Pixels Per Inch needs to be standardized 🔍
maandree at member.fsf.org
Wed May 4 18:17:46 UTC 2016
For projectors, I think it would be best if the dimensions
could be configured.
On Wed, 4 May 2016 11:12:38 -0700
"Jasper St. Pierre" <jstpierre at mecheye.net> wrote:
> What are the dimensions of a projector, whose
> pixels-per-inch or dots-per-inch value is a distance of
> how far away the projector is for the wall, or, in a
> keystoned case, isn't even constant across the display?
> For limited scenarios, you can make it work (with
> caution, see ). But we cannot calculate a sensible DPI
> value in the general case.
> On Wed, May 4, 2016 at 10:45 AM, Mattias Andrée
> <maandree at member.fsf.org> wrote:
> > On Wed, 4 May 2016 19:01:09 +0200
> > Alberto Salvia Novella <es20490446e at gmail.com> wrote:
> >> Mattias Andrée:
> >> > What's wrong with dots per inch?
> >> How can an application reliably know which is the
> >> current pixel density of the desktop?
> > Well, you cannot know anything reliably. The EDID
> > does contain all information you need for DPI, however
> > with limited precision. X.org reports a bogus DPI. But
> > if pretend that all monitors' dimensions are in whole
> > centimetres, than the number of pixels per centimetre
> > can be calculated
> > ppc_x = output_width_px(monitor) /
> > output_width_cm(monitor); ppc_y =
> > output_height_px(monitor) / output_height_cm(monitor);
> > Notice that this is easier to calculate than the pixels
> > per inch.
> > ppi_x = output_width_px(monitor) /
> > output_width_cm(monitor) * 2.540; ppi_y =
> > output_height_px(monitor) / output_height_cm(monitor) *
> > 2.540;
> > But why is pixels preferred over dots?
> > _______________________________________________
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> > xdg at lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/xdg
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