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Date Posted: 07:22:42 08/01/00 Tue
Author: Michel
Subject: Re: Envision Library Oddities (but new user as well!)
In reply to: Chris Swinney 's message, "Re: Envision Library Oddities (but new user as well!)" on 15:12:58 07/31/00 Mon

Hi Chris,

I'm a bit confused about this. I think the image must have been saved again by windows imaging to use compression tag 6. The libtiff library (on which the Envision tiff support is based), does not support tag 6, so it cannot write an image with compression tag 6. If you just save the image in the demo, and reload it, that does work?

Best regards,


> Thanks for the response. I shall look at the pallet
> property in more depth.
> However, the TIFF problem may be more involved than
> you first think. After altering the code slightly in
> the demo, I forced a scanned in image to save with
> JPEG compression within the TIFF file. This produced
> the desire result, a multipage grayscale image, who's
> page's used JPEG compression. This image was able to
> be read by windows imageing but when trying to read
> the image back into the demo program, we end up with
> the same error, even though the demo program created
> the image in the first place! I assume that the demo
> creates JPEG compression for TIFF files in the same
> way as single JPEG files (i.e. using JPEG compression
> 7), which read fine, so I am unsure why this error
> occurs.
> This is now a little out of my league but I wonder if
> it may give you some insight.
> Again thanks for the help so far.
> CHris
> >
> > For the TIFF related problem, I have done the steps
> > you indicated, and indeed the error "compression tag
> 6
> > not supported error" is raised. I do find this
> > strange, because compression JPEG "6" is obsolete in
> > the latest tiff spec, and I wonder why Windows
> Imaging
> > is using it. This is not supported by Envision. The
> > more common JPEG compression tag has the value "7".
> > You can get more information on this at this link
> > <a rel=nofollow target=_blank href="ftp://ftp.sgi.com/graphics/tiff/TTN2.draft.txt.gz">ftp://ftp.sgi.com/graphics/tiff/TTN2.draft.txt.gz</a>
> >
> >
> > Best regards,
> >
> > Michel
> >

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