Re: pixels, bis

["Bruce Roorda" <possum1@softhome.net>]

<x-charset iso-8859-1>There's a fundamental difference between a geometric point and a pixel.  A
point is defined as having no dimensions.  It never has a lineal size and
never acquires dimensions or magnitude.  An infinite number of points will
fit in any length of line segment.

A pixel represents a general, finite area which is always two-dimensional.
You don't have to assign magnitudes to its two dimensions until you map it
onto a specific area, such as a group of phosphor dots on a monitor.

The area a pixel represents doesn't have to be square.  Earlier computer
monitors used rectangular pixels; I think the Mac was first to use a monitor
with square pixels.  So the size of a pixel area needs to be specified in
two dimensions.  Specifying a resolution of 300 pixels per inch, for
example, implies that the pixel represents a square area with length and
width both one three-hundredth of an inch.

Bruce Roorda
Possum Hill Farm

LAURIE SOLOMON wrote:

> Without getting to deep, pixels are picture elements which are like points
> in geometry; they are dimensionless in themselves.  They acquire
> dimensionality from outside of themselves in that their measure or
dimension
> depends on the lineal space that they are fit into.  Thus, a pixel within
a
> 300 pixels per inch resolution equals 1/300 of an inch; whereas the same
> pixel in a 600 pixel per inch resolution equals 1/600 or an inch; and so
on.
> The lineal dimension  of inches, centimeters or whatever are defined in
> terms of units that measure the space or scale of the outputted display (
> monitor or print) that contains the pixels. Thus when you change the scale
> or lineal sizing of an image without also deliberately holding the number
of
> pixels per inch constant, you automatically alter the resolution (pixels
per
> inch) proportionately and thus the dimensionality or size of the picture
> elements or pixels.  How many points make up a one inch line?  The answer
is
> it depends on how many you define as being there which then tells you
lineal
> size of each point in that one inch line.
 (snip)

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