Pixstat can work with the number of pixels or with any of the
following units: µm, mm, cm, m or inches. If units are used, then the resolution
of the picture (in pixels per unit of length) has to be indicated via the
Option menu. The resolution can be different in
horizontal and in vertical direction, but klicking on the
equal button forces them to be the same. It is also possible to
let the resolution being variable by checking the option use resolution from
picture file or scanner if available. If the resolution indicated on
the main window differs from the resolution set via the
Option menu, then it must be because this option has
been checked. Beware that the resolution saved with a picture file is not always
correct, depending on the software which they were edited. The information about
the resolution may especially get lost if picture files are saved in GIF format,
in which case the (not meaningful) resolution of the screen would be used
instead of the true original resolution. If in doubt, measure the length of an
object with a ruler and compare with its length as given by Pixstat.