> From: lilley <lilley@afs.mcc.ac.uk>
> | 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 +-------------------------------------------------------------------+ | Manchester and North HPC Training & Education Centre | +-------------------------------------------------------------------+ | Computer Graphics Unit, Email: Chris.Lilley@mcc.ac.uk | | Manchester Computing Centre, Voice: +44 161 275 6045 | | Oxford Road, Manchester, UK. Fax: +44 161 275 6040 | | M13 9PL BioMOO: ChrisL | | Timezone: UTC URI: http://info.mcc.ac.uk/CGU/staff/lilley/ | +-------------------------------------------------------------------+