[GIS] Exporting high-resolution world map image from QGIS

print-composerqgisqgis-2

I'm trying to get some (very) large world map images (think 10k x 10k pixels etc), but can't seem to do it with QGIS.

Manually adding smaller images to a larger one works (albeit slowly) for continental landmasses, but not for various mid-ocean islands etc, as I've no reference points handy.

The "Save as image" command only saves what's on-screen at the moment, the "Print Composer" system ditto.

Ideally, I'd hit a button & QGIS would export the entire project to a single giant .tiff image, or perhaps a series of tiles.

Best Answer

Go for print composer. Increase the page size and resolution. Add the map and if you want to create a map of the whole world, make sure you zoom to full extent. Then save as image. If the size is not big enough, increase the paper size further. A0 with 300dpi should easily be possible if you have enough RAM.

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[GIS] Printing High Resolution Open Maps

You can make screen copies of the Openlayers background (without your vector data) in higher zoom levels with File -> Save picture as...

In a next step, you can stitch several screenshots together to get a raster file with the same zoom level you used, but greater than one screen.

If you use that as background instead of the Openlayers tiles, you get a higher resolution background for printing.

Only thing I do not know if this is according to the license policy of Google and bing.

PyQGIS Export – Exporting Composition as Image

To get a list of existing composer windows:

composers = iface.activeComposers()

Then, you need to get a reference to a specific composition:

c = composers[0].composition()

Render the page as an image (0 refers to the page number):

image = c.printPageAsRaster(0)

Save the image to disk (first argument is the filename, second is the format):

image.save('output.png','png')

So, the entire code should look something like this:

c = iface.activeComposers()[0].composition()
image = c.printPageAsRaster(0)
image.save('output.png','png')

Best Answer

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[GIS] Printing High Resolution Open Maps

PyQGIS Export – Exporting Composition as Image

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