Re: Zipping image files

From: Louis H. Sharpe (lsharpe@PICTUREL.COM)
Date: Mon Jan 28 2002 - 23:36:50 CST

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Message-Id: <200201290538.g0T5clg14673@sitelicense.arizona.edu>
Date:         Mon, 28 Jan 2002 22:36:50 -0700
From: "Louis H. Sharpe" <mailto:lsharpe@PICTUREL.COM>
Subject:      Re: Zipping image files
To: mailto:IMAGELIB@LISTSERV.ARIZONA.EDU

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David:

Applying Winzip to TIFF files will be lossless and is a reasonable thing to do. (This is the simple answer; stop reading here if you wish!)

An alternative is to use zip compression within the TIFF file format. zip compression looks to be a reasonable alternati e to LZW compression *within* the TIFF file format. Many viewers do not support LZW compression owing to its patent prob ems. zip compression is free of these.

Which approach will be more comprehensible to an archeologist 1K years from now is a tough question. (rare-artifact42.ti
or rare-artifact42.tif.zip; maybe it's a wash, maybe .zip is better.)

If you are speaking of preservation images, I assume you are retaining full grayscale or full-color data. zip compressio
will work reasonably well with these. (It does not work particularly well when applied after Group 4 compression of bin ry images--the problem to which I believe Mr. Liu alludes, although Group 4 bitonal images would not make good preservat on images.) zip compression will work better in proportion to how free of noise your image source is. Generally, lower n ise is obtained with higher illumination. Since illumination intensity falls off as the square of the distance from the ource, the best way to strongly increase illumination is to place the illuminator nearly on the imaged object. Line-scan sensor based devices (such as scanners) generally work this way. Microfilm camera-type devices (such as digital cameras) typically place the illuminator at much greater distances and thus would get higher noise and poorer compression.

In response to Mr. Liu's comments:

I would not place any preservation images into any proprietary file formats. The forthcoming JPM, JP2, JPX and MJ2 file ormats are part of the internationally standardized JPEG 2000 family of file formats (www.jpeg.org) and provide many of he features needed in a preservation environment.

I am not aware of any Adobe intentions to update the TIFF file format, since the more proprietary PDF is much more strat gic to them. As near as I can tell, TIFF2002 is only the Thailand International Furniture Fair 2002, although I would lo e to see Adobe make me a liar.

JBIG, introduced in the early 1990s, was poorly received, owing to is encumbered patent status. JBIG2 looks much more pr mising for text compression and does indeed have a bright future (and you can use both it and JPEG 2000 in the JPM file ormat).

Lou Sharpe Picture Elements Inc mailto:lsharpenospam@picturel.com

At 03:50 PM 01/28/2002 -0500, you wrote:
>Hi David:
>
>We are an offshore digital content conversion company in Michigan, U.S., with operation centers in China with XML codin
, OCR/ICR and data entering capabilities. Everyday, we need to transfer a lot of TIFF images to China for processing. So
we have some experience on using Winzip.
>
>Unfortunately the TIFF is a compressed format so WinZip/PkZip will not help you much to decrease file size. I assume wh
n you mentioned images files, they are in TIFF format. Zipping will not affect the image quality when unzipped.
>
>I think the new compression technology from Lizzard Tech called DjVu could help you on preservation side. They can get
ome images to 10% - 20% of the usual TIFF file size. The problem is that currently DjVu is somewhat expensive to use o
a large scale scanning project. Once you have saved an image in the DjVu format, people can read the image in a free d wnloadable DjVu viewer, similar to Adobe Acrobat Reader for PDF files. There are other new compression technologies comi g soon, such as Tiff2002 and JBIG, but these are not widely in use now.
>
>Please let me know anything more we could help.
>
>Regards
>Michael Liu
>CompuPacific International
>www.compupacific.com
>42243 East Ann Arbor Road
>Plymouth, MI 48170
>734-453-9001(phone)
>734-657-1042(cell)
>----- Original Message -----
>From: "David Adams" <mailto:David.Adams@NATLIB.GOVT.NZ>
>To: <mailto:IMAGELIB@LISTSERV.ARIZONA.EDU>
>Sent: Monday, January 28, 2002 2:41 PM
>Subject: Zipping image files
>
>
> > Does anyone know if there is any form of change to digital image files by using WinZIP or 'zipping' applications?
> >
> > I am interested to know if this will have an affect on TIFF files that are to be used for long term preservation.
> >
> >
> > David Adams
> > Team Leader - Copying and Digital Services
> > National Library of New Zealand
> > +64 4 4743151
> > Visit "Papers Past" Online 19th century New Zealand newspapers
> > http://paperspast.natlib.govt.nz
> > Visit "Timeframes" New Zealands leading source of heritage images
> > http://timeframes.natlib.govt.nz

