W3C home > Mailing lists > Public > www-style@w3.org > December 1998

Re: the whole pixel size dilema

From: Todd Fahrner <fahrner@pobox.com>
Date: Wed, 16 Dec 1998 17:43:03 -0800
Message-Id: <v04011703b29e085048b8@[]>
To: bill brissette <billb@gbcom.com>, www-style@w3.org
y'all wrote:
 " i'm not sure if it really matters how big a pixel is defined as, as I see
 " it, one pixel, one square of color, is one pixel. If everything on the
 " screen is measured in pixels, then the term pixel is relative to the
 " screen resolution. Right? why not just set the standards for rendering
 " type and info to be relative to one screen pixel on any particular
 " machine? as long as a pixel doesn't vary from one side of the screen to
 " the other, it shouldn't effect the layout, just the size of the image.

It's all in your last phrase: "the size of the image".

If your pixels are too small, so is your image. And if your "points"
rasterize into a fixed number of pixels, then so is your text. So The Right
Thing To Do is to scale, which is in fact what happens when you print.
Printers tend to have very small pixels - 1:1 is generally worthless. (Try
printing a 10px letter from IE3 sometime: you'll see 10 unscaled printer
pixels. This is a bug. Similarly, I consider it also a CSS support failing
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%).

I take it as given that within 10 years, interactive displays will have
physical resolutions at least equal to low-end print. I don't want the Web
to shrink or distort down that hole.

So the key is to know the appropriate scaling factor when your pixels are
unsuitably small for 1:1 display of raster data (such as GIFs, JPEGs,
PNGs). The reference pixel provides the basis for such scaling, correlating
literal raster data pixels with useful values in absolute or user-space
(inches or degrees of visual angle).

Pixel scaling from a common reference or "virtual" pixel is essential for
achieving predictable rendering results across media and devices,
especially over time.

Note that Netscape 4.x scales raster data based on a 1/120" reference pixel
when printing. Tsk.
Todd Fahrner           The art of letters will come to an end before
fahrner@pobox.com      AD 2000... I shall survive as a curiosity.
                                                  - Ezra Pound, 1910
Received on Wednesday, 16 December 1998 20:43:13 UTC

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