Hello again

Oh, I was just thinking about it theoretically, and trying to spare a 
separate rescaling phase.

Probably it's not practical, but my view is that if people are not using 
units like meters or feet but still want the symbolizers to remain the 
same size on paper (or on screen), regardless of resolution, then all 
sizes should be given in millimeters, inches, etc (that is, explicitly 
specifying what the user really wants). Giving it in pixels is simpler 
but in this case it seems like saying "I want the symbolizer to show on 
paper the size it would show on screen using 20 pixels and 72 DPI, so 
please fix that size because I am now using 300 DPI". Shouldn't he just 
say that the size is 20/72 inches?

On the other hand, rescaling the map with a user given value looks like 
a valid functionality anyways - it gives flexibility, and who knows what 
the user may want to do? :). What do you think about a simple rescaling 
parameter? In this case, he could state something like 
scalefactor=300/72 (instead of saying that the original DPI is 72 but he 
now wants 300). Does it make sense to you?

Anyway, my point was just that I don't think this is the best way to 
handle this particular case, but I understand it may be impractical to 
have everybody change their symbolizer sizes from pixels to inches or 
millimeters.

Oh yes: I had not thought about mm, cm, inches, etc when I did the 
UomRescaling code. If we were to do that someday, I guess we would have 
to split the current "mapScale" parameter (given in pixels/meter) into 
its two components: a usual cartographic mapScale such as 1:100000 
(stating that 1mm on the screen equals 100m in the real world) and a 
resolution or DPI value (specifying how many pixels fit into each mm or 
inch)

So, that's it! :)

Milton

PS: just to make it clear, I am just chatting around and speaking my 
mind. This feature should not have any impact in anything I am doing, so 
I really have no objection to whatever solution you implement!


> So I'm confused... what do you suggest I should do for people that want
> to get a printout at 300dpi out of a GeoServer GetMap request so that
> it looks like on screen (no reduced size symbols?).
> 
> I looked around because I remember MapFish somehow sends the target DPI
> to MapServer exactly for printing purposes and found this:
> http://mapserver.org/development/rfc/ms-rfc-55.html
> 
> They call it defresolution and it's doing basically what I'm suggesting,
> multiplying all symbol sizes by targetDpi/standarDdpi.
> 
> Can we find any agreement on how we should call this so that I can move
> on and deliver this functionality? :-)
> 
> Cheers
> Andrea
> 

-- 

Milton Jonathan
Grupo GIS e Meio Ambiente
Tecgraf/PUC-Rio
Tel: +55-21-3527-2502

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