On Sat, 10 Aug 2019 at 01:55, Israel Brewster <ijbrews...@alaska.edu> wrote: > > Thank you. QGis did indeed allow me to open my Shapefiles and save them as > SVG (though it messed up the viewBox attribute, so I’m still trying to figure > out how to get that to not crop the image).
That's due to an unfortunate, long-standing Qt bug (Qt SVG export from QPainter ignores clipping paths). Nyall > --- > 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 8, 2019, at 8:19 AM, Francis Herne <m...@flherne.uk> wrote: > > 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 > > ________________________________ > 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> 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 > https://lists.qt-project.org/listinfo/interest > > > _______________________________________________ > Interest mailing list > Interest@qt-project.org > https://lists.qt-project.org/listinfo/interest > > > _______________________________________________ > Interest mailing list > Interest@qt-project.org > https://lists.qt-project.org/listinfo/interest _______________________________________________ Interest mailing list Interest@qt-project.org https://lists.qt-project.org/listinfo/interest
