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help with question

voodoo

Posted 22 March 2006 - 02:40 PM

name two compression standards for graphic files and state a difference between them?

i can't find it in my notes sad.gif.

dfx

Posted 22 March 2006 - 03:13 PM

JPEG and GIF? Ok I don't do computing lol.

John

Posted 22 March 2006 - 04:23 PM

Lossless and Lossy

take a guess at what the diffrence is.

@dfx

JPEG and GIF are standard file formats, just so you know for next time tongue.gif

Dave

Posted 22 March 2006 - 04:30 PM

yip lossless and lossy are the two variants

lossless would be things like winzip(not graphics i know)

and lossy would be like gif and jpeg

ermd

Posted 25 March 2006 - 04:27 PM

QUOTE(Dave @ Mar 22 2006, 04:30 PM) View Post

and lossy would be like gif and jpeg


In the our notes, GIF was stated as lossless I believe. I always thought it should be lossy - if you've got more than 256 colours to begin with, YER GONNA LOSE SOME AIN'T YA.

So either our notes/SQA syllabus or whatever is wrong.

Also - ADPCM. How the hell is that lossy. RGH. SQA for teh lose. Noobs.

Dave

Posted 26 March 2006 - 12:16 AM

i should probably have done this before opening my big mouth above but ok GIF is lossless which i should have known as it came up in a class at uni - applications and implications.

A GIF file is a bitmap basically so its 256 bit colors only so no good for photos. It uses a compression known as LZW (also perhaps some other stuff) LZW is what we learnt in that class and is used in pdf's and stuff including encryption hence lossless

ADPCM is definetely lossy- clue being the A in the name meaning adaptive it uses amplitude compression of pulses and this particular varient decreases the bandwidth of a modulating pulse more than normal of a given sampling rate. Using samples is also what gives is the name lossy as well


if you dont understand what i am saying i got all this from wikipedia....or perhaps you dont care:P

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