Re: TIFF2GIF query

From: Bob Savage (bsavage@STANFORD.EDU)
Date: Thu Apr 19 2001 - 11:58:00 CDT

Next message: Ellen Maclean Buckland: "Locking print from CD-ROM"

Previous message: Julie Dees: "Re: jpe query"
Maybe in reply to: David Adams: "TIFF2GIF query"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

Message-Id: <200104191701.KAA14640@dns.ccit.arizona.edu>
Date:         Thu, 19 Apr 2001 09:58:00 -0700
From: Bob Savage <mailto:bsavage@STANFORD.EDU>
Subject:      Re: TIFF2GIF query
To: mailto:IMAGELIB@LISTSERV.ARIZONA.EDU

<pre> Another reason that you could see an increase in file size is that both GIF and JPEG have a larger bit depth per pixel. Bi-tonal files save only one bit per pixel (on or off) whereas GIF uses 8 bits per pixel (so each pixel can have one of 256 colors), and JPEG uses 24 bits to save the pixel as being one of approximately 16 million color possibilities. Since you are starting with bitonal images I cannot imagine you will be seeing any file savings by converting to either file format. Further I would really recommend that you avoid the JPEG format because it will cause a degradation in your information due to the compression algorithm it uses.

The reason someone would normally try to use GIF or JPEG instead of TIFF is that they are starting out with a file that is already saving 24 bits per pixel (TIFF supports multiple bit depths) and so in their case they are either reducing the number of bits used to encode each pixel (GIF) or using a severe compression system (JPEG) to shrink file size. You should probably stick with TIFF.

Best of luck,

Bob Savage
----------------------------- Media Preservation Unit Stanford University Libraries mailto:bsavage@stanford.edu

-----Original Message----- From: IMAGELIB [mailto:mailto:IMAGELIB@LISTSERV.ARIZONA.EDU]On Behalf Of David Adams Sent: Wednesday, April 18, 2001 10:07 PM To: mailto:IMAGELIB@LISTSERV.ARIZONA.EDU Subject: TIFF2GIF query

For interest I have tried using photoshop to make a conversion from the bitonal TIFF file to a GIF and JPEG format and each time the file size increased. I assume that this should be expected as the bitonal TIFF file is a
'compressed image format' to start with. (ITU Group 4 compression)

</pre>

Next message: Ellen Maclean Buckland: "Locking print from CD-ROM"
Previous message: Julie Dees: "Re: jpe query"
Maybe in reply to: David Adams: "TIFF2GIF query"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]

This archive was generated by hypermail 2b29 : Thu Apr 19 2001 - 12:05:46 CDT