You should definitely look at QGIS: https://qgis.org/en/site/index.html
It's open-source and has an excellent map-rendering implementation including shapefile support. -Francis H -------- Original Message -------- From: Israel Brewster <ijbrews...@alaska.edu> Sent: 8 August 2019 16:55:49 BST To: Brad Pepers <bpep...@me.com> Cc: Interest <interest@qt-project.org> Subject: Re: [Interest] Zooming with QGraphicsView/QGraphicsItem I do have .shp files for the coastlines - perhaps I could convert those to something I could use? If I can get vector data, how would I go about utilizing it? I played around a bit with loading different image files, but so far the performance has been unacceptable - the entire app locks up for several seconds when displaying the higher resolution images. I think Vector would be a better way to go, if I can figure out how. Thanks! --- Israel Brewster Software Engineer Alaska Volcano Observatory Geophysical Institute - UAF 2156 Koyukuk Drive Fairbanks AK 99775-7320 Work: 907-474-5172 cell: 907-328-9145 > On Aug 7, 2019, at 10:12 PM, Brad Pepers <bpep...@me.com> wrote: > > In the end the answer is to get the coast as vector data instead of a raster. > The raster is going to be at a fixed map scale and any scale above or below > is going to extrapolate or interpolate the results eventually ending in poor > results because there just isn’t the information needed or too much > information is being lost. Having different resolutions should help and you > can keep multiple levels and switch between them at appropriate times (LOD). > Those are your best bets if you can’t get the actual vector data! > > -- > Brad > > > On Aug 7, 2019, at 12:01 PM, Israel Brewster <ijbrews...@alaska.edu > <mailto:ijbrews...@alaska.edu>> wrote: > >> I have a QGraphicsScene/QGraphicsView that I am using to display a map (and >> some data). The map is in the mercator projection, with the x and y >> coordinates of the scene corresponding to map coordinates, so the background >> images are rather large. Images are loaded into a QGraphicsObject which is >> then added to the scene. The object types are defined by a third-party >> library, so I don’t have the option of using different objects, such as >> QGraphicsPixmapObject or something. >> >> This works fine when I’m zoomed in to the map. Coastlines are nice and >> sharp, with no issues: >> <Screen Shot 2019-08-07 at 9.50.10 AM.png> >> >> However, when I zoom out, the coastline becomes quite pixelated, and >> difficult to see in places: >> <Screen Shot 2019-08-07 at 9.50.28 AM.png> >> >> How can I fix this? My first thought was to change the size of the >> background image so it could scale better, but that didn’t seem to help. In >> retrospect, this makes sense: at the end of the day, the background image >> has to be the correct size for the mercator projection, so while I can >> certainly change the pixel density, the overall size, and thus how much >> scaling is needed to display a given area, is fixed. >> >> --- >> Israel Brewster >> Software Engineer >> Alaska Volcano Observatory >> Geophysical Institute - UAF >> 2156 Koyukuk Drive >> Fairbanks AK 99775-7320 >> Work: 907-474-5172 >> cell: 907-328-9145 >> >> _______________________________________________ >> Interest mailing list >> Interest@qt-project.org <mailto:Interest@qt-project.org> >> https://lists.qt-project.org/listinfo/interest >> <https://lists.qt-project.org/listinfo/interest>
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