P.S. - I need to use TIFF files rather than some other format due to the
final applications that will be using the images, and also because of the
extremely large size (up to a foot wide by 100+/- feet long) of the
documents that are being imaged.
----- Original Message -----
From: "Kevin Myers" <[EMAIL PROTECTED]>
To: "gimp users" <[EMAIL PROTECTED]>
Sent: Sunday, October 06, 2002 4:31 PM
Subject: [Gimp-user] 3 or 4 bit grayscale images
> Does anyone out there know of any way that gimp can be used fairly easily
> create 3 or 4 bit grayscale TIFF images (rather than 8 bit)?
> Most applications, including gimp, seem to be geared towards 8 bit
> images. But, I'm involved with a hardcopy document archival project where
> or 4 bit grayscale TIFF images would be preferable for the following
> 1. 8 bit grayscale files require far too much space.
> 2. 8 bit grayscale files can't be compressed effectively unless you use a
> lossy algorithm such as JPEG. Some loss in image quality IS acceptable
> my project, but JPEG compression can introduce additional artifacts into
> image, and that is NOT acceptable.
> 3. 1 bit black and white images are not acceptable for my project because
> they don't show any intermediate shade variations that may be important
> any number of reasons, including resolving faint handwriting on a form
> includes other very dark features.
> 4. 3 bit (8 shade) and 4 bit (16 shade) grayscale images are the primary
> contenders for my project because they DO provide acceptable
> of varying shades in the original, and ...
> 5. The drastic reduction in the number of shades produced by using 3 or 4
> bit grayscale instead of 8 bit grayscale makes the images MUCH more
> susceptible to LZW and other compression algorithms. A 3 or 4 bit
> image using LZW compression is typically 10 to 20 times smaller than the
> corresponding 8 bit image.
> So far, I've succeeded in getting gimp to produce indexed tiff images
> on 8 and 16 gray shade pallettes that I've created, and that by itself
> quite a bit. However, it still introduces sizeable additional overhead
> the tiff file to store the pallete look-up table, that shouldn't be
> necessary. It ought to be possible to merely store the images directly as
> or 4 bit grayscale instead.
> Does anyone out there have any ideas or suggestions? Possibly some other
> scriptable tool that can manipulate tiff files, other than gimp?
> Thanks in advance for any help that you may be able to provide.
> Kevin M.
> Round Rock, Texas
> Gimp-user mailing list
> [EMAIL PROTECTED]
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