Friday, 28 December 2012

QGIS Print Composer experimentation

So far all the maps that I have produced with QGIS have been screen dumps saved as bitmaps, which is directly supported from within the application (Google Earth has a similar feature). These are then pasted into Word documents, whereby other content is added to the document and it is then saved as both Word and PDF formats. Today I discovered how maps can be exported into other formats directly from QGIS. The software has a feature called a Print Composer that is specifically designed for outputting a complete map based on the current view of the QGIS main window. It can then export that map into several formats, including SVG and PDF. SVG in particular has the advantage of being a vector format. Maps exported into this format can be printed at any size and will scale cleanly without jaggies, which is a severe limitation of bitmap formats. It is therefore possible to create the highest quality output maps using these formats compared to what can be achieved with bitmaps, already I am noticing some issues with how the bitmaps are rendering when printed out so that is why I am keen to see what can be achieved  When I zoom in in Word to the bitmaps then the issues like jaggy rendering are pretty obvious and this limits their usefulness, whereas with other formats print quality can be made higher. This is also a consideration for other types of output, for example if printed out as Q4 is.

The next challenge is how to use the SVG or PDF for different things? Word doesn’t directly support SVG (even IE9 didn’t directly support it until v9 was recently released) so there is going to be a problem trying to put SVGs into Word documents. I would have to look at perhaps editing in another editor (perhaps in OpenOffice) and saving to format such as PDF. I looked at Acrobat as the official Adobe PDF editing solution, but it is very expensive to purchase except in the educational edition. OpenOffice supports SVG from recent editions (as it is now produced by Apache). Another option is to save to PDF in QGIS and then use Word 2013’s capability to import the PDF into a Word document. It would be interesting to know what format it converts graphics into by this process. The graphics I am seeing in a Word document that was imported using this system are very sharp compared to the bitmaps I have been putting together so far. The part that won’t scale well is the terrain relief background, which is a raster format, but that isn’t so important, and in fact with the contour lines, you can theoretically dispense with it altogether, because those lines show all the detail you need to know about landscapes.

So I will have to have more of a play with these features to see how useful they will be for the future. One limitation of Print Composer is that at this stage it doesn’t support multi pages. Each page would have to be separately exported to its own PDF and then it would have to be opened in Word and the graphic copied to the current Word document. On the other hand in Print Composer you can easily rezoom or pan the map view so you don’t have to go back into QGIS and change the view to see something different in the composer. So when it comes to outputting your maps they can easily be all done from the Composer as the map object is in effect its own view (according to the currently displayed layers etc).