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<html>
David: 
 Applying Winzip to TIFF files will be lossless and is a reasonable thing to do. (This is the simple answer; stop reading here if you wish!) 
 An alternative is to use zip compression within the TIFF file format. zip compression looks to be a reasonable alternative to LZW compression
*within* the TIFF file format. Many viewers do not support LZW compression owing to its patent problems. zip compression is free of these. 
 Which approach will be more comprehensible to an archeologist 1K years from now is a tough question. (rare-artifact42.tif or rare-artifact42.tif.zip; maybe it's a wash, maybe .zip is better.) 
 If you are speaking of preservation images, I assume you are retaining full grayscale or full-color data. zip compression will work reasonably well with these. (It does not work particularly well when applied after Group 4 compression of binary images--the problem to which I believe Mr. Liu alludes, although Group 4 bitonal images would not make good preservation images.) zip compression will work better in proportion to how free of noise your image source is. Generally, lower noise is obtained with higher illumination. Since illumination intensity falls off as the square of the distance from the source, the best way to strongly increase illumination is to place the illuminator nearly on the imaged object. Line-scan sensor based devices (such as scanners) generally work this way. Microfilm camera-type devices (such as digital cameras) typically place the illuminator at much greater distances and thus would get higher noise and poorer compression. 
 In response to Mr. Liu's comments: 
 I would not place any preservation images into any proprietary file formats. The forthcoming JPM, JP2, JPX and MJ2 file formats are part of the internationally standardized JPEG 2000 family of file formats
(<a href="http://www.jpeg.org/" eudora="autourl">www.jpeg.org</a>) and provide many of the features needed in a preservation environment. 
 I am not aware of any Adobe intentions to update the TIFF file format, since the more proprietary PDF is much more strategic to them. As near as I can tell, TIFF2002 is only the Thailand International Furniture Fair 2002, although I would love to see Adobe make me a liar. 
 JBIG, introduced in the early 1990s, was poorly received, owing to is encumbered patent status. JBIG2 looks much more promising for text compression and does indeed have a bright future (and you can use both it and JPEG 2000 in the JPM file format). 
 Lou Sharpe Picture Elements Inc mailto:lsharpenospam@picturel.com 
 At 03:50 PM 01/28/2002 -0500, you wrote: 
<blockquote type=cite cite>Hi David: 
 We are an offshore digital content conversion company in Michigan, U.S., with operation centers in China with XML coding, OCR/ICR and data entering capabilities. Everyday, we need to transfer a lot of TIFF images to China for processing. So, we have some experience on using Winzip. 
 Unfortunately the TIFF is a compressed format so WinZip/PkZip will not help you much to decrease file size. I assume when you mentioned images files, they are in TIFF format. Zipping will not affect the image quality when unzipped. 
 I think the new compression technology from Lizzard Tech called DjVu could help you on preservation side. They can get some images to 10% - 20% of the usual TIFF file size.   The problem is that currently DjVu is somewhat expensive to use on a large scale scanning project.  Once you have saved an image in the DjVu format, people can read the image in a free downloadable DjVu viewer, similar to Adobe Acrobat Reader for PDF files. There are other new compression technologies coming soon, such as Tiff2002 and JBIG, but these are not widely in use now. 
 Please let me know anything more we could help. 
 Regards Michael Liu CompuPacific International 
<a href="http://www.compupacific.com/" eudora="autourl">www.compupacific.com</a> 42243 East Ann Arbor Road Plymouth, MI 48170 734-453-9001(phone) 734-657-1042(cell) 
----- Original Message ----- From: "David Adams" <mailto:David.Adams@NATLIB.GOVT.NZ> To: <mailto:IMAGELIB@LISTSERV.ARIZONA.EDU> Sent: Monday, January 28, 2002 2:41 PM Subject: Zipping image files 
 
 
> Does anyone know if there is any form of change to digital image files by using WinZIP or 'zipping' applications? 
> 
> I am interested to know if this will have an affect on TIFF files that are to be used for long term preservation. 
> 
> 
> David Adams 
> Team Leader - Copying and Digital Services 
> National Library of New Zealand 
> +64 4 4743151 
> Visit "Papers Past" Online 19th century New Zealand newspapers 
>
<a href="http://paperspast.natlib.govt.nz/" eudora="autourl">http://paperspast.natlib.govt.nz> 
> Visit "Timeframes" New Zealands leading source of heritage images 
>
<a href="http://timeframes.natlib.govt.nz/" eudora="autourl">http://timeframes.natlib.govt.nz></blockquote></h ml>

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