Re: JPEG scanner stuff

Stephen Williams (steve@icarus.com)
Wed, 04 Aug 1999 07:46:33 -0700

njl98r@ecs.soton.ac.uk said:
> What exactly comes out of your scanners? Is it just a JFIF standard
> header followed by JPEG image data?

Well, JFIF is really just an APP marker and some constraints on the
JPEG stream that follows. DQT and DHT markers, and all the other required
markers to make a fully formed JPEG compressed stream are present.
So I'm not quite sure what you mean by "JFIF header followed by JPEG
image data."

If the image is color, I've had one component per scan, combined the
color components in a scan, etc. The SOF marker describes the internal
structure. The scanner boards have hardware jpeg compressors that can
produce the JFIF images, with a little help from a micoprocessor.

The IJG libjpeg software has no trouble reading these streams.

-- 
Steve Williams                "The woods are lovely, dark and deep.
steve@icarus.com              But I have promises to keep,
steve@picturel.com            and lines to code before I sleep,
http://www.picturel.com       And lines to code before I sleep."

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