec either directly, or via authoritative references,
documents the compression formats.

Further, since PostScript (doh!) supports these formats,
you can simply use the Filter implementations
in PostScript (e.g. GhostScript) to decompress data.

   BugBear