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Re: the whole pixel size dilema

From: Chris Lilley <chris@w3.org>
Date: Tue, 29 Dec 1998 23:57:22 +0100
Message-ID: <36895E52.43F5A2D8@w3.org>
To: benjaminh@epic.co.uk
CC: www-style@w3.org


Benjamin Hardcastle wrote:
> 
> > that IE3,4, or 5 will not scale pixels in raster artwork and HTML elements
> > such as tables when the logical resolution of the system is set to 120dpi
> > or "large fonts". It should scale by 25%).
> >
> Graphics only scale well when you have a scaling factor of multiples of 100%. 

That is not true. It is true that if a particular briowser implements
scaling badly, then it is better not to scale. However, that is not the
same thing.

> If
> you were to scale by 125% do you interpolate the extra pixels? 

Yes, using either bilinear or (preferably) bicubic interpolation.

> Do you do nearest-neighbour? 

Not if you want to look at the result and retain your lunch.

> Think of how that would affect a simple shape such as a
> circle. You would either get a blurred image (interpolation) or discontinuities
> in the image (nearest-neighbour).

It isn't that bad. Photoshop users scale images all the time.

>  Of course, this is all fine if the image is a
> vector one rather than raster. 

Exactly, which is why W3C is working on an XML vector graphics format.

> How much burden can a UA take? After all, it
> would have to do some form of conversion on the image to scale it. For
> interpolation, the UA would have to convert to 16 or 24 bit to scale properly.

Yes it would, good point. If there is inadequate color availability (ie
8 bitindexed, or, worse, the dreaded "web-safe" fixed palette) then
scaling images shows up this lack.

For an example of a browser where the images and text can be made to
scale together, try Opera 3.51 (you need 3.51 rather than 3.5 to get the
PNG support).

--
Chris
Received on Tuesday, 29 December 1998 17:54:56 GMT

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