> scott preece said:
>
> > 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.
>
Legibility should normally be increased with a larger display area,
assuming you don't get make the image too big for your display ;), as
long as the number of pixels you use on your screen is an integral
multiple of the number in the bitmap. If the author specifies a minimum
display size for an image, that should not be a problem to honour; if the
granularity of the image is higher than the granularity of your screen,
you could expand the image (probably by order 20% or so) to cover the
same number of pixels, while if the screen has a higher granularity you
could remap each pixel to an N x N block of pixels, where N is the minimum
number to make the image larger than the desired minimum size. This
should preserve the minimum size and maintain legibility. As Chris
pointed out, a fixed size is obviously much harder to render, but it
would be good to be able to prescribe a minimum.
David
Work: seibert@hep.physics.mcgill.ca Home: 6420 36th Ave.
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