On 26/02/2019 17.23, Martin Dobias wrote: > Hi all > > Whenever I use a background map like OpenStreetMap on my high-res > laptop screen (192 DPI) in QGIS, the labels are tiny. That is > "natural" because tiles are made for screens with ~96 DPI where the > size of labels is just fine. When I look at OSM tiles in the browser, > I can see that the browser displays the tiles scaled ... so even > though the tiles do not look super crisp, at least I do not need a > magnifying glass to read labels. > > A similar problem I have encountered before is when using tiles from > WMTS/XYZ in print/PDF output: with higher resolution of print the > rendering engine picks very detailed tiles which again may contain > very tiny labels. > > I would like to fix this in QGIS but I am wondering what would be the > correct approach. > > One simple (and wrong?) solution would be to just scale tiles of all > tile layers, but I guess if the service displays some raw imagery it > would be wasteful to scale them as this unnecessarily would remove > details which could be still shown on high res display. > > Other solution would be to introduce a new flag for WMTS/XYZ layers > where users could set native DPI. By default this flag would be > disabled, but for services like OSM one could explicitly set their DPI > to 96 and get the tiles scaled accordingly. This would need an update > of raster block request API as well where we would also need to > specify output DPI in addition to output width/height (but that should > not be a big deal). > > This solution could also work nicely with services that provide > high-res tiles (using 512x512 for each tile instead of 256x256) - > right now QGIS thinks they are 256x256 so instead of a magnifying > glass one needs a microscope - you can try it [1]. Setting explicitly > DPI of high-res tiles to 192 DPI should also fix also that issue. > > My only worry is if this setting is not going to be too difficult to > use for ordinary users... But maybe a combo box would make the choice > easier: "Normal resolution (96 DPI)" / "High resolution (192 DPI)" / > "Custom resolution" (with a spin box). > > Are there any opinions / ideas how to deal with that?
Hi Martin, not sure if this is helpfull, but Matthijs of the OpenGeoGroep.nl created a hidpi tilecache for mac users not so long ago for an Dutch, osm based base map. I asked him what he did. He says (translated): "Yes we serve two versions, eg" http://www.openbasiskaart.nl/mapcache/wmts/?SERVICE=WMTS&REQUEST=GetTile&VERSION=1.0.0&LAYER=osm-nb&STYLE=default&TILEMATRIXSET=rd&TILEMATRIX=5&TILEROW=16&TILECOL=15&FORMAT=image%2Fpng http://www.openbasiskaart.nl/mapcache/wmts/?SERVICE=WMTS&REQUEST=GetTile&VERSION=1.0.0&LAYER=osm-nb-hq&STYLE=default&TILEMATRIXSET=rd-hq&TILEMATRIX=5&TILEROW=16&TILECOL=15&FORMAT=image%2Fpng "Only the tileing protocol metadata is not really prepeared for HQ tiles. I now set it up i a way that for HiDPI tiles you have use the same TILEMATRIX, TILEROW en TILEROW, but you receive either a 256x256 tile or a 512x512 tile depending on the TILEMATRIXSET. But you have to fool the tile server a little, so if you use current URL (http://www.openbasiskaart.nl/mapcache and layer with HQ in QGIS) you get big labels." Maybe you can use the service to check/test? (note hq is only in EPSG:28992) Regards, Richard Duivenvoorde _______________________________________________ QGIS-Developer mailing list QGIS-Developer@lists.osgeo.org List info: https://lists.osgeo.org/mailman/listinfo/qgis-developer Unsubscribe: https://lists.osgeo.org/mailman/listinfo/qgis-developer
