Re: Method to get zoomed in or zoomed out AWT image from and ImagePlus or ImageWindow?

Posted by dscho on
URL: http://imagej.273.s1.nabble.com/Method-to-get-zoomed-in-or-zoomed-out-AWT-image-from-and-ImagePlus-or-ImageWindow-tp3688583p3688589.html

Hi,

On Thu, 15 Apr 2010, Frederic Hessman wrote:

> Some older CCD cameras used detectors that were not squares (in digital
> spectroscopy, for instance, one doesn't really care), but since imaging
> is now driven by digital photography, most pixels are indeed squares.

No.

> In astronomy, where the "World Coordinate System" behind the pixels is
> often of interest, there are very elaborate means for calibrating pixel
> versus physical space, even to the point of all-sky pixelisation
> (HEALPix).  In astronomical photometry, depending upon whether one wants
> to conserve surface brightness or total number of photons, the question
> of how to interpolate or resample is a tricky one indeed.

Our discussion is not about the arrangement of pixels. It is about their
shapes.

A pixel will in almost all cases be a point sample of a signal, and that
point sample can be modeled mathematically as a convolution of the signal
with a kernel, the so-called point spread function (which does not need to
be independent of the coordinate, or for that matter, of the signal in
general).

And even with modern CCDs, that point spread function can be modeled
better by a 2D Gaussian bell than by a 2D rectangular function. The most
important point to keep in mind is that adjacent point samples have an
overlapping support from which they draw information.

Ciao,
Johannes