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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: Blurry JPGs when using FileUpload 1.2.1
Date Mon, 16 Jun 2008 13:53:15 GMT
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Bob,

Bob Carpenter wrote:
| I didn't know that ImageIO reduces quality with each pass.

It's not so much ImageIO as JPEG in general. JPEG is lossy compression
which means that each time you encode a JPEG image, you lose some detail
because of the cosine coefficients that are dropped to perform the
compression.

This is amplified by the probability that you are reading a JPEG at a
certain level of detail (say "90%" JPEG detail) and writing it out at
another level (say, "50%" detail).

| ImageIO is used
| at least twice for each file because it gets stored as a BLOB and is
served
| to clients by saving to disk then reading back in with ImageIO.

You should try to avoid JPEG interpretation of your image files unless
you actually need to do image processing. You ought to be able to read
and write raw bytes a lot of the time. That will significantly improve
the performance of your application, too!

- -chris
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