[6765] in www-talk@info.cern.ch
Re: Interlaced vs. Non-interlaced GIFs
daemon@ATHENA.MIT.EDU (Chris Lilley, Computer Graphics Un)
Tue Nov 22 09:59:39 1994
Date: Tue, 22 Nov 1994 15:26:52 +0100
Errors-To: listmaster@www0.cern.ch
Reply-To: lilley@v5.cgu.mcc.ac.uk
From: lilley@v5.cgu.mcc.ac.uk (Chris Lilley, Computer Graphics Unit)
To: Multiple recipients of list <www-talk@www0.cern.ch>
John Lewis writes:
[attributions deleted]
>>>> Frame -> postscript @ 150 dpi -> scale 50% -> GIF
>>>> This results in an nice anti-aliased image.
>>Yes. I wish more people would do this.
> Perhaps someone could go into this in a little more detail?
> What do you mean by "Frame"?
Many DTP programs put figures in frames which can then be anchored to the text
flow, a particular point on the page, or whatever.
> Do you mean save it (the random image) as a
> postscript file at 150dpi, then scale that image by 50% and save as a gif?
Close.
It is a program doing this, not the user. The program saves out each figure -
not an image, a line drawing or diagram - and converts it to an image at 150
dpi. By scaling down (this is called resampling in Photoshop) an antialiased
image at 75dpi results, so that, say, a diagonal black line on a white
background comes out as black pixels with grey ones at the edge. You would
imagine this would make the image fuzzier - infact it removes annoying jaggies
so the image looks higher resolution than it is.
--
Chris
