Newsgroups: comp.multimedia,sci.image.processing
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From: ewhv05@castle.ed.ac.uk (J Lloyd)
Subject: Re: Tips for low-resolution, screen-only viewing?
References: <39lfvm$5ft@zephyr.isi.edu> <Cyy6xy.CGK@festival.ed.ac.uk> <39vio5$70r@unicorn.ccc.nottingham.ac.uk>
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Organization: Edinburgh University
Date: Mon, 14 Nov 1994 09:19:17 GMT
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paxjc@vax.nott.ac.uk (Joe Cutting) writes:

>>I use a 800x600 screen resolution. I found that using 400dpi scans
>>creates images that look a bit small on screen and will try 600dpi
>>instead. If you can crop the image after scanning that will save a lot
>>of memory, then use a programme like LViewp1.8 or some other to save the
>>file as JPEG for big savings in file size.
>>
>>Jeff Lloyd
>>
>>
>Shurely shome mishtake? VGA screens display only about 72 dpi (I think macs have about 80)
>so if you want the picture to appear same size as the original having more dpi than 
>this is a waste of space. However, rather than set your scanner to a low
>resolution it seems to work best if you scan at high resoulution and then resample 
>the image using something like Corel PhotoPaint.
>If you're working with machines like PCs and Macs (not SGIs) convert all photos type 
>images to 256 colours rather than true colour (24bit).
>Finally unless you get into something fancy (and slow) like fractal compression
>JPEG compression is the best for photo type images although GIF compression
>is sometimes better for diagram type pictures (and quicker to decode too).

>N.B. If you are putting images on a WWW server always display only 
>a thumbnail picture which is clickable to download the larger version.
>Your local link may be pretty quick but someone trying to access your
>site from the other side of the world will give up pretty quick if they
>have to wait forever for the pictures to appear.

Perhaps I should have said that I am scanning 35mm slides. For a
reasonable sized image I scan at 600dpi. This is rescaled to a small GIF
for a thumbnail which can be clicked for the JPEG image. If you want to
see the results, look up the following URL:

http://www-ersp.div.ed.ac.uk/home.htm

and look in the "museum" page.

Jeff Lloyd


