> On Aug 10, 2019, at 12:08 AM, Nyall Dawson <nyall.daw...@gmail.com> wrote: > > On Sat, 10 Aug 2019 at 01:55, Israel Brewster <ijbrews...@alaska.edu > <mailto: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
I see. Well, in a sense it actually worked out well for me. When I tried to export the full map image, some of the smaller features (particularly some of the Aleutian islands in which I am most interested) weren’t saved to the SVG at all (even when zooming in on the resulting SVG they didn’t show up). It was only when I limited the save to a portion of the map that I got all the features. I was thinking I was going to have to use two or three smaller SVG’s, each with a portion of the globe, but since the clipping paths were ignored, the SVG I got actually *did* contain all the data - I just had to futz around with the viewBox to get it to show it all :-) So yeah, that’s a bug, but in this *specific* case the bug actually worked in my favor :-) --- 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 > > >> --- >> 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 <mailto:Interest@qt-project.org> >> https://lists.qt-project.org/listinfo/interest >> <https://lists.qt-project.org/listinfo/interest>
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