From basic oversampling

I have a large image file (one range) that doesn't fit in my ram. I would like to read it as a nump (data) array and plot it with matplotlib, possibly using imshow(data)

. I know how to do this for a small image. But how can I do this for a large file? Of course, it is quite possible to change it (perhaps scipy zoom) before plotting. But how can I reprogram it before reading as numpy, because reading a large file into memory is not possible.