Re: Non-square pixels test

Posted by Gabriel Landini on Dec 04, 2005; 12:13am
URL: http://imagej.273.s1.nabble.com/Non-square-pixels-test-tp3704327p3704329.html

On Saturday 03 December 2005 23:26, Prodanov, D. (FYS) wrote:
> I don't see the idea behind such a test. If it tests the camera,
> then you can image a square object and read the measurements directly.
> Apart from this setup I don't see how you can test if
> a pixel is "square" or not. Do you have a particular application in mind?

Hi Dimiter,
Of course you are correct. The problem is that I posed the question
incorrectly.  :-/
I wanted to put a test in the Particles8_Pluse pluing to warn the user about
using the plugin when the image has non-square pixel and he/she has taken
care of calibrating it by inserting the pixel widht and height with the
Image>Properties dialog.

Since my plugin assumes square pixels and it does not use the calibrated
units, using images with aspect ratio pixels different to 1 will return
incorrect results. (the plugin assumes that 2 side-neigbours are 1 unit apart
and 2 corner neighbours sqrt(2) apart).

Until I modify the plugin to use calibrated units (one of these years), this
test is the least I could do to avoid getting flawed measurements.
Wayne's suggestion works fine.

If the images were captured with non-square pixels devices and the user has
not calibrated the image either, then there is not much I can do to prevent
misuse of the plugin.

Thanks for the feedback.
Cheers,

Gabriel