JOhnny
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 Image Prep for the www

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  JPEG Compression

JPEG compression is an 24-bit "lossy" compression algorithm. The image is cut up into quarters and tested for color change. Each quater is further divided up until the comressor knows which parts of the image are odd. Then the odd pixels are thrown out. The Unfortunately, the tossed pixels are ussually the "line information" I was talking about in the GIF section of this presentation. So, unlike GIF, JPEGs are NOT for text and line drawing sorts of things.

You don't believe me? Here are a few examples copressed with a little compression, some compression and a lot of comression.

51 K

18 K

Notice that there is a lot of compression, yet the background looks pretty good!

14 K - Not much smaller but highly crappy!

8 K - Useless!