[mapserver-dev] Scales and raster maps

[Frank Broniewski]

Am 2013-08-09 11:40, schrieb thomas bonfort:
> Well that's where you have to factor in dpi if you want do something
> minimally generic (i don't consider passing a retina=yes or using
> different mapfiles to be a suitable solution). I've just added a
> couple of tests to show how you'd do it with mapserver, which involves
> using map.resolution (i.e. dpi) and adjusting requested image size:
> https://github.com/mapserver/msautotest/commit/715683be8f598f5e03d6e11351ccb4f8aaef23e7
>
> in essence
> a request for size=100,100 and resolution=144 will produce an image
> that is identical, once scaled by 50%, to an image produced with
> size=50,50 and resolution=72
>

Hi Thomas,

just to get back to the topic (I was on holiday last week). First, thank 
you very much for writing the test - I never used this parameter 
(map.resolution) before so this is really helpful for me.

So you're using the resolution parameter to scale the content/symbology 
to another size. Problem I see with this is when you are using pixmap 
icons / symbology. Those would get scaled up to and be blurry, wouldn't 
they? That would be an argument for a separated mapfile in my point of 
view. All I want to state here is that a factor (map.resolution) isn't 
the solution for everything, cartography wise. You might even want to 
change the font to enhance readability if you're using a retina display [1]

And again, while these are valid concerns on your behalf (including the 
ones in your other posts), I'd still like to see a pixel-resolution 
based parameter to help me style my layers (turn styles on or off). 
This would be really helpful to synchronize other pixel-resolution based 
applications with Mapserver.

While I understand that you hesitate to include another mechanism that 
does more or less the same than the existing MIN- and MAXSCALEDENOM 
parameters I think the effort would be fruitful. I can't be the only one 
who is struggling to display the right map at a certain zoom level, 
especially when you're using a chain of applications like Mapserver -> 
Mapproxy -> OpenLayers.

If I'd know more about Mapservers' programming language I'd try to make 
a patch for that myself, but I'm only more or less efficient with Python 
and Javascript, being more a cartographer than a programmer. But if I 
can do anything to help me to convince you and the team to implement 
this I'd be willing to help as much as I can.


Many thanks again,

Frank


[1] http://brooksreview.net/2012/08/retina-font-choice/





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