[gdal-dev] Get a rough overview image via RasterIO

[Oliver Eichler]

Hi,

zooming out of a raster map is always a very resource hungry task as a large 
area of points have to be read and reduced to the viewport size. 

For a steady map RasterIO does the perfect job. However if the user zooms out 
of a map very fast via mouse wheel RasterIO eats up too much time to allow a 
smooth zoom. 

Thus my question: Is there a way in GDAL to get a quick overview picture for 
smooth zooming.

Oliver