Re: style sheet scalability (was: Specifying style notation in <link>)

lilley (
Tue, 5 Dec 1995 15:53:59 +0000 (GMT)

scott preece said:

> From: lilley <>
> | Some image formats, such as TIFF and PNG, can give the desired display
> | dimensions of an image (and by implication, the number of pixels per
> | inch). Should this size be honoured?
> | I would say no, if the browser is going to do a quick and dirty
> | rescaling job and mess up the image. (Then again browser do quick and
> | dirty colour reduction jobs and further screw up the image quality, so
> | why not?)

> While the discussion of image quality is important and needs to be
> considered in answering the question, it's also important to remember
> the reason for the original question [...]
> While the quality of the rendering is probably important
> to people using images for this purpose, making sure the text is large
> enough to be read is *critical*.

You appear to me to be making these assumptions:

a) image quality is nice but inessential
b) legibility is paramount (fine) but largely independent of graphic quality
c) legibility is increased by rendering the image in a larger display area.

However, as image quality falls, the first thing to be lost is legibility.

Further, a well constructed antialiased image (at, say, 72dpi) containing
text will be more legible if displayed 1:1 on a 110 dpi screen - thus making
it too small - than if it were scaled by a factor of 110/72 by pixel
replication - which would make it bigger, but drop the quality right down.

> In that context it makes a lot of
> sense to be able to specify a preferred display size for an image (and,
> perhaps, an indication of how much the author cares about variation.

Try actually doing that, and see how the legibility suffers. Remember
we are talking about scaling factors of at most 50 - 200% and more
likely 80 - 125% so Walter's suggested hints of integer scaling do
not apply.

In summary, if you believe legibility is critical - and I have no problem
with that - then you cannot just dismiss image quality as an optional extra.

Chris Lilley, Technical Author and JISC representative to W3C 
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