From: billd@cray.com (Bill Davidson)
Subject: Re: Claudia Schiffer Part [0 of 15]
Organization: Cray Research Superservers Inc., San Diego CA, USA
Date: Fri, 18 Dec 1992 01:39:02 GMT

In article <1992Dec16.123310.1@vax1.umkc.edu> khill@vax1.umkc.edu writes:
>In article <7834@news.duke.edu>, patki@soc.duke.edu (Phillip Atkison) writes:
>>In article <1992Dec10.161324.22744@canrem.com>, victor@canrem.com (Victor Kamutzki) writes:
>>>Filename:    cs24_2.jpg
>>>Format:      JPEG
>>>Description: Claudia Schiffer - converted from Targa to JPG using Q=90
>> 
>>Q=90 must be one of the most inefficient methods of conversion in regards
>>to file size. I took the 600K jpg file, read it into xv and saved it as
>>a gif. It currently takes 64K to store (AND IT EVEN LOOKS BETTER!)
>
>	I must agree.  The purpose of JPEG is to reduce file size at the sake
>of quality.  However, when you use Q=90 you are getting practically the same
>image.  If you are going to use Q=90 then why even JPEG, just post the Targa
>file.  MOST people have (or can get) converters/viewers for their machines.

Ignorance, as usual, is rampant.

The file saved as a GIF cannot possibly look better from xv.  Xv
doesn't do that.  Xv does make the picture automatically smaller unless
you invoke it with the -nolimit option.  Those cs24_?.jpg pic's were
huge.  I have a 1280x1024 screen and due to the fact that I always use
-nolimit xv attempted to display them much larger than 1280x1024.  The
smaller GIF picture is inherently inferior because it (1) is resized to
much less resolution than the original and (2) can have at most 8 bits
of color depth whereas the JPEG can go up to 24.

At Q=90, and equal resolution, the JPEG will most likely be smaller than
the GIF.

cs24_2.jpg is a 1275x1650x24 full color JFIF file and uses 601441 bytes.
If you uncompress this into a PPM file it is 6311267 bytes.  Huge.

Xv displays the image on my screen (without -nolimit) at 825x637x8.  If
I resize the PPM file to this size, it is 942138 bytes.  When I convert
this to GIF format it comes out at 277246 bytes which is a hell of a
lot more than 64K.  Xv must have degraded the image even more to get it
down to 64k.  When I convert this to JPEG with Q=90 it comes out at
72623 bytes.  Admittedly, when I converted to GIF I used the PBM+
utilities.  Doing it with xv produces a GIF of 331246 bytes!

>--- Please do not FLAME on this statement to post Targa pics.  Targa
>is one of the better file formats for pics since it is nothing more than the
>raw 24 bit (8 bit each for R, B, G) data of the picture.  If the poster wants
>to be really polite he can convert it to an 8 bit GIF, but this would lead
>some loss of quality.

Conversion of a 24 bit image to GIF results in much more loss of
quality than JPEG at Q=90 ever could.  If you will remember, the
original poster was talking about posting these pics in Targa format at
first but he was feeling a little bit of anxiety at posting them
because the were multiple megabytes each.  By using JPEG at Q=90, he
got them down to a little over half a megabyte.

You pro-gif weenies need to get a clue.

--Bill Davidson
-- 
People in the computer industry use the word "user",
which to them means "idiot".  -- Dave Barry
Newsgroups: alt.supermodels