QGIS compositing is not limited just to between layers, but also for elements in the Print Composer. How is this useful? Every want a non-rectangular map? With 1.9 alpha, you can use an SVG to affect the elements under it. On the right, the svg. On the left, the map element inside the Print Composer.
Overlay the two with “Blending Mode” set to “Normal” and the svg covers the map.
Set the svg blending mode to “Dodge”, and we get an interesting mask, as well as (in this case) some additional affects related to the two different shades in our svg.
The svg shapes can be anything:
But let’s try something more meaningful, for example, using an svg to mask our map of a peninsula:
For your inner cartographer– behold! A non-rectangular map! Wrap some text around that puppy and call it art.
BTW, the map itself is a fake summer aerial created with povray, a winter aerial, and a little tinting of the winter aerial using blending mode “multiply” in the map itself. But that is the topic of another post… .