how to start with geotiffs

[LukaszKowalski2013]

Hi,

I have a fairly simple task, but I don't know how to do it with your library even after reading examples.

I want to read a geotiff with your library. Multiply every value by 0 and save it to the same file. Later on I want to change it to polygon, so I have boundaries of the raster.

Can you help me with this?