convert array to tuples?
HI folks, What's the fastest way to convert a numpy array to tuples? Unfortunately, not all packages take arbitrary sequences when they are expecting a list of tuples. In this case, I'm using PIL's ImageDraw, and want to do: draw.line(points) (points is an Nx2 numpy array of ints) but if I pass in an array, I get, oddly enough, nothing. NO error, just nothing drawn. if I do: draw.line(points.tolist()) SystemError: new style getargs format but argument is not a tuple So I seem to need tuples. This works: draw.line([tuple(p) for p in points.tolist()]) but that seems like it would be slower than it should be (to be honest, not profiled). Is there a faster way? Maybe numpy should have a ndarray.totuple() method. -Chris -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception Chris.Barker@noaa.gov
On Tue, Apr 5, 2011 at 7:02 PM, Christopher Barker <Chris.Barker@noaa.gov> wrote:
HI folks,
What's the fastest way to convert a numpy array to tuples?
Unfortunately, not all packages take arbitrary sequences when they are expecting a list of tuples. In this case, I'm using PIL's ImageDraw, and want to do:
draw.line(points)
(points is an Nx2 numpy array of ints)
but if I pass in an array, I get, oddly enough, nothing. NO error, just nothing drawn.
if I do:
draw.line(points.tolist())
SystemError: new style getargs format but argument is not a tuple
So I seem to need tuples. This works:
draw.line([tuple(p) for p in points.tolist()])
but that seems like it would be slower than it should be (to be honest, not profiled).
Is there a faster way?
Maybe numpy should have a ndarray.totuple() method.
-Chris
How about fixing PIL... I know that there is not a good track record of getting patches into PIL , but did you get to the bottom of it and find how draw.line is implemented? BTW, is it drawing anti-aliased lines ? - Sebastian Haase
On 4/5/11 10:52 AM, Sebastian Haase wrote:
How about fixing PIL... I know that there is not a good track record of getting patches into PIL , but did you get to the bottom of it and find how draw.line is implemented?
no. I haven't. And yes adapting PIL to use the buffer interface for this kind of thing would be great. I also have wanted to do that for wxPython, where it would be welcome, but still haven't gotten around to it.
BTW, is it drawing anti-aliased lines ?
Not with the ImageDraw module, but there is a new AggDraw module that should be more pretty. On 4/5/11 11:49 AM, Mark S Niemczyk wrote:
Just a suggestion (I am very new to Numpy), but wouldn't
draw.line(tuple(points.tolist()))
accomplish what you want.
nope, tolist() creates a list of lists -- tuple() only converts the outer list to a tuple, which I why I did the list comprehension. On 4/5/11 10:53 AM, josef.pktd@gmail.com wrote:
does a structured dtype work?
Good idea -- I'll give it a try -- indeed it does: dt = np.dtype([('x', np.int32),('y',np.int32)]) draw.line(points.view(dtype=dt).reshape((-1,)).tolist(), fill="rgb(0,255,0)", width=4) but it's not any faster, alas. The fastest I've come up with is putting the elements in a single 1-d list. PIL can take either a sequence of tuples: [(x,y),(x,y),...] or the flattened version: [x,y,x,y,x,y,x,y,...] So this is the fastest: draw.line(points.flatten().tolist(), fill="rgb(0,255,0)", width=4) Thanks all, -Chris -- Christopher Barker, Ph.D. Oceanographer Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception Chris.Barker@noaa.gov
On Tue, Apr 5, 2011 at 1:02 PM, Christopher Barker <Chris.Barker@noaa.gov> wrote:
HI folks,
What's the fastest way to convert a numpy array to tuples?
Unfortunately, not all packages take arbitrary sequences when they are expecting a list of tuples. In this case, I'm using PIL's ImageDraw, and want to do:
draw.line(points)
(points is an Nx2 numpy array of ints)
but if I pass in an array, I get, oddly enough, nothing. NO error, just nothing drawn.
if I do:
draw.line(points.tolist())
SystemError: new style getargs format but argument is not a tuple
So I seem to need tuples. This works:
draw.line([tuple(p) for p in points.tolist()])
but that seems like it would be slower than it should be (to be honest, not profiled).
Is there a faster way?
Maybe numpy should have a ndarray.totuple() method.
does a structured dtype work? Josef
-Chris
-- Christopher Barker, Ph.D. Oceanographer
Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception
Chris.Barker@noaa.gov _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
Just a suggestion (I am very new to Numpy), but wouldn't draw.line(tuple(points.tolist())) accomplish what you want. Based on my reading, the ndarray.tolist method would return a Python list of elements; then Python's built-in tuple function would complete the conversion. Regards, Mark On Apr 5, 2011, at 12:02 PM, Christopher Barker wrote:
HI folks,
What's the fastest way to convert a numpy array to tuples?
Unfortunately, not all packages take arbitrary sequences when they are expecting a list of tuples. In this case, I'm using PIL's ImageDraw, and want to do:
draw.line(points)
(points is an Nx2 numpy array of ints)
but if I pass in an array, I get, oddly enough, nothing. NO error, just nothing drawn.
if I do:
draw.line(points.tolist())
SystemError: new style getargs format but argument is not a tuple
So I seem to need tuples. This works:
draw.line([tuple(p) for p in points.tolist()])
but that seems like it would be slower than it should be (to be honest, not profiled).
Is there a faster way?
Maybe numpy should have a ndarray.totuple() method.
-Chris
-- Christopher Barker, Ph.D. Oceanographer
Emergency Response Division NOAA/NOS/OR&R (206) 526-6959 voice 7600 Sand Point Way NE (206) 526-6329 fax Seattle, WA 98115 (206) 526-6317 main reception
Chris.Barker@noaa.gov _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@scipy.org http://mail.scipy.org/mailman/listinfo/numpy-discussion
participants (4)
-
Christopher Barker -
josef.pktd＠gmail.com -
Mark S Niemczyk -
Sebastian Haase