Re: Image formats

Subject: Re: Image formats
From: Brad Jensen <brad -at- elstore -dot- com>
To: "TECHWR-L" <techwr-l -at- lists -dot- raycomm -dot- com>
Date: Tue, 9 Apr 2002 00:48:41 -0500



----- Original Message -----
From: "Alfred P M" <pmalfred -at- emailaccount -dot- com>
To: "TECHWR-L" <techwr-l -at- lists -dot- raycomm -dot- com>
Sent: Monday, April 08, 2002 7:08 AM
Subject: Image formats


>
> Hi
>
> I am new to this list and I looked through the archives, but I
didn't find any information on this topic. I am looking for a
comparison of the following image formats -- GIF, JPEG and PNG
>
> I did look on the web and found numerous articles on this topic,
with advice about which format to choose, etc. However, what I am
looking for is a comparison (data) of the compression that each of
these formats provide.
>
> For example, lets say you have a 100 Kb GIF file. What I am
looking for is the equivalent file
> size in PNG and JPEG of the same file when converted?

A PNG file will be approximately the same size as a GIF file.
These are lossless compressions. Every bit of information is
stored while compressed, and restored when decompressed. JPG is a
lossy compression. That means that when you compress and image to
JPG format, you lose some of the information. When you decompress
it, you do not get the same bits
of information back that you started with. JPG is generally used
for photographs, where the loss is less noticeable. It is much
smaller than GIF or PNG. How much smaller, depends on the quality
setting you choose.

If you want to see how large the original image is, save it as a
BMP, which is basically an uncompressed image with some header
information on it.

PNG was developed when a certain computer company asserted a
patent right over the compression method used in GIF, and started
asking larger and more visible companies to pay royalties for
using it. A patent is 17 years long, hopefully it will be over
with soon. Meahwhile PNG works great, and I don't buy any
computers from them anyways.

I've had some solicitations from a company that claims that any
time you buy or sell something over a computer network (such as
the internet) you are violating their patent if you aren't a
licensee.

Of course, if you play your stereo loud enough that your neighbors
can hear it, it's a public performance, and you owe somebody some
money. Same for music on hold.

> I know that there are different "factors" you can tweak to get
levels of compression and
> asking this type of question may be not give me the true
picture. However, I need to find
> out information, so if you could let me know if there some site
that gives
> this kind of information, etc. I would appreciate it.
>
>
> Thanks
> Alfred

You are welcome

Alfred B Jensen



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References:
Image formats: From: Alfred P M

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