Andy, You are quite right, the image itself does not have a resolution. What I meant was change the resolution that mapnik assumes that you will print the image at, so that your 12pt font appears at 12pt size on the printed page etc. There is an implied resolution of (I think) around 90ish pixels per inch as you say.
Graham. On 15 June 2011 13:42, Andy Allan <gravityst...@gmail.com> wrote: > On Wed, Jun 15, 2011 at 1:23 PM, Parveen Arora <o...@parveenarora.in> > wrote: > > On Wed, Jun 15, 2011 at 10:10 AM, Graham Jones <grahamjones...@gmail.com> > wrote: > >> Hi Parveen, > >> Do you mean resolution (pixels per inch) or level of detail (which icons > >> appear at which zoom level?). > > Yes I meant to pixels per inch. > > > >> You can change the resolution if you use mapnik2, but that is something > you > >> would want to do for printed output rarher than a web based map? > > Yes, someone asked me to print them for his area, but one I printed is > > not of good quality. > > So I wants to increase the resolution of tiles for local OSM Tile Server. > > OK, so it's impossible to change the resolution of images, since they > don't have a resolution. Images only have a number of pixels, that's > it. > > When stuff is shown on screen it's usually shown around 90 pixels per > inch. Most times when you print a webpage then it'll assume that you > still want to print at 90 pixels per inch, regardless of the DPI of > the printer. In order to look crisp, you want to find a way to > instruct your printer to print at more pixels per inch, say 250 pixels > per inch. Again, don't confuse this with the DPI setting of the > printer, since that's about number of ink droplets on the page, and > not to do with pixels per inch. > > Now to make things like the width of a road or icon of a church stay > at the same size, you would need to increase the number of pixels they > are measured in. So a road would need to be e.g. 15 pixels instead of > 5. That usually involves changing the stylesheets, although there is > work on this going on in mapnik2 to allow this to be controlled > without editing the stylesheet. > > You could have a look at the "oversize" tiles that CloudMade produce. > http://developers.cloudmade.com/projects/tiles/documents . You can see > in the second example everything is drawn bigger, so that if you were > to print out at 180 pixels per inch it would look the same size as a > normal map, but you'll end up with a better looking map. > > Finally, if you are printing it's often worth ignoring all this stuff > and just printing from SVG. You can get SVG output from the Export > tab. > > Cheers, > Andy > -- Graham Jones Hartlepool, UK.
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