Message-Id: <mailto:199409181020.FAA08738@library.wustl.edu> Date: Fri, 16 Sep 1994 01:04:37 +0000 From: Frank Dunn <mailto:frank@BRAZEN.DEMON.CO.UK> Subject: Re: 8-bit vs. 24-bit color To: Multiple recipients of list IMAGELIB <mailto:IMAGELIB@ARIZVM1.BITNET>
>I agree, Nick. I've been weighing what to use on the CD version of an
>imaging project, and I 've pretty much decided to go with JPEG for just
>that reason. The image file sizes I was comparing were:
>*1.8 MB Original 24-bit color TIFF image (512x768)*
At that spacial resolution it would be worthwhile considering fractal image transform compression ( AKA .FIF ). The downside is that it really requires hardware compression but decompression is fast in software and the files are generally a lot smaller than JPEG at Q2.
>857K Compressed (Lossless LZW) 24-bit color file
>404K Tiff 8-bit color (uncompressed)
>268K Tiff 8-bit color compressed with LZW
>205K JPEG (JFIF type) 24-bit color, compressed at quality level 2 (highest)
>89K GIF (which is 8-bit color and uses a variant of LZW compression)
GIF's LZW isn't as good as run length encoding (RLE) for 8 bit (paletted) files, it will result in larger files.
>Pamela
IMHO its quite feasible to tell the difference between a 24 bit TIFF and the same file JPEGed at a high Q level, the DCT algorithm in JPEG tends to enhance edges for one without considering the possible changes in the images colour gamut.
Frank. Library Manager (Images).
mailto:Frank@brazen.demon.co.uk News International Newspapers Ltd., mailto:Frank_Dunn@delphi.com 1 Virginia Street,London,UK, E1 9BD. CompuServe:100012,23 +44 171 782 6384/6 +44 171 782 5213 fax "It must be jelly 'cos jam don't shake like that"