Re: Measuring areas...

Posted by Gabriel Landini on Jun 18, 2007; 4:44pm
URL: http://imagej.273.s1.nabble.com/Measuring-areas-tp3699083p3699086.html

On Monday 18 June 2007 16:26:59 Christophe Leterrier wrote:
> I would think that a pixel is
> more a surface unit than a length unit. A 4x4 pixels square is a 16
> pixels area, or 16 pixels^2 if you prefer.  Strictly speaking I'd say a
> pixel is a square that have a 1x1 pixel dimensions, so it's also a
> pixel^2 (I mean, for most acquistion systems, rectangular pixels do
> exist also).

Not always. A pixel may also be considered a point. Otherwise one could not
draw/analyse lines.
If you consider pixels to be sampling points, then a 4x4 pixel square has an
area of 9 pixels^2 (since you count from the centre of the sampling points as
the vertices of the polygon (and a square of 2x2 has an area of 1).
There are more ways to handle areas and perimeters of polygons in discrete
space. Because of this, Particles8_Plus plugin gives both the Area and the
Pixels in a blob. You can have lots of pixels and no area.

Cheers,

G.