[Numpy-discussion] array is not writable

Charles R Harris charlesr.harris@gmail....
Wed Aug 26 23:43:13 CDT 2009

On Wed, Aug 26, 2009 at 10:34 PM, David Warde-Farley <dwf@cs.toronto.edu>wrote:

> On 26-Aug-09, at 11:49 PM, Mark Wendell wrote:
> > Figured this much out: if I do an np.copy of the original array to a
> > new array, then I can edit individual 'color' values with impunity. So
> > I guess the original array from the pil object still shares memory
> > with that image object somehow, making it unwritable?
> I'm going to guess that it's because PIL is still responsible for that
> memory, not NumPy. I don't really know how this stuff works but
> asarray() would just give you a view onto that chunk of memory; since
> NumPy didn't allocate it, it probably doesn't want to modify it. Not
> sure if you can get away with not making a copy in this situation.

I expect you can. It's the unreadable arrays that are a problem...

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