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<div class="moz-cite-prefix">On 30-06-16 04:25, Glynn Clements
wrote:<br>
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<blockquote
cite="mid:22388.33579.411923.396851@cerise.gclements.plus.com"
type="cite">
<pre wrap="">
Paulo van Breugel wrote:
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<pre wrap="">I am creating some maps (png format) using the GRASS_RENDER_IMMEDIATE=cairo
and d.* calls. I am setting width and height based on a final desired
300dpi for the output image (i.e., pixels = # inch x 300).
However, the font size as can be set in e.g., d.legend is, I assume, based
on the assumption that the output image has a DPI of 72. Is there any way
to set the DPI of the output image?
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For the cairo driver, I believe that the font size is the size of 1-em
in pixels (the cairo documentation says "user space units"; in the
absence of any additional transformations, I believe that this means
pixels).</pre>
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The em is a relative measure, and depends on the font size. What
this thus tells is that the cairo driver uses the screen resolution
(dpi) to determine the font size / pixel ratio. The screen
resolution of computer screens nowadays is commonly 96 dpi (my
screen is 1920x1080 pixels at 20.05 x 11.28 inch, so indeed 96 dpi).
The font size of the legend text created with d.legend is thus based
on the assumption that the output map as a dpi of 96 dpi. To
determine the font size of a map that is to be printed at 300 dpi,
the font size in d.legend should be set at 300 / 96 x 12 = 37.5 (I
tried this out and in my case this is indeed correct).<br>
<br>
In ps.map one can define the required font size and dpi, and the
calculation above is done automatically (I assume it can get the
screen dpi from somewhere?). My question was basically if there is
an option to tell d.legend (and other d.* functions) the intended
resolution (dpi) of the output map, but I guess the answer is no.
This may be logical given the focus of ps.map on print and the d.*
family on on-screen-display. But in the light of the GSoC
cartography suite project, it might be something to consider adding
an option to set the output dpi for the map?<br>
<br>
<br>
CSS requires that <code>1px</code> must be exactly 1/96th of an
inch in all printed output. <br>
<blockquote
cite="mid:22388.33579.411923.396851@cerise.gclements.plus.com"
type="cite">
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