Re: [matplotlib-devel] Wind Barbs Full Patch

[John H. <jd...@gm...>]

On Thu, Jul 24, 2008 at 10:00 PM, Ryan May <rm...@gm...> wrote:

> What else is confusing is how that relates to DPI.  When I change the
> figure's dpi, using set_dpi, (and redraw), I get physically *bigger* barbs.
>  To me, if I'm actually specifying pixels, there's no way that they should
> get bigger when I change the DPI.

When you increase the dpi, the canvas gets bigger (inches*dpi equals
canvas size in pixels).  If you are drawing in pixels, and not
scaling, the barbs should look smaller, since they are a smaller
proportion of the canvas size.  So if this explanation is right, the
barbs will look smaller with larger dpi.

> Then I also can't figure out what the PS backend is doing.  If PS is
> hardcoded to 72 DPI, why does passing dpi=72 to savefig() have any effect?

ps should be unaffected, but dpi dependent backends will.  By setting
the dpi to be 72, it should make the *other* backend look like the ps
backend and the ps backend should be unaffected.

JDH