Subject:
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Re: The Mavica (was Re: ThrowBots elements are cool)
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Newsgroups:
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lugnet.publish
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Date:
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Tue, 2 Feb 1999 23:41:56 GMT
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Viewed:
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1398 times
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I don't know if this is common knowledge or not ... I know I found it the
hard way:
jpeg does not necessarily mean "lossy" compression. You can (with a
conversion program, I use Firehand Ember), convert from .xxx to .jpg without
loosing information. The tradeoff is the amount of compression vs the
quality.
.bmp means Bitmap, which means each pixel is represented by a color point
and uses x bits (however deep your palette is (let's say 24 bits)). So a
640x480x24bit .bmp will take 640x480x3 bytes of storage, 921,600 bytes
(almost a megabyte). In most pictures, there are pixels that are the same
color. When you convert to .jpg, you are typically asked for a "quality"
number. I don't know the exact technical method, but it uses an sliding
average to try and "force" pixels to be the same color which results in
lower storage requirements.
As a test, I just took a 1024x768x8bit .bmp that was on my laptop (came with
the IBM) and converted it to .jpg using various settings:
Original file, 770KB
Worse (0%), 14KB
70%, 102KB
80%, 136KB
85%, 168KB
90%, 231KB
95%, 379KB
Best (100%), 762KB
At 70%, there is visible degradation, but at 95%, you get a 50% space
savings and the degradation is not that noticeable. I don't know about the
rest of you, but my hard drive and ISP both place restrictions on the amount
of data I can store, so does my wallet, so using that space to my advantage
is a must.
I'll try tonight and take a picture off my website and post it in multiple
quality settings so you can see what kind of losses are made and post a URL.
Mike
-----
Mike Faunce - mfaunce@earthlink.net
Mike Stanley wrote in message ...
> James Brown <galliard@shades-of-night.com> wrote:
> > All the website says about it is:
> > Bitmap (Non-Compressed) Mode:
> > For the best images choose the non-compressed mode to display your • images in
> > a bitmap format (VGA only).
>
> What that means is it can only store a 640x480 (VGA) image in bitmap
> format. So I guess it's 1024 in jpg or nothing.
>
> --
> Unofficial listing of weekly US Lego Shop at Home phone specials
> http://www.lugnet.com/lsahs/
> 800-835-4386 (S@H USA) / 800-267-5346 (S@H Canada)
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Message has 2 Replies:
 | | Re: The Mavica (was Re: ThrowBots elements are cool)
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| (...) Starting with a 256-color image probably won't give you the best comparision. If you've got a 24-bit image 'lying around', try your tests on that one. There's also a variation of JPEG, called (in Paint Shop Pro) "progressive encoding". Does (...) (26 years ago, 3-Feb-99, to lugnet.publish)
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