Re: JPEG Compression

[P3D John Ohrt <johrt@xxxxxxx>]

P3D Greg Marshall wrote:

> While there IS a lossless form of JPEG it is almost never used

The Clementine mission used it (a lunar exploration science mission
freebie from the military!!! all image data is available free.

> I don't think it uses LZW.

I'm pretty sure it does, but really, all that counts is the finished
size.  In a real life image, lzw is not efficient anyway.

>   But hasn't GIF been extended to support 24-bit images?

The last spec I looked at was 1989. It didn't then.  Anyway why pay for
something when superior products are free?

BTW, a better lossless compression technique than lzw is zip using the
optomize compression switch. The input file can be any bitmap format
version of .bmp, .tga, .tif, .pbm etc.


> Where can I find out more about PNG?

PNG (Portable Network Graphics) Home Page:

http://quest.jpl.nasa.gov/PNG/


Thanks for the info on jpeg.
--
John Ohrt,  Regina, SK, Canada
johrt@xxxxxxx



